belt noise

[chris989]

Hello All,

V2500 5.7.

I installed an onboard air system from littleshopmfg. It is a york 210. Prior to the install my engine/belt system was as expected. The ac would kick on and the usual noise would accompany it.

Now, with the second pump and a longer belt I get a horrible hum/vibration somewhere when the OE AC comes on. I can not see or hear anything under the hood but when in the cab it is that low rumble and resonates. Like when you can hear a subwoofer from a car 50ft away at a stop light.

Any ideas? Belt to tight? too loose? The tensioner feels right

https://www.littleshopmfg.com/gm-4-3...ompressor-kit/

[chris989]

Should have said the harmonics are only at idle, Once on the gas it goes away.

[Pontiac1976]

Look down over the shroud if the belt is seem to be bouncing a fair amount might be loose
if the engine not be running long ( you just started up place you hand on top of the alt pay attention to the belt does not get close to the belt fingers feel for vibration then the a/c pump again watch the belt does not grab your finger. Or a auto Stethoscope if you want be safer. (when the belt is not running the longest part between pulleys should have about 1/2 play in the middle when you press on it. Oh those alt's are know to have bearing go bad a lot more then any other AC Delco alt's

[chris989]

It appears the noise is coming from the compressor. This is the last R4 compressor i will ever deal with. The first two failed in less than a month, the 3rd lasted a year and this 4th compressor lasted 4 years. It is undercharged so not to run too much head pressure but I think even thought they are listed to run 134a they just can't deal with the pressures.

I am going to install a sanden, buy brackets, make hoses and hopefully be done with it for the last time.

Chris

[Sabaka454]

I would look at the mounting of the York.

[chris989]

Still have t he noise, Update,

Still chasing this horrrible sound. Went to the AC shop and they said exhaust, exhaust shop said motor mounts, Anyway, I have installed new motor mounts, cut off the exhaust and installed new and replace the R$ with another AC delco R4 and the sound is as bad or worse.

the tensioner, idler, belt, PS pump are all new. The water and alt are 3 years old and show no signs of failure. Today i will remove the york OBA completely and if htat does not fix it I will do the alternator tomorrow.

I will try to take a video of the noise in the event someone stumbles across this thread with the same issue in the future..

[Corts60]

My low mile 86 suburban makes this same noise/rumble at idle as well with the ac on. I’ll be interested to see what you find out. My engine is 100% stock, so I’m not sure what is going on

[Just call me Sean]

I use a piece of heater hose as a stethoscope to listen for where weird noises are coming from.

[Dead Parrot]

Is the AC idle compensation circuit working? On an old carb setup, there was a simple solenoid that bumped the idle speed up when the AC comp came on. Without that, some motors would start vibrating a lot because they were idling too slow, or they would simply die.

Fuel injection setups should have a similar feature even if implemented differently.

[chris989]

Originally Posted by Dead Parrot

Is the AC idle compensation circuit working? On an old carb setup, there was a simple solenoid that bumped the idle speed up when the AC comp came on. Without that, some motors would start vibrating a lot because they were idling too slow, or they would simply die.

Fuel injection setups should have a similar feature even if implemented differently.

I have a TBI,, it adds IAC steps when there is a call for AC

[chris989]

I found the issue after ~1000 of wasted $$ and time.

I removed the OBA compressor from LittleshopMFG and presto, noise gone. york210 is new and the fabricate nice brackets but something is a miss. Everything was perfectly aligned and when i call for OBA it works perfect. When the engine is running and not calling for AC it is perfect. Only when it called for AC and running a ~111" belt around the York OBA did it create the harmonics.

Crazy enough,, under the hood, everything sounded smooth,,, no noise, no vibration but apparently harmonics and acoustics are fickle. Like the drone of my 40 series flowmaster on a different build.

I am kicking myself for not taking it off sooner. I am confident when i contact LittleshopMFG they will have "never heard of it" and "never had an issue".

The clutch on the york appears perfect and spins freely so i do not know if getting another would make a difference. I doubt any of it is returnable.

I hope this thread saves someone in the future.

Chris