A very very hot back wheel and even hotter disc

[A lex]

If its been driven for extended periods (very hot) then it might be time for a new disc and pad(s) too.

Happened on my V70 D5, it needed a refurb exchange calliper at about £250 from memory.

[RoyMacDonald]

New rear calliper and pads (mine virtually melted) also change the brake pipe as that can get damaged by the heat even if it looks OK. Agree about not driving it far. I think my bill was about £350

[laundryman]

having just had this a couple of weeks ago (see earlier post) i replaced the piston and seals on both sides (with a touch of red grease). Blowtorch job on siezed side. Unfortunately the disc got eaten too so full set of discs and pads as well.

[andyKent]

Hi again,

Thanks all for further info - it helped a lot (and made me take seriously how hot wheels are serious).

In the end, I diagnosed it by taking the wheel off and removing the caliper and refitting. The wheel was free again to rotate (by hand) whilst jacked. Then I pushed the brake a few times and it locked (still jacked). So, I knew it wasn't the handbrake and ordered caliper and brake fluid.

The sliding caliper pins (in the old caliper) undid fine (using the 'spanner on torx bit' trick) but were badly stuck (in the rubber housing, which was utterly dry and full of grime). My solution was to put a screwdriver (flat bladed) into the gap (where the thread is visible after unscrewing the pins and using the screwdriver as (gentle) lever against the threads (very gently and aiming to lever on the end of the pin ultimately, away from the thread). Knowing I had a new caliper (with new pins) I could do this quite aggressively and popped them out rapidly. If I was going to replace, I'd do it very gently.

When the caliper and fluid arrived I got around to taking off the old (original) caliper bracket (2004 car) and found that the two bolts of the caliper bracket had already been rounded a good bit by a previous owner (probably sticking caliper previously, fudged into action) and I proceeded to complete the job of rounding them (after WD40 and wire brush, repeated about 10 times and some hours of letting the WD40 penetrate to no avail). I tried all the sockets and spanners in two toolkits (both brand new) and all slipped and rounded. There was no room to hammer on a smaller socket.

After wringing my hands for a while I went online and found out that the bolts are 'stretching' bolts. This seems to mean 'soft metal' and 'one use only'. So, I then had to reassemble the brake and drive over to Volvo to pick up some new bolts (with threadlock). That gave me time for more handwringing about what to do once I got the new bolts.

Since I now knew that the degree of brake binding was proportional to how hard I broke (since it would stick more or less where I put it), I knew I had to drive very gently and brake as little as possible on the trip to Volvo (1 hr round trip). I also stopped every 10 mins and checked that the wheel wasn't getting too hot (I had all my tools and jacks in the boot, so could have stopped and released brake if needed). In this way I got to Volvo and picked up the bolts and got home without getting the wheel too hot. Bolts were £1.50 each or so.

After I'd picked up the bolts I started to worry about getting the rounded bolts out. I don't have welding torch (or know how) and was not confident that even a drill would help given the space back there and given my lack of general competence. So, I went back to this forum and (eventually) found a somewhat less than emphatic response in this thread: http://www.volvoforums.org.uk/showth...t=rounded+bolt mentioning "Irwin Bolt Grips". I got a set of these from homebase (also driving very gently and minimising maximum the pressure on the brake pedal) and they worked perfectly. Bolts out.

Then, after I had got those bolts out I considered the connector which attached the hydraulic brake line to the caliper (after I'd attached the hose clamp). This was also rusted and stuck but came loose without much bother (tiny bit of careful WD40 and wire brush). However, the nut was not independent of the connector, so this meant that as I turned the nut the whole rubber pipe began to twist. To avoid damage to the connector/nut/pipe/etc, I ended up turning the (removed) caliper around to avoid twisting the (old) rubber pipe and doing the reverse to install the new caliper. Not ideal but worked.

Bleeding was done using first a 'gravity bleed' (which is where you just leave the bleed nipple undone a bit until fluid starts 'weep out' after the hose clamp is removed) and then a bottle (half filled with fluid) with a transparent pipe (ending below the level of the fluid). The bubbles are visible in the pipe from the front of the car where I was pushing the brake. I stopped pushing the brake when I saw the bubbles stop travelling down the pipe (into the bottle, where the pipe ended below the level of the fluid to stop air getting back in).

It would indeed have been a 1-hour job, if not for the rounded bolts.

I guess that the rear brakes on the xc90 suffer (and ultimately get stuck) from being driven very conservatively - I never hit the brakes even remotely hard (did an advanced driving course when I was young and was taught to look ahead as far as possible to brake well in advance). In fact, for anybody who doesn't get good MPG from their D5, check your rear brakes. My MPG went through the roof after fitting the new caliper and the acceleration is better than it has ever felt. This thing has been dragging for a long time.

