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Old 01-13-2015, 12:29 PM   #1
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How much engine movement is normal/how much means bad motor mount

On my boxster, the motor mount was previously replaced 9/16/2010 at 23,000 miles ago. In the service record it says "Customer observed loud banging from back of car. Replaced engine mount."

I don't have any banging, and my shifter cables don't move when I am accelerating, but today I took a little drive with the passenger seat out and the front engine cover removed (I actually forgot that I had not put the cover back until I had left the house and felt the warm breeze blowing out... felt pretty good actually)

I peeked back there during some acceleration and noticed that when I get on the gas, the engine kind of "lifts up" a little, maybe 1/4" to 3/8" of an inch (no way to measure but that is my best guess) and if I let my foot of the accelerator pedal rapidly the engine drops back down about the same amount. When it gets to the end of the movement in either direction it kind of bobbles a few times until it stabilizes in the new position, either deflected during acceleration or at rest during idle). If I rev it up in neutral the engine has a very slight rotational movement to the right.

Does this seem normal or is it time for another engine mount already? That seems awfully soon if it is but the car was a PA car before I bought it and may have sat outside/salt/etc (unsure if those are a factor but figured I would mention it).

Thanks

Steve

PS it sure gets noisy when I get on the gas with that cover off...


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Old 01-13-2015, 01:27 PM   #2
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I just was able to watch these video from Kenny Boxster's thread:

Boxster Motor Mount Tips & Pointers

I am going to take a few left/right turns on the way home and peek to see if the engine moves side to side, but I don't think it does. After watching his video I think my engine movement might be normal and within the limits of the motor mount. I guess if it was a solid racing mount then instead of deflecting and compressing all that vibration/etc would be transmitted to the body of the car and to me

Then I will put that cover back on, I am afraid I am going to put a sleeve or something back there and get it tangled up... I would not have left the house if I had remembered it was off (it was on when I took my first test drives but I took it back off to verify the belt was running smoothly...)

Steve
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Old 01-13-2015, 01:29 PM   #3
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I am no expert here but I would think that you are probably fine. Think of how much torque is being applied during acceleration. I would think if the mount was bad then the engine would move more. Maybe someone else can help out a little better here?
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Old 01-13-2015, 01:32 PM   #4
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I replaced my front mount due to the vibrations felt around the 3,000 RPM mark. After the new mount was in it is nice and smooth. The engine doesn't vibrate as much on startup either. Do you feel vibrations around 3,000 RPM?
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Old 01-13-2015, 02:34 PM   #5
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I don't feel very much vibration at idle or at 3000 but with that cover off the noise sure picks up around 3000. On the way home I found an isolated road and did some quick slaloms and the engine did not move about the yaw axis at all. I think I may for a stiffer mount at some point since I am mostly driving the car at autox and de but I think I am good for now.

Thank you.

Steve
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Old 01-13-2015, 02:50 PM   #6
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I seem to remember Brad Roberts (who knows much more than I) commenting awhile back on this topic. He suggested having someone stand behind the car while it is idling and watch the exhaust tips as the driver pulls away. If they deflect quite a bit downward you are due for motor mounts. Hope that helps..........

BTW.....Many years back I replaced my front motor mount with a Pedro's unit, immediate noticeable difference (in a positive way) then with a Box S with ~ 34k miles on it.

Last edited by coreseller; 01-13-2015 at 02:54 PM.
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Old 01-13-2015, 03:07 PM   #7
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You may not be experiencing a full failure, but I think its definitely on it's way out. When you feel a clunk at takeoff, its fully gone. I replaced mine with a motor mount from the 987. Fits perfect. Not that expensive to replace if you buy a good used one, not very hard to replace either. I would recommend replacing
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Old 01-13-2015, 04:26 PM   #8
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I will have my son video me driving off and see how it goes...
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Old 01-13-2015, 04:42 PM   #9
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I wish I would have discovered this before doing my WP, I understand that the WP is much easier with the engine down and the engine mount much easier with the coolant hoses disconnected.. Blah...

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Old 01-13-2015, 07:07 PM   #10
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I wish I would have discovered this before doing my WP, I understand that the WP is much easier with the engine down and the engine mount much easier with the coolant hoses disconnected.. Blah...
Correct! I've replaced motor mounts 4 or 5 times on my various Boxsters. When I had to do a WP a couple of months ago (my first time), I didn't hesitate to remove the mount first. The WP R/R was quite easy. Caveot: I get to do all this kind of work with my car on a lift....certainly makes these jobs easier!

What did I notice regarding a failing mount? Two things mostly: the resonant vibration around 3K rpm and a little bit of roughness at idle.

