AutoXdriver

I've read about how Porsche was able to make our big fours as smooth as a six, and some even say smoother - almost as smooth as a V8 - by incorporating the balance shaft system. If these engines are so smooth why do we go through motor mounts like oil filters? It's either got to be the engine is not smooth or the mounts suck. If it is the latter why doesn't someone make a decent mount? Should I take some off a pinto? <img src="graemlins/soapbox.gif" border="0" alt="[soapbox]" />

Sasha

I think the reason mine failed (just one - passenger side) is because the power steering fluid was leaking/sipping from reserviour(spelling) intake hose onto the crossmember, then onto the mount - and over the years helped eat through the rubber into hydrolic part of it...
My driver's side mount was just fine...
It was fun replacing it, though!

Mich924S

Speaking of that..I'm noticing that at night, with the headlights on, my right headlamp shakes at idle. Is it the motor mount? 41k miles.

tt9714

Think heat....extreme heat. Have you ever taken a look at how close the passenger side motor mount is to the exhaust headers? There isn't much more than a thin aluminum heat shield between the exhaust and the rubber mount.

Sasha

Mich924S,
I had the same problem. It is not a motor mount. There is an adjustment screw on the lowest part of the headlight bracket. Screw it in, so the rubber stop hits the chassis frame. It will stop shaking. I know it is not clear from my explanation, but if you look at it, it is obvious how it works...

Thanks.

Mich924S

Thanks for the tip I will look at that!

AutoXdriver

Bump...

Anyone have any other theories besides heat?

abduln

It has nothing to do with the relative smoothness of the engine, even without the balance-shafts the mounts would not be significantly affected by the vibration.

It really is a matter of heat, and to a far lesser degree torquing of the engine when accelerating and decelerating.

Regards,
Abdul

Skip

Nope, heat and age kill them - and, both are unavoidable. Leaks kill them faster still.

Folks have used header insulation around the mount to help... not sure how well it works.

Skip

jim968

First, I know I've seen several references to fairly early failures of cheaper after-market mounts here over the past few years. Are the factroy mounts holding up better?

Next, I know the factory mounts went thru some evolution & improvement over the years.

FWIW, I was just under the 968 twice this week (one trip still to go when the new starter gets here ), and the mounts appear to be original. This makes me wonder if the 968 mounts are longer-lived than the earlier ones, and if the 968 mounts will fit on the earlier cars???? For reference, mine's a '94 with ~71K miles on it.

If they'll fit, this might be a worthwhile retrofit for folks having repeated problems, even if the up-front cost is more.

(Now all I have to do is see if I can get one more start out of it this morning to get it up on ramps, or if I get to play jack up & block up... then hope UPS gets the starter here tomorrow...)

Jim, always somethin'

Toolmaster

Jim968 -

The 968's use the "updated" 951 motor mount which seems to hold up much better than the earlier parts.

If you're going to replace them, get a factory part rather than the aftermarket, as it does seem to be that the factory ones last much longer.

Heat and fluids do kill these things. The mounts themselves are hydraulic, meaning they are fluid filled. Constant expansion and contraction of the fluid inside it due to the proximity of the exhaust, etc, does a number on them. Some leak, some loose their ability to rebound - almost like shocks.

I used aftermarket ones the first time I replaced mine, and they died in a year. I then put factory ones in there, and they're still strong at 2 years.

HTH!