DIY: Post mortem on stuck brake calliper (Disc-o Inferno!) Topic is solved

[proton17]

Hi all,

Longtime lurker with first post. I own a late-2009 XC90 purchased used in 2011. I love this car but it has been neglected and abused due to some health and family circumstances (more on that in another thread). I know this has been covered well elsewhere, but thought I'd relate my recent experience with a stuck calliper (and lots of rust).

Recently I noticed a burning smell and a departure from the usual brake feel. Just by feeling the heat given off, it was clear the left front calliper was stuck. I happened to have a thermal camera I use for work, which illustrates the issue nicely:

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Closer inspection of the affected rotor shows it was getting really hot! (this was a few minutes after ten minutes of driving):

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That's over 650 degrees F.

Here's a video showing the culprit after removal, with my son stepping on the brake pedal:




(as I mentioned and as you can see from the level of corrosion, this car is in desperate need of some TLC).

Closer inspection showed that the seal on the faulty piston had failed:

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I also managed to snap off the bleed nipple, which is no big deal since the calliper was trashed anyway. Attempts to manipulate the seized piston with various means showed that it was really solidly stuck.

After some cleaning, runout on the rotor was miraculously still within specification (these are some beefy rotors!):

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You can see where the pads had settled against the rotor - these spots required some more aggressive cleaning with a wire wheel and abrasive pads. Note also that I would not attempt to reface the rotor with the small 3-jaw chuck shown (stronger fixation would be required), but it was adequate for assessing the runout.

Perhaps due to the heat, things were really badly seized on the left front. I ended up replacing the left front brake pipe with some 3/16" line bent to match the original. The nipple at the "upper" end (mating with the ABS Modulator) was in good shape, so I was able to re-use it (which is good because it didn't seem to be a standard brake line fitting).

The nipple at the calliper end (10mm diameter, 1mm thread pitch, unthreaded lead section) was readily available from a local Auto Parts place. The fittings require a bubble flare. The left front brake pipe is a fairly short length and easy to remove (you have to take out the air intake box and fuse box to unscrew the upper end from the ABS modulator).

On the right side, I cut the original brake pipe just short of the nipple leading to the rubber brake hose (I replaced the left pipe due to damage from my overly rough attempts to unscrew the brake hose). There is enough slack on the right side to put a new nipple and flare, but the exterior polymer coating on the original Volvo brake pipe made it impossible to slide an aftermarket nipple onto the pipe. I ended up stripping a bit of the coating off for the bubble flare, and drilling out the bore of my new nipple on the lathe (a lathe is not essential but makes it very easy to centre-drill the fitting - the amount of material removed is tiny). Other than this I followed the procedures outlined elsewhere on MVS.

I installed remanufactured front callipers on both sides (around $100 each from Ultra Auto Parts) along with new brake hoses. Flushed the system with new brake fluid using the Motive pressure bleeding system, which works great (thank you MVS!)

After bedding in the new pads, the brakes are working great and I can proceed with all the other work this car needs. I am going to replace the left front ABS sensor and tone wheel, as I am still getting an ABS tone wheel code and can imagine these have been fried by rust and the heat from the stuck calliper.

[proton17]

One other note regarding the replacement calliper:

My 2009 has the 328 mm rotors and double-piston calliper. For some reason, the Auto Parts dealer I worked had these parts listed as being for a 2010 XC90 in their database. To avoid getting the wrong calliper, it seems important to indicate the rotor size and number of pistons. From what I've read here and elsewhere, the rotor size and calliper can vary within the model year.

[proton17]

As suspected, the tone wheel was broken. The end of the ABS sensor was gouged as well, so I replaced both the sensor and the wheel. Each part was around $80CAD.

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Before fitting the new tone wheel, I took off all rust on the mating surfaces with a wire wheel. It was not necessary to pull the axle out of the transmission to do this. The tone wheel went on without too much difficulty, probably due to erosion of the mating surface due to corrosion. It was still quite snug. If the fit of the new tone ring onto the axle was tighter, I might have had to pull the axle out to use bench top tools or a press to install it. In my case it just took patience and careful tapping in a star pattern (and I did not have them impression that the axle would have parted easily from the engine/transmission).

Despite all the rust, the axle joints moved very smoothly and the rubber seals were intact. The hub bearing also seemed in very good shape. The hardest thing was loosening the lower bolt on the steering knuckle - in addition to penetrating oil this required heating the nut with a torch and the highest setting on my impact driver. I used a couple of flame protector sheets, when applying the torch, to shield the plastic ABS clip above the nut and the rubber seal below.

Routing the new ABS sensor cable required removal of the air cleaner and fuse box again, but with practice this has become a three minute job. Access to the clips for the sensor cable is a bit tight, but doable.

