How to tell if the engine mounts are bad?

wczimmerman · Post by **wczimmerman** » 20 Apr 2020, 17:03

I have seen much on the upper mount and the transmission torque mount failing but I haven't seen much on the symptoms of that. The upper mount on my XC70 was replaced by the prior owner about 10K miles ago/5 years but I have no record of the lower torque mount being replaced (and the owner had records for everything). The vehicle has 145K on it now but it's been in the desert its entire life.

I'm asking because I'm chasing down a slight vibration at highway speeds.

Post by **- Pete -** » 20 Apr 2020, 17:28

The lower one is cheap, like $26-28.

Is the vibration felt under load? Coasting? Both?

wczimmerman · Post by **wczimmerman** » 20 Apr 2020, 17:37

I was mistaken...the lower one was replaced at 93K miles (2012).

I would describe it as cruising speed. You don't feel it under load and it's only above 60mph. It's a high frequency vibration (if that makes sense) and seems to go away for a few seconds when you hit a rough spot on the road (bumps, etc).

Rear control arm bushing replaced at 140K
Front ball joints and control arm bushings at 140K
Tires rotated and balanced (with one wheel that seemed to give some trouble to the shop) within the last month

Post by **oragex** » 20 Apr 2020, 17:47

The two main engine mounts are fairly durable on these cars (actually these are problematic on the diesel engines which have vacuum engine mounts), and should not be causing engine vibrations unless someone lowered/rised the engine without removing the mount bolts. While there, you may want to check the right lower one at the crank pulley, it looks like this www.youtube.com/watch?v=y4nvecLGeOU

The lower torque one has very little rubber on it - one part may develop side movement but I don't it's important, while the other piece of rubber is very thin and I guess at most it will make a small knock and allow a little bit more movement but nothing serious.

First thing, try finding out which brands were the parts installed - cheap brands fail within months

I'm assuming you mean vibration in the steering wheels ? Besides the obvious wheel unbalance, wrapped brake disc, uneven wheel lug torque, or even stuck caliper sliding pins, I see two reasons for steering vibrations at speed: play in either of the drive axles at the CV joints, or very worn control arm bushings (this later one will usually cause more vibration under acceleration or going uphill).

As for engine vibrations at idling, I think these are for most part caused by old subframe bushings on these cars, but that should not cause steering shacking when driving the car

wczimmerman · Post by **wczimmerman** » 20 Apr 2020, 17:53

I appreciate all the responses!

The vibration can be felt in the steering wheel and in the seats. At idle, everything is buttery smooth and under 60 mph, everything is also smooth.

All parts and service were done at the Volvo dealers as I have stacks of invoices detailing everything. Rotors: done, brake pads: done and more.

After the last rotation and balance, the vibration did improve some.

I went out and checked the lower torque mount for any play and I could wiggle it a little but not enough that I would call too much in my "still learning" opinion.

Post by **SuperHerman** » 20 Apr 2020, 22:54

Have you looked at the drive shaft? Center carrier bearing is what I would focus on. Maybe dried out CV where it attaches up front.

Post by **oragex** » 21 Apr 2020, 08:29

wczimmerman wrote: ↑20 Apr 2020, 17:53 I appreciate all the responses!

The vibration can be felt in the steering wheel and in the seats. At idle, everything is buttery smooth and under 60 mph, everything is also smooth.

That's pretty much an axle play (either or both sides). Here's how to test for play : no need to lift the car, have wheels straight, grab the axle shaft near outer (wheel side) CV joint and try to push/pull along the axis of the axle

wczimmerman · Post by **wczimmerman** » 21 Apr 2020, 08:45

oragex wrote: ↑21 Apr 2020, 08:29
wczimmerman wrote: ↑20 Apr 2020, 17:53 I appreciate all the responses!

The vibration can be felt in the steering wheel and in the seats. At idle, everything is buttery smooth and under 60 mph, everything is also smooth.
That's pretty much an axle play (either or both sides). Here's how to test for play : no need to lift the car, have wheels straight, grab the axle shaft near outer (wheel side) CV joint and try to push/pull along the axis of the axle

I'm guessing that any play indicates a failed axle? Front? Rear? Both?

Post by **oragex** » 21 Apr 2020, 09:31

Oh, I see it's an XC70. For the rear ones I wouldn't worry for now. Even if they got play, rear wheels will cause chassis vibrations only at higher speeds - like 80mph and above. As for front ones, a small axial play doesn't mean they will necessarily vibrate - they may or may not. It's also hard to define what 'small' play means. Perhaps anything more than 1-2mm movement would be significant. A tiny barely perceptible play may not be a problem. Also worth replacing them one at a time.

wczimmerman · Post by **wczimmerman** » 21 Apr 2020, 13:48

Ok, I checked all 4 axle shafts:

Both fronts had zero movement. Everything was tight.
Both rears had what I would consider significant play (half inch of movement?). They were moving equally but without a known good vehicle to compare I don't know if the rears are different from the fronts, fine as is, or needing replacement.