I've had a problem for 2-3 months. It started out as a slap slap slap or tap tap tap sound at idle. This noise ONLY happens at idle, but it comes and goes. It is present about half the time.

At first it sounded like what the old fan belts sounded like when one started to separate and the loose or separated part was slapping something every time the belt went around.

So I pulled the serpentine belt but it is in new condition. I spun all the pulleys and none are noisy. I spun the fan clutch with the belt on and it is not noisy. So far I've pulled the serp belt four different times and spun the pulleys four different times, and all are smooth.

With the serp belt off, and the engine running, the sound goes away completely, so I know it's not the vacuum pump, P.S. or turbo. I did that 3 separate times.

Lately it has turned into a whistling sound, but again, only at idle. The turbo boots all look fine, and since it does not make this sound when the serp belt is off I know it's not the boots.

I took an old vacuum cleaner extension hose and put one end to my ear and held the other end on the generator, the idler pulley, the A.C. pump, and the vacuum and PS housings and can't hear the noise transmitted through the hose.

Since the noise goes away when I'm driving, I'm thinking it might be the fan clutch. But maybe not.

Anyone got any ideas?

 

Water pump, check the weep hole under the pump.

 

Didn't think of that since the water pump pulley turns with no noise. What am I looking for at the weep hole? Also the water pump was replaced 2 years ago.

 

The water pumps are such poor quality and the first sign of any coolant at the weep hole means the seal has gone so the bearing will not be far off. If it is the water pump there are 3 different ones all will fit but they have different ratings.

 

Might also want to check the belt tensioner.

 

The weep hole is clean and there is no sign of coolant.

 

Belt tensioner was replaced 2 years ago. When I spin the idler pulley it feels smooth.

 

It takes less than 10 minutes to take the fan clutch off. I would just remove the fan with clutch and put a few miles on it without it and listen for your noise.

 

Thanks Deere Country. I'm looking for a 36 mm wrench right now.

 

You bet, I have a pneumatic fan tool set but if the nut is stubborn when trying to remove it a small ball peen hammer and a few hits to the flat sides of the fan clutch nut will aid greatly in loosening the nut for you.

 

I would certainly try removing the fan but should that not be it the AC compressor pulley might spin good but the compressor itself or the amount of charge might be the problem. At idle there is not as much airflow through the condenser so head pressures will be greater and more torque required to turn the compressor when it's engaged causing the belt to flap around. The compressor is commanded to run in all positions except OFF and VENT. The amount of belt flap is amazing when there is high head pressures for whatever reason. Over charged, a slight blockage, poor air flow through the condenser, a kinked line.

 

I did a "fix" on my AC so it only comes on when I specifically turn the switch to AC. If I've got it in regular, heat mode, the AC won't come on, even if I put it in Defrost. I have to put it in AC Defrost for the AC to come on in Defrost.

And when I do turn the AC on, the noise isn't any different. 36,000 miles ago I had a new AC pump installed. Getting ready to pull the fan clutch.

 

I might be wrong on this one but on the Cummins engine is there a second hole close to where the belt tensioner pulley mounts, about 1 1/2 inches away? If so do you have it in the correct location?

 

I'm not sure. Although I usually do my own work, on this idler pulley/bracket I let him replace it.

 

OK. I went and got a mechanic's stethoscope. With the serp belt on and the engine running all I can hear, no matter where I put the end of the stethoscope is the injection pump pounding out 14,500 psi of fuel.

Shutting the engine off, and with the serp belt off all the pulleys are silent EXCEPT the damm water pump! Even tho it turns smoothly, and even tho the weep hole is not leaking and even tho I can't hear anything by naked ear alone, when I put the stethoscope on it I can hear a squealing with every rotation. So I am gonna go get a new one tomorrow and put that sucker on.