Kobalt 60 gallon pump replacement

[Rise of the 65]

I have a Kobalt 60 gallon compressor. The pump went up and I’d like to get is sold at Harbor Freight. My concern is my tank says 7hp, 60 gallon, 135 max psi, 13.7 SCFM. The pump I want to get is 3.7 HP, 155 max PSI. I don’t want to turn my cast iron tank into a ticking time bomb by putting more PSI in it then called for. Would adding this new pump with 20 more max psi be safe to do?

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[The Cobbler]

that's the max pressure for the pump. if you are using the original pressure switch it will cut out at the same pressure as before .
that 7hp rating is likely false , snap a picture of the motor plate .
is the pulley on the pumps the same size , same belt width etc?
also have you diagnosed what went bad on your original pump?

 

[Snapped-off]

That's probably what the original compressor was rated for. See if you can find a stamp or label on the actual tank.

 

[Rise of the 65]

that's the max pressure for the pump. if you are using the original pressure switch it will cut out at the same pressure as before .
that 7hp rating is likely false , snap a picture of the motor plate .
is the pulley on the pumps the same size , same belt width etc?
also have you diagnosed what went bad on your original pump?

No diagnoses, just takes a very long time to build pressure. I figured the piston rings were shot. I’ll check the tank. It’s in a pretty tight compressor room. I’ll see what I can come up with.

 

[Rise of the 65]

That's probably what the original compressor was rated for. See if you can find a stamp or label on the actual tank.

Rank plate.

 

[Rise of the 65]

that's the max pressure for the pump. if you are using the original pressure switch it will cut out at the same pressure as before .
that 7hp rating is likely false , snap a picture of the motor plate .
is the pulley on the pumps the same size , same belt width etc?
also have you diagnosed what went bad on your original pump?

Motor plate, pulleys are 2 different sizes. Pump pulley is considerably larger.

 

[goblue1998]

You need the welded tag on the tank. That will tell you the pressure rating.

 

[finn]

No diagnoses, just takes a very long time to build pressure. I figured the piston rings were shot. I’ll check the tank. It’s in a pretty tight compressor room. I’ll see what I can come up with.

There would be a lot of oil carryover into the air tank receiver and air lines if the rings were shot.

My guess is that your pump has a reed valve system, and the thin valve plate is cracked, making it hard to build pressure.

You should be able to pull the head and examine the reed plate, replace as required, and install a new head gasket. That would potentially get you a few more years of service without cobbling on a new pump, dealing with pulley ratios, mounting a new compressor, belt mismatches,met c.

Just a thought before you jump in.

 

[The Cobbler]

takes a very long time to build pressure. I figured the piston rings were shot.

I would not jump to conclusions. a simple leak in the discharge line can do what you're experiencing . or as above, a reed valve . better to do some diagnosing than jump in to a new pump

 

[Rise of the 65]

There would be a lot of oil carryover into the air tank receiver and air lines if the rings were shot.

My guess is that your pump has a reed valve system, and the thin valve plate is cracked, making it hard to build pressure.

You should be able to pull the head and examine the reed plate, replace as required, and install a new head gasket. That would potentially get you a few more years of service without cobbling on a new pump, dealing with pulley ratios, mounting a new compressor, belt mismatches,met c.

Just a thought before you jump in.

I’ll take a look at my dryer to see if there’s any oil in it. If not maybe I’ll look into popping the top. I’ll have to figure out what pump it is so I can order the right stuff. Thanks for the suggestion.

There would be a lot of oil carryover into the air tank receiver and air lines if the rings were shot.

My guess is that your pump has a reed valve system, and the thin valve plate is cracked, making it hard to build pressure.

You should be able to pull the head and examine the reed plate, replace as required, and install a new head gasket. That would potentially get you a few more years of service without cobbling on a new pump, dealing with pulley ratios, mounting a new compressor, belt mismatches,met c.

Just a thought before you jump in.

well I can official rule out the reeds. On to looking for leaks.

 

[Rise of the 65]

I would not jump to conclusions. a simple leak in the discharge line can do what you're experiencing . or as above, a reed valve . better to do some diagnosing than jump in to a new pump

Just ruled out the Reed so now onto leak hunting.

