[850] Brake Caliper Dust Seal Unseated Topic is solved

[ToriWhite]

See Attached image, is this dangerous to drive on? For the life of me I couldn't get it to sit right when I saw it, but both of my calipers are in the same condition.

I was trying to hunt down the cause of a slight squeal that occasionally occurs on the first couple seconds of when I press on the brakes - so obviously I bought and went under to replace the pads. Word of the wise: Check that your pads are actually low before buying new pads; mine were only 1/2 height of the new ones. Rotor within mm tolerance, no ridge either. Even after new pads and a layer of grease on everything, squeal persists. Could it be related to this?

Any advice on reseating one of these guys with a hobbyists toolset? I tried poking around but the rubber was very soft and close to tearing

[scot850]

Those are probably both toast. Once those are like that water gets behind the seal and the pistons rust eventually preventing them returning to a 'rest' position away from the rotor. This will cause a squeal.

You may be lucky and be able to re-build them with new seals, but until you get the pistons out you won't know if the caliper is re-buildable.

Easiest is to get a pair of re-build units or used ones from PnP/junkyard.

If you get re-built units, swap your slider pins over as most of the re-built units supply really poor quality 'pot' metal pins which don't like to be removed when new, let alone in a couple of years.

Check the condition of the slider pins and make sure they are smooth. Sand if necessary and use brake lube.

Neil.

[FireFox31]

tl;dr: Braking is critical. Caliper failure is expensive at best and life threatening at worst. Newly rebuilt calipers must have their boots checked for improper seating. Check your caliper boots annually.

I am no expert and this issue is important, so double check what I say.

I believe this is dangerous and should be addressed immediately. I believe brake fluid could escape the unsealed boot, leading to loss of braking. I am certain that this loose boot will allow water and contaminants in to your caliper piston, damaging it, eventually causing it to freeze in place. It could freeze closed which would overheat and ruin your pads and rotors (requiring you to replace pads and rotors on both sides), and may eventually overheat your wheel, tire, and other adjacent rubber suspension components.

I have been plagued by failing calipers on my 2000 V70. I had five calipers fail in five years, all purchased and installed by a Volvo dealership. Taking the matter in my own hands, I saw the fifth caliper failed from a loose boot allowing debris in, letting the piston rust, seizing it clamped on the rotor. Pictures of the breach and the piston damage are attached. I bought a Volvo branded rebuilt caliper from FCP, inspected it before installation, and found the caliper boot was not fully seated by the rebuilder! A picture of the improperly installed seal is attached. Who knows how many of those calipers I bought from Volvo had the seals unseated before installation. Always check the boots on rebuilt calipers.

Read cn90's brake caliper DIY. At the end of the thread, read JimBee's tip for seating caliper boots.

I recommend everyone check their caliper boots once a year. I use cn90's wood block method but without disconnecting the caliper:
1. Remove the caliper from the rotor.
2. Insert some 1/2" wide wood shims to fill the space slightly less than the pad+rotor width.
3. Step on the brakes to extend the pistons onto the blocks.
4. Remove a shim.
5. Repeat steps 2-4 to gradually extend the pistons until the boots are easily visible.
6. Examine the caliper boots for tears or separation at the piston heads or caliper bodies.
7. Retract the caliper boots using break pad spreader tool or C-clamps.

With the calipers partially extended, a caliper boot which has slightly unseated from the caliper body can be reseated by carefully pressing the boot back in place using a large flat head screwdriver. Study cn90's caliper boot illustration and you'll see that you must slip the boot lip into the ridge in the caliper body. This is how I fixed the unseated one on my newly rebuilt Volvo branded caliper.

Your caliper boot is vastly unseated, so the best solution is to entirely remove the piston, inspect it for corrosion, and if serviceable, reseat the boot. Use cn90's wood block method to remove the caliper, drain its fluid, insert a block, and expel the piston with shop air, then remove the piston and boot. Any rust on the piston surface which contacts the caliper body means it is ruined. In this case, it is easiest to replace the caliper, then inspect the boots on the rebuilt calipers you receive before installing them.

