Horrible screeching noise from engine: with the belt OFF. Is my engine toast?

**Bugsi** · 11-11-2016

https://dl.dropboxusercontent.com/u/...2021.24.59.mp4

Noise starts out after the car warms up, after driving 15 to 20 minutes, or just letting the engine run while in Park.
It sounds like it's coming from everywhere, but here's what we've done to rule out various things:

-Belt has been replaced.
-Water pump has been replaced. (Twice, just for good measure.)
-Tensioner assembly has been replaced.
-Power steering pump has been replaced.
(Note: Those items were original and needed replacing, even though they were not the cause of the noise.)
-Harmonic Balancer has been replaced.
-Torque converter has been replaced.
-Transmission filter and fluid has been changed. Nothing unusual was found in the pan.

I thought it must be a spun bearing, so we dropped the oil pan and the bottom of the engine looked pristine, no metal fragments anywhere. Oil was clean. My mechanic obviously can't figure out what it is, so I'm turning to the experts here. Any ideas of what this could be, or what my next troubleshooting step should be to isolate this?

Finally, it does this WITH THE BELT OFF, so it's not the AC compressor or the alternator.

When it starts making this noise, it does it gradually, sounding something like a chicken clucking:
https://dl.dropboxusercontent.com/u/...2021.16.04.mp4
(some guy asks me about his flat tire while I'm filming, and I have to tell him I don't work there.)

Other than this noise, the engine runs perfectly, and the transmission shifts perfectly. This is super frustrating and I've spent a truckload of money on it without finding the actual cause.

**Scottydoggs** · 11-11-2016

take the oil cap off, fire it up, if the sound is gone the pcv is clogged up.

**Fivefingerdeathpunch** · 11-11-2016

Wouldn't it be funny if the 2 dollar part fixes it?

**Bugsi** · 11-12-2016

Originally Posted by Fivefingerdeathpunch

Wouldn't it be funny if the 2 dollar part fixes it?

That would be awesome. I'll give it a shot.

**cheatah faheatah** · 11-12-2016

Sounds to me like something could be rubbing on your crank pulley? Maybe something fell down in there?

**Bugsi** · 11-12-2016

Warmed it up, got it squealing. Pulled the oil cap off. There was a vacuum and a big SUCK in of air when I pulled off the oil cap, and the engine died. I walked across the street and bought a PCV valve. Popped off the MAP or whatever the sensor thing is over the PCV valve seat, and there was NO PCV valve in the car at all. Put the PCV valve in. Car runs REALLY WELL (just idling in a lot), can pull the oil cap off and engine still runs. Been idling a half hour or so and no screeching. So far so good.

**Scottydoggs** · 11-12-2016

wow, didnt expect it to be missing. sound s like the 2 dollar part does the fix.

**Bugsi** · 11-12-2016

Originally Posted by Scottydoggs

wow, didnt expect it to be missing. sound s like the 2 dollar part does the fix.

$3.27 at O'Reilly's.

**Scottydoggs** · 11-12-2016

by far the cheapest part you have changed to date tho lol now you got good used spare parts to hold on to.

**cheatah faheatah** · 11-18-2016

I've followed this thread, and how does a missing or clogged pcv (positive crankcase ventilation ? right?) cause that kind of noise?? Severe pressure/vacuum going where?

**Scottydoggs** · 11-18-2016

its sucking in air from every where it can when the pcv is messed up.

**blueguy** · 11-18-2016

Easy way to tell is just yank out the dipstick.

Should pull plenty of vacuum lol

**Bugsi** · 11-19-2016

Originally Posted by cheatah faheatah

I've followed this thread, and how does a missing or clogged pcv (positive crankcase ventilation ? right?) cause that kind of noise?? Severe pressure/vacuum going where?

It was apparently the sound of the engine sucking air in from any tiny place it could squeeze air in. I'm not sure exactly where that was, but it's completely gone after installing a $3.27 PCV valve. Now that I know what it was, there were a number of other symptoms that are all neatly explained by not having a PCV valve.
- The horrible screeching noise, of course.
- The extraordinary suction pulling on the oil filler cap.
- There had been a lot of oil leaking around the oil pan gasket. (But in our hunt to fix the screeching we pulled the pan and inspected the lower end of the motor and re-gasketed it.)
- The oil rapidly became filthy black in just five weeks, with just a few hundred miles put on the car.
- I noticed a puff of blue smoke out the exhaust when the car was first started.
- A persistent P1404 diagnostic trouble code kept throwing. That's an "EGR closed position performance" error, and replacing the EGR valve had no effect in solving it. It was pretty clear that nothing was wrong with the EGR system, and yet the computer kept insisting that there was.

All of these things, it turns out, are extremely typical problems associated with PCV system faults. Oddly, a failed PCV valve apparently almost never throws a trouble code associated with a failed PCV valve, but it's apparently quite common for it to throw codes associated with the EGR or other emissions system parts.