 

[Citation]

Couple of things. It appears you have a Campbell Hausfeld, not a Kobalt compressor (CH does make compressors sold under the Kobalt brand). If the compressor is slow to build pressure it might be a bad head gasket or valve (valve plate). Both would be cheaper and easier to fix vs a new pump. Get a picture of the pump as well as any model numbers on the pump itself. CH used a similar family of inline twin cylinder pumps for many years. Parts are common.

If you decide you need to replace the pump I would suggest getting one of the Harbor Freight pumps. They are cheap and work. You want the "3hp" (or is it 3.7hp now) version. You need to make sure the motor doesn't spin the pump too fast or bog down under load. The motor will have a rated speed (something like 3450 rpm). The pump will also have a rated speed range. You need to side the motor pulley so the pump isn't going too fast or slow. Odds are good that the factory pulley is fine for the HF pump but you should check just in case. The HF pump might need new mounting holes drilled in the top plate and might need a new copper pipe from the pump to the tank check valve. None of this is too hard but fixing the original pump is likely your best option.

As others noted, the pump doesn't set the compressor's cut off pressure. That is the pressure switch. Since you aren't intending to change the switch you shouldn't have any issues with the new pump over pressurizing the tank. However, if your current cut out pressure is higher than the max pump pressure (the older HF pumps were only good to 145psi) then you may have to turn down the cut out pressure (done via adjustments to the pressure switch).

One of these might be the pump you have

Amazon.com

3 HP Campbell Hausfeld VT4923/VT490000AV Compressor Pump Replacement

Shop this 3 HP Campbell Hausfeld cast iron air compressor pump model VT4923/VT490000AV. Durable replacement pump for Speedaire, Husky, and Kobalt compressors.

compressor-source.com

Both are rated at 3hp (fine with your motor) but I wouldn't be surprised if the "3.7 hp" models used the same pump just run a bit harder.

 

[Rise of the 65]

Couple of things. It appears you have a Campbell Hausfeld, not a Kobalt compressor (CH does make compressors sold under the Kobalt brand). If the compressor is slow to build pressure it might be a bad head gasket or valve (valve plate). Both would be cheaper and easier to fix vs a new pump. Get a picture of the pump as well as any model numbers on the pump itself. CH used a similar family of inline twin cylinder pumps for many years. Parts are common.

If you decide you need to replace the pump I would suggest getting one of the Harbor Freight pumps. They are cheap and work. You want the "3hp" (or is it 3.7hp now) version. You need to make sure the motor doesn't spin the pump too fast or bog down under load. The motor will have a rated speed (something like 3450 rpm). The pump will also have a rated speed range. You need to side the motor pulley so the pump isn't going too fast or slow. Odds are good that the factory pulley is fine for the HF pump but you should check just in case. The HF pump might need new mounting holes drilled in the top plate and might need a new copper pipe from the pump to the tank check valve. None of this is too hard but fixing the original pump is likely your best option.

As others noted, the pump doesn't set the compressor's cut off pressure. That is the pressure switch. Since you aren't intending to change the switch you shouldn't have any issues with the new pump over pressurizing the tank. However, if your current cut out pressure is higher than the max pump pressure (the older HF pumps were only good to 145psi) then you may have to turn down the cut out pressure (done via adjustments to the pressure switch).

One of these might be the pump you have

Amazon.com

3 HP Campbell Hausfeld VT4923/VT490000AV Compressor Pump Replacement

Shop this 3 HP Campbell Hausfeld cast iron air compressor pump model VT4923/VT490000AV. Durable replacement pump for Speedaire, Husky, and Kobalt compressors.

compressor-source.com

Both are rated at 3hp (fine with your motor) but I wouldn't be surprised if the "3.7 hp" models used the same pump just run a bit harder.

I will check the other parts you mention. At this point I might as well try troubleshoot what I have. If all else fails you suggest the 3.7HP HF pump but put the original pulley from the old pump on the new pump. If I have to start mathing I’m in trouble. lol BTW thank you for such a great in depth reply. Your post along with the other posts have been extremely helpful. I have been scratching my head about this thing for 2 weeks and my project car needs stuff media blasted.