Your piston boot can be replaced (if damaged) or reseated (if perfect) if the piston and and caliper body are rust free. New boots are readily available from parts websites. Reinstalling the boot and piston is tricky. I believe I used this procedure:
With the piston removed from the caliper, seat the top of the boot on the piston.
Pull the bottom of the boot down so it extends below the piston.
Lubricate the piston and caliper hole with brake fluid.
Insert the bottom of the dust boot into the caliper, engaging it with the rim where it belongs.
Push the piston back into the caliper.

You could try to rebuild the caliper yourself. New boots are readily available from parts websites. Pistons are available from the UK and we're currently planning abscate's caliper part group buy. You'd need to hone the inside of the caliper as well. You may want to sandblast, prime, and paint the exterior of the calipers. I'm about to dive in to this for my rear calipers but haven't started the research yet.

Post pictures of your pistons and caliper body. Let us know how it works out. Good luck.

[LOB]

What kind of grease have you both been using? To me it looks like the dust seal has swollen because you/the workshop have been using petroleum based grease and not the proper silicon grease. Five calipers failing in five years? That has happened to me once owning five Volvos for 30 years.

I wouldn't however consider it acute dangerous to drive with a bad seal as long as the piston is moving freely. The brake fluid will not leak because of a flimsy seal. But it should off course be fixed asap.

[abscate]

See Attached image, is this dangerous to drive on? For the life of me I couldn't get it to sit right when I saw it, but both of my calipers are in the same condition.

I was trying to hunt down the cause of a slight squeal that occasionally occurs on the first couple seconds of when I press on the brakes - so obviously I bought and went under to replace the pads. Word of the wise: Check that your pads are actually low before buying new pads; mine were only 1/2 height of the new ones. Rotor within mm tolerance, no ridge either. Even after new pads and a layer of grease on everything, squeal persists. Could it be related to this?

Any advice on reseating one of these guys with a hobbyists toolset? I tried poking around but the rubber was very soft and close to tearing

Piston.png

Since there is no water in Davis, you can spray that with silicon spray and work that back into place with a plastic spudger Or a wooden coffee stir stick.

Here are some calipers to practice rebuilding skills…oooooof…….#sarcasm

[ToriWhite]

... swap your slider pins over as most of the re-built units supply really poor quality 'pot' metal pins which don't like to be removed when new, let alone in a couple of years.

I've read about this prior, thinking I'm going to buy new ones- don't have the time/space/tools to rebuild, closest PnP's 4 hours away.. Man I miss being near a pnp; broke cv boot? replace the whole CV joint for $15, why not!
Thankfully they 'felt' 'OK' when I used the caliper pressing tool from Oriellie's for my pad replacement, nothing gritty or grinding.. so it could be worse, like Abscates

Thanks for the sanity check! Time to spend more money.. yay..

[abscate]

If you are keeping the car 5 years plus, think about going Volvo at 3-4x the price.

The rebuild quality has fallen considerably and it’s getting worse. The slider pins in the rebuilds are now pot metal and will corrode, although they will last in your arid climate.

[cn90]

Besides PnP junk yard, another good source for piston is ebay.

Some people part out their cars and list the used caliper for sale (about $25-$40 range).

Check to be sure the boot is still good and piston OK.
Buy it and rebuild using ATE seal kit. If the boot and piston are OK, you can use it as is.
Now you have an Genuine caliper for cheap.

PS: The calipers at local parts stores are questionable.

Anyway, search ebay for "Volvo 850 brake front caliper", then click "Used"...

This is an example of it for $22, free shipping:
https://www.ebay.com/itm/234100177463

[abscate]

The problem with the eBay approach is the presence of VOLVO on he caliper has no relation to its status as OE or not. Most of the rebuilds with junk parts are so labelled.

[scot850]

Many people do not realise or know that Volvo has a lifetime warranty on parts fitted at the dealer. Make sure that calipers are included on that as they may consider them a wear item. On such an important item as brakes it is worth considering that route if there is a dealer near enough to you. I know the problem is of many dealers being of poor quality these days but surely they can manage brake calipers and get the system flushed at the same time.

Just booked the 'R' into our new dealership for a smoke test on the EVAP system as I have no time or inclination to try to figure out where the leak is. Unless it is an easy access (cheap) repair I will probably put the car away and wait until I can get a hoist is the rear has to be dropped again (car not mine!).

Neil.