Hi I’m new here, I’m really frustrated with my 2003 Freightliner Classic. Detroit 60 series 12.7l
I’ll try to explain it.
Driving on the highway, the compressor builds up to about 125 and cuts out, then if I tap the brakes a couple times til the air is down around 105-110psi, it makes a hissing air leak kind of sound when I hard accelerate but when I let off the pedal the noise stops completely. This goes on until the instant the governor cuts back in and starts building pressure again to 125 psi.
Then it happens all over again. Air down, hiss on acceleration, and quiet when I let off.
Also seems related to my turbo boost. I don’t get quite as much boost when I hear the leak.
I have leak tested all my boots and intercooler etc, and all good there. It seems associated with the compressor/ air dryer? Any ideas?
I hear the compressor is somehow connected to turbo boost?
many ideas would be greatly appreciated!!
Air hissing only under load accelerating seems air compressor and boost related
Discussion in 'Heavy Duty Diesel Truck Mechanics Forum' started by Freightshaker03, Apr 11, 2021.
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The air compressor gets filtered air from the intake charge air cooler system. The leak you hear when pulling hard is either the hose going to the air compressor or a leak in the charge air cooler system. Have the charge air cooler system checked by taking apart the system where the turbo supplies air to the intake air charger cooler and block up the system by the intake manifold. Pressurize the system by adding air into the manifold where the manifold pressure gauge, just a simple 3/8th fitting and an air chuck screws right into it. Plumb a gauge with the air chuck and pressurize the system and see how much air you loose in 15 seconds. you should be able to hear the leak st this time. 2 or 3 lbs air loss is normal, but more than that you have problems. The engine oem usually say 5 lbs loss in 15 seconds is normal, but it is so they can get out of warranty work.
Rideandrepair Thanks this. -
Carefully inspect the air compressor intake hose for damage or loose connections. Also check all of the pipes from the turbo outlet to the engine intake. If all seems OK, then perform the pressure test outlined by mnmover above.
Rideandrepair Thanks this. -
A spray bottle with soapy water will find your leak
Rideandrepair and Don379 Thank this. -
I'd think maybe the pop off valve on compressor or purge valve on dryer.
You said it quits when the compressor engages and starts building air again, even if on the throttle hard?Rideandrepair Thanks this. -
Rideandrepair and lester Thank this.
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Thanks for the help!Rideandrepair Thanks this. -
How would I check the valve on the compressor though?Rideandrepair Thanks this. -
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I would just change the pop off valve and the purge valve.Rideandrepair Thanks this.
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