Craftsman 4 ton floorjack rebuild

Jeeper · Oct 5, 2012

A few months back my 4 ton Craftsman Pro stopped working. The jack started it's malfunctioning when sometimes it wouldn't lift all the way, then it wouldn't left anything up. I bought a new Arcan from Costco and the old CM has just been sitting there. Saw HiBall's tutorial come up again, so I thought I'd rip into it.

Here are some pictures. I got it torn down. I think it's the cup seal as there are some scratches on it. I did take apart the valves but i marked them and counted the threads so they should be the same and already reinstalled. I took them out to check the seals.

The seal looks like it's a 24x40x10mm. Hopefully Hiball has one. This is part of an experiment and part if i can get it to work it will be good to have an extra jack in the garage. Plus I hate throwing it away for a cheap seal.

Removed the power unit:

Removing the tank nut. Luckily my friend texasspartan bought the 55mm beta socket when it was cheap.

Ram is out:

I would love to know what each of the screws do. I have pictures of what's underneath each cap.

The seals on the ram:

The grooves in the seal:

Jeeper · Oct 6, 2012

Here are some more accurate measurements that I posted on the tutorial thread.

The actual measurements are 24.2mmx39.34mmx9mm. That is WITHOUT the backing washer.

fdny136 · Oct 6, 2012

i just replaced that seal on a craftsman 2 ton.unfortunately my nephew messed wih the valves.would you have the settings for the jack or which goes in what bore, I would love to see the pics of whats under each screw..thanks

Jeeper · Oct 6, 2012

Here is the break down that i have of the valves. It's working from left to right with the piston rod point up. I put the number of turns i counted. You may have to download and lighten one of the earlier pics to see where the screw slot is pointed. I wish I knew what each of the screws acutally did. Looking over Hiball's tutorial, he mentiones working, crossover, overload valves. This one has 4 so not sure how to make sense of them.

Hope this helps.

First one on the left was just a cover for another screw. I pulled the cover but didn't mess with the first one.

Second one from the left. 5x turns..

Third one from left. 14x turns.

The one on the right. 7 turns.

Jeeper · Nov 15, 2012

I had some weekday time to run by the local hydraulics shop today and picked up a new seal for this. The seal is a 24mm x 40mm x 8 mm. In order for it to fit right I had to alter the backing washer. I did this by sanding of the step that interlocked with the previous seal. Hiball mentioned this when I PM'd him. The washer ended up costing $6 locally plus driving across the city 2x (once to order and once to pick up). I would have just bought from Hiball but for some reason held out hope I could find the exact seal (with the step to interlock with the backing washer).

Anyway, got everything installed and it works. I did forget the metal tube screen but figured it wasn't worthing tearing apart again as it was floating in the tank when i pulled it apart. Also the jack is slow to return when released as I am sure the seal is new and much better than the stocker. I can tell it's loosening up some as I have ran it through it's paces.

It's not the best jack but worth the $6 to get it working again.

The backing washer in the middle of sanding it down flat:

The new pretty blue seal:

Back in action:

Jeeper · Nov 18, 2012

So i walk out to my shop and see some fluid under the jack. I find the rubber plug has popped off and some fluid came out. Assuming there was some air build up in the tank that caused the plug to blow off. Any ideas on what cause this?

Hiball · Nov 18, 2012

Jeeper said:
So i walk out to my shop and see some fluid under the jack. I find the rubber plug has popped off and some fluid came out. Assuming there was some air build up in the tank that caused the plug to blow off. Any ideas on what cause this?

Could be numerous things, probably a combination of too much oil and some trapped air.

Jeeper · Nov 18, 2012

Hiball said:
Could be numerous things, probably a combination of too much oil and some trapped air.

I am sure i had too much oil in. filled it all the way up. Is there a recommend bleeding fill procedure?

Hiball · Nov 18, 2012

Jeeper said:
I am sure i had too much oil in. filled it all the way up. Is there a recommend bleeding fill procedure?

Way too much.. The oil level should rest just above the inner cylinder when peering through the hole, or roughly 5/16" +/- below the fill hole.

