[flash]

this is exactly why i asked the questions i did.

 

i am betting on exhaust hangers being shot or missing.  the one up towards the front would be my first thing to check.

 

the other thing that might be happening is motor mounts.  they are oil filled, and when they get old, and get hot, they sag.  that could be just enough to make something make contact

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[edm]

Thanks AZ968, funny to see your in Arizona as I go to Scottsdale (Moms , and Sisters place ) and my boys live in Surprise, I go there every 2 months to see my Boys and Grandkids.


Thanks Flash, but the motor mounts are brand new.

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[968workaholic]

Tiptronic motor mounts are different than manual motor mounts, make sure the right ones were installed, just one more thing to check lol

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[flash]

agreed.  all the more reason i was asking the questions i did.  i would suspect brand new parts long before i would suspect old ones.  had i have known those were brand new, they would have been the first thing to look at.

 

it's counter-intuitive, but most people make the very common mistake of thinking a brand new part is not the cause of a problem.  frequently it is exactly the cause.

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[edm]

will do, Thanks to all

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[ds968]

But the thump is in the rear of the car, so if the motor mounts are possibly to blame ( not doing their job as well as they should ) are you guys saying the entire drive train moves as a result of it and the place that movement stops is at the rear of the car when it " bumps " against something and causes the thump ?

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[RS Barn]

I don't remember anything that took extended driving to show up? Max?

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[flash]

dan - yes - it may not seem plausible right away, but it is if you think about the fact that the entire drivetrain is solidly locked together.  when you lift or drop one end, it has an affect on the other end.  i have seen the exhaust hit things and make a racket after the car warmed up.  i have seen the motor mounts sag when warm, and cause the exhaust to hit the lower brace.  this kind of thing is especially true of tiptronic cars, where the transmission is much heavier, but most of the supporting parts are no different.

 

there are plenty of things that change as things warm up.  i could even do the math to tell you how much the motor mounts change in height relative to heat expansion (though it would give me a mean headache and cost me a few bottles of wine).  the concept is pretty basic stuff any mechanic should know and be able to measure though.  that's why there is a minimum tolerance measurement on the mounts.  they take into consideration the change due to heat.

 

the first thing i would do is verify the part numbers of the motor mounts, and measure them.  then, i would inspect carefully the exhaust hangers.

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[Ryan]

Note RS Barn has 968 posts

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[94SilverCab]

  Forever enshrined

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[az968]

geez, and it wasn't even a profound post, what a let-down :unsure:

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[ds968]

Profound or not    I'm thrilled to see Pete and Max back in ( our forum ) action ; the wealth of 968 information between them, and/or singularly, is phenomenal so it'll be of immense value to everyone here !       

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[ds968]

As for the heat-induced noise symptoms, just to follow up on Flash's comments ;  it's surprising how many things can be affected by that heat factor -  I understand noises when things are cold and on start up like my loud alternator bearings, or belt squeaks, or other annoying sounds which all go away after the car has been driven for a few minutes and warms up, but the lack of any sound whatsoever all the way up until the car gets really hot after being driven for at least half an hour and only then they start manifesting ...like my ( suspected wheel bearing ) whirring rumble on turns, and rocks clonking in a bag going uphill or on moderately quicker take off from a stand still.              

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[Bulti]

A comment on the motor mounts, just in case: if they are not OEM, they could have failed almost the minute they were installed.


So, check if they are the real deal.


On Clark's Garage they mention a minimum (!) height of 60 mm between the load bearing surfaces of the installed mount. If I'm correct this applies to 968 mounts as well (manual transmission). I for one discovered that my brand new non-OEM ones were total rubbish.

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[Bulti]

And maybe it's worth checking if the brake pads aren't rattling in the calipers. I had a strange clunk that came and went for a very long time before I discovered it was just a brake pad making the noise.

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[edm]

I don't think it's the brakes or pad because it is a noticeable "thud" or "thump" underneath the rear. Thanks for the input.

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[williamoss]

Profound or not    I'm thrilled to see Pete and Max back in ( our forum ) action ; the wealth of 968 information between them, and/or singularly, is phenomenal so it'll be of immense value to everyone here !       

For the less knowledgeable what is Max's handle on the site?

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[williamoss]

Now for my thoughts of a thumping noise. When I bought my 968 coupe from Pete, he gave me a set of wheel pacers. They are approximately 3/4 inch
thick. When I put them on I got a thumping noise on the right rear not the left rear. I took them off and the noise went away. Is it possible you
have some sort of spacer on those wheels?

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[edm]

Max, welcome back, I don't know if you remember me. It must have been the month after the Sandy storm in NJ I dropped off the car at you shop for a few weeks, it was a 1993 Cab Tip amazon green.


no spacers, the 17" wheel and tire was purchased at Tire rack, while the 16" wheels are OEM.

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[968workaholic]

My 968's are starting to blend together, unless it was one that needed a ton of tlc lol. As for the wheel/ spacer combo, it sounds like the setup may have not been hub centric, causing the noise. I have seen a few cars with this, but it manifested as more of a vibration rather than a clunk/thud

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