I bought a very inexpensive 98 Box a few years ago that needed its maintenance brought up to date. Even after replacing spark plugs and other maintenance I was dissapointed to find that I still felt a little roughness at idle (easily compared to my 2000S). I noticed that even with the roughness, the tach was rock steady.

After replacing the mount, the roughness vanished and the car felt brand new. Lesson learned! I've bought three other older Boxsters since and the replacing the mount is one of the first things I do.

BTW, every mount I've swapped was torn. Even on my 2000S that really didn't exhibit any symtoms. All the cars had over 100K miles on them when I did the replacements so all were due.
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Old 01-14-2015, 04:23 AM   #11
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replaced my mount in 2010 at about 75k miles.had the tell-tale vibration around 3k rpm. it seemed like one day it was good, next day it was bad. but i guess i had just gotten used to the feeling as it was going out.

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Old 01-14-2015, 06:11 AM   #12
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Hi,

i have a question concerning the engine mount. Is the engine mount of the 987 S identical to the engine mount of the 986 S?

In germany we have an after market supplier called Lemförder. He produces engine mounts for the 987 S which cost much less than Porsche OEM parts. Part number of the Lemförder motor mount is 34705 01. Porsche part numbers are: 98737502302, 98737502303, 98737502304, 98737505702. So at first sight it seems to be a 987 part and not compatible to a 986S. But if the parts qould be identical this would be a bargain.



Thanks and regards
Markus

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Old 01-14-2015, 06:21 AM   #13
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Hi,

i have a question concerning the engine mount. Is the engine mount of the 987 S identical to the engine mount of the 986 S?

In germany we have an after market supplier called Lemförder. He produces engine mounts for the 987 S which cost much less than Porsche OEM parts. Part number of the Lemförder motor mount is 34705 01. Porsche part numbers are: 98737502302, 98737502303, 98737502304, 98737505702. So at first sight it seems to be a 987 part and not compatible to a 986S. But if the parts qould be identical this would be a bargain.



Thanks and regards
Markus
Should be the same. I replaced my 1999 (non S) with a 987 mount. I don't know whether the 987 mount was from an s or not, or if they are even different.
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Old 01-14-2015, 06:29 AM   #14
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If it has never been replaced you are likily due for replacement. The rubber gets old and cracks. Just replaced mine with 55k. For me the sympton was a sloppy shifter with 2 gear being sometime difficult to engage. After replacement it shifts like new.
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Old 01-14-2015, 08:59 AM   #15
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Far as I know I'm still running on my original mount so will be something I look into in the spring. Can someone give me a rough estimate of what that repair would cost (part and labour)? I already have some projects on the todo list and unfortunately, I do have an annual budget to stay within. Thanks!
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Old 01-14-2015, 09:11 AM   #16
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For me the sympton was a sloppy shifter with 2 gear being sometime difficult to engage. After replacement it shifts like new.
Uuh, that sounds exact like the problem i have

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Originally Posted by OklahomaBoxster View Post
Should be the same. I replaced my 1999 (non S) with a 987 mount. I don't know whether the 987 mount was from an s or not, or if they are even different.
Thanks.

my mount has part number 986 375 023 05 (2003 Boxster S). So i did a little Google serach and found that the part number has changed from 986 375 023 05 to 987 375 023 05.

But i haven't found an aftermarket part made in germany right now. We will see.

BtW: Lemförder is a subsidiary of ZF.

Thanks & regards
Markus
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Old 01-14-2015, 09:44 AM   #17
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Quote:
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Far as I know I'm still running on my original mount so will be something I look into in the spring. Can someone give me a rough estimate of what that repair would cost (part and labour)? I already have some projects on the todo list and unfortunately, I do have an annual budget to stay within. Thanks!
101 projects has this as very simple job requiring only a floor jack.
Under $200 for a new 987 mount and 2 hours of DIY time.
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Old 01-14-2015, 09:46 AM   #18
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Originally Posted by Smallblock454 View Post
Uuh, that sounds exact like the problem i have


Thanks.

my mount has part number 986 375 023 05 (2003 Boxster S). So i did a little Google serach and found that the part number has changed from 986 375 023 05 to 987 375 023 05.

But i haven't found an aftermarket part made in germany right now. We will see.

BtW: Lemförder is a subsidiary of ZF.

Thanks & regards
Markus
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Old 01-14-2015, 10:00 AM   #19
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Pelican Parts shows the 987 part number as a replacement for all first generation Boxsters.
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Old 01-14-2015, 01:05 PM   #20
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Thanks for the hint!

Regards
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