Jeeper · Mar 21, 2013

Got a question for Hiball or Edgar. This jack works well. It can pick up the cars and trucks I need it to. I did notice it was leaking oil. I figured maybe it was the wiper seal on the tank nut or the tank seal. I cleaned everything up and realizes the oil is coming from the fill hole. It looks like the tank keeps getting air in it and pushing oil out the fill plug. In have noticed that if I let the air out of the plug after use it doesn't let any oil out.

I assume I am getting air as I pump the jack. If I pump the jack with the plug off, I can hear it gurgle. This is after filling and bleeding so I don't think the air is coming from a too low fluid condition. Is this most likely a failed pump seal? When I rebuilt it earlier all I did was put a new u-cup seal.

uniballer · Mar 21, 2013

I have one that the release screw(dont know exact part name?) has swivel end?
Anyway, I have broke two, why?
After the original it has been hell, installed right, and not getting rough!

pop pop · Mar 21, 2013

Jeeper, this may or may not be your problem, or mine for that much. I built a Walker 93632 recently and short filled it, pumped up half way. Finished filling it and it would raise and lower normally. Set it aside and later found oil coming out of the vent. Cleaned it up and cycled it a few more times, no leaks. So a couple of days later i see it has up chucked through the vent again. Thinking some air got trapped and compressed in the lift cylinder, I pumped it up then tilted it on its end so the cyl vent would be at the high point and released it down. That would purge any air in the cylinder, which is the only place air could have been compressed and still in it. Results is no more puking, not a drop.

WILLIE*WILL · Mar 21, 2013

Mmmmmm

Hiball · Mar 21, 2013

It is possible for a weak pump seal to ingest air into the system, it also sounds like you might have too much oil in the reservoir. A reservoir that isn't venting properly can also cause poor performance/air ingestion issues also.

Jeeper · Mar 21, 2013

I had it at the right level oil level, just above the inner cylinder, it did the same thing. Even took some oil out and it had the same problem. Think I will dive into the pump.

Hiball · Mar 22, 2013

Jeeper said:
I had it at the right level oil level, just above the inner cylinder, it did the same thing. Even took some oil out and it had the same problem. Think I will dive into the pump.

Have you tried running it without the vent? Again if the breather isn't doing its job it can create a vacuum and cause issues with the oil transfer from pump to cylinder.. Especially after repeated use.

EDGAR · Mar 22, 2013

Jeeper

Do not dive into the pump. Your problem is that you have a rubber plug not sealing correctly. All jacks, whether floor jacks or bottle jacks, will get some air pressure on the oil tank even after only one full lift, if the plug is sealing correctly. If you use the jack repeatedly in a short period of time, the problem compounds. A worn out rubber plug can leak oil and also let air in into the tank.

There could be a couple of situations were air can come into the pump.

The first one: When you pump the jack, some air may enter the pump tank by a leaky rubber plug as the lift arm rises. Now you have some air that must come out of the tank as the oil is coming back into the tank when you open the release.The oil return port is ususally located high on the pump and in line with the fill hole, and when you open the release, a lot of oil is coming back to the tank. More often than not, this stream of oil hits the bottom of the leaky rubber plug. As this oil is streaming back, some of it is carried out by the air rushing out of the tank. Remember, this air is being forced out of the tank so it may be somewhat pressurized. And this could happen even if you have the correct oil level.

The second: With a good rubber plug, a vacuum is created inside the tank and it increases the more the lift arm rises. If you have an o-ring that may be marginally sealing, because it is half way worn out, some air may enter the pump tank through this o-ring because the vacuum will draw in the air in by force.

Anyway, air under pressure in the tank is a common occurrence with a good solid plug. The reason some jacks use breathers is because the jack will perform as it should and not be affected by the vacuum created inside the oil tank when using a solid plug. In some cases, with a solid plug, and when the pump piston seal is somewhat worn out, the suction created by the pump piston ( when you lift the handle) may not be enough to overcome the increasing tank vacuum, resulting in less oil pumped by the pump piston.

It is always a good idea to replace all the seals when repairing a pump and not just the u-cup. O-rings do not last forever and these are supposed to be changed everytime a pump repair is done.

