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?