Engine mounts - durability

[nfearn]

I have recently noticed that there is a little bit more of a mild jolt than previously on the occasions where I close the throttle a bit more quickly than normal and also when de-clutching as the revs drop to near-idling rpm when slowing to a halt.

My initial diagnosis is that the engine mounts are getting a bit tired. The car has 88K miles on it now.

My questions:

i) Is this a fairly typical mileage by which point the mounts are getting too old to do their job properly?

ii) Is there a third (and fourth?) mount at the front of the engine, aside from the two at the rear?

Any other tips and advice is welcome. I do seem to recall, for example, that the C4 mounts are both stiffer and cheaper than C2 items. Is that right?

 

[John Maddox]

Mine still has original mounts at 182k miles with no problem. I did fit its third spoiler wall this morning though and it's fourth oil cooler fan resistor at the weekend !!

 

[LK_991GTS]

You're correct about the c4 mounts. A worthwhile change. Maybe your dmf is causing what you are experiencing.(assuming yours is a manual)

 

[nfearn]

ORIGINAL: Lawrence

You're correct about the c4 mounts. A worthwhile change.

Hi Lawrence

Worthwhile in what sense? Do they make a noticeable difference to the engine's mass moving around at the rear of the car when cornering?

 

[38F3E1]

There is a third mount at the front attaching to the gearbox.

I would fully investigate the dual mass flywheel before assuming it is an engine mount problem.

Ian.

 

[gm997_1]

I have a C4, 85k, manual, and the engine mounts are absolutely fine, clutch also, yet have similar symptoms to Nick's.

Very low speed on/off the throttle makes a mild wallow, not quite a jolt, at standstill, and slightly more so moving off in 1st from standstill, no throttle. A lot of 993s have these or similar symptoms, in varying degrees, and cars with dmf in general for that matter.

It's a sign of a less-than-100%-but-not-terminal dmf. May well get progressively worse, of course to the point it does fail, but it depends on how it's driven. Mine's been the same for the last 15k miles - and been tracked - but no discernible difference whatsoever. The problem WOULD likely get worse if I abused it in low speed conditions, eg taking off at lights or parking, but to avoid that I ease the car into gear and drive away at a touch more revs, about 300-400, which helps with th ecrankshaft already spinning. Completetely unnoticeable to passengers. So long as I don't weekly slam it off into a wheelspin start, or constanlty move off with no revs, it should be good for 10s of k more miles still.

 

[nfearn]

Graeme

Interesting post - thanks.

I will see what I can feel next time I drive it.

 

[nfearn]

Having driven the car fairly extensively today I don't think I have a problem. Everything seems pretty tight to me now so perhaps I was just getting paranoid.

 

[gm997_1]

Yes, Nick, it's my hunch you'll find normal driving through the gears up, down and at speed everything's fine and tight, but only the slow revs stuff that manifests the slight jolt you mention.

Just use the engine slightly differently, to 'protect' the dmf, as in my post above, and you'll most likely be fine. Also when slowing down at lights for example through the gears, instead just coast on the brakes from about 20 to 0 mph to compensate for the slight play in the 2 plates.

The brakes can take it (and that's even what the driving test advocates these days as brakes are way way better than they used to be, for those of us old enough to remember that you were always advised to slow down using the gears 30+ years ago) []!!

 

[nfearn]

Thanks for the input Graeme.

My standard approach to slowing is all brake and no gear anyway (this is standard "Roadcraft" procedure), so hopefully that should be DMF-friendly and we have a way to go yet.

 

[gm997_1]

Excellent, Nick, re your DMF, and, yes, Roadcraft has it right on braking - I too am an IAM man and IMHO their fundamentals are still valid today. Will be very interesting to see if they'll add a paragraph or more when it comes to driverless driving in 2015 (or however quickly Strasbourg will allow the legislation to be altered [&:] ) !!

 

[vitesse]

Graeme,that explains a lot-I've puzzled long & fast about why those most enjoyable laps with your car around Anglesey were so different--I've now realised that your personage must have been a cardboard replica & the car was driving itself[]

 

[Graham S999tle]

Hello, I have just replaced the engine mounts on my '94 Carrera 78k mile on the clock. The right hand (drivers side) mount was foobah! Visual give away was the right hand exhaust tip noticeably lower than the left. Tactile give away was feeling the underside of the mounts from the top of the engine bay, I could almost get a finger in-between the "flange" and the main body of the mount itself (no gap on the passenger side). Other indications were gritty/crunchy changes from 1st to 2nd when the engine was cold and less than comfortable start from stationary and poor low speed "controllability".