My recommendation is to get a new rubber plug and try it before taking apart the pump. Check if the fill hole is out of round or if it has some damage, like a nick, that would prevent the rubber plug from sealing correctly. These plugs should seal perfectly otherwise the jack would leak its oil when transported from the factory to the store if they are stored upside down during transport and storage. Even jacks that use breather plugs are shipped from the factory with solid plugs and the owner of the jack is supposed to change it to the breather plug, which should come in the box the jack comes in.

Below see a link to pressure relief vents fittings that open at a certain pressure range and a picture of vent fittings (always open) that could be adapted to floor jacks. Although these are grease fittings, air will flow through them. Second picture from ALEMITE.COM.

http://www.saeproducts.com/pressure-relief-grease-fittings.html

Hiball · Mar 22, 2013

EDGAR said:
. In some cases, with a solid plug, and when the pump piston seal is somewhat worn out, the suction created by the pump piston ( when you lift the handle) may not be enough to overcome the increasing tank vacuum, resulting in less oil pumped by the pump piston.

Jeeper

This... Is exactly what I was referencing, for what they are... Rubber plugs do a fair job of regulating the pressure inside the reservoir. In "My" experience I've found that even a New plug will let enough positive air exhaust to keep problems at bay. Although... If enough oil is displaced in short amounts of time, coupled with poor sealing conditions you will notice increased problems or poor performance. Generally when a jack comes into the shop that see's a lot of use on a daily basis, I tap the vent and use the HW/omega style of vent. I've found they are less problematic, as I stated earlier pull that plug cycle the jack a few times and see if it eliminates your "gurgling" sitsuation, if it does... Now you have troubleshot your problem and the next step is to decide what solution is best suited.

1. A open vented system protected by a filter material (not good it you transport your jack or decide to turn it upside down)

2. Find a new plug that will control the positive/negative air pressures without taxing the seals and keep contaminants out.

3. Find a plug that is closed and operates off a ball/seat/spring to regulate pressures. Ie: HW/omega or similar to what Edgar linked. Although.. Funny story the older HW's used those grease zerts on the reservoir and it wasn't uncommon for people to bring them in and be full of grease.. Lol.

4. Thread the plug and use a rubber washer/bolt and close the system when idle and open it when in use.

If it doesn't alleviate your air situation even after you bleed the system, you need to start looking into the pump piston. <--- or since your becoming a old hand with floor jacks, just replace that 10 cent oring... Lol

Jeeper · Mar 22, 2013

Edgar, I am not sure I agree that the fill plug is not sealing. The reason I say this is I can pump the jack several times, release the jack then you can pull the plug partially and you can hear the air rush out. Seems like it seals fine, unless its acting like a check valve and letting air in but not out until enough pressure builds up that it forces oil and air out through the plug.

Also I was reading posts off Hiballs from a while back and if you hear gurgling while pumping the jack, it indicates the pump is pulling in air. Why would it pull in air with the plug off and jack bled? Seems the intake would be fully submersed in oil at that point.

Really I should just replace all the seals, pump, plug. They aren't expensive and not time consuming.

Hiball · Mar 22, 2013

Jeeper said:
Really I should just replace all the seals, pump, plug. They aren't expensive and time consuming.

If you continue into hydraulic service career.. You will find out its best to replace everything the first time, the reward isn't worth the risk. Again.. If your jack operates normally with a open reservoir system, there is only *1* possible way Air can be entering the hydraulic system and all fingers point to a weak rod seal on the pump piston.

EDGAR · Mar 22, 2013

Jeeper

Are you 100% sure the oil is coming from the plug? Sometimes the oil can leak from the ram and drift back under the bottom of the tank ending closer to the pump body than the front end of the pump. From there it then drips to the floor.

Have you seen a line of oil actually coming from the plug and going down by the side of the tank? Or have you seen only oil under the tank?

Oil could come out a leaky plug only at the moment you are lowering the jack for the reason I explained in my previous post. If the oil level is OK, you are going to have air under pressure above the oil and the only thing that should come out afterwards is air. For the oil to come out the plug from one day to the next, it would require that the oil somehow rises up to the fill hole and then be pushed out by the air pressure that could be leaking out slowly. But what could make the oil rise up to the fill hole if the air is going to be always above the oil?

