Engine Smoking & Intermittent High Pitch Noise

I heard a few high pitched noises from the engine the other day, but it ran fine. Let the Boxster idle today for 10 minutes and when I returned it had stalled out. When I re-started the engine immediately began smoking and had an electrical smell. I was able to pull into the garage and shut it down. What next?

1998 Boxster with 68,000 miles.

That the engine is exhibiting the smoking and stalling means any diagnosis that requires running the engine is risky, very risky.

My WAG is AOS. That electrical smell though... Perhaps that's just your nose and brain putting a label on oil that is being fed to the engine by a failing AOS.

However.... the smoke could be water vapor and the smell is coolant/antifreeze. Any fluids coming from the exhaust exits? Oil? Or water? Be careful. Water can loosen soot and a drop of water can be dark like oil but if you touch it and get some between your fingers you'll be able to tell it is water and not oil. Or vice versa.

What is the coolant level like? Check the oil level.

If coolant level low... then there's a cooling system leak into the engine. This can be anything from a leaking head gasket, a cracked block, or head.

If the oil level is low then AOS.

Now to add to the confusion the oil level may be ok even high if coolant has gotten into the oil.

Thus you might consider removing the oil filter housing and pouring the contents out into a clean drain pan. If any water...

If free of any water, then at least coolant is not getting into the oil.

Regardless, I'd strongly urge you to not start and run the engine any and be sure when you call for a tow you state the car's not a runner. You might go so far as to remove the fuse for the fuel pump so the tow truck operator can't try to start and run the engine behind your back. Or arrange to follow the truck to the shop and be there when he unloads the car nd the car is then pushed into the shop.

Sincerely,

MarcW.

and no signs of any fluids leaking. I did have an AOS installed about 4 years ago. I will remove the engine cover to take a look. The latent smell also seems like it could be burning rubber or a belt. I replaced the main engine belt about 2 years ago. The smoke was pretty major as if the engine was on fire. Thanks for the advice and I will not be starting it up until I can make some more observations and then get it towed to a shop.

And not necessarily meaning they've gone bad or are burning up, but perhaps you should have a look around the spark plugs.

turn to the belt. An idler roller bearing may have seized or the tensioner may have lost its tension or perhaps an accessory drive is for some reason exerting a huge drag or has even seized.

You'll need to expose the engine from the top and you'll need to expose the engine by removing the in-cabin engine access panel.

Use a good light and look at the belt very carefully.

With the noise and smoke I would think if the belt were the cause of this the signs should be quite clear, but look carefully. The belt is tough and could take alot of abuse before it is in tatters.

If you see nothing amiss no signs of any electrical fire or some hose or piece of plastic/paper/etc laying on an exhaust manifold, you can note the belt's routing, its direction of rotation and remove it and start the engine.

If the belt or an accessory drive was somehow responsible for the noise/smell by removing it and starting the engine you can shift suspicion once again to the belt or idler roller/tensioner bearing or accesssory drive provided the noise/symptoms are present upon a cold start or appear shortly (within say 30 seconds or so.

Sincerely,

MarcW.

Just want to make sure there are no complications with this approach. Thanks for the advice. This will be my next project once it warms up a bit.

... the water pump, the alternator, the power brakes and the air conditioning.
So, you can run the engine for a few minutes with no harm done, especially if the engine is cold and the battery is fully charged.
Happy Boxstering,
Pedro

Pedro Bonilla
1998 Boxster 986 - 311,000+ miles: [www.PedrosGarage.com]
PCA National Club Racing Scrutineer - PCA National HPDE Instructor - PCA Technical Committee (Boxster/Cayman)

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Racecar spelled backwards is Racecar

"Racing is life. Anything before or after is just waiting" ... Steve McQueen as Michael Delaney in "LeMans"

"If you wait, all that happens is that you get older"... Mario Andretti

"Being second is to be the first of the ones who lose" ... Ayrton Senna

you're ok and the engine's ok running the engine a bit.

(After my Boxster lost its coolant from hitting a tire carcass and busting a radiator the next day I drove the car from the gas station parking lot across the street to the Wichita Porsche dealer's service area with no coolant in the engine and no harm done.)

But you want to keep the running time to a minimum.

A few seconds, 30 or so, even 60 seconds is ok. When you start to run the engine closing in on two minutes... I'm a little uncomfortable with this. The engine's probably not going to suffer any harm, but I'm not going to make any promises.

The belt removal test and engine start is best used when the noise appears right at cold start or shortly thereafter. While the engine's probably ok even if you ran it a few minutes with no belt, one doesn't want to risk doing more harm to the engine in an attempt to diagnose a problem.

Sincerely,

MarcW.

I had been away from PPBB for quite some time and am glad to see Pedros Board is filling the void!

Pedro Bonilla
1998 Boxster 986 - 311,000+ miles: [www.PedrosGarage.com]
PCA National Club Racing Scrutineer - PCA National HPDE Instructor - PCA Technical Committee (Boxster/Cayman)

---

Racecar spelled backwards is Racecar

"Racing is life. Anything before or after is just waiting" ... Steve McQueen as Michael Delaney in "LeMans"

"If you wait, all that happens is that you get older"... Mario Andretti

"Being second is to be the first of the ones who lose" ... Ayrton Senna