I also note that the Irwin Bolt Grip idea came from a thread about the trusty 850. Thus, the XC90 has come of age in the tradition of Volvo. Perhaps, if enthusiasts, such as those of this forum, begin to take up arms with the commitment of the 'old Volvos, good for a million miles' crew, we will start to see a few XC90s make it into and beyond the 250k miles mark.

And, one final tip. Each time some such 'maintenance' comes up, get a quote from a Volvo main dealer for the work and then tell your wife. Then, do the work yourself and be a hero. In this way, over the last 2-3 weeks, I've saved about £2,500 in labour (oil/filters, mounts, abs rings, caliper). It beats being the 'good-for-nothing husband who plays with his car for the whole weekend and gets everything covered in oil'.

Andy

[andyKent]

Originally Posted by A lex

If its been driven for extended periods (very hot) then it might be time for a new disc and pad(s) too.

Happened on my V70 D5, it needed a refurb exchange calliper at about £250 from memory.

For the record, I got my caliper for about £110 (PFS parts), I guess rebuilt but could have been brand new. No exchange necessary and rapid delivery.

Andy

[RoyMacDonald]

Originally Posted by andyKent

For the record, I got my caliper for about £110 (PFS parts), I guess rebuilt but could have been brand new. No exchange necessary and rapid delivery.

Andy

Did you change the brake hose as well? The indi who did mine for £350 said that he always changes that pipe now as he's had them fail occasionally afterwards through being overheated for a period outside of their design tolerances.

Roy

[cheshired5]

I would never clamp a brake hose.
Most that I see aren't squishy rubber that just pops back to shape but in fact have a metal core so if you clamp it, you risk permanently deforming the core and restricting fluid flow.
You're also not going to lose that much fluid anyway if you leave the reservoir cap in place and let the hose hang and any small amount lost is replaced by the new fluid you have on standby.
The metal core in the hose is also a reason why braided "upgraded" hoses are a waste of money and are probably only worth doing on motorbikes, where standard hoses can still be a bit last century.

[andyKent]

Originally Posted by RoyMacDonald

Did you change the brake hose as well? The indi who did mine for £350 said that he always changes that pipe now as he's had them fail occasionally afterwards through being overheated for a period outside of their design tolerances.

Roy

No I didn't change the hose and will have to monitor it for a while to be sure of things (and I will the connector to the caliper).

In principle, I suppose the heat generated depends on how hard you brake when the caliper binds/sticks and how far/fast you drive with it stuck. I guess I drove for a week or two with it binding to the point where the mpg noticeably dropped and the car felt sluggish but it never got to the point of glowing discs or boiling fluid. I never push the brake pedal hard, so it never got the chance to bind at high pressure (tend to drive it like an oil tanker).

Plus, I expect that they can get twisted pretty hard during removal if the connector is as corroded as mine was, and I went to great lengths not to twist mine for this reason.

Anyway, yes, in principle, if I had thought of it in advance (and had more time to fiddle) I should have changed the hose too.

Andy

[andyKent]

Originally Posted by cheshired5

I would never clamp a brake hose.
Most that I see aren't squishy rubber that just pops back to shape but in fact have a metal core so if you clamp it, you risk permanently deforming the core and restricting fluid flow.
You're also not going to lose that much fluid anyway if you leave the reservoir cap in place and let the hose hang and any small amount lost is replaced by the new fluid you have on standby.
The metal core in the hose is also a reason why braided "upgraded" hoses are a waste of money and are probably only worth doing on motorbikes, where standard hoses can still be a bit last century.

Yep, this sounds sensible. I rather thought the clamp was also about air (to prevent issues later with bleeding) and I also had some idea that the clamp would prevent back pressure (and potential damage upstream in the brake system) if I had to compress the piston (which of course there was no reason to do, but I hadn't realised that).

And, mostly, the clamp was general advice on the 'net so I hedged my bets and followed it. As you can tell this was my first brake job of any kind, so will be able do it with more consideration/confidence next time.

Ta!

Andy

[cheshired5]

Originally Posted by andyKent

Yep, this sounds sensible. I rather thought the clamp was also about air (to prevent issues later with bleeding) and I also had some idea that the clamp would prevent back pressure (and potential damage upstream in the brake system) if I had to compress the piston (which of course there was no reason to do, but I hadn't realised that).

And, mostly, the clamp was general advice on the 'net so I hedged my bets and followed it. As you can tell this was my first brake job of any kind, so will be able do it with more consideration/confidence next time.

Ta!

Andy

That's fair enough and all part of the learning curve.
That said, you will still find seasoned mechanics clamping hoses.
Even if you were winding/pushing in a piston, you alleviate any pressure by opening the caliper bleed and allow the fluid to escape there.
The fluid in the caliper has had a hard life and is the worst quality in the whole system so you want it out and refreshed not pushed back up the pipes and reused.