I have to agree that if you push the plug to the side right after using the jack and it lets out air, that the plug is sealing enough that it retains some air under pressure. But it still could be leaking little by little, so it releases the pressure over a short period of time, like for example, from one day to the next. A good sealing plug would retain the pressure over a long period of time. Even so, as I mentioned above, oil should not come out because it is away from the fill hole bottom when this leak is happening, like about 3/16” under it. With a tank full of oil, this could happen, but then, the plug would probably pop out the moment the lift arm goes down because you are going to have to much oil plus the trapped air in there at the same time. And if the plug does not pops out, the arm may not go down all the way.

The only oil that could come out is the oil on the surface of the plug and near the fill hole, but this should be a very minimum amount.

Dry the exterior of the pump, specially the bottom of the tank, pump the jack up a number of times so it creates air pressure in the tank and let it sit for a day, without letting the air out, and then check if the oil is coming out the ram or from the plug. Turn the jack upside down and look at the point were the ram comes out the pump and see if there is any oil there.

If oil comes from the plug, it is certainly a mystery, for it should not happen with the correct oil level.

As I mentioned in my previous post, air coming into the pump is something that is of common occurrence. If you are going to open the pump, you may want to consider adapting a breather plug to it, or thread the fill hole and use a small bolt and an o-ring to seal the bolt. This should provide a better seal than the plug you have right now.

Still, my recommendation is to first try changing the rubber plug, for it could be leaking little by little over time. This may save you having to take apart the pump unless you want to change the o-rings anyway.

Jeeper · Mar 23, 2013

I am not 100% sure the oil is coming from the fill plug. I just notice that it leaks, usually after I leaving sitting and it only leaks when the tank has pressure. If I release the pressure by venting the tank and it doesn't leak. I guess it's possible it's leaking out of another seal as pressure builds up and forces it out. I was guessing its the rubber plug because there seems to be some oil residue around it. I will do some experimenting but it sure seems like the pump is pushing air into the system.

Other than sears parts, is there anywhere you can buy the rubber plugs?

theoldwizard1 · Mar 23, 2013

EDGAR said:
If oil comes from the plug, it is certainly a mystery, for it should not happen with the correct oil level.

Sounds like an overfill to me !

Jeeper · Mar 24, 2013

All right, all right Edgar was right..kind of. I pumped the jack and released it to build up some pressure in the tank. This time I did not relieve the pressure from the tank and I did it in the morning so I could check it throughout the day to hopefully find the source before it had fluid under it. Turns out it is leaking from the pump and maybe a little from the tank nut seal.

So now I am pulling apart the pump. How do you disassemble the pump? I am guessing hold the spring up somehow and undo the nut with a wrench. I attempted to pull the spring off but when you try to undo the Phillips screw on top of the piston rod, the rod just spins. Anyone have some pictures of one of these disassembled?

EDGAR · Mar 25, 2013

Jeeper

Since the pump piston can't come out from the bottom of the pump body, that means that it must come out by pulling on it. I have to assume that it has a nut around the pump piston that is screwed into the pump body that holds it in place so the spring won't pull the piston out, and the spring is over that nut. If that is the case, try using a couple of vice grips with long jaws (long nose) to compress the spring, hopefully upwards so it uncovers the nut holding down the piston. Put one on each side of the spring and try to pinch at least three turns of the coil spring. That way you may be able to remove the whole pump piston assembly with a wrench and even change the o-ring(s) without having to take apart the cap over the spring. It must have maybe an inch of pump piston inside the pump body so it should be easy to replace the seals. I have used the vice grips in that way and it has worked for me.

Or,

Maybe you can use some type of bearing remover, like the ones that have a bolt on the center to push down on the shaft/piston and compress the spring. Eventually you will have to replace all the o-rings because when one starts leaking, the others are not far behind.

Hiball · Mar 25, 2013

It's been a day or two, but that screw in the top does release that top cap, it requires keeping the pump piston from turning though, but to get the assembly out you have to unscrew it from the block... Either pry up that last coil and slip a wrench on the nut or as Edgar said compress some spring coils. It helps to have 3 hands...

Jeeper · Mar 25, 2013

Spent a little time getting the pump apart.

