Screeching noise from my engine - HELP!

[jmoore16]

Ok - Here is my story.

My wife's '94 347 convertible was running great until the end of last driving season (we live in Michigan) when her car developed a strange sound. Everything is great when the engine is cold but after about 5 minutes of driving and warming up, a screech develops from the front end accessories. I kind of sounds like a bearing in an alternator that is getting ready to seize up. I thought it was the alternator when I packed the car away because the screech would change in pitch at idle, and I could change the pitch with engine RPM.

I pulled her car out of storage a couple weeks ago to get it ready for the summer. I have a automotive stethoscope so I used it to find the screech. Alternator case? No. Power Steering pump? No. Water pump? No. I unhooked the fead belt and expected the noise to go away. Nope! Noise is still there so I think that I ruled out the alternator, water pump and power steering pump.

I searched the forums for similar problems and the closest thing I could find was the distributor. I put a new distributor in but unfortunately, the noise is still there.

Does anybody have any idea what this could be? Timing chain? Cam bearings? Rod or main bearings? What does a car sound like if it has spun a bearing? My oil pressure is good and the sound is not there when the car is cold.

I am at a loss. Thanks so much for your help.

John

 

[trav_19]

does the noice change when there is more throttle?? louder quiter or no change??

 

[jmoore16]

The noise changes...

The noise doesn't get louder, but it does change pitch. The pitch goes a little higher in frequency as I get the car up to about 1500 to 2000 rpm and then it stays constant.

 

[trav_19]

...hmmm is it in colder weather its not belt squeal is it? i ask because when its colder my car does this too, did you check the tensioner pulley and the idler pulley as well?

 

[jmoore16]

Not belt squeal...

I can take the belt all the way off and the noise is still there. I don't think it is the belt.

 

[trav_19]

well if you have no belt maybe its the harmonic balancer.... its not lifter noise is it?

 

[jmoore16]

New harmonic balancer...

I lost the old balancer on her car in a big way so it is only about three months old. A lifter noise is more of a tapping so I think this is something else but who knows. Besides, I think that the lifter would make noise all the time. True?

 

[trav_19]

hmmm i think im getting stumped here ...my guess would have been lifters but you said its only when its warm....maybe its there but just gets louder or noticeable once the car warms up??

 

[HISSIN50]

Can you hear it if you remove the belt and turn the motor over by hand?

 

[jmoore16]

Turn the motor over by hand...

I will check.

Back in a few...

 

[jmoore16]

A bad roller lifter...

I finally found a noise through the stethoscope that sounds a little like the noise I hear from 20 feet away. I can get it if I touch the forward most, left hand upper to lower intake bolt. This leads me to believe that I have this noise in the valley of the block? Roller lifter with a bad bearing? Bad cam bearing?

Thoughts?

Thanks to all for your help...

John

 

[jmoore16]

Turning the motor over by hand...

Wow, if you can do this, you are a stud.

Too much compression for me to turn the motor over fast enough to hear the noise. I can turn the motor over about an 1/8th turn at a time and I only hear compressed air escaping.

Signed,

Wimp, uh...

I mean John.

 

[jmoore16]

I have a video of the noise... Bad quality...

How do I get it up on the site? It is from my cell phone (all I have) and it sounds like a regular 5.0L with a lumpy cam at the airport with a jet plane landing over your head...

I can send it to anyone who e-mails me. Steedanorth at hotmail dot com.

Thanks,

John

 

[jmoore16]

Distributor loading the cam?

Somebody told me today that it could be the cam rubbing against the cam thrust plate. I agree that this could be it. I was also told that it might be useful to loosen the distributor hold down and lift the distributor up to load the cam away from the thrust plate. Really!!!

I am afraid that I will pull the oil pump driveshaft right out of the distributor!

Has anybody done this?

Also - I checked for intake leaks and I don't think this is my problem.

John

 

[jmoore16]

Bad Cam Bearing...

I think I found the problem. I took the cam out and found a nick in the cam bearing about a 1/16 in by 3/8 in by about 10 to 20 thousands deep. Would this cause the noise when the engine is hot?

Also - Has anyone changed a cam bearing while the block was in the vehicle?

Thanks to all for the help.

John

 

[Guero]

Does the noise sound like this? http://media.putfile.com/pictures-95

 

[jmoore16]

Doesn't sound like this...

Does the noise sound like this? http://media.putfile.com/pictures-95

If someone can help, I have a video of the noise from my camera phone. It will make you cringe as it sounds like a jet airplane landing at the airport!!!

Your sound? I would look at the idler pulley on the tensioner or the tensioner itself. What was the sound?

John