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Sitting on the side of the road Loud engine rattle on 91 S4

3K views 28 replies 10 participants last post by  Robertinwc 
#1 ·
Hi all

I'm sitting on the side of the road waiting for the tow truck. Just drove about 12 miles through San Pablo Dam Rd. A lovely winding hilly road here. When I came to the end I back off the accelerator and heard a loud rattle. Pulled into a empty parking lot and it's definitely an engine rattle / knock. Not good.

I didn't over rev. Maybe 3500??

Engine oil is topped up

Any ideas? Prior to this she was smooth and quiet.

Thanks!!
Robert
 
#3 ·
Sorry to hear about your troubles. Did you have oil pressure before the engine was shut down? How about the engine temp, was it normal? Rattling noise could just be loose exhaust or fan shroud that has come loose. Nothing leaking from the engine? Hopefully its something simple like that and not actual engine damage. Let us know how you make out.
 
#4 ·
Hey Steve. Thanks for the note. Got towed home. Oil pressure was good. Temp was also. I started it briefly and it was running rough. Never ran rough before.

I was thinking maybe the cam chain got too slack. ( the car is new to me. Only Had it 3weeks). So I took the valve cover off. Chain is tight.

Have the plugs out to try and turn in over by hand but don't seem to have the right sized socket. So instead I turned it over with the starter. Turned fine. No noise.

I'm thinking engine noise combined with rough idle it might be valves??

Can the variable timing go bad and do something like this?

I'm at a loss as to possibilities.

Any input GREATLY APPRECIATED!!!
 
#5 ·
Have you checked out the spark plugs for health?

A compression test would then be good.

If you have only had it three weeks, you may not really know how solid the engine vacuum system is- check the main rubber intake boot to make sure it's still seated properly, and any other vacuum lines.

Sometimes that boot can work it's way loose if the motor mounts are worn and the engine moves too much...
 
#6 ·
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#7 ·
Thanks for the input guys!! Good idea to check the cam timing and I should do valve clearances too!! Although I don't think the cams are off timing because the engine has been running so sweet.

In response to someone suggestion that I check non engine items I've been poking around a bit. I did find the pulley on the water pump can rock back-and-forth a bit. Not much. But When it does it makes a clunking sound. Are water pumps supposed to have that movement ?? Maybe I found my problem? It would be a engine speed occurance. The car has sat for a long time prior to my purchase and I don't think that's good for water pumps.

Thoughts?
 
#9 ·
I did find the pulley on the water pump can rock back-and-forth a bit. Not much. But When it does it makes a clunking sound.
not normal

you could remove the belt to waterpump and start it up (it won't harm it for a short time), if the noise is gone, you have a bad waterpump bearing, maybe even the pulley has just come loose (less likely though), which is a lot better than engine damage!

not sure how easy that is on a US S4 as I guess it will have aircon, and, you might have to remove the big ribbed belt first.
 
#10 ·
Vin

I checked the timing marks on the cams and main crankshaft pulley tonight. They all lined up the way they are supposed to. Thanks for that link on how to find tdc! Also checked the valve tolerances and they are all a little tight. I'm going to start a new thread and get some feedback on whether I need to adjust now or can I hold off a bit.
 
#11 ·
Spiderserie4

Good idea. Today I rechecked on movement of the pulley. It's definitely there. Small but enough to make a metallic clunk. I've taken the belt off and when I'm done with putting the valve cover back on I may just try to start it to confirm that the issue. Although I may just move forward with replacing the water pump.
 
#13 ·
Btw I did make an attempt to check compression but my gage is leaking. I could see the needle jump up to about 125 or so but then quickly drop. So I think the compression is ok. (I knew from using the gage before that it was leaking)

While 125 is low, the engine is cold and with a leaky gage I didn't get the advantage of several cranks building pressure.
 
#16 ·
Yeah the water pump clunking is not normal and is almost certainly the source of your noise.

Water pumps can be strange. On my Milano I had a pump that made a lot of noise, and had lots of play in the pulley, yet it was not leaking and the car ran at's normal temperature.

I had a Ford van that was leaking like a sieve through the weep hole in the water pump, yet the water pump pulley was solid as a rock. When I removed the pump the pulley was still solid, so apparently the seal had failed but the bearings were still good. Presumably if I had left the pump in place, kept filling it up with coolant, the bearing would eventually have failed from being exposed to coolant and the pulley would have developed the rocking motion that is the normal sign of impending water pump failure.

Bye
 
#21 ·
Several suggested that a water pump always leaks before failing.
if the bearing has failed
but, you wrote: I did find the pulley on the water pump can rock back-and-forth a bit. Not much. But When it does it makes a clunking sound.

the pulley itself might have come loose from the pump....tried to get a wrench on the 3 bolts there? are they loose?
 

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#22 ·
Spiderserie4

Good idea. I did check that earlier and they were tight. I've got the old water pump off now and the impeller is plastic/ nylon and the shaft definitely moves and there is a clunking noise when it does. The new water pump is rock solid by comparison. I've cleaned up the front of the engine, put a new lip seal on the crankshaft and I'm starting to put the car back together. Hopefully I'll have it back on the road tomorrow afternoon
 
#23 · (Edited)
Update!! It was loose nuts on the exhaust manifold! So after replacing the water pump and front crank seal, and the belts and radiator hoses, I started it up and I STILL had the horrific noise. I couldn't believe the car had a major mechanical malfunction, but my this thing sounded really bad.

I found myself scouring the forum here and came across an old post where someone had a similar situation as mine and it turned out to be the exhaust manifold hold down nuts. The thing is they said it sounded like a mechanical noise, and NOT an exhaust noise. So I went out to the garage and all of them were loose. By several turns. And they could easily be spun by hand!!! So I tightened them up and it was over...

I never imagined it could be those. Like I said it didn't sound like an exhaust noise. And most exhaust manifolds I've dealt with are a huge pain to get those nuts loose. You're worried about them breaking when you try to take the manifold off!

So I'm back on the road, with many smiles per mile. Thanks to all who responded, and what a resource the collective knowledge here is. Without that old post it would have never occurred to me to check the manifold nuts.
 
#27 ·
I agree!! Not wasted time. All that work should have been done anyway. Old water pumps, hoses and belts, plus a leaking front crank seal. There was so much built up crud on the front of this engine that I took a putty knife and it literally peeled off in strips. Now I have much more confidence in it and I know a lot more about this car. And it's prettier under the hood. :cool:
 
#28 ·
Glad you got it all sorted and are back on the road.

I would never have guessed exhaust manifold nuts.

Will have to keep that in the memory bank.

Vin
 
#29 ·
Vin, that's one of the reasons I had to tell people here. And put it in the archives. I never would think of exhaust manifold loose, and like said before, it didn't sound like an exhaust leak. This was a mechanical sound.

It also explains why it kept getting so much worse so quickly. As the nuts backed off it got worse, and the worse it got the nuts backed off more.
 
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