Squeal at idle when hot...

[cefolar]

I had a similar post a couple of months back and thought I had the problem taken care of - but it's back and driving me NUTS!!

I have 4.6 DOHC motor in my 47 Ford - I have replaced every front accessory (P/S Pump, Idler, Altenator and Water Pump) and new belt. The car starts and idles great - oil pressure is about 80-90 psi cold, drops to 30 psi hot but a flick of the throttle sends it back to 60-70 psi instantly. All seems good there.

Car drives good and shifts good it's got an AODE 4R70W.

My problem is at hot idle i get this steady squeal that sounds like a bad accessory bearing, when it bring it up to about 1500 rpm squeal goes away. At first I thought it was P/S fluid aerating (switched to Lucas Heavy Duty) seemed to help a little. The kicker is when I turn the car off - the squeal slowly diminishes like when you stretch the opening of a ballon while letting the air out for a second or two - doesn't do it every time - but most times.

I replaced the IAC valve because someone suggested that - the sound seems low middle of the engine, maybe even near the transmission but I can't think of anything that would be "spinning down" after the engine is shut off. I've checked all the vacuum lines twice but it really sounds metallic and not "a whistle" like I figure a vacuum leak would.

I've built over 10 cars and this one has me stumped!!! Any suggestions would be greatly appreciated!!

 

[COramprat]

First...sounds like a sweet car.

If the sound diminshed when you added the Lucus Oil to the PS pump that may be where it lies but I've never actually heard one go bad.

Checked for any vacuum leaks?

 

[Superhereaux]

have you changed anything on the engine recently?

throttle body, gaskets, injectors?

if you want to eliminate all the front accessories and pulleys wait for the noise to show up, remove the belt then restart the car for a few seconds

 

[Rusty67]

if you want to eliminate all the front accessories and pulleys wait for the noise to show up, remove the belt then restart the car for a few seconds

That is some good advice right there. Let us know how that works out.

 

[Shiroelex]

I was going to suggest trying running it without the belt as well, to try and eliminate any rotating item as the culprit. If it's not that, then try spraying some throttle body cleaner into the throttle body while it's running. You'll have to keep the rpm up, of course. If the noise goes away, then I'd bet it's an intake gasket somewhere leaking.

If the noise is still there after that, then it could be the woodruff key in the crank dampener on the front. I've seen a situation where someone installed some underdrive pulleys with the pulley installer, and didn't have the keyway lined up. It pushed the woodruff key back, and was rubbing on something making a terrible noise. Usually, this noise is noticed right away, and is pretty unbearable to drive with.

I'm sure you've tried a new belt, and have ruled out the tensioner/idler pulleys and A/C compressor? I went through a belt in about two months on my 01.

 

[cefolar]

Not sure I want to run the engine without the water pump turning - I guess for a few seconds it would be ok but makes me nervous. I haven't changed anything on the engine. Brand new P/S pump - but I guess anything is worth a try...

 

[Superhereaux]

don't be nervous, running without the belt for a few seconds won't hurt anything


fuel injected i assume? does your car have the ability to throw a check engine light?

 

[cefolar]

It does have the ability to throw a code - not throwing any though.

 

[cefolar]

Ok - you won't believe this but it is freaking me out. I let the car get to hot idle and got the squeal....I pulled the PCV valve out of the drivers side valve cover...sound disappeared. Put the PCV valve back in sound came back.

Is it possible to pull too much vacuum from the motor?? It's just not computing to me. Since I pulled all the emission controls out of the car I am running the PCV valve to T and going to the 2 vacuum connections on the plenum (it's actually a 97 Mark VIII motor) and the valve (??) from the passenger side valve cover to the vacuum connection under the throttle body.

Should I just cap off one of the vacuum sources? And anybody have any idea where the squeak could be coming from - I checked all the intake bolts and injectors and everything is sealed.....

 

[Rusty67]

Ok - you won't believe this but it is freaking me out. I let the car get to hot idle and got the squeal....I pulled the PCV valve out of the drivers side valve cover...sound disappeared. Put the PCV valve back in sound came back.

Is it possible to pull too much vacuum from the motor?? It's just not computing to me. Since I pulled all the emission controls out of the car I am running the PCV valve to T and going to the 2 vacuum connections on the plenum (it's actually a 97 Mark VIII motor) and the valve (??) from the passenger side valve cover to the vacuum connection under the throttle body.

Should I just cap off one of the vacuum sources? And anybody have any idea where the squeak could be coming from - I checked all the intake bolts and injectors and everything is sealed.....

Is it anew PCV valve ? It is possible the valve is bad and that is why its making noise.

 

[cefolar]

I don't think it is the PCV valve (although I am going to buy 2 new ones) - if I pulled the valve out of the drivers side valve cover sound went away. If I pulled the one out of the passenger side valve cover - sound went away so it's not the valve making the noise.

Anyone think it is possible that there is so much negative crankcase ventilation I could actually be sucking oil vapor off the rings?

 

[Superhereaux]

I don't think it is the PCV valve (although I am going to buy 2 new ones) - if I pulled the valve out of the drivers side valve cover sound went away. If I pulled the one out of the passenger side valve cover - sound went away so it's not the valve making the noise.

the valve itself is not making the noise but is likely the cause, no crankcase ventilation. either that or one of the lines is plugged with carbon or gunk

the noise will go away if you take off the oil cap or take out the dipstick

 

[4.6andSlicks]

the valve itself is not making the noise but is likely the cause, no crankcase ventilation. either that or one of the lines is plugged with carbon or gunk

the noise will go away if you take off the oil cap or take out the dipstick

Interesting, I'd try that. Could it be a bad valve cover gasket that's allowing air in when under vacuum?

 

[cefolar]

I am going to try that tonight with the oil cap or dipstick. It doesn't appear to be an issue with insufficient crankcase evacuation but actually OVER evacuating. With manifold vacuum pulling pressure from both valve covers. I'm sure any reduction in vacuum (especially in the head) will eliminate the squeal.

Based on this thread - in this situation a leaking valve cover gasket would be a good thing as it would reduce negative crankcase pressure. I'll keep you posted....thanks for all the input.

 

[Taurusx71]

I was curious if anyone ever found what the problem was. I have a 99 mustang v6 that when it gets warm it started making a squeel that sounds like a bad belt or pulley but is coming from somewhere on the drivers side possibly under valve cover. Any ideas would be greatly appreciated