Socal_Tom

Good morning. I am working on waking up the '87 S4 automatic from OR and I have a vibration I believe is related to collapse engine mounts.

After doing some research here it appears that the easiest way to test for failed engine mounts is to rev car up in park and look to see if the engine rocks when being rev'd up and down.

My engine is completely rock steady, which suggests the mounts are bad.

My question is if bad mounts would manifest as vibration at certain rpm ranges. More specifically - this S4 idles very smoothly and pulls very well but has a vibration that sets in around 2200-3000 rpm and then fades. This occurs in park (not moving) and when underway with the transmission engaged.

May not be related, but thought I'd ask.

Thanks in advance for the coaching.

FredR

Folks have reported vibration at around the 1400 and 2800 rpm points linked to mount degradation and when my S4 mounts went I noticed something along those lines.

kmascotto

The easiest way to check if your mounts are toast is measure the height from your intake manifold to the cross bar. if your mounts are good...it will look like this...if the straight edge (level) is hitting your cross bar...the mounts are bad.

kmascotto

and my jump post cover was removed for other work

FredR

Bullsh*t!

Socal_Tom

Ha ha, oh man, I am staying out of that one.

Thanks for the picture - makes it super clear.

My mounts have definitely collapsed, and good to hear that others with a similar condition have experienced the same vibration in a similar range.

Thanks gentlemen!

Bertrand Daoust

Tom,

Is the pressure on the flex plate has ever been released - checked?

Might also be something to look at.

Socal_Tom

Good morning - the trust bearing was checked and all was well, I believe that covers the flex plate being OK? Yes?

kmascotto

Haha...

kmascotto

I believe Roger still sells the Volvo mounts, which work well

Socal_Tom

Thanks, just bought some window switches from him and it was a good experience.

FredR

+1

Mrmerlin

FWIW the most accurate way to determine if the mounts are good is to look at the bottom of the oil pan,
if its level with the cross member then they are good.

FWIW the cross bar mounts can bend and if this happens then it will move the bar upwards.

If someone has fixed this,
then they might have used a sledge hammer to hit the mounts thus bending them down.

NOTE the vibration your talking about could also be coming from a failed TT damper
thats why it was installed to eliminate vibrations from 1800 to 3200

SeanR

Easiest way to test is to pop the hood, get in the drivers seat and look at the top of the engine. Crank the car and if the engine moves they are fine, if it's not moving either you didn't crank the starter or you have failed mounts.

Why make this harder than it needs to be.

Socal_Tom

My motor mounts have collapsed based on this and the engine level/height test.

Haven't personally gotten the car on a lift yet to check everything else, such as the TT.

Thanks gentlemen!