coriard

Hey all,

Here's the scoop. Whenever I am in gear and am using the pressure of the engine to slow the car down (usually down hills), I'll get one of two symptoms. When I am using an average amount of engine pressure to slow the car (2-3k RPMs down an average hill), it will make a metal on metal 'whack!... whack!... whack!.. whack whack!' sound that gets faster. Or, if I am in a high gear and going down an average hill at low RPMs, like 1500 RPMs, over time it will start to shoot enough lighter smoke out the back, so that I can easily see it in the rear view.

Earlier, I had a very helpful guy on here say piston rings. But now I know these symptoms in detail. Keep in mind, who knows if they are related. And my clutch is pretty worn. Could that be the issue?

THANKS!

Loudgoldwing

The rhythmic metal pounding on deceleration is likely your timing belt tensioner clanging against its housing because it has failed. Think of it this way:

When you accelerate, the top side of the timing belt is pulled taught like the top side of your bicycle chain when you're pedaling. When you decelerate, or go down a hill, the top side of your chain would then go slack, right? The timing belt is the same way, but there is a spring-loaded tensioner mounted above it. When the top part of the belt goes slack, the spring-loaded tensioner pushes against the top of the belt, pushing against the slack and keeping the belt from slapping up and down.

What seems to be happening is that the spring in your tensioner is shot, so as you decelerate, the slack of the top of the belt is flapping up and down, bouncing the now zero-tension tensioner up and down against its metal housing. When you speed up, the top of the timing blet goes tight again, and no more tensioner-bounce clanging.

Drawing the next logical conclusion, the slack in your timing belt is causing your exhaust valves to open a little prematurely, and allowing a bit more unburnt fuel than usual to blow out the back. Hence the smoke you're seeing in the mirror.

I can tell you that your vehicle is currently on a downward spiral toward the wrecker's yard at the moment. This isn't something to mess with when you drive a car with this specific engine. Whoever replaced your thermostat may not have replaced/reinstalled the timing belt and tensioner properly. If the timing continues to deteriorate, the intake valves might still be open (and protruding into the combustion chamber) when the piston is in its upward stroke. This engine is designed to run in a VERY specific timing pattern to avoid this scenario, as it is one of the few catasrophic failures this otherwise bulletproof engine can experience.

This is kryptonite bro. Please don't mess with it.

coriard

Excellent reply. Exactly what I needed. THANK YOU.

Here's the situation. I'm a college student who can't really afford to have a timing belt, tensioner, water pump job done on this car. And while this sounds like neglect, I love this car and Audis in general, but that's just the truth. So here's my point: Is there harm being done if I go down EVERY hill in neutral unless I'm accelerating? That's how I've been driving the car since I first figured out these symptoms.

If this would allow the car to continue on without any more damage done, then in a year, when I get a real job, I'll be able to fund the surgery this awesome car wants and needs.

CRAZY_RUSSIAN

i dont think its going to last that long! you are lucky its still running! you should be able to do this job with a basick set of tools

coriard

(Just to clarify your guys' point...) But a timing belt and tensioner job will do the trick? The car is still worth my time, yeah? It will all be straightened out if this job is done? I don't have the expertise or confidence to do it myself. I'll need to pay someone to do all that.

bronxnativ

Water pump, tensioner, and timing belt replacement in a shop will cost between $500-600.00. Is it worth it, yes!!!! Anyone will tell you that our cars last longer than an energizer bunny. I too am a college student. Dont you have a financial aid check coming next month for fall semester???? Might be wise to invest part of it in your car, ESPECIALLY if its your only source of transpo.... Not trying to get personal, just trying to offer suggestions

Loudgoldwing

Based upon the (now more detailed) explanation you've given... Yes, I sincerely believe that this is your issue.

I also sincerely believe two other things:

One, I personally love my vehicle enough that I wouldn't want to tackle this work myself... and that's saying something. This is a VERY precision-required set of tasks we're talking about here. Can I do it? Yes. But, every hiccup and sputter that I feel from that point forward would scare the Hell out of me.

Look at it this way. You've made it this far without a major expenditure on this vehicle. The Teutonic Piper is now calling your account due. So, do you sell your body to some well-to-do cougar for a night of well-lubricated delectation in order to scare up some jing? I guess it depends on how much you need your own ride. Because you know as well as I do that spending $600 on a car you know is a FAR better bet than $600 on buying a car you don't know.

So, suck it up, Buttercup. Go shirtless in front of a couple of your frat-bros' Moms. Shake your money maker. You'll think of something to come up with the cash if it means that much to you.

And two, your car is dying. No foolin'. No BS. Dying... as in floating at the surface of the fishtank, right-side-up and gills still moving, but if the cat even looks at it cross-eyed from across the room, it will flip over and end up in the toilet.

Tellin' ya. Kryptonite.

coriard

Alright. This is a dicy situation for me. Just got off the phone with the mechanic who has done everything else for me on this car. He's done a lot of work on this engine on lots of B5's.

Loudgoldwing, I pretty much summarized your thoughts behind the clunking and the smoking, and he thought that the clunking tensioner was a realistic thought, but he thought that it fixing the smoking shouldn't be expected.

Here's my point. If I'm going to have to the tensioner, I might as well have him do EVERYTHING that he can reach while he's there. The bill for that will probably be around $1100 or so depending on everything else he does. Valve cover gaskets, cam tensioners, etc. (I think that's what he said).

And while I want to keep this car for years and years, the way it is driving now has been reliable. Last weekend, I just did a 700 mile round trip to a friend's wedding with NO problems.

So... I'm not questioning your judgement, but I am only trying to get to the bottom of this. Is there ANYTHING else you could think of that could cause these symptoms? Perhaps something in the drivetrain causing the clunking and something else causing the smoking? I just don't want to drop a grand and not have a problem fixed. (And yes, I know it should be done anyways, but rent comes first, and I can't exactly ask my dad for a $1200 loan from his wallet without decent assurance that everything on my car will be fixed for good.)

Thank you Loudgoldwing, bronxnativ, and crazy_russian for the replies. Cougars are in short supply during the summer, maybe there will be some who will offer a pretty penny when they come to move their daughters in here in a month or so. 8)

Loudgoldwing

Timing belt tensioner... definitely.

Smoking on deceleration... I know that there is an automated system that changes the fuel/air mixture ratio on deceleration. It IS possible that whatever it is that does that is malfunctioning and blowing too richly out the back end.

Lemme do some research and get back to you.

coriard

Thanks again Loud, looking forward to your reply.