How do these motor mounts fail? Do they break like the 240's motor mount or do they deflate?

Paul

Dear malloy1,

Hope you're well. The motor mounts in 900 series cars are not the solid rubber blocks used in the 200 series cars. The 200 series mounts relied on the elasticity of the rubber. Over time, heat and stress cause rubber to lose its elasticity. The 200 series mounts would break: the top and bottom steel mounting plates might separate from the rubber, into which the plates had been embedded.

The 900 series motor mounts have steel mounting plates and a rubber shell, in the center of which is a viscous gel. That gel helps to damp engine vibrations.

The 900 series motor mounts slowly lose elasticity, as the rubber ages. In extreme cases, the mount will rupture, and the gel will leak. You will feel the vibration through the floor pan, because the engine is resting on the steel frame.

You can assess motor mounts' condition by looking at the gap between the oil pan's bottom and the top of the cross-member under the oil pan.

When the motor mounts are fresh, there will be about 1/2" (13mm) of space between the oil pan's bottom and the top of the cross member. You should be able easily to insert your fingers into the gap.

As the mounts age, that gap narrows. By the time the gap is about 3/16" (4 mm), it is time to replace the mounts.

As a result of a road hazard, I had replaced the motor mounts on a '93 940 (September, 2004). Those mounts are still in good order.

Driving on relatively smooth roads prolongs motor mounts' service life. Driving on poorly-maintained roads, or deeply-rutted dirt roads will shorten motor mounts' service life. Turning and braking gently prolongs motor mounts' service life. Abrupt stops and sharp turns - that cause the engine to lurch - put extra strain on motor mounts.

Hope this helps.

Yours faithfully,

Spook

If you are talking about the kind of acorn shaped hydraulic mounts they gradually collapse over time. You need to have a small gap between the oil pan and cross member. A 1/4" minimum comes to mind, but don't quote me on that. Don't get the cheaps ones, they won't last. I think I got a pair from Tasca for a decent price a couple of years back. Mike

Volvo motor mounts have been a weak design going way back to the 140, probably even earlier. Volvo's official excuse is that the mounts are designed to give way and allow the engine to drop under the car in a front end collision (versus coming through the firewall).

I don't buy this for two reasons: 1) There is really nowhere for the engine to drop because the cross member (and the ground beneath the car) are in the way; and, 2) In the event of a serious frontal impact the sheet metal, hood, radiator and radiator support will absorb a great deal of the impact. All of the front end collisions that I have seen the engine was still intact.

I think that it is just a weak design, with low quality parts. The mount will either break or the rubber deteriorates. Usually the passenger side mount fails first. Turbo mounts are supposed to be sturdier than n/a mounts, but I have never been able to get more than 3-4 years out of a Volvo motor mount.

This has not been a problem on other makes that I have owned where the mounts usually last 10+ years and well over 100K miles. That said, I think that overall the Volvo is very well made car and seems to outlast just about everything else on the road - except for maybe Mercedes.

"I don't buy this for two reasons: 1) There is really nowhere for the engine to drop because the cross member (and the ground beneath the car) are in the way"

Honestly, you should look through the gallery at some of the accident photos. It actually does work that way including the tranny tailshaft jacking up whole car up and the valve cover being crushed at its mid point by the firewall. Apparently it takes about a 70 MPH closing speed to break all four cross-member bolts for the engine but it take a lot less on the tranny.

Personally I think the 240 mounts were pretty darned good with the left one lasting virtually forever and the right one lasting 150K miles or so if protected from oil during oil changes. Tranny mounts on the automatics only seem to last about 50K miles, though.

The mounts on my 760 were a different story.

I concur about the 240 engine mounts. I thought they were pretty darn good! I had my car for 10 years and didn't replace one. AFAIK they were the originals at 300K when the car was sold. The passenger side mount's gap was narrowing however.

Did replace the tranny mount once.

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95 855 GLT Sportwagon 214k, sold - 90 244 DL 300k