1995 Park Avenue - 3800 squeak on startup when hot and others

[chibuick]

Hi, all I recently had the upper plenum replaced at a shop and the tech told me he cleaned the throttlebody from carbon as well. After getting it back now every time the car starts up warm I hear this squeak. I also hear it when driving down the road and RPMs come down from about 2000 to 1400. I thought it was the serpentine belt, but the sound is very clearly coming from the right side of the engine bay. I thoroughly cleaned the serpentine belt as well. This issue only happens when the car is hot. On a cold start there are no noises at all. Anyone have any ideas?

 

[HotZ28]

There is no mention of how old the current serpentine is?? You can clean an old belt, but it may be stretched & cracking on the drive surface. It sounds like the "screech" is coming from the belt trying to drive the alternator.

 

[RD_Atlanta]

That sure sounds like a pulley bearing (i.e. tensioner) or something in the serpentine area. But your confident its not on that side?

 

[02LTD2.0]

Use a mechanics stethoscope to search for the source of the noise. If you don't have one then a long screwdriver held up to your ear would suffice.

 

[DrivenDaily]

That alternator doesn't sound so good, either. It could be one or both of its bearings complaining.

Since you can obviously reproduce the noise, stick a hose in your ear (small like an engine air hose or your wife's vacuum hose) and use that to narrow down where in the engine bay it's coming from. At least then it won't be just some side or corner, but a more specific spot.

 

[chibuick]

alternator is brand new. Tensioner and belt I’m not sure but there are no visible cracks and this sound started only AFTER I got the car back from the shop that replaced the upper plenum (had the throttle body and fuel rail off, etc). Here’s a pic of when that shop had it apart.

I may need a hose or mechanics stethoscope to better diagnose then or a vacuum line hose. I’m currently on a long roadtrip with friends and stuck trying to fix breaking things while we’re on the road. I appreciate you guys responding.

 

[chibuick]

It only happens when engine is warm, and I’m starting the car or I’m driving down the road and RPMs dropping from about 2k to 1400 or when holding steading at about 1500. Happens in all gears and whether transmission torque converter is locked up or not.

For some reason it sounded a lot louder on the underside…like it was coming from the oil pan / trans pan, but that could just be the sound bouncing off the ground and making it sound louder to me.

 

[02LTD2.0]

When it's idling take off the oil cap and listen for a change.
I'm thinking it could be a PCV issue.

 

[chibuick]

When it's idling take off the oil cap and listen for a change.
I'm thinking it could be a PCV issue.

OK, I will check that. I’m also getting an intermittent check engine light.

 

[chibuick]

When it's idling take off the oil cap and listen for a change.
I'm thinking it could be a PCV issue.

Woah!!! Super hard to get the oil cap off at idle and when I take it off the car nearly stalls. PCV valve?

 

[HotZ28]

When you removed the oil cap, was there a sucking sound from the valve cover, or did you have air pressure blowing out? If you have a vacuum, the PCV is doing it's job, if crankcase pressure is building in the engine, the PCV needs to be checked, Remove it & shake it, if it rattles, it's not the problem!

 

[chibuick]

When you removed the oil cap, was there a sucking sound from the valve cover, or did you have air pressure blowing out? If you have a vacuum, the PCV is doing it's job, if crankcase pressure is building in the engine, the PCV needs to be checked, Remove it & shake it, if it rattles, it's not the problem!

It’s sucking air but more air than it ever has when I take the cap off. In the video you’ll see it almost makes the engine stall. It never did that before. I looked at the PCV valve and the small o ring for the valve and metal spring were missing. I bought the kit to put those on. Gets delivered later today.

 

[chibuick]

Update : fixed.

The shop that did the intake plenum did not put the spring nor o ring on the PCV valve. Got an Amazon kit delivered and all fixed. Thank you guys for the help and 02LTD2.0 for guiding me to the PCV system and oil cap! Wouldn’t have gone that route without that tip. Thank you.

 

[02LTD2.0]

That very same thing happened to me about 20 years ago. Glad it's an easy fix as it was for me.

 

[02LTD2.0]

Another thing to be aware of is to be very careful when removing the MAP sensor. I broke one a few years ago when I did the UIM on my previous Buick. Thankfully I was able to glue it back together and just chalked it up to another "learning" experience.

 

[chibuick]

Another thing to be aware of is to be very careful when removing the MAP sensor. I broke one a few years ago when I did the UIM on my previous Buick. Thankfully I was able to glue it back together and just chalked it up to another "learning" experience.

Interestingly on this 95 Park Avenue there is no MAP sensor. I was looking for it but there’s no sensor or connector. My 02 LeSabre has it though and I almost broke that one taking it out!