Cloud9...68

I apologize in advance if this is going to be a long post, but I want to make sure I give everybody all the relevant information of my extremely frustrating problem on my '92 968 mostly-track car. Here's the chain of events, all of which involve my engine mounts directly or indirectly:

1) In November of 2019, while doing a track session, my car dumped half the oil in its crankcase. Investigation revealed an oil line from my dual oil coolers had been sliced, apparently by one of the pulleys. Further investigation revealed both of my engine mounts were toast - in particular the one on the passenger side literally crumbled in my hands, but the other one was also split pretty bad. The mounts were about 13 years old, so I chalked this event up to mounts that had outlived their service life and consequently failed in the heat of battle, allowing the engine to move enough to allow the pulley to hit the oil line. So I replaced the line, and replaced the mounts with Lindsey Racing "Ultra Mounts" because they seemed like a nice design, and they're a little cheaper than Porsche OEM mounts. I also replaced the connecting rod bearings out of caution since I had lost so much oil (the ones I pulled out looked brand new).

2) At my next track session, about mid way through, I noticed the car vibrating quite a bit, and saw black smoke in my rearview mirror, so I immediately pulled in, to discover that I had again dumped a bunch of oil on the track. I also noticed the power steering tightener dangling loose, attached only on one end. So I rode home from my second consecutive track session in a tow truck, and began investigating. The cause of the oil leak was quickly apparent - the bolt securing the lines to the block had backed halfway out. I also noticed that the rubber isolator piece in my right Ultra Mount had completely shredded, and I also discovered that my balance shaft belt was ridiculously loose, causing the alignement of the balance shafts to be miles out of alignment. Many teeth on the belt had worn very visibly as well, so I assume the balance shafts were essentially freewheeling, creating the bad vibrations. And when I say the belt was loose, I want to emphasize that it wasn't the kind of loose that happens because it needs an adjustment a few hundred miles following a belt change - it was literally drooping. But surprisingly, the bolt securing the belt tightening eccentric was fully tight, as were all the other nuts and bolts in the belt assembly, so I have no eartly clue how the belt got so loose. Maybe the belt itself was defective (it was a Conti belt). So my theory was that the loose belt was the root caused the vibration which shook loose the oil line bolt, the bolt securing the power steering belt tightener, and several other random bolts, and that this extreme vibration somehow destroyed the engine mount rubber isolation piece. So I replaced the belt, making damn sure I tensioned it correctly, and left the covers off so I could easily check its tightness on a regular basis. I replaced the rubber isolation piece from my right Ultra Mount with a new piece.

3) After getting everything back together, I've been driving it on the street (bought a set of spare wheels and street tires); I've put maybe 300 miles on it since getting everything back together. Initially, everything was very smoothe, but today, I noticed a pretty bad vibration, particularly at idle, and when pulling away from a stop, so I look under the car when I got home, and I'll be damned if the same engine mount's isolation piece isn't shredded again! The BS belt tightness is fine. The car has not been to the track since the most recent mount replacement, and I've actually been driving it pretty gently.

So, either there's something fundamentally wrong with the design or build quality of the Ultra Mounts, and I need to go back to Porsche OEM mounts, or there is something that is causing these mounts to fail very rapidly. It's strange that it's always the right mount, since there's no evidence of heat damage (I can easily pull the shredded rubber isolation piece out by hand). Yes, I put the heat shield back. My transmission mount is original, so of course I need to replace it, but there's no sign that it's actually weak - I can barely move the transaxle when I try jerking it from side to side. The car also shifts very smoothly, despite its age.

Does anybody have any experience with these Ultra Mounts? Before I order a set of Porsche OEM mounts (which have gotten ridiculously expensive, but oh, well), is there anything anyone can think of that I could check that could explain why my car is so rapidly destroying its mounts? Thanks in advance.

Chris White

are you sure you have the balance shaft gears in the correct keyway? it sounds to me like the mount failures are not a cause but a symptom of the real problem.

Cloud9...68

That's a valid question - I haven't removed the balance shaft sprockets over the past several belt changes, and was careful to get the gears in the correct keyways the last time I removed them. Seeing as the issues I'm having are very recent, and the fact that the engine revs very smoothly to redline, tells me it's probably not a balance shaft keyway alignment issue, but it sure wouldn't hurt to check it, since I agree that it's seems more likely that the continual engine mount failures are a symptom of the problem rather than the cause.

Any idea why the passenger side mount is the one that keeps failing, while the driver's side mount is fine? Also, any experiences out there with these Lindsey Racing Ultra Mounts? Thanks.

Dave W.

Since the engine is tilted to the right, the passenger side mount carries most of the weight.
If the balance shafts are out of phase, the extra vibration will be most apparent around 3k rpm.
Be sure to use genuine Porsche engine mounts, they're better than the cheap 'equivalents'. Also, since it's a track car, make sure your not shocking the driveline with aggressive upshifts and downshifts.