Fitted C4 mounts (cheaper and stiffer than C2), took about 2 hours to do. Result - car is bl**dy transformed!

Gear changes are a delight, car feels even more stable, start stop traffic is pain free, setting of from stationary is completely pain/stress free. Even the Mrs is starting to enjoy driving it.

Downsides - a slight increase in NVH as in slightly more mechanical noise in the cab, mainly gearbox. The Mrs is starting to enjoy driving it!

Regards, G

 

[Mark Elder]

ORIGINAL: Graham S999tle

... Other indications were gritty/crunchy changes from 1st to 2nd when the engine was cold and less than comfortable start from stationary and poor low speed "controllability".

Fitted C4 mounts (cheaper and stiffer than C2), took about 2 hours to do. Result - car is bl**dy transformed!

Gear changes are a delight, car feels even more stable, start stop traffic is pain free, setting of from stationary is completely pain/stress free. Even the Mrs is starting to enjoy driving it.

Downsides - a slight increase in NVH as in slightly more mechanical noise in the cab, mainly gearbox. The Mrs is starting to enjoy driving it!

Regards, G

Very interesting. Mine is a C4, but I have these symptoms (and 78K miles nearly). Why would gritty gear change when cold be impacted by engine mounts? Understand the rest.

 

[gm997_1]

> Colin. Damn, my secret's out...[8|]

But you have a point, Colin, maybe my meaning's got lost somewhere along the way - to clarify, I'm on about electronickery you get on all the latest cars, ie lane change assist, auto maintaining of distance from car in front, cruise control, front + rear-facing cameras, auto obstacle detect inc emergency stop, etc etc. A car can technically drive itself already without the driver.

> Graham, you must be just down the road to me. Damn, I used to be the 'only 993er in the village'! We'll have to meet some day. PM me if interested. []

 

[Graham S999tle]

ORIGINAL: Mark Elder

ORIGINAL: Graham S999tle

... Other indications were gritty/crunchy changes from 1st to 2nd when the engine was cold and less than comfortable start from stationary and poor low speed "controllability".

Fitted C4 mounts (cheaper and stiffer than C2), took about 2 hours to do. Result - car is bl**dy transformed!

Gear changes are a delight, car feels even more stable, start stop traffic is pain free, setting of from stationary is completely pain/stress free. Even the Mrs is starting to enjoy driving it.

Downsides - a slight increase in NVH as in slightly more mechanical noise in the cab, mainly gearbox. The Mrs is starting to enjoy driving it!

Regards, G

Very interesting. Mine is a C4, but I have these symptoms (and 78K miles nearly). Why would gritty gear change when cold be impacted by engine mounts? Understand the rest.

I am active on another 911 forum where I picked up the information. Apparently when your mounts are tired your rear droops[]. This affects the geometry of the gear linkage, which in turn affects the gear selection. Primarily felt when the engine/gearbox is cold. Mine was OK when first purchased but got noticeably worse and then I spotted the droop of the right hand exhaust tip relative to the bumper cut out. I confirmed this with the finger test [8|] and could feel that the right mount had dropped as there was a gap that I could get my finger in. The other forum recommend moving up to the C4 mounts for C2 owners and I can now fully concur. As the C4 mount is a different physical configuration you wont be able to do the finger test so not sure how you will ascertain if yours have sagged. Again, I have read that there is a "life" to these mounts, they are oil filled and start to leak (my RH one had, LH OK), C4 mounts have less oil/fluid than C2.

 

[Graham S999tle]

ORIGINAL: graeme


> Graham, you must be just down the road to me. Damn, I used to be the 'only 993er in the village'! We'll have to meet some day. PM me if interested. []

Hi Graeme, was a bit of a shock to spot your location as well. To be fair I thought I was No.2 but there is a Red 993 RS recreation in Horwich as well!

 

[LK_991GTS]

ORIGINAL: nfearn

ORIGINAL: Lawrence

You're correct about the c4 mounts. A worthwhile change.

Hi Lawrence

Worthwhile in what sense? Do they make a noticeable difference to the engine's mass moving around at the rear of the car when cornering?

Apologies for disappearing and not answering. I have found the C4 mounts to be worthwhile in the sense of all the positives mentioned above by others; particularly crisper gearchange and reduced engine mass movement on 'enthusiastic' cornering.