Would a bad unloader make the compressor kick on too fast ? Put a pressure gauge in the wet tank to see why it kicks on in 15 sec after it shuts off. My wet tank drains down to 107 from 125 in 15 seconds then stops draining when the compressor kicks on so the unloader is doing somthing here (can the unloader drain the wet tank when unloading the air compressor before it kicks back on?) With the truck off and at 125 psi it drains down to 107psi then stops draining the wet tank because that is the kick on pressure. So is the unloader the culprit here? M925A2
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Unloader Issues?
- Thread starter plainside
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Yes to the unloader kicking in and out to soon or a hole in the line that runs from governer to unloader.
Did you check for air leaks everywhere? Need to check running with spring brakes off and truck aired up too don't forget.
Was the Govener ever working correctely.
Don't believe the unloader would drain the wet tank but been wrong before.
Did you check for air leaks everywhere? Need to check running with spring brakes off and truck aired up too don't forget.
Was the Govener ever working correctely.
Don't believe the unloader would drain the wet tank but been wrong before.
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Thanks, no holes anywhere. I shut the ball valves off to the primary and secondary tanks to isolate that as well. I hear no leaks (if any they are very slight) with the truck off. Leaks down to 107 due to the governor telling the comp. to unload. then does not leak down the wet tank when pumping (compressor not unloading). but when unloading it runs that wet tank down fast. I have isolated it to the unloader because with the truck off at 125 psi it bleeds down fast to 107 unloader set to unload, then leaks very slow after 107,.
dawico
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Spray your compressor with soapy water. My unloader leaks like a sieve even after tearing it apart twice (new gaskets once, gaskets and gasket sealer second time). I am not sure if it slows down at a certain pressure though but my truck seems to be doing the same thing.
I think the non-steel top is a weak point and flexes.
I think the non-steel top is a weak point and flexes.
Well I hooked up an air compressor to the emergency glandhand and brought the wet tank up to 125psi and disconnected the unloader line going into the intake of the engine and air is going out that line to the intake. Then right on 107psi it stops leaking out because the unloader shifts back because then the compressor kicks on (well it would if the truck was running, I was using air compressor remotely). So new unloader valve? If so, is that the 2 bolts on the side of the compressor or does the top part have to be replaced as well/??
dawico
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The two bolts on the side hold the intake line on.
I am not sure what part needs to be replaced. There are two springs inside there, gaskets, and seals.
The unloader will come out but you have to take the top off the compressor too. This includes draining the coolant (the two lines coming in from the right). I had to use a chisel to break the head loose off the compressor.
A ratcheting wrench (1/2") is your friend to get the rear bolts out.
I am not sure what part needs to be replaced. There are two springs inside there, gaskets, and seals.
The unloader will come out but you have to take the top off the compressor too. This includes draining the coolant (the two lines coming in from the right). I had to use a chisel to break the head loose off the compressor.
A ratcheting wrench (1/2") is your friend to get the rear bolts out.
dawico
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My unloader leaks like a sieve but will still keep up with one emergency glad hand open. The compressors pump very well.
Have you sprayed it with soapy water to see if yours is leaking also? The unloader leaking could cause the issues you are experiencing as it sounds similiar to what mine is doing.
Have you sprayed it with soapy water to see if yours is leaking also? The unloader leaking could cause the issues you are experiencing as it sounds similiar to what mine is doing.
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It's not necessary to drain the coolant to service the unloader. Just pull the 4 bolts and leave the jacketed head on the compressor. The unloader comes off with the top plate. Here is a picture of mine when the gasket was being replaced. Unloader was cleaned at the same time. The compressor head is still on with coolant in it.
dawico
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I wonder what is different. I could not get the rear bolts out seperately. I tried everything.
Since I am going to tear mine apart again I will give it another go.
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Those 2 rear bolts are a pain to deal with but it can be done without pulling the compressor or IP.
dawico
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I stand corrected. It can be done but what a PITA. Now to get it back in..........
dawico
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I temporarily relocated the fuel return line out of the way but that is all.
I am just replacing and sealing the gasket in mine because it leaks out of the housing. I have no clue what parts you are going to need to replace.
Did you spray it with soapy water and see if your housing is leaking?
dawico
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I rebuilt mine today and will test it tomorrow. It was doing the same as yours, constantly kicking back on. I will let you know if I finally got it sealed up and if the situation changes.
dawico
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It leaks much less (just a little foam on one side, no bubbles) and seems to kick on less often. It took a while to get a normal run with the CTIS topping off the tires. I think the compressor/ unloader issue is pretty much solved for my truck. It pumps better than it ever has.
I think I have some minor air leaks to track down though and that will help. The gauge stays right at 120 psi whether pumping or not. I find that somewhat odd but I think the gauge has some lag time.
I will update after a little more run time to be sure the reseal holds.
I think I have some minor air leaks to track down though and that will help. The gauge stays right at 120 psi whether pumping or not. I find that somewhat odd but I think the gauge has some lag time.
I will update after a little more run time to be sure the reseal holds.
dawico
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No part numbers. I took the unloader to an auto parts store and ended up with a gasket sheet and cut my own. I didn't replace anything else. I cleaned everything up and lubed the moving parts. I had my unloader stick on me before so the copper colored slider got special attention. All the seals were in good shape, I don't have a local Cummins dealer, and don't like to wait for shipping so I just went for it.
The first time I tore it apart I just replaced the gaskets and it leaked pretty bad. The second time I used new gaskets and hardening gasket sealer. It still leaked just as bad. This time I used a new gasket and silver Permatex RTV gasket maker. Now I just have a little foam on one side with soapy water spray.
The gasket at the compressor head has held fine (below the two coolant lines and the air outlet). It was just the gasket at the unloader that was causing problems and leaking. I put a bead on both sides of the gasket and finger tightened it like the directions said. I let it sit for about two hours and tightened it up. I also spread some on the shanks of the bolts as it leaked there too. Then it sat overnight.
With very little leaking the compressor definitely has more time between cycles. My secondary tank holds pressure much better too. It used to be empty overnight but now it stayed up at 70 psi. The primary usually stayed up there overnight. It may be unrelated but it is a change.
I wasn't sure if the silver Permatex was the one to go with over the red, so time will tell. I probably wouldn't have had so many issues if I got factory gaskets but it is what it is.