Cloud9...68

Ah, yes, it makes sense that most of the weight of the engine would be on the right side.
For the blink of an eye before the mount failed, the engine was very smooth throughout the rev range, including at 3000 rpm.
I understand the recommendation to use genuine Porsche engine mounts, but before I fork over $600 (!) for a pair of new mounts, I want to make sure there isn't something going on that can explain this most recent failure, because the last thing I want to do is use the uber-expensive Porsche mounts as guinnea pigs.
If anything, my data acquisition graphs suggest my shifts are way too gentle and lazy - I'm easily losing a half second a lap as a result, but I haven't had a chance to work on that, because my car keeps destroying its engine mounts.

MAGK944

I know we have had this discussion before but just entertain me and before you get new mounts would you rotate your rh (lower) mount 180 degrees and see if it runs smoother.

Btw you can get the genuine mounts cheaper by going to one of the Porsche dealerships who sell online like Sonnen. Still $500 but a saving of $100 right there.

Cloud9...68

It's too late to do that - the rubber isolation piece on the RH mount is already completely destroyed.
I had a long discussion with Dave Lindsey today, and he suggested I look at whether I possibly unwittingly loosened the bolt that holds the Ultra Mount together as I was tightening the lock nut the holds the mount to the cross member. Also, as we were talking, I remembered I had a lot of trouble getting the thread from the bolt in the mount to go through the hole in the cross-member on the right side, so we're wondering if I damaged the isolation rubber piece as I was struggling with this step. I will remove the mounts either later this week or over the weekend to investigate to see if the bolt is still snug in the mount, or if there is any evidence of damage to the mount from my struggles to get it to go through the hole in the cross-member. I have a hard time believing there is anything fundamentally wrong with the design of the Ultra Mount, and it looks to be well designed, and their quality appears to be excellent. Jason from Paragon told me he's never had any complaints from anyone he's sold these mounts to, and Dave told me the same thing, and they've been selling them for nearly 15 years.

MAGK944

Oh man sorry I must have keyboard dyslexia. I meant to say balance shaft cog not mount. So, rotate your rh (lower) balance shaft cog 180 degrees and see if it runs smoother.

HY M8NC

I Agree with MAGK - it's always good to make sure the balance shaft cogs are correct - and the tensioner is turned the right way. As far as the mounts, I have semi solid engine mounts and trans mount. I have been told several times that if you have factory trans mount, and semi solid engine mounts - the car won't like it. Basically the driveline becomes a pendulum in the car connected stiff at one end and soft at the other? Dunno if it's true. And you mention the trans mount seems good. Just thought I would throw that out-

Cloud9...68

I agree it's good to check to confirm I have the balance shaft cogs set correctly. However, as I said, I set everything several belt changes ago, when I replaced my rollers, and haven't touched them since, and the engine has run extremely smoothly all that time, so it seems very unlikely that that's my problem, but it doesn't hurt to check. I hesitated because I don't have the special tool that holds the balance shafts still while I removed the bolts holding the cogs in place, so it's a bit of a pain.

951and944S

No way a balance shaft timing issue will destroy an engine mount.

As far as the weight of the engine, it would be the driver's side under as much if not more stress because it is being stretched to counteract the weight if the weight was any issue at all, which I seriously doubt. An engine will practically sit unattended on a garage floor on the oil pan, and the mounts are further outboard than the limits of the pan dimensions.

944M3

On my NA daily driver, I developed a really bad engine vibration that was giving me headaches. I had changed the mounts to after market solid rubber mounts less than 5k miles so didn't suspect them (I believe they were Meyle). Jacked the car up and found the passenger side motor mount bolts backed out. No idea how long it had been that way but the rubber was holding on to the bottom metal part of the mount by a thread. Once I removed it I was able to manually tear the rubber off the metal mount. Again, no idea how long it had been that way but with the mount being lose against the engine, the vibration literally tore it in half.

I purchased the Ultra Mounts for my 951. I remember having a hard time tightening the center bolt down against the rubber isolator. I used a vice and a long breaker bar and still wasn't able to compress it down to the documented spec. I never installed them though as I decided I didn't want to deal with the vibrations (for sale if anyone is interested). I purchased OEM for the 951. super smooth.

944M3

Forgot to mention, a few months after rebuilding the 951 engine I developed engine vibration. The mounts where new. Long story short, I looked at the timing belt (it was about 2k miles old) and it had stretched or the belt tensioner slipped, but my balance shaft cog was off by a couple of teeth. Lined the timing up again and tightened the tensioner. Was back to normal after that.

333pg333

Might be worth looking at upgrading the Trans mount too.

MAGK944

From experience I can definitely tell you it will. If the lower cog is 180 degrees out (easy to do on a later car), the vibration at certain rpm will be worse than having no belt at all. I’ve seen a 5 month old mount break in half due to that. However it seems that isn’t the op’s issue so we’ll move along...