I had a rear caliper binding on the Passat, so I took it apart, poured brake fluid all over me, the driveway and my tools (as you do) then I found it very difficult to push the piston back in. So I pulled the entire thing apart and cleaned it all up. I have a few questions:

1) The piston is a bit polished, but all the corroded gunk cleaned off. How pristine does it have to be to be serviceable? Caliper wasn’t leaking. But then again the one on the other side failed last year so maybe this was about to go.

2) Can you even get seals? Do I need to replace the square seal?

3) Will I die and should I just get a new caliper? Is rebuilding calipers a thing?

1) piston is fine so long as there are no cuts or deep scratches that will cause damage to the seal.
2) I wouldn’t replace the seal even if you can get one. They don’t really wear out etc…
3)You should be fine so long as you keep everything clean and only use Brake Fluid to lubricate anything. Be very, very careful not to get Mineral oil on/in anything.

It is on motorbikes, google passat brake caliper rebuild kit, and there are some available

If one matches yours it’s a go-er.

I’ve just been reading about it. I’m questioning if I need new seals or not.

You should be able to get either just the seals, the seals and a new piston, or a whole new caliper. Pays yer money and takes yer pick. New rear calipers for most years of Passat seem to come in for circa £70 on ebay, so I’d be tempted to just swap the whole thing for less hassle…

Aye, I did a full rebuild on a mondeo caliper, worked just fine then I discovered I could have bought a refurb for about the same and it’d have saved a ton of effort and looked nicer too

I reckon you only usually have to do the seals on most car calipers when something’s been outright damaged, especially the outer seal, but ymmv.

I trust, after all this work, you’re going to paint the caliper? Red or yellow seems the norm, although I’m not sure which colour makes you stop faster… 😉

If it all looks ok and wasn’t leaking I wouldn’t replace it.

The square seal performs more than one function. The fact it’s not leaking doesn’t mean its not fecked. The square seal deforms when the brake is depressed and when the deformation reverses it pulls the piston back in again. If the seal is old I’d be having it out and replaced with a new one especially if you already have the old one exposed.

If you’ve ever changed successive sets of brake pads on a car and noticed that the service life of the pads is getting shorter it’s probably down to the seals. As the seals harden with age they don’t pull the piston back as efficiently. I’d change them.

I’ve done it on calipers that were hard to get genuine replacement

Common as a passat.id not bother.

Seals , a new piston , and the work involved was near as much as a caliper.

Anything else would be like replacing the clutch but not the release bearing as it felt ok ….

Google BIGG RED for brake parts, you can buy pistons, seals etc individually or as kits or even send yours off to be fully refurbished.

If its sticky or leaking then I would get new seals as the minimum, pistons should be OK as long as there are no scoring or pitting to the polished surfaces.

Clean everything up and use red rubber grease for the seals.

A new caliper from GSF runs at £180. So I reassembled it anyway. There was gunk all on the piston that I scraped off, so perhaps that was the problem. The brake operates as normal under the foot pedal – it releases fine – it’s only when the handbrake screws the pad on that it doesn’t release. Which is rather odd as having disassembled it I can see that the motor screw simply pushes on the piston in the same was as the brake fluid pressure does.

It’s either the gunk on the piston or the old seals that were the problem.

I bought one of those bleeding devices that fits onto a tyre and pushes fluid from the reservoir. Only I didn’t do the cap up properly and poured about 600ml of brake fluid through the engine compartment and onto the drive 🙁

I bought one of those bleeding devices that fits onto a tyre and pushes fluid from the reservoir. Only I didn’t do the cap up properly and poured about 600ml of brake fluid through the engine compartment and onto the drive

Yea, that’s about standard. Those things are a massive, steaming pile of shite.

Just tested it out. When the engine’s running, the pedal sinks every so slowly when pressing hard on it. When the engine’s off, it doesn’t.

No visible leaks though. However there’s a lot of talk about this – seems that I might need to do the computerised bleed process to guarantee no air bubbles.

Computer bleed should only be needed if you are breaking into the ABS circuit if it’s anything like Citroen.

I used a 50cc syringe to pull fluid whilst doing the 2 man method. Pulls a lot of air through the threads on the nipple but still gets everything sweet.

Yeah there’s some debate over the ABS thing.

There’s a VCDS procedure that flushes out the ABS pump into the MC from where you can then bleed it out. I should at at this point that the fluid in the system is many years old so probably needs a flush as much as it does a bleed.

Sounds like every modern diesel engine vac assisted brake. (Except edukators)

Oh aye, I was wondering about this- is it possible to get brake pipe end cap things that you can thread on when you remove a caliper? That’d be ace. I had a google last night but couldn’t find anything. Obviously you can clamp a rubber hose but that’s inelegant

molgrips

Subscriber

I bought one of those bleeding devices that fits onto a tyre and pushes fluid from the reservoir. Only I didn’t do the cap up properly and poured about 600ml of brake fluid through the engine compartment and onto the drive

Aye, they’ll do that. Partly because they’re a bit crap but also because 30psi in a tyre is way way more than is a good idea for this. If you want to use them then the best way is to buy a filler cap for your car off ebay and adapt the fitting for it, and then use a mostly flat tyre, IIRC 5psi worked well for me but that could be bobbins.

But sucking through with a big syringe is pretty much as effective unless you’re doing a whole system

I let the spare down to 20 which is the recommended pressure. It was ok with the cap done up tightly. Still, buying a 5l of brake fluid just in case!

Update on the caliper. It works fine as a brake but the handbrake has a funny turn. The motor is ok but the internal winding mechanism jammed. On examination the screw thread forced its way past the stop that was designed to prevent it screwing itself tight. Could be because I tried to open it with VCDS when it was open, but shouldn’t have done this IMO. Tried to mod it but failed, so on top of everything else I’ve gone for a new caliper.

Next job is a flush including ABS pump with VCDS.

Update, as I know you’re all dying to find out.

Used the computer to activate the bleed process for the front two, it only expelled a little bit of fluid though each time. I should have done all four that way, I guess, but I didn’t because I didn’t want to leave it sitting whilst I faffed around with wheels and jacks. But probably no reason why I shouldn’t have.

Anyway, the pedal seems ok now but it still sinks slowly at idle if you press hard. But at roundabouts and stuff, it doesn’t seem to. I guess I don’t really know how the servo assist actually works so I can’t figure out if it’s an issue. Pedal feels normal in driving.

brakeparts.co.uk

These guys also sell loads of parts for overhauling calipers. For the price over one caliper I did both rear calipers on my van.

The provide all the different types of grease needed in the pack.

They even get parts like handbrake return springs, slider pins, bleed nipples and pad retaining springs.

Looks like you have put the caliper back together, but red grease for brake piston re-assembly ( special compatible with seals)
And I had a load of hassle with a brake caliper that turned out to be some tiny corrosion on the edge of the disk backing which stopped the pad retracting correctly 30 second fix when it is all disassembled but I had fitted the new calipers before I found what was happening.

MOT pass!

The tyre-based bottle setup for pushing fluid though did work pretty well in the end, once I made sure the cap was on the reservoir. I’d recommend it.

As an aside, as I was using the spare to do it I realised that the car is meant to have 215/55/R16, but I’ve been running 205/55/R16 for the last 50k miles! Bugger.