Diagnosing motor mounts ('87 924S)
 

I am brand new to the transaxle cars. Finally got my 1987 924S (5-speed) "barn find" running. I am stoked although there are a lot more things to do to the car.

One of the problems is lots of vibration at idle. Above about 1,200 RPM it smooths out somewhat. At about 1,500 PM on up the vibration is gone. I increased the idle to about 950 RPM as recommended on another thread. No change. I suspect it's the notorious 944 motor mounts.

Although I'm not opposed to just replacing them since they are a known problem anyway, I'd prefer to actually know how to make sure they are the problem. Suggestions for steps?

Also, is there a best practice for buying the new mounts. Did Porsche fix the factory parts or is there a high quality aftermarket that is recommended?

Vibration at idle is almost certainly motor mounts though the term “vibration” is open to interpretation so it could be something else. Is your t̶i̶m̶i̶n̶g̶ balance belt fitted correctly? If it is off or 180 degrees out on the lower shaft (common mistake) this will also cause vibration.

Best way is to inspect them for leaks and measure the heights as per the manual. There are no good quality aftermarket mounts, genuine Porsche mounts are the only ones that last and provide no vibration.

I think I've got the belt on correctly ...
 

It is a pronounced vibration. The car runs strong otherwise and I'm very pleased with the performance. This was the first time I ever drove a 924/944 and I was pleasantly surprised. If you're referring to the balance shaft belt and cogs, I quadruple checked it, using guidance from Bruce Arnn and Clark's Garage tutorials. I also used Bruce's tools which are excellent BTW. Pretty sure the car won't run and would probably grenade if the timing was 180 degrees off. Based on the sight checks, it was spot on when I took the belts off. I also looked at the YouTube videos that were produced by seemingly competent people.

Gratefully, there are no leaks anywhere with anything since I went over the car. I'm holding my breath but so far so good.

Thanks for the recommendation on buying the Porsche made parts. That has been my preference when available with most everything I've done so far.

Oops I meant balance, corrected my post. It’s quite a common error getting that lower balance shaft 180 degrees out. I’ve heard experienced folk swear that it’s correct as they followed instructions yet I found it 180 out. However it’s easy to diagnose as it will vibrate at around idle and also quite badly at one other specific rpm in the rev range, otherwise ok elsewhere including at max rpm.

Sounds like you have everything covered though, like I said check the mounts are to spec in accordance with the manual.

Anything is possible ...
 

I'm a shade tree mechanic but I kept checking the markings on the balance shaft cogs because it was clear from everything I read that they aren't intuitive and it is exceedingly common for them to be 180 degrees off. As you said, that doesn't mean I got them right.

The good news is that there doesn't seem to be another rev range that the vibration comes back. I only took a short test drive since I can't get tags without an emissions test so I suppose there could be one but I didn't feel it. I did run it near red line a couple times so I was pretty close to all rev levels.

I looked at the factory manual and the Haynes and didn't find any specs for motor mounts. I suspect there is a procedure as well to find out what the specs are while on the car. Any hints are very welcome.

The top half of this may help:

http://forums.pelicanparts.com/uploa...1565020080.jpg

Source: 9technik

Sounds like classic motor mounts. I am running Meyle mounts from FCP Euto. Many people say they won't last, I hope they do.

There is vibration with Meyle the moment you fit them, not like worn mounts but it’s still there, whereas with Porsche mounts there’s nothing. Another problem with Meyle is they go out of spec really quickly, if you get 6 months out of them you’ve done well. Then again most folk probably think the vibration is ok and it’s not until they completely fail and start clunking that they change them.

http://forums.pelicanparts.com/uploa...1565034000.jpg

Thanks for the bulletin and more advice on the parts
 

This is fantastic.

BTW, got the car Colorado emission tested this morning and it passed but not by much. It qualifies for collector car status so I won't have to mess with it every other year like a regular car, every five years instead.

I agree 100% on the Meyle mounts. They were great for the first couple months after I installed them but seemed to slowly degrade after that. Vibration is no where near as bad as failed mounts but still noticeable when cold. I drive mine all year round so I can tell you there is a difference between a -20 degree C cold start on fresh mounts vs ones that are a year old.


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Cost is the culprit
 

Reading between the lines, it sounds like most of the notorious 944 motor mount problems come when owners use after market parts rather than Genuine Porsche after the original parts fail. Porsche parts cost about five to six times more money. Do the Porsche-made parts last five or six times longer? If you take into account paid labor or the time and aggravation for DIYers you probably come out about the same. Might as well have the better part.

This actually brings up another question. Lindsay Racing makes mounts that appear to be much tougher but more rigid than standard. They look like they would last forever. Is the problem with using those that you get no real improvement in driveability and comfort than failed stock parts for a daily driver?

Another question: It sounds like a lot of the problem is the mounts are not protected from engine heat. Has anyone tried using a heat resistant foil wrapping to lower their heat damage?

When I bought my car in 1986 I didn’t need to change the original mounts for over 15 years (92,000 miles), the Porsche set I replaced them with are still on the car and still good.

The Lindsey mounts cause noise, harshness and vibration, they are fine for a dedicated track car where that doesn’t matter and the oil pipe and fuel rail issues have likely been addressed.

The rh mount is subject to more heat than the lh mount, there are heat shields on both mounts but if you run without an under tray it’s likely the airflow isn’t correctly directed to the mounts, so yes that may be an issue that could be addressed by wrapping.

Great advice!
 

That is all I need to know to be sure to buy the Genuine mounts.

My car doesn't have the tray but I finally found one and ordered it. The bulletin you included also pointed out that one of the air vanes in the tray should be redirected to help keep the mounts cooler. After that, wrapping them seems to be a good idea too (belt & suspenders can't hurt).

No problems to report with my Meyle mounts, this is the second summer where they are getting a decent amount of use and they have been fine. If someone has installed pics of genuine installed Porsche mounts on a 968 or S2 maybe I can compare that to mine. Or a video showing vibration.

When I was shopping I determined that there were no recent reports of problematic Meyle mounts and that the company also had issues with some other rubber parts in the past but had improved. I suppose it comes down to the quality of the elastomer and manufacturer.

Thanks, Jfrahm!
 

More input and experience is always better than less.

Porsche 95137504204

Probably won't find the mount any cheaper (remove asterisks):

https://www.sonnen*porsche*oem*parts.com/oem-parts/porsche-front-mount-95137504204?c=Zz1lbmdpbmUmcz1lbmdpbmUtbW91bnRpbmcm bD0xJm49QXNzZW1ibGllcyBQYWdlJmE9cG9yc2NoZSZvPTkyNC Z5PTE5ODcmdD1zJmU9Mi01bC1sNC1nYXM%3D

$195 each is a good price for OEM, I'm still OK with the risk saving $300 with Meyle until it's determined that the current parts fail early. I nave not seen any recent reports of such.

$195 each is a good price for OEM, I'm still OK with the risk saving $300 with Meyle until it's determined that the current parts fail early. I nave not seen any recent reports of such.

Motor mounts were the answer
 

As was nearly universally recommended, replacing the motor mounts was the solution. The car is now driveable, better than driveable. And as everyone also said, they are a bear to replace. Thanks to all.

I have a new set of URO motor mounts I’ll be testing ... once I get to that stage of the proceedings. John