Air Compressor Oil Leak Help

[VKB123]

Hi all. Long time lurker but only my 2nd post on GJ. Thanks for the add! Hoping for some sage air compressor advice. I picked up an old Speedaire 20 gallon hot dog air compressor from an old timer who was downsizing. He showed me it worked properly before I bought it. I only paid $50 CDN (he just wanted it gone)! He was a carpenter and looks like he used it mainly for framing. Model number is 3Z355H with a 2Z499 pump. It's all original and looks to be 34 years old based on the date stamp on the electric motor. It works great! Quiet, builds and holds pressure, and cuts in and shuts off per spec. My plan was to simply change the oil and belt and then use as is. When I drained the oil it came out like black tar and only 150ml drained out.

Well, I ended up taking the entire thing apart to clean and degrease it. I boroscoped the tank and all looks good. I even took apart the motor to clean it. I then reassembled it, added new Amsoil ISO 100 (SAE 30/40) synthetic oil, and put a new belt on it. I called Grainger and they were amazing. They e-mailed me original copies of the compressor and pump manuals. The manual says fill oil to the bottom of the oil fill screw and this is what I did - this corresponds to 550ml of oil.

Thankfully it fired up and still runs like a champ. I soap tested all the connections and it doesn't leak air. However, now it dribbles oil at the junction of the crankshaft and flywheel. I've attached some pics with the belt guard removed showing the area of the leak (tip of my tool is also pointing to the oil leak). Based on the parts diagram, I suspect the oil seal is worn and leaking. The oil seal is still available to purchase.

Here are my questions:

1. Can I simply change the oil seal and will this solve my leak?
2. Did I add too much oil even though the manual says to fill to the bottom of the fill hole?
3. Do I need to rebuild the pump (the pump rebuilt kit is still available) even though it is building pressure and seems to work fine? I have never rebuilt an air compressor pump (frankly I don't even really understand how it all works!).

This compressor will get light use to fill tires, blow out drain holes on my cars, and do a yearly winter irrigation blow out. I could probably live with the oil leak but I'd prefer to fix it up as long as it makes financial sense.

Thanks in advance and sorry for such a long 2nd post!

 

[Jswain]

First make sure the breather (right above your oil leak) is cleaned out & allowing the crankcase to vent.

Then take a stop watch and time what it takes to fill the tank from 0-cutoff and make sure it is within reason of what it should be for CFM

CFM's your Air Compressor can Produce

Calculate the actual cfm's of your Air Compressor

www.spikevm.com

Online calculator or post your numbers here

Also check if you're getting much oil in the tank when you blow out the drain valve. Reason being as it could be leaking past the piston rings and excess pressure in the crankcase is helping push that oil out the seal.

Honestly none of these are that big of a deal, and if parts are available fairly easy and straight forward to fix. Or the fix may be keep a jug of oil around and check it everytime you use it or once a week/month/year depending on how much it leaks.

 

[VKB123]

Thanks for such a quick and thoughtful reply! The breather and foam filter element (in the breather) are clean. The hole at the bottom of the breather is patent. I have only used this new-to-me compressor a few times but I drain the air from the tank after each use. I have not seen or felt any oil dripping out the bottom of the tank. When I scoped the tank I could see some oil residue on the tank lining (I presumed this was normal?).

To clarify, to test the fill time, start timing at 0 psi until it shuts off at full fill (135psi for my unit)?

Thanks again!

 

[Jswain]

Yessir then input the time in seconds, tank size, and differential pressure(135) to get your CFM.

You can do it from any pressure (100-135 for example) but 0-full will give a better picture

 

[VKB123]

I’m doing it now and will report back!

 

[VKB123]

Okay took 3m29s (209 seconds) to fill from 0-135 psi. 20 gallon tank. According to the calculator you attached this is 7.0cfm (200L/min).

Can you now tell me what this means?

Also, now that the unit was running, here is a pic showing the oil leak.

Thanks!

 

[VKB123]

From the original manual, here are the specs I found for this unit 3Z355H. Looks like it should be 9.2cfm? Does this make sense? Can you help me understand what these numbers mean? Thanks!

 

[Jswain]

Correct so you are slightly under but not by much. If you can get your hand on the breather safely without getting hit but the pulley while its running does it blow your finger off the post or just lightly puffing air?

 

[VKB123]

Actually, just checked again and cut out is 125psi (not 135psi). Ran the numbers again and this gives 6.5cfm. I will try the breather assessment now and report back!

 

[VKB123]

Very tight space and didn't want to lose my fingers! I carefully removed the breather with a needle nose plier while the unit was running. I then carefully put my finger up against the empty hole. Was lightly puffing air (not blowing hard). There is definitely oil in the breather and the foam filter too.

 

[msharley]

Many of the older compressors are not "synthetic oil" friendly.

SAE 30, NON DETERGENT was what was usually required....

Me? I'd let the seal weep....next time you change oil? Use the SAE 30 ND with about 1/5 of the volume LUCAS OIL STABILIZER....

You may do more damage trying to change the seal (unless you have the seal puller, some require drilling two holes in them...what do you do about drill shavings?...to mount)

 

[Jswain]

6-7cfm for that pump sounds pretty good and if it's not blowing your finger off hard I wouldn't worry about piston rings.

I'm in the let it weep and watch the oil camp

 

[VKB123]

Thanks guys! Not looking to spend more money refurbishing this unit than it’s worth so appreciate the honest advise! My concern is a full pump rebuild kit is still available through Pacific Air Compressors ($100USD). I believe it also comes with the oil seal. Not sure when it will no longer be available as the unit is over 3 decades old! What would push you to rebuilding the pump?