Tried to use a puller along with a large adjustable wrench. The puller worked fine but the pump nut was just too much for my loosely mounted vice, wobbly work bench and adjustable wrench. Couldn't apply enough force and when I did the wrench slipped off.

So I got smart. Took the pump back put of the vice, put a screwdriver socket on my 3/8 nitrocat impact and pulled the screw out off the top of the piston. The spring is almost fully extended so it didn't shoot off. The impact can spin the screw while leaving the pump rod stationary.

Then I pushed the rod all the way in and used a 34 mm deep impact socket on my 1/2 impact and spun the whole pump assembly right out. Here it is...

Inside the pump housing...

Inside the pump is an oring...

I count 4 orings. One on the pump piston, 2 on the outside of the pump and one on the inside of the pump. The upper one on the outside looks square but suspect it has just flattened out over time.

Hope the all match up to ones in my assortment kits. I have both the metric HF and SAE HF kit and the metric performance tool kit from northern tool. The metric kits between the 2 places actually have different sizes. I should be covered for anything with the exception of a large cross section oring which at first glance I didn't see any but will see when I pull the old ones off compare them.

Hiball · Mar 26, 2013

Jeeper was there only 1 backup on the Pump Piston itself? Looks like a big gap between the bottom of the Oring and the End of the Piston, Maybe its just the angle... but it looks like maybe there should have been a backup on the bottom also.

EDGAR · Mar 26, 2013

I have seen such gaps in pump pistons in a fair share of chinese jacks. And specially in the mini jacks. Also, I have seen in many occasions that the o-rings are rather lose in the inside diameter and instead of the o-ring having a squeeze as it should, on the inside diameter, when installed in the piston groove, the squeeze is obtained when the piston is inserted in the cylinder. This promotes that the o-rings leak in less time than a properly sized o-ring would. Sometimes they even use a slightly larger size o-ring and expect it to get to the right (smaller) size when inserted in the cylinder, also a reason why you have many leaky pump pistons in chinese jacks in a few years or even a few months. Apparently, they use whatever o-ring similar in size they have available in stock instead of buying the right size just to save money.

Many of the bad reviews you see in the Sears reviews and other sites about having a leaky jack that doesn't lift anymore are due to this improperly sized o-rings and wide grooves combinations. The wider grooves may also promote twist of the o-rings if the fit of the mounted o-ring is to tight in the cylinder, because the o-ring can move too much back and forth promoting the damage of the o-ring. Once an o-ring starts twisting it can start leaking. In a well designed pump, only a minimal space should be left for the o-ring to expand sideways, when a piston is inserted in a cylinder, to prevent the o-ring from moving back and forth.

As for the back up, only the upper is required in this applicatrion as this is the direction (going down) that makes the force. On a cylinder that operates in two directions, like the ones used in heavy machinery, two are required (one on each side) because it applies force in two directions.

As for the Jeeper pump piston, if he finds a back up of that size, he can, and should, mount it but only to prevent the o-ring from moving too much in the groove. It certainly won't affect the operation of the jack.

Hiball · Mar 26, 2013

EDGAR said:
I have seen such gaps in pump pistons in a fair share of chinese jacks. And specially in the mini jacks. Also, I have seen in many occasions that the o-rings are rather lose in the inside diameter and instead of the o-ring having a squeeze as it should, on the inside diameter, when installed in the piston groove, the squeeze is obtained when the piston is inserted in the cylinder. This promotes that the o-rings leak in less time than a properly sized o-ring would. Sometimes they even use a slightly larger size o-ring and expect it to get to the right (smaller) size when inserted in the cylinder, also a reason why you have many leaky pump pistons in chinese jacks in a few years or even a few months. Apparently, they use whatever o-ring similar in size they have available in stock instead of buying the right size just to save money.

Many of the bad reviews you see in the Sears reviews and other sites about having a leaky jack that doesn't lift anymore are due to this improperly sized o-rings and wide grooves combinations. The wider grooves may also promote twist of the o-rings if the fit of the mounted o-ring is to tight in the cylinder, because the o-ring can move too much back and forth promoting the damage of the o-ring. Once an o-ring starts twisting it can start leaking. In a well designed pump, only a minimal space should be left for the o-ring to expand sideways, when a piston is inserted in a cylinder, to prevent the o-ring from moving back and forth.

