Mechanical Chirping/Squeaking at low RPMs

[patrick]

Hi everyone! Please bear with me, this is my first thread, but this is driving me crazy and I'm hoping for some help. Our van has a new noise. Ok, it's a 7.3 Quigley EB-50, so it makes plenty of noise as it is, but this one is definitely new.
After getting a new turbo and associated plumbing, and then replacing both valve cover gaskets, the van left the shop with a chirping/squeaking noise that occurs mainly at lower RPMs, and is particularly noticeable right after shutting down the engine, and also when starting up. It is less noticeable at speed, but that could be just because it's being masked by general engine noise.
It sounds like it's coming from the center dash area, or up near where the windshield meets the dash. It's more of a chip chirp chirp noise than anything else, but it's hard to pinpoint, especially over the din of the engine.
The shop has gone over the van multiple times and is confident the noise is not the result of the work performed, and indeed, it doesn't really seem like they were working in the area where the noise comes from. The next steps they propose are a total dash removal, which is pretty spendy just to see if they can find the problem.
I've removed the center console, doghouse, stereo, and checked everywhere under the hood for anything rubbing or loose, but I haven't found anything. And yes, I've pulled the CO2 and other detectors, but it's not that noise.
Has anyone else experienced this, or can anyone think of other areas to look? Any help would be greatly appreciated. Thanks is advance.

[carringb]

Steady chirp-chirp-chirp as almost always a belt idler or tensioner pulley going...

One thing that makes vehicle noises hard to diagnose is the source is rarely where you hear it.

[patrick]

Thanks for the quick response! If it ever stops raining, I'll have to check that out. Now that I think of it, it does sound reminiscent of when I (so proudly) replaced the timing belt on my subie, but not the idler gears and tensioning pulleys. Live and learn I guess. Or not in my case.

[Bbasso]

My water pump make a chirping sound just before it went bad.

[1der]

Vacuum pump, since it a diese and if equipped, can make that type of noise. It is also belt driven.

[Bbasso]

When my vacuum pump failed it was quiet during and after. I just suddenly lost power brakes...

[patrick]

Thanks everyone for the responses! I spent some time on this today, and I couldn't find anything with a mechanic's stethoscope and the engine running. I was particularly looking at the belt system, idlers and water pump, alternator, etc.
I finally thought to have my wife start up the engine while I listened (it's easier to hear the noise with the starter turning, but the engine not yet firing), and while I was leaning over the engine compartment, she got in and slammed the door, and then I heard a chirp or two - even before she started the engine, but as the door closed. So I really think this is a mount, or some sort of friction, or something loose.
The upside is I'm a little less worried as we set off for central CA, then running the coast to Port Townsend WA. But I'm still going to spend more time on this. But if it occurs even without the engine running, I'm less freaked out. Thanks again.