This is an ongoing work, Comments welcome.
Before we get into the how, let's examine the what and why.
On the left is the new mount, the old one is still installed on the right. Externally, the only thing you can see different is the height of the feet + flange. The new mount is a full 1/8" thicker, the old mount has worn itself down on the footings. This means moisture can get into the top, and causes:
Note how the rubber has detached from the sleeve somewhat, but the entire thing has rusted and built up tons of scale. This pushes against the rubber, tightening the range of movement. So not only is it bouncing up and down, it's not absorbing laterally as it should.
Looking up at old bushing pre-removal (without bottom plate installed) we can see the bloated center. What isn't easy to see is the sag lines on the sides.
*Also note in the above photo that you can see a red (body color) metal nub inside the bushing. This is only on the left rear mount, and is for locating the subframe when removed from the body. It also makes this mount MUCH more of a pain. You can't pry as well, and the internals of the bushing have much less give when trying to collapse the casing. The driver's rear, and both pass side mounts are the same part, the driver's front is slightly oval tho, and is not interchangeable. That one is next, I'll update if it poses any special issues.
Ok so you've decided to replace your mount.
The tools i used:
The mirror, sockets, cheater pipe, flashlight, are all for normal usage.
The putty knife (MUST be very stiff) I sharpened with a stone. it doesn't need to be knife sharp, but edges help with cutting. The brass brush with 1/2" square wooden handle is essential as a spacer (and brush).
The screwdrivers: a stubby is great, you want older tools with rounded edges (less marring of subframe) and solid handles you can beat/push on with hammer/prybar.
Notice the bent tip. This was an old accident with fortuitous results. The bushing curves, having the curved tip is great for not damaging the subframe and for getting purchase when prying. Highly recommend.
Position a floorjack where it can support the corner of the subframe where the mount is. This helps keep the frame from sagging (not really an issue unless many bad mounts, but caution is good), and allow you to lift the car up a bit to increase the working room.
The subframe bottom plate is in the upper corner of the picture.
1) remove the 3 bolts, 2 14mm, one 18mm. the 18m is on there at like 85nm + 120deg so use your cheater.
2) using putty knife and hammer, cut off the bottom ring of the mount
Notice the "feet" hanging down. You want to remove as much of that ring/flange as you can, ideally the front or rear half at least. use the edge of the putty knife to get purchase and it isn't hard.
3) the fun part...
Use a flathead screwdriver to "cut" the plastic body (not too sharp, don't want to score the metal) vertically at one of the openings in the mount, then use a larger diameter (1/4" or 7mm) philips head to collapse the mount at that location. Takes 2 minutes to type, but expect it to take much much longer if it's your first and you're lying on the ground next to your car. I kinda forgot to take pictures of this, but you can use your imagination. the white of the bushing is visible against the frame. Using the front of the car as 12, looking up from the ground at the bushing) Remove from 9-3 and then insert screwdriver between plastic and subframe at about 10:30. You're looking to miss the side supports and the bump stop, this makes more sense once you have a mount in hand. Prying at this "gap" in the bushing after removing the reinforcing edge, the plastic outer will cave in, and the bushing will pretty much fall out. The screwdriver tip should be right against the bump on the outer casing of the bushing (again, helps to look at one).
You can see the happy moment where it literally will pop down and out. For this nubbed mount i had to chew a bunch of the side out, the rust inside had packed the bushing and i couldn't get enough space to collapse it. Without the nub it would have taken less time.
Take breaks. It sucks. having a lift would be awesome, but I don't have that option. It will come out, just don't think it'll be fast. The 3 I've done have taken 4 hours, 2 hours and 3 hours each, the first took forever because I had no method to use, the last sucked because of the nub. Working in the 8" space isn't much fun either, jack up the car some if you like, but at your own risk.
Use the prybar to push up on the screwdriver to force it between the bushing and subframe. You'll know you're pushing too hard if the car lifts.
4) Pressing in the new mount.
First you want to clean out the subframe. a brass brush and some pb blaster work great. use a cloth ot your finger to make sure you didn't make any nasty metal gouges that are going to make pressing the new one harder. Don't leave dry exposed rust, treat it with something.
The empty socket. note the opening in the side, this is where the ridge on your mount ends up, and what you have to overcome to get it out.
I rub a thin layer of lube (i used plastilube) on the outer casing of the mount, it seems to help it get started at least.
Here's where the 1/4-20 nuts come in... low-temp hot glue helps keep them in place.
The notch (aftermarket) or tab (volvo) on the mount should line up with the notch in the subframe. This is pretty important, double check.
They distribute the pressing force of the plate onto the casing of the bushing. Without them you deform the bushing and crush the feet. Essential. can be larger, but not smaller.
You may find removing a set of the nuts for a couple turns helps even out the mount if it starts tilting. This is NOT like the upper torque mount. It cannot twist out, but even is better.
The chunks of wood help keep the subframe from scraping into the body during pressing. Once the mount is in far enough so that the rubber pushes out the top, you need to reposition the blocks. For this final 3/8" of pressing in, you'll need to use some very dense wood, i find the brass brush handle works great - just make sure the rubber will clear as it goes in.
Make sure you CLEAN AND LUBE the bolt before you use it to press the mount in. The mount of force used to press it in isn't as much as needed for final torquing.
And the new mount installed and torqued down (not restretched tho). Volvo recommends replacing the bolts as well, tho i did not. Your call. I used aftermarket mounts, they had a thicker plastic casing than the original mounts on the car.
The old mounts:
Upper left was driver rear, lower left was passenger front, right was passenger rear. Rust got into the rears, but was juuuust starting to eat the front. The bushing had completely detached on one rear, the other it was held in by scale.
This is not the only way to replace the mounts. dropping the subframe and beating them out with a hammer is one. Another is to use the special tool volvo made. It cuts the sides of the bushing out, so that the metal sleeve drops out. the casing is then very easy to remove. Cutting the bushing out with a hole saw is an option, but it's not easy. I tried.
The volvo tool uses the body and a fancy spacer or 3 to accomplish the same thing i have done, but a bit faster and easier, for about $150 if you can find one. Again, getting the car on a lift would make this easier.
So after replacing the mounts, what did i experience? Much smoother ride, better steering response, tighter steering (no clunks), less body roll on corners, more even braking, much less cabin vibration. Basically everything is better.
why did they fail? Well, this is a new england car, it spent it's first 145k in southern NH, and the next 30k here in boston with me. I suspect it sat at some point, but i see zero evidence of body work or accident. Once water was allowed to get in, the ending was inevitable. How did water get in? I suspect rough roads combined with other worn components put too much stress on them. Once they had worn down their footings, it just got progressively worse. The internals are not really meant to bear the weight, once the sides had to support the vertical forces they were out of their range. the top lip is much more of a wiper lip than anything supportive, once it can no longer reach the frame it's useless.
How can you check yours? Visually. the foot of the new mount is 5/8" including the plastic flange. If you feel the frame move a lot when turning the steering wheel (one hand on frame, one on wheel from outside) you can get an idea. The bottom plate shows some rub marks too, but it's hard to quantify those. These are just rubber bushings, if you've had to replace all of the rest of your mounts, it only stands to reason these might be next.
Edited by MyCarIsRed, 11 August 2010 - 02:46 PM.