I feel a bit stupid about it. Some of the basic things you should do when you acquire a used L36 with sketchy history is basic maintenance: Change the oil and filter, change the air filter, change the fuel filter, and at the very least, take the PCV valve out to make sure that it's present, and at the very least that it rattles and can pass air in one direction. I did all of that except the PCV. To be completely honest, even after 17 years of L36 Bonneville ownership, I didn't even know where the PCV valve was on these cars. I had no idea it was under the MAP sensor, and frankly, I didn't even know what the MAP sensor was. I'd dealt with the IAT, the EGR, and the MAF, and all the filters, but never had to deal with the MAP or PCV before. I think it's particularly odd that the PCV valve was *missing*. My only explanation is that a mechanic that my neighbor had servicing the car when she owned it must have pulled it to replace it during a tune-up, and simply forgot to put one back in it. Once done, it's a freaking mystery unless you deliberately check for it. Very sneaky and extraordinarily weird symptoms until you look back on everything after the fact, and now it all makes a great deal of sense.

**cheatah faheatah** · 11-19-2016

Thank you for that prompt and extensive reply. However now I have a few follow up questions.

1.) How is your engine pulling vacuum on both sides ? If the "P" in PCV stands for positive, then if your pulling vacuum in the bottom end shouldn't it be negative crankcase ventilation? I thought pcv was there to let pressure out from, say, piston ring blow-by (compression chamber pressure escaping past the rings) Example: I had an 83 Bronco with rings so bad (from abuse, my bad, 20 year old me knew EVERYTHING, Ya right) that after a short trip on the highway, I would find the dipstick had "shot" up 8 inches or so...

2.) I know you didn't pinpoint the actual source of the noise, but what do think it was? Some thing like a gasket vibrating? Like a blade of grass between your thumbs, or a Kazoo reed?(How many times are you going to see "Kazoo" in this forum? LOL )

3.) Forgive my ignorance, but where is said pcv valve? I've never really noticed it. In other vehicles I've owned it was through the valve cover. You state it's under MAP sensor. Manifold Ambient Pressure, right? Please let me know where to look. (06 GP base)

4.) Why would the missing valve cause "blockage" ? If it's missing,wouldn't there be a free exchange of pressures/vacuums ?

Again, THANK YOU, and I look forward to conversing with you again..............E

**J57ltr** · 11-20-2016

The noise is from the seal rubbing on the balancer because of the suction. I had a friend that had this happen on a 96' bonniville after having the upper intake exploded and had it replaced but they left out the PCV.

**CrazyGuy03** · 11-20-2016

The ol screaming seal. Usually you see these pop
up when people install an intercooler plate and the pcv passages are
blockee

**Bugsi** · 11-20-2016

Originally Posted by J57ltr

The noise is from the seal rubbing on the balancer because of the suction.

Hey thanks for this detail. It's very helpful to know what the heck that was. Replacing the balancer was the first step we took to try to cure the problem, because it really did sound like it was coming from the balancer! This helps explain it.

**cheatah faheatah** · 11-21-2016

Originally Posted by cheatah faheatah

Thank you for that prompt and extensive reply. However now I have a few follow up questions.

1.) How is your engine pulling vacuum on both sides ? If the "P" in PCV stands for positive, then if your pulling vacuum in the bottom end shouldn't it be negative crankcase ventilation? I thought pcv was there to let pressure out from, say, piston ring blow-by (compression chamber pressure escaping past the rings) Example: I had an 83 Bronco with rings so bad (from abuse, my bad, 20 year old me knew EVERYTHING, Ya right) that after a short trip on the highway, I would find the dipstick had "shot" up 8 inches or so...

2.) I know you didn't pinpoint the actual source of the noise, but what do think it was? Some thing like a gasket vibrating? Like a blade of grass between your thumbs, or a Kazoo reed?(How many times are you going to see "Kazoo" in this forum? LOL )

3.) Forgive my ignorance, but where is said pcv valve? I've never really noticed it. In other vehicles I've owned it was through the valve cover. You state it's under MAP sensor. Manifold Ambient Pressure, right? Please let me know where to look. (06 GP base)

4.) Why would the missing valve cause "blockage" ? If it's missing,wouldn't there be a free exchange of pressures/vacuums ?

Again, THANK YOU, and I look forward to conversing with you again..............E

anyone?

**idrivejunk** · 11-21-2016

It's Manifold Absolute Pressure. PCV valve is under a cover with two bolts, on top of the blower or upper plenum, at least on 97-03. It is calibrated to control vapors in the crankcase and allows them to be burned rather than vented to atmosphere.

**J57ltr** · 11-21-2016

Originally Posted by cheatah faheatah

anyone?

I have thought about this and have never come up with an answer other than the by installing the PCV the noise and vacuum stopped. I never really gave it anymore thought than that. I have also seen people leave out the O-ring, or have a completely clogged one and cause the same thing.
The PCV is located under the MAP at the passangers side of the intake manifold on top opposite the throttle body on NA engines and is under the 2 bolt cover on the drivers side rear of the supercharger near the throttle body on supercharged cars.

2. The noise is the seal in the balancer being pressed against the shaft and that's what causes the squealing.

3. Above.

4. Above.

I don't know how it causes it I have just seen it and it always led to the PCV issue. I would like to know an explaination to this as well because it causes a hell of a vacuum in the crank case when there is an issue as if the manifold vacuum was being applied to the crank case as well. That's the only explanation I have but I know the source of air is traveling out of the case and into the intake tube which is basically just where it's pulling filtered air after the MAF.

Jeff