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Old 03-31-2011, 04:26 AM   #1
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Replaced Engine Mount - Pics of Old Mount - And a Mystery for the Experts

Hi all,

I replaced the front engine mount on my 99 boxster. The job itself was not hard - I'd recommend doing it at the same time as the fuel filter and, if at all possible, the coolant/thermostat. Here's my tips for those who haven't done it:

1. Drop the plastic undertrays, take both plastic straps holding the coolant tubes in the tunnel off (allows the hard plastic coolant tubes to move around alot). If you are smart, go ahead and drop the large coolant hoses too and just replace the coolant when you are done.

2. Make sure you have a 3/8 and 1/2" ratchet (or a adapter), 6" extensions for both, a 15mm and 7mm socket.

3. Buy a 15mm flat ratcheting wrench....for the love of God, buy the ratcheting model.

4. When done, put the new mount back on the engine and tighten, then jack the engine back up (easy to do with a quality jack since the engine doesnt put alot of weight on it), then thread the engine mount YOKE studs through the yoke into the chassis using a 7mm socket (it fits onto the head of the stud). Make sure it's fully seated. Then put the nut on the stud and tighten. Slowly tighten one on each end, then do the same in the middle. Make sure the yoke is fully seated against the chassis. Tighten these with a torque wrench....they are delicate threads and will strip out of the chassis.


So, here's my old mount - 59k miles, not really driven hard for most of them:


Now here's my mystery: the mount I pulled off the car had a solid-face style of construction and mounted using only 3 bolts to the engine.

However, according to online sources, Porsche only used the solid-face mount from 97-98 and then moved to a grid-style. I have a 99.

Further, according to online sources, if i had a 3-bolt style mount I should have the 3-bolt style housing - I should not have had a 4th bolt hole in the engine nor a bolt there. But I did - I have the 4th bolt hole AND I had a bolt there....

And it gets better - the bolt that was in the 4th hole was improperly sized for an engine mount. It looked right, but it was threaded from top to bottom and was not long enough to grab the engine through the mount. It'd only be threaded without the mount there.

Here are pictures of the old mount face and part number:

So what's going on here? My father bought this car in ~2002-2003 with 30k miles on it from CarMax. I don't have the maintenance records before that time. Either this is the original mount, or the mount was replaced back in the early years with a mount from an earlier model.

The only way I can figure that happened was if this got an engine replacement, and they had a variety of mounts sitting around. Engine replacements were certainly common back in those days.

Am I totally off base here? Is this really the original and I've just spun a tale? If I'm on the right track, any suggestions for how I figure out if this car had some sort of major engine work done to it?

Thanks all.


P.s. I also think this mount was replaced in the past because two of the studs stripped out of the chassis on me. Now, I could've been attacking them wrong, but I wonder if they were previously cross-threaded or way overtorqued with an air tool.

Car'll lightly drive and idle just fine with only 2 studs/nuts holding the yoke to the chassis....and both of them on only one side of the yoke! Taking it to my mechanic today to get it sorted out.

Edit P.P.S. I just noticed again how "fresh" the bolts going through the original mount look in the above photos. Hrmmm...

99 Boxster 5spd - 64k miles

06 Civic SI - 114k miles, D.D., unbelievably reliable and fun to beat on everyday.

08 Legacy GT 5spd - 74k miles.

Last edited by JoeFromPA; 03-31-2011 at 10:13 AM.
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Old 03-31-2011, 06:32 PM   #2
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Thanks for the nice write-up, I store these away so I can quickly find them, I'm thinking about doing mine, doesn't shift as smooth as it should and I hear this might help. Again thank you!
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Old 03-31-2011, 06:42 PM   #3
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Thanks Joe. I ordered an AOS and a motor mount from suncoast with 20% discount with the online coupon (Cheap ). I will be installing them in 2 weeks when I pick up the car. You're write up and photos will come in handy.

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Old 04-01-2011, 03:03 AM   #4
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My post is more of a "this is the stuff I wish had been written explicitly" in the DIY guides on pelican parts and pedros garage.

I cannot stress enough how much easier this job would be if you drop the coolant hoses - however, you'll then need to re-fill and burp the coolant. AFAIK, that's relatively easy as long as you burp it correctly, but some people have had issues getting all the air out of the rather complex system.

Also, Pedro mentions getting new rubber spacers (they are about 1/8" thick, slide over the mounts protruding metal where the bolts go through, and you can see them in my side by side pic). Mine were in brand-new condition, but my OLD mount and new mount had different shapes to the inner metal piece inside the rubber. So I wound up taking a utlity knife to the spacers and shaving off a bit of very, very hard rubber. Worked just fine, just giving you a heads up.

Don't be shy about using pb blaster on the bolts, but DO wear eye protection under there. There's alot of crap that will fall on your face - I was washing it out of my hair for 15 minutes in the shower - and even regular eye glasses barely protected my eyes.

You will want a 1/2 drive socket for the 15mm bolts that you can access with a socket - though they are "only" tightened to 34lb/ft (supposedly), mine required a 1/2" drive and bracing my foot against something to push my entire body weight into it before it broke free. A 1/2" breaker bar would obviously be even better.

You can do this by only jacking up the rear of the car (I did), but I'd be very hesitant to proceed that way without alot of protection. You'll be shifting alot of the car's weight around, and the front wheels will neither have an emergency brake or a transmission lock to hold them in place.

If you keep the coolant hoses in place (the big rubber ones), just know that you can really can manhandle the hell out of them - you'll need to to get the mount out and back in. Just make absolutely sure you took both plastic brackets off - the ones holding the black plastic coolant hoses in the tunnel running to the front of the car.


So far, my 1st to 2nd shift does not feel much better but I have barely driven this thing. I suspect my next step will be trans fluid.
99 Boxster 5spd - 64k miles

06 Civic SI - 114k miles, D.D., unbelievably reliable and fun to beat on everyday.

08 Legacy GT 5spd - 74k miles.
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Old 04-01-2011, 07:55 AM   #5
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Excellent lessons learned! Thanks for taking the time and effort to help the next guy.

1999 996 C2 - sold - bought back - sold for more
1997 Spec Boxster BSR #254
1979 911 SC
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