New Question about "droan" noise and motor mounts?

[Vroom]

12/2/01 New possibility: I’ve taken my 86 951 to Rennwerke in Elmsford, NY. After a preliminary test drive, they found the noise, and are 90% thinking that the noise is from the motor mounts being weak, and a harmonic vibration/droan being caused by that. They’ll look in to it further next week. Apparently, they had used a lever to pry the engine up from the mounts and the noise quieted, not sure if completely or not? I was told that when a “mount” is healthy, you can’t see the bolt/nut. You can see them on this car. I was told that if the motor mounts are the problem, the parts themselves run about $100 each and that the labor on one is easy, and the labor on the other is harder. Are there two motor mounts or more? Do motor mounts cost this much on a 951? Has anyone else had harmonic noises from weak mounts? Is one mount hard and one easy? What do you think?

Thanks, Ave




10/17/01 Noise continues from engine exhaust area. Has anyone been through this?

The noise comes on after the car warms up and while driving. A droan between 1900 and 3000 rpm, in gear or in neutral. Rennwerke in Elmsford, NY, agrees with my tech, it’s not hurting the car. The parts guy at the local dealer said there was a service bulletin regarding exhaust manifold double walled pipes, on 944 Turbos, breaking up, and that the new replacement parts would solve that problem, but that it was an expensive job.
Have any of you had the same problem? It drives me crazy. When I get off the highway, I can still make the noise by idling in the 1900 and up range. But a minute later, it’s gone.
If I can determine which part is the culprit, then the mechanic can change it. He just doesn’t want to waste my money looking for it. I’m hoping that it’s a problem some of you have also had, and that you can lead me to the culprit??
Thanks,
Ave 1986 944 Turbo 140K

[JoelChicago]

You and I have similar problems. I also have higher miles on my '86. I have a real harmonic problem with my car (low frequency vibration is about enough to make me crazy), and it's definitely the mounts. It's not about the bolt visibility, it's about how long they've been in there, hardening and shrinking.... I found that you can buy the mounts for about $55 and have them installed. It's about 4 hours labor, I was told, to get both done. Can't get it done under $300, basically.

As for the exhaust, that's exactly right. There are replacement parts. Again, I have a similar problem, but not very pronounced - sounds more like a heat shield rattle on mine, so mine's probably a little worse than yours, but I hear the groan at select RPM as well. When I get the time, I'm diving into it.

[Scott R]

Replace the mounts. I have gone through this issue twice now. Once on my NA and once on my 951. The mounts are liquid filled and leak over time, and get weak. I purchased a set off EBAY for $40 and replaced them myself. Took 1.5 hrs per side. Easy procedure and only requires basic tools. Here is a link to the procedure:

http://porsche-944-garage.tripod.com/

[Vroom]

Thanks guys. I never suspected the mounts until my new mechanic mentioned it. He says the mounts new from Porsche are about $101.99 each and he's allowing 3 hours labor for this job. Ian's Parts confirmed that new mounts run about $95 each through him. Though lesser expensive aftermarket mounts are available in the $65/mount range.

Did you have the same droan noise and did it clearly go away?
Have either of you had problems with the exhaust pipes or short pipe coming out of the turbo causing droan/groan noises in all gears, fully warmed up , in 1900 to 3000 rpm range?
Ave

[Scott R]

My vibration was causing all sorts of weird noises. But on another note I had a droaing whirring noise on my 85.5, and it turned out to be a roller beaing for the balance belt.

[geoffbaltz]

From my earlier reply:

My 86 951 had a terrible rattle that we couldn't find either.

1st) Thought the O2 sensor was rattling in the exhaust - that was fine. Still rattled.

2nd) Thought the double-walled downpipe had separated - replaced it with 3" SS downpipe and cat bypass from fabspeed. Still rattled.

3rd) Checked the turbo, the heatshields, and anything else that might be loose. Still rattled.

4th) Replace the small (8" long) pipe that comes right off the turbo and the downpipe bolts to. THAT WAS IT!! That pipe is double-walled also and had split on the inside where the inner pipe is welded at the flange on the turbo side.

Smooth as silk now and no noises.

I have the original part still - I will snap some shots tonight and post them here of the split on the inner portion of the pipe.

BAD NEWS: THIS PART IS NOWHERE TO BE FOUND IN THE USA. I HAD TO ORDER FROM PORSCHE AND IT CAME FROM GERMANY AND TOOK ABOUT 10 DAYS. $400 FOR THE PART.

I would NOT replace it with a used one either. You are just asking for problems. This pipe is subjected to some serious temps and the expansion and contraction takes it's toll. Not easy to get to either.

**************************

You might as well replace the mounts since they are inexpensive and the job is simple. I hope that is it. If not, I still think that the pipe off the turbo is your problem.

Good Luck again.

-g

[eimkeith]

As I stated before, (and in agreement with Geoff) - it sounds like it is the downpipe from the turbo (that's what that 8-11" or so piece is called...)

If you have to replace it, you might as well go for the 3" one from SFR for $350.00...

I'd live with it until you had to do turbo maintenance or upgrade - It is a PITA to deal with.

[Vroom]

Well, the motor mounts were changed. But, noise is still there. They checked the timing belts and discovered that they were over tightened, so they re tensioned them. But now say the noise is even worse.

The rep from Porsche is going to come down to the shop soon and will drive the car with the shop manager to try to isolate the problem. They are trying to avoid charging mechanic's time to search for this.

Anyway, I will mention what you guys have said and see if that helps.

Let me know if you have any other thoughts on this.
Thanks.