I will likely drain the oil and refill with conventional 30W ND with oil stabilizer too!

 

[Jswain]

The amsoil is a really good oil, I would wait until it leaks itself low and determine how long that takes.

What does the manual say to use for oil for that pump? Could just need a different weight, regardless I highly doubt the amsoil is what is making it leak

 

[Sumboodie]

I had no idea Granger made Speedaire compressors.

I have one in my shop that came with the place. No idea the size or if it even works, it's on top of the bathroom and I haven't been up there yet.

 

[VKB123]

Owner’s manual says “good grade 10W30 detergent type oil”. Everywhere I read said use non-detergent SAE30 (ISO 100). That is why I sourced out the Amsoil (was hard to find at a reasonable cost!). Should I actually put in detergent oil? I’m not adverse to changing the oil seal (I’m mechanically inclined even though I’ve never done it before). Appreciate your ongoing advice!

 

[chris142]

The leak is why it was low on oil.

 

[Jswain]

It might take 20 years to leak the oil out though. I wouldn't change the amsoil for ANY oil to try and stop the leak.

 

[VKB123]

Got it! I’ll leave it be! I’m not sure if the oil have EVER been changed by the previous owner given the appearance of the sludge I drained from the crankcase! These units must be built like a tank!

 

[PoorUB]

I have the same compressor.......sort of.

When I bought it, the compressor was missing, paid $20 for it less the pump. Found a used pump and rebuilt it and got it running. Ran it for about a year and the motor fried, bought a new motor. I sold it to my father in law and he used it for years. He passed away a few years ago and my mother in law told me to take it back if I wanted it, as there was something wrong with it. I got it home and the tank was rusted out. I stripped all the parts off the tank and tossed it all in the attic of may garage.

My dad passed away last fall and he had an air compressor with a shot pump and no motor. The tank he had had been replaced at some point and was in great condition, so I used that tank and I have the compressor up and running again.

Considering other than a couple pipe fittings and perhaps the motor pulley it all has been replaced is it still the same compressor?

 

[VKB123]

Great story! Thanks for sharing! Built like a tank…

Thanks again @Jswain for your interest and help! Super nice community!

 

[seber]

Compressor pumps are a super easy build. I just finished one last week. Not only are they easy but for me at least enjoyable to work on. No tight spaces, no frustrating parts. Just straight forward build. I'd knock it down and make it perfect. If you have to make reed valves, that is a separate can of worms. I've done it using electro etch. It's the only method I know of that does not leave a burr or warp in the final part.

 

[MacMcMacmac]

Whenever you change the oil, put in a 10 or 20 weight non detergent oil. No additives of any kind and definitely not a motor oil. Parts for these are everywhere. They were made for decades and I'm sure are probably the single most common pump ever sold for home use. They went through several different cylinder head designs, so to keep things simple, a universal head was listed as the only one available years ago. They are dirt simple, even a bit crude, but work well for a long time. The usual failure mode is a screw holding a reed valve falls out and holes a piston.

 

[VKB123]

I'd knock it down and make it perfect.

Shoot @seber! You used the p-word! My whole mantra is trying to make things perfect so you hit a nerve!

The question I’m grappling with is, if the pump is working well (quiet and building air at 6.5cfm) do I even need to rebuild it? Wondering if I could just replace the oil seal (or simply live with the weep as others have suggested) and run as is? Full pump rebuild kit is $100 so not crazy expensive but twice the cost of a $50 steal of a deal! In the end I know it’s my call but I’m a newbie here on GJ so constructive advise is appreciated!

 

[MacMcMacmac]

This pump us giving you as much air as it ever will. If you are on the prairies you will have to derate for altitude. Id use it as is until I knew the tank was OK before throwing money at it.

 

[VKB123]

I’m on the coast so pretty much at sea level. This approach is very sensible. Thank you!

 

[VKB123]

Following up on this. Couldn’t live with the oil leak despite the opinions to “let it weep”! Decided to source out a new oil seal from Zoro. Shipping was more expensive than the part but was about $10USD all in! Changed the seal tonight and leak fixed!

Took the time to clean everything as I went along. Was even able to “mop up” the sludge in the bottom of the crankcase once I opened the bearing cap on the side of the pump. New Amsoil SAE30 and good to go! Hopefully good for another 34 years!

Here’s a quick DIY in case anyone finds themselves in this situation:

1. Drain oil.
2. Remove belt guard (if present).
3. Remove belt.
4. Remove set screw holding flywheel to crankshaft.
5. Use bearing puller to remove flywheel (I used a small 2-jaw puller but a 3-jaw will work too).
6. Remove the 4 bolts (circled in blue in pic) holding the bearing cap to the crankcase. Slide the bearing cap (red in pic) off the crankshaft but be careful not to damage/break the underlying cap gasket.
7. Remove the oil seal (yellow in pic) from the bearing cap with a small hook.
8. Take this opportunity to give everything a good clean. You will be looking into the crankcase. I “mopped up” the sludge sitting at the bottom of the crankcase. Clean the backside of the bearing cap and ensure the hole for the breather vent tube is free of sludge and patent.
9. Slide the bearing cap back over the crankshaft and secure the 4 bolts to the crankcase. Don’t forget the gasket!
10. Slide the new oil seal over the crankshaft and carefully tamp in place until flush (I used a small brass punch).
11. Reassemble the flywheel, etc. Fill with fresh oil. Should be golden!

My leak is totally gone! Some pics below. Hope this helps someone else one day!

 

[sienta]

Few days back I was also facing air compressor oil leakage issue, luckily I found this detailed article where they have discussed 90+ common air compressor problems and there solutions, and I fixed my compressor all by my own with the help of this article