After reassembly and road test, the brakes were working fine and all (brake-related) warning lights and VIDA codes were cleared. I noticed that VIDA allows monitoring of brake disc temperature, which would have been useful in diagnosing the stuck calliper. Reassuringly, both left and right front disks now match closely in temperature (shown here tested on a long downhill):

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There seems to be a glitch in the axis labeling, and the correct upper/lower limits on the Y axis are 119C and 39C respectively for the front discs (the 918 and 0 values apply for the rear brakes). As one would expect, the rear brakes are somewhat cooler - I added the rear disc temperatures mid-recording and the plot traces are not auto ranged.

I am guessing the temperature monitoring works by way of changes in the DC resistance of the ABS sensors adjacent to each disc (while the speed sensing works by looking at the AC modulation frequency induced by the tone wheel).

Next project is to fix a leak around the catalytic converter.

[nedc]

Wow, seeing all that rust makes me appreciate being in a place where we hardly get Winter (South Carolina). But the fact that it's nearly 100F here today is the price we pay...

[proton17]

Wow, seeing all that rust makes me appreciate being in a place where we hardly get Winter (South Carolina). But the fact that it's nearly 100F here today is the price we pay...

I was going to say, can you tell we don’t live in Arizona?

The poor XC90 has been parked on the street it’s entire life. From 2018-2020 there was a period where I was not able to drive (or wash) it much. We live in a hilly part of Montreal, and the city uses a *lot* of salt in the winter.

[cn90]

Thanks for the photos, they are very educational!

That is precisely the reason brake caliper seizes: the cover boot is cracked (could be road debris or old age etc.),
allowing water/salt to get in corroding the piston. Once the piston is corroded, it won't move any longer...or it moves but does not retract causing seizing...

For those who live in snow/salt area, corrosion happens whne salt + warm weather, so:
1. If you can inside in the winter, the corrosion will accelerate bc of the warmer environment,
So, even small amount of water (garden sprayer) to spray on brake calipers etc. helps.
You can do this if parking inside garage.
For outside parking, then wait for a day > 0C, go to a self-serve car wash and rinse the salt.

2. Around late March or April, spray the under chassis with a garden hose a few times to rinse the salt off.

A little bit of maintenance goes a long way.

Also, if one has the ATE rebuild kit, you can rebuild the brake system once every ley's say 10-12 yrs. And usually you only do this once. I posted the ATE brake rebuild tricks in P80 1998 S70 forum...

[proton17]

Thanks for the photos, they are very educational!

Thanks for the recommendations! I noticed in some other threads on the topic that there has been some discussion about how hot things can get. The thermal camera and Vida plotting function gives a nice illustration of this!

I think my situation represents a "worst case" of what happens when the undercarriage is neglected in a snow/salt climate. Our garage is too small for the XC90, and it's been parked on the street since I bought it used over ten years ago. In the best of cases it requires some diligence to trek out to local car washes after our frequent heavy snowfalls. From 2018 to 2020 I was recovering from a serious injury, and the car was not driven (or washed) much.

The good thing for us is that it's a second car that I use mainly for hauling my two greyhounds, and renovation materials when needed (my wife gets a company car which is updated every few years). Our small garage is my workshop, so I have some space and flexibility to deal with the maintenance issues as they arise. The XC90 won't fit in the garage, but I have set up a system where I can safely lift the car on our small sloping driveway.

I will be happy to keep this car another ten years, but need to make an honest assessment about whether the rust situation is terminal.

For those who live in snow/salt area, corrosion happens whne salt + warm weather, so:
1. If you can inside in the winter, the corrosion will accelerate bc of the warmer environment,
So, even small amount of water (garden sprayer) to spray on brake calipers etc. helps.
You can do this if parking inside garage.
For outside parking, then wait for a day > 0C, go to a self-serve car wash and rinse the salt.
2. Around late March or April, spray the under chassis with a garden hose a few times to rinse the salt off.
A little bit of maintenance goes a long way.

Yes indeed - if you don't want your car to look like mine, these are really good suggestions! For some reason there are not many self-serve carwashes around me, which might have something to do with the climate. Most of the drive-throughs around don't do much on the undercarriage, so I'll have to figure something out going forward.

Also, if one has the ATE rebuild kit, you can rebuild the brake system once every ley's say 10-12 yrs. And usually you only do this once. I posted the ATE brake rebuild tricks in P80 1998 S70 forum...

I will check this out - I needed to get my XC90 back in service and the rebuilt calibers were only $100 each but I like the idea of restoring things. My rear callipers will also need some attention soon.

My next project is to address corrosion around the rear catalytic converter, so you can expect to see more rust soon!

[AndreyKo]

What tool did you use to make this photos? (with temperature)

[proton17]

What tool did you use to make this photos? (with temperature)

I used a FLIR thermal camera. I have one for industrial applications, but you can now get fairly cheap units that work in conjunction with a smartphone. If you search on Amazon or similar you will find many models. None of them are dirt cheap, but the price is really coming down.

These are incredibly useful for diagnosing all kinds of things. The one I have is so sensitive that you can see a "heat print" from your hand after touching a wall. The print lasts for several minutes...