Thread: Engine squeal, vacuum related *UPDATE* Problem Solved (see last post)

First off, I just made an account here so you could say I'm new to the forum, although I've been reading through the many pages here for quite some time.

Here's the story....(with a bit of background info)

First off I'm a 16 year old guy so please bear with me here. Just a couple of days ago I (as in "myself") purchased my (as in it's truly "mine") first car, a '98 Grand Prix GT with 156k. It's white, 2dr model, with tan leather, sliding sunroof, HUD, power seats, mirrors and locks, dual climate control, and Pontiac's version of "chrome" rims. I don't think I did too bad for $2200, but we all have our opinions .

Anyways, when I was looking at the car I was told upfront it had a vacuum leak and (obviously) idled rough, but ran fine down the road when drawing in more air (which it does run good down the road). When I purchased it it did have a ever so slight noise coming from the engine. I attributed this to the vacuum leak issue and thought nothing more of it. After pulling in the driveway, however, I got looking around and found that someone had routed the belt incorrectly causing it to rub on the oil filter base. No problem, the belt had survived the almost 2 hour interstate drive home (in which I was getting 31-33MPG according to the monitor *big grin*) and didn't have any major signs of damage, nor did the oil filter base. Next on my list of things was to fix the vacuum leak (it does have a few other problems, some of which I might be asking about later, but that's beside the point).
I figured out that someone had drilled (yes, I said drilled) a hole into the extension for the oil fill. After a bit of duct tape I got the vacuum leak temporarily fixed, but managed to get a God-awful screeching/squealing sound from near the belt-side of the engine.

I've eliminated the possibility of it being any pulleys ceasing up (took the belt off (again) to test that) and have narrowed it down to something vacuum related (which I realize doesn't mean much).
I've read up on some people having a similar problem with the PCV valve, but I've taken the valve out and tried numerous things while plugging/un-plugging the hole in the extension and regulating air flow with my finger acting as the PCV valve. Between myself, my mechanic dad, and my also-mechanic uncle, we think there is another vacuum leak somewhere between the oil fill extension and the PCV valve.
All 3 of us are stumped except for thinking it could be something manifold related (as it does have the plastic manifold *sigh*).

So, if any one here could be kind enough to enlighten me with any possible ideas as to why and where this noise is coming from I would greatly appreciate it (and so would my neighbors ears)!!

Sorry for having such along post, but it's frustrating trying to fix one problem and meanwhile creating a more complex, and much, much noisier one.

As your father and uncle probably concluded, by drilling the hole, they caused a breather/leak that would keep the car from squealing.

On the pcv. There should be an o-ring on the bottom of the valve and then the ring on the cover of the valve with a spring on the cover that holds the valve down and seals the bottom ring. Typically the most likely causes are a missing ring or spring.

Please get a overall picture of the engine/engine bay and post it up. (in case someone also routed/plugged the evap lines or something else odd. Only other thing I could think of is if the lower intake end seal (rubber gasket at the ends of the lower intake manifold were out of place and it was pulling in air from there. Less likely...but yes.. I once managed this feat!

Thanks so much for replying Bill. I just went out and checked and everything is there and in the correct places. Matter of fact, the PCV valve and the seals look to be pretty new.

I will go out and snap some pics of the engine ASAP, but I'm just hoping I can upload them with my all-so-fabulous dial up internet.

Also, I'm not sure if it will help or not, but my dad and I did try the poor man's trick of trying to find vacuum leaks by using a spray can of starting fluid. I think we sprayed everywhere there is to spray but we couldn't get any response from the engine. That left him scratching his head.

Anyways, I will definitely try to get some pics posted up here. Thanks again.



-Edit-
Ok, I just snapped a basic pic of the engine. Not really sure if you want a picture of anything specific or not, but hopefully this is somehow helpful.



I imagine there are cleaner engines/engine bays out there, but I'm focusing on getting it running first.

Rough idle, runs fine otherwise? I've heard vacuum leaks whistle, but not squeal. A common leak is right off the lower intake manifold near the alternator.

Might be a long shot, but unplug the mass airflow sensor and see if it runs different. Maybe a clogged fuel filter? Fouled spark plugs?

I will definitely try unplugging the MAF sensor, I don't think it's a fuel filter or plugs, but the MAF sensor is worth a shot.

I would describe it as more of a squeal than a whistle. It actually sounded like I had a pulley seizing up, but I've since ruled that idea out. It produces the noise with or without the serpentine belt on the car.

Yes, it does idle rough due to the vacuum leak, but it runs absolutely perfect down the road when it has the leak.

