1996 850 Strong Vibration During Braking

[PeteB]

Hmmm, so you need an 11mm flare wrench for the bleeder and flare nuts on the calipers - an odd size anyone know of a good source for a quality wrench at a decent price?

We worked on it this past weekend and only had time to do one side in the rear. I told my son that it was serviced by the dealer for about the first 60K miles and that it probably had the shims - it did. The obvious problem was that the caliper and Volvo pads were VERY rusty to the point that they were seized and probably dragged for a while. Outside pad was still working inside no longer moved enough to apply pressure. I think that the droning and massive vibration is due to the single pad bending the rotor as the brake is applied.

The pistons still looked fine and moved freely in the caliper but we decided to look for a rebuilt pair. Went to the only open auto parts store that had a pair and bought them.

They did not look good so we just cleaned up the old caliper, greased up the contact areas and put it back together with new pads, shims, and rotor. Pads move very freely now and it seems to be fine. I might look for a better pair of new/rebuilt calipers - any suggestions for a source?

Plan to do the other side this weekend. Braking is much improved.

PArking brake adjustment, if I am remembering correctly, is star wheel up until rotor does not turn freely then back off 5 teeth?

Wanted to bleed it, but did not have an 11 mm flare wrench and was worried about cracking the bleeder. Soaked it with PB Blaster for next time.

[dosbricks]

A box-end wrench will work on the bleeder. Lowe's has a set of three flare nut wrenches which are strong and reasonably priced. 11mm and 14mm for brake work are included. The line nuts are very tight and if corrosion is an issue they need to be PB'ed well in advance.

[PeteB]

Yes right a box will work on the bleeder but I didn't have an 11 mm in that type either.
We needed the flare type because we were going to do the front flexible lines also.
Thanks for the Lowes tip - perfect and a good price, I did google it but did not find Lowes.

Any suggestions for the best caliper rebuild company?
Also, what about a rebuild kit for the fronts which are not rusted but could probably use new rubber parts? Tried FCP, maybe Rock Auto?

[abscate]

11mm is a common nut size on brakes, I have a combination offset11mm flare, 8 mm bleeder hex in my toolkit. Don't remember brand though. Get a good one as a cheap one will round off. You can pretty much tell quality by price or brand

[PeteB]

Remembered correctly that I needed the 11mm flare wrench to replace the lines but forgot that I eventually found that I had an 11mm 6 point deep socket that I used to open one of the front bleeders. Forgot that I was nervous about breaking the rear, I did soak it with PB Blaster. We need to open the rears so that we can flush the system and if they break we will get new/rebuilt calipers.

I found that all of the bleeders were SERIOUSLY rusted, one entire face of the 6 points is nearly gone. The 6 point deep socket still gripped well and I was able to open it. I should probably replace them. Interesting that the flare fittings on the connections to the brake lines showed nearly no signs of rust.

Thanks again for all the tips.

[abscate]

Definitely replace. That will make the next 10 years of bleeding easier.

That sounds funny.

[PeteB]

The 11mm flare wrench in a set is on sale at Lowes in case anyone else is looking ~10$.

We finished the rear this weekend and used the NAPA rotors, Volvo factory rear pads and shims,
and Cardone rebuilt rear calipers from FCP. I'm not really liking these rebuilds but the old ones
were really pathetic, the amount of rust was just unbelievable. It was obvious that the inside
pad was dragging since the area all around it was rusted as if it had been under water for 100 years.
The opposite side mostly just had surface rust. If I remember my chemistry correctly the rate of
reaction (corrosion) doubles for every 10 deg (probably Celsius) increase for most chemical reactions.
Clearly, the area near the inner pad was much hotter, I should post a picture since it is hard to
believe how bad they were.

A few tips on bleeding, since I've read that some people are unable to get solid brakes after
replacing calipers:
If you are flushing, flush the lines while you have the old calipers off so that you do not fill the new caliper with old fluid.
If you forget to pre-fill the new caliper with brake fluid, have the assistant pump the brake until
there is some pressure or even just 5 times with the bleeder closed, this builds up some pressure
so that when you open the bleeder the pressure pushes a lot of fluid into the caliper. It took
about 2 or 3 of these to fill the caliper. Don't forget to put in the pads to hold the pistons.
When you get to the point that you have some pressure, or some after a few pumps of the
brake open the bleeder minimally and close it shortly after some fluid is flowing.
A hose on the bleeder (with an open end wrench to turn it) tilted up provides brake fluid at
the opening of the bleeder so that no air is trapped in the system right as the bleeder
is closed.

Front and back are done now and there is no vibration or rumbling sounds. My son says
they are perfect.

We believe that the way to prevent this in the future is to apply a
thin layer of high temp brake grease along the guide areas of the caliper and to redo
it once a year - during a tire rotation is probably a perfect time.

[PeteB]

I forgot to mention one more finding. The brakes had previously been worked on by the dealer and they still had the original retainers on the rear brakes. They looked significantly different from the replacements so I noted how they sat when in place. It looks like angled spring metal provides some returning force on the pads for the originals since they actually touch the pads - I should have taken a picture. The new retainers, from what I could see, only touched the caliper and it was hard to see that they served any sort of purpose at all. We cleaned up the Volvo retainers and reused them. This is a serious flaw in the aftermarket parts if I am seeing it correctly.
Here's a picture from the nice blog page of the typical aftermarket retainer, where I think you can see that it doesn't actually touch the brake pads - I'm certain that the Volvo part does:
http://volvo850wagon.files.wordpress.co ... cn0490.jpg

It can be seen that the horizontal part of the aftermarket retainer touches the caliper, and with mine did not touch the pads. The Volvo parts had some clearance to the caliper and clearly touched at the pads. I'll look for a picture online or try to take one next time we have a rear wheel off.

[PeteB]

Picture of the very rusty caliper, note how the rust is so much worse on the side that probably dragged more:

[jreed]

Wow. Great shot. That's the rustiest caliper I've seen in a while.
It does look like the stainless steel half-shims are present between the caliper and pads... that's a good thing.