mystery compressor noise

[a5redwing]

Hey guys back again, so here we go. I have a 355/380 e7 and a Bendix compressor. In the morning while engine is cool I have no noise, but after my compressor builds up a few times and gets hot, when the turbo kicks in there is a choppy noise while pressure builds up. Once the drier pops off it stops. This is the way it is most of the day. By afternoon and everything is hot I hear it EVERY time the turbo kicks in. It will not make a noise while idling or revving the motor. The compressor stops building pressure at 130 but when the turbo is working hard only 120. Is the compressor, governor, a air line bad? I check all my turbo boots and related. I has to be something dealing with that compressor, right? Thanks for any help.

[theakerstwo]

That sounds like a AD4 drier which would be a problem with the purge valve letting turbo boost bleed out the bottom when it should be closed. Mine did it for a while and then stopped.

[bbigrig]

We have a 2006 CHN Rawhide with a 460xt with the same noise during build up. The compressor stops making the knocking or slapping noise at cut out pressure (130 psi) When we first started noticing the noise it sounded like cam or roller lifters starting to fail. But it's definetly in the compressor of our truck. This unit has just over 680,000 miles. it has only gotten noisy in the last year or so and dissapears when the compressor cuts out. Mind you our truck has the single lung meritor compressor. are you sure your compressor is a bendix? I have heard the same noise on another truck with the same 1 lung meritor compressor but not a bendix. the only fix for the knock or slap on the meritor is replacment of the unit.

[a5redwing]

We have a 2006 CHN Rawhide with a 460xt with the same noise during build up. The compressor stops making the knocking or slapping noise at cut out pressure (130 psi) When we first started noticing the noise it sounded like cam or roller lifters starting to fail. But it's definetly in the compressor of our truck. This unit has just over 680,000 miles. it has only gotten noisy in the last year or so and dissapears when the compressor cuts out. Mind you our truck has the single lung meritor compressor. are you sure your compressor is a bendix? I have heard the same noise on another truck with the same 1 lung meritor compressor but not a bendix. the only fix for the knock or slap on the meritor is replacment of the unit.

No I'm not sure it is, but the Mack mechanic that looked at it said it was. He thought it was the intake line for the compressor until I figured out it went along with pressure build up.

[a5redwing]

That sounds like a AD4 drier which would be a problem with the purge valve letting turbo boost bleed out the bottom when it should be closed. Mine did it for a while and then stopped.

I know my pressure bleeds off a little from the drier, that could make sense. Any ideas on how to locate noise while idling?

[jaysm35a2]

Im no help here but I wish you well and hop its a simple fix.

My trucks in the shop now having a new compressor put on it.

[a5redwing]

Here's what is was: the intake on the compressor's gasket was bad. A little gasket maker and problem solved! Thanks to everyone who answered.

Edited September 17, 2011 by a5redwing

[a5redwing]

Im no help here but I wish you well and hop its a simple fix.

My trucks in the shop now having a new compressor put on it.

i didn't mean to down your reputation, I was trying to figure out what those buttons were and accidentally clicked it. Sorry.

[rhasler]

i didn't mean to down your reputation, I was trying to figure out what those buttons were and accidentally clicked it. Sorry.

I added one just for good measure.

[jaysm35a2]

10-4 . Anyone know why a air compressor that goes on the 711 engine would be around 700 bucks??

[a5redwing]

I added one just for good measure.

Good deal. I found another post he had and added one too.

[a5redwing]

10-4 . Anyone know why a air compressor that goes on the 711 engine would be around 700 bucks??

Is that reman or without the core?

[jaysm35a2]

Its without core. Its not the exact same one thats on my truck im told. They charged about 300 more , its $1070.00 and I keep mine.