As for the back up, only the upper is required in this applicatrion as this is the direction (going down) that makes the force. On a cylinder that operates in two directions, like the ones used in heavy machinery, two are required (one on each side) because it applies force in two directions.

As for the Jeeper pump piston, if he finds a back up of that size, he can, and should, mount it but only to prevent the o-ring from moving too much in the groove. It certainly won't affect the operation of the jack.

To.. Edgar

:lol_hitti

I Think sometimes you just want to disagree with me and then in the End you come around to my way of thinking, It just takes you awhile to get there.

To.. Jeeper

No way i would ever let something leave my shop that "Appeared" to have that much gap, Especially in a Piston application.. The Backup only does its job when the Oring is in Contact with it, Obviously the Down pressure is Much higher than what Up Pressure is in this case, But on the Upstroke it can and will pull that oring away from the backup and create that Initially gap which during the Transition will cause twisting/rolling/premature wearing of that Oring, Especially if it encounters any Vacuum issues.

IMO

Jeeper · Mar 26, 2013

Hiball said:
To.. Edgar

I Think sometimes you just want to disagree with me and then in the End you come around to my way of thinking, It just takes you awhile to get there.

To.. Jeeper

No way i would ever let something leave my shop that "Appeared" to have that much gap, Especially in a Piston application.. The Backup only does its job when the Oring is in Contact with it, Obviously the Down pressure is Much higher than what Up Pressure is in this case, But on the Upstroke it can and will pull that oring away from the backup and create that Initially gap during the Transition that will cause twisting/rolling/premature wearing of that Oring, Especially if it encounters any Vacuum issues.

IMO

I will confirm later today but I am pretty sure the gap is there and there was nothing that consumed it. What are some options? Edgar mentioned another back up ring. What about an additional oring? That would be easier to find for me than another backup ring.

Hiball · Mar 26, 2013

Jeeper said:
I will confirm later today but I am pretty sure the gap is there and there was nothing that consumed it. What are some options? Edgar mentioned another back up ring. What about an additional oring? That would be easier to find for me than another backup ring.

The Issue i see with simply putting another Oring is you that your Split Ring backup has a flat side (match the groove) and concave side to "Match" the Oring and its job is to prevent Extrusion under pressure. If you put the Oring "Behind" the Backup you have now taken that solid base that the Backup previously had and replaced it with a Pliable Oring. If you put the 2nd Oring.. in front of the First, Well Thats Not only backwoods Ghetto.. that First Oring "Will" extrude under load with No Groove or Backup to contain it.

NOW... We are simply talking about a Hydraulic Jack, Its Not Rocket Science.. Your not dealing with Load bearing seal, its simply the transfer portion of the Jack. IF you are having issues finding a Backup Locally (best scenario), I would rather see the space taken up with a Oring (same size/Back side) or a small Nylon Washer (backside) versus the Alternative.

Post up a Better picture of the Gap.. Maybe it was the Angle that made it look worse than it was. Regardless if that Jack Initially came from the Manufacturer with a Gap.. Its a Bad design and 2 Wrongs dont make a Right.

Jeeper · Mar 26, 2013

Up close. Definitely a gap.

EDGAR · Mar 26, 2013

For HIball

I was not disagreeing with you. Jeeper's pump piston has too much gap. I was just stating that some chinese jacks have a bad design of the pump piston because they machine grooves that are too wide for the o-ring and back up combination. I have seen this in the cheaper floor jacks and in bottle jacks.

It was also a heads up for anyone trying to repair their own chinese jack, so they don't get surprised or baffled if they find a gap too wide for the o-ring and back up because this is a common occurrence in chinese jacks. This does not happen in better designed pumps.

And as I mentioned, this design promotes faster wear of the o-ring than an o-ring mounted in a properly sized groove.

I also agree that mounting two o-rings together, is not the best idea because of the extrusion thing. Maybe if it were a square section o-ring, it would be better than nothing, if a hard back up is not available, but it would also be a matter of local availability. Still, there is the need to fill the gap with something adecuate to prevent the o-ring from moving back and forth.

