Join Date: Oct 2018
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Need HELP understanding my air brake system and compressor!
I'm encountering a tricky situation with the air compressor on my 1991 International 4900, with the DT466.
So, a while back my air compressor (for the brakes) stopped working. It just stopped making pressure one day. I bought a replacement and installed it. Well, after about 600 miles of driving it started making a strange sort of high-pitched noise, AND I began to see a lot of evidence of oil in the compressed air, AND it began to slowly lose its capacity to make air (taking longer and longer to fill the tanks). Well it was still under warranty so I brought it back and got a replacement, which I then installed. The compressor is made by Haldex.
Before finishing the installation I checked for coolant flow through the compressor head (check) and also for engine oil flow through the compressor crank (check). Amazingly, however, this brand new compressor is also not building up air pressure, AND it's making the same high-pitched sound that the other one did when it started to fail. I think it's pretty unlikely that it is defective, straight from the factory, so I think there must be something else going on and that's what I'm trying to understand.
I now believe that the high pitched sound is actually coming from the air intake to the compressor. It has a block component which looks like some sort of reed-type valve, and I think the sound is coming from that. I actually don't know which way is the correct way to install that valve block, so I guess that could be part of the problem.
The other component that I think might be at fault is the air dryer / unloader. This is the component that dumps air when the pressure builds up too high. OR.. it could be the governor, which is a small assembly that bolts to the side of the compressor head, contains a spring-loaded valve of some sort, AND sends two hoses off in the direction of the dryer / unloader. As you might be able to tell, I don't know too much about this circuit. But it seems to me that it might be implicated. For instance, if the dryer / unloader OR one of the hoses going to it is clogged, it might be tricking the compressor into not making pressure. To be honest that theory doesn't seem to make a whole lot of sense; I think the compressor should just be making pressure all the time and letting the governor and unloader dump air when needed. But I'm just grasping to understand what's going on here...
OK, thanks for making it this far...
Please let me know your thoughts, if you have some insight about this problem.