If the vacuum leak (the drilled hole in the oil fill extension) is left untouched (i.e. it still has the leak) the car has no signs, symptoms, or other hints of anything other than the vacuum leak being wrong.
If you start it up with the leak it will obviously idle rough but as soon as you plug the hole it will produce this God-awful squeal for about 3 seconds, then it will go away and idle fine. Then if you unplug the hole it will (again) produce the same noise which also lasts for 3 or so seconds. After the 3 or so seconds it won't make the noise anymore, but will start to idle rough again due to the vacuum leak.

Just to make it perfectly clear, the car runs down the road PERFECT if the vacuum leak is left untouched. In fact, it will not produce the noise at ALL if the leak is left untouched from engine start to stop. With the leak unplugged, the ONLY thing that seems wrong with the car is the rough idle (which is caused by the vacuum leak of course). But if you plug the leak it turns into a whole different ballgame.


Anybody think it would help if I tried to get a video of the problem?

Didn't see the updates yesterday. I wanted and overall pic because sometimes a guy will do something and it'll be old enough to look stock etc. and we may pick up on it.

Pull the oil cap off and plug that hole. Start it up. Clearly you have the cap off so there's a big hole. Put your hand over it. Does it have vacuum or pressure? It sure sounds like the crankcase isn't ventilating properly. The UIM has a hole that comes up from the ctrankcase in the LIM to the bottom of the PCV, then it comes up through...and into another passage and into the UIM in a tube in the top of it. Try and check that tube or passage by blowing air into it. If there is restriction then that would build pressure in the crankcase. Also take a tube and try to pull air up through the bottom of the pcv area to see if there is a clog in the LIM leading to the pcv. Might be a bit of a stretch, but it sounds like the pcv system is blocked somehow.

Originally Posted by BillBoost37

Does it have vacuum or pressure?

It's got vacuum, and plenty of it. It wants to suck your finger (or hand) down the oil fill cap, it's got that much vacuum.
I don't mean to try and shoot you down when you're trying to help, but I don't think anything could be plugged because, if I'm thinking correctly, that would build excess pressure, not excess vacuum.

Plainly said, somebody was pretty darn smart to figure out that by allowing the crankcase to take in air (i.e. the vacuum leak in the oil fill) it would prevent the car from making the noise. It's just my own opinion, but somebody was trying to cover something up by giving it the vacuum leak (which could explain why the hole was drilled into the extension). Now it's just a matter of figuring out what they were trying to cover up.....

Ok, just an update here...

Now, I almost bet somebody is going to say something along the lines of "I told you so!" but I'm gonna say it anyways.
Just ran up to the auto parts shop and bought a $3.18 PCV valve, came home, put it in and Viola! no more engine squeal.

I'm not out of the woods yet, still need to fix the vacuum leak, but at least it doesn't make noise anymore.

This car is still probably going to end up torn apart though as today I checked oil and it was roughly 2 quarts low (which I realize is pretty low). I added 2 quarts of oil just for the time being, waited several minutes for it all to drain down, checked oil level again and, upon seeing it was where it should be, started it up. Then I proceeded to watch it fill the whole garage up with white smoke . Even with the new PCV valve and the hole plugged in the oil fill extension something still isn't right.
Dad says it's gonna get torn apart, so yay...

Ok, finally figured out the problem as to why there was vacuum in/on the crankcase. After taking off that plastic intake thing (don't ask about how that went...) we were welcomed by oil...and lots of it. At this point it was like "W-T-F?!" how/why is there a standing pool of oil IN the intake .
After a bit of checking through service manuals we found the problem: someone had taken the intake off and had forgotten to replace 2 bolts that sit inside the intake. It just so happens that if these two bolts are missing (which they were) you have two direct passages from your intake to the crankcase. With the hole in the oil fill extension plugged the car was trying to suck air, which was now oil since the hole was plugged, up from the crankcase through these two holes into the intake where it was burning the oil....thus fogging half the county up with white smoke.

So, after I get those 2 bolts replaced and the intake back together (along with draining all the oil from the intake and replacing fluids etc etc) I'm HOPING that this car will finally run right.

Awesome.. there's always an answer to the oddest issues. And it's logical once found.

Got her all put together the other day, started it up for a minute and finally got to hear it run normally. No more idle at 2.5-3k RPM, no more rough starts, and it doesn't stall when you take the oil cap off. I'm happy .

Not too bad for homemade bolts either (yea mofo's, got out the hacksaw and tap and dye set and made my own bolts for it )


Still gotta get some antifreeze for it though cause the sh!t that came out of it was all water.....that and then do an oil change