An alternative could be to mount an o-ring, the back up and another o-ring, in that order, as only the first o-ring would be subjected to the oil pressure and would be backed-up, and the second o-ring would just act as a soft spacer between the back up and the metal of the pump piston. This is better than nothing.

Jeeper · Mar 26, 2013

Help me understand why a second slightly smaller oring not be good? I would think if the second oring, placed on top (based on the last picture), that had a slightly smaller outer diameter would help keep the oring from sliding while not being part of the sealing surface, hence not be an extrusion issue.

While the piston was forcing fluid, the oring would be pushed against the backing washer. When the pump was pulling fluid from tank, it would be forced against the other oring. Better than before and not much force would be going against it since fluid is not under pressure.

Just a thought. I figure at the minimum i put a new oring on, don't make any other changes and it works like it did for the last ~7 years.

Hiball · Mar 26, 2013

Jeeper said:
Up close. Definitely a gap.

Jeeper that is way to big of a gap, I've Never seen anything remotely close to that come from the factory that wasnt a QC issue. Did you buy this jack New? I've literally torn down several hundred maybe into thousands of import jacks and the majority of them use Orings as rod applications and haven't run across anything like that. With that said.. Very few of the quick lift jacks utilize that style of piston head, most use rod seals in the cylinder. I'd be willing to bet that either they goofed from the factory or its missing a backup.

The First Picture was kinda Iffy.. and when my Eyes scrolled across it, It Screamed "Something isnt Right Here", This Picture is twice as bad...

Hiball · Mar 26, 2013

Jeeper said:
Help me understand why a second slightly smaller oring not be good? I would think if the second oring, placed on top (based on the last picture), that had a slightly smaller outer diameter would help keep the oring from sliding while not being part of the sealing surface, hence not be an extrusion issue.

While the piston was forcing fluid, the oring would be pushed against the backing washer. When the pump was pulling fluid from tank, it would be forced against the other oring. Better than before and not much force would be going against it since fluid is not under pressure.

Just a thought. I figure at the minimum i put a new oring on, don't make any other changes and it works like it did for the last ~7 years.

It just depends on what your wanting out of this Jack, Its obviously your property thus you have to deal with any issues that arise down the road. There is a couple different ways you can handle the situation, as i stated in #32, If you cant find a Suitable backup/spacer i would probably Utilize the Oring on the "Back side" versus the front. Mainly because even with a Smaller Oring its still gonna want to extrude Inside the Oring behind it. If you put the Oring behind the Backup its still gonna allow the backup to conform to the front Oring under pressure. My Scenario is Different than yours, along with the Advice that comes with it, if i treat a customers jack like that, it Fails and he decides to open it up.. I look like a Hack.. My Grandfather and I didnt build our reputation by doing work like that. Will putting a smaller Oring in front (towards the pressure) Work? Probably? For How Long? Dunno.. Its Not a Terribly Hard to get to that Pump Piston Assembly, So its not gonna hurt for you to make some Trial runs. The Main thing is.. You have to eat that space up.. That is way too much Wiggle Room.

EDGAR said:
For HIball

I was not disagreeing with you.

My Bad.. When i first read your post, I thought you were trying to say Jeepers Piston gap was "Normal".. That Thing screams "Somebody Mucked up" to me.

Jeeper · Mar 26, 2013

I actually bought that jack new from Sears on a Craftsman Club deal. It actually has worked petty well over the years.

Hiball · Mar 26, 2013

Jeeper said:
I actually bought that jack new from Sears on a Craftsman Club deal. It actually has worked petty well over the years.

Im really surprised.. I just cant imagine that oring not deforming/twisting and offering poor sealing performance over the Years. The only think i can figure is the "Inside" Rod seal must have kept it at bay.

Jeeper · Mar 26, 2013

I loaded up some new orings. For now I plan on putting it back to stock and see how it goes. Only issue is that the cross section of the orings is a little large. The upper one on the outside of the pump shredded as I screwed the pump into the housing. I will have to put some oil to see if I can get it back together without wrecking the orings. Can't tell if the ones I picked from the HF kit are larger cross section or if the old ones are just a compressed and there is a trick getting it all back together.

Craftsman 4 ton floorjack rebuild

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