Brake Calipers - Air Cooled.

[Flat Six Pete]

I was out in the X5 E53 two week ago, Its done 124K (4.4 LPG converted) when there was a vibration on the steering wheel. As the suspension was was up to date and aligned I figured maybe the wheels wanted balancing. When I pulled into the balancing place he pointed out that one of my calipers was sticking, indicated by the wheel bolts being very hot to touch and the whole assembly hot by comparison to the other side. He stated that was my problem. I had the wheels balanced anyway and a new caliper did seem to sort out the problem a week later. Brilliant tow car as in 8 years it has always started first time bar once.

As the 993 is approximately 25 years old and the calipers on that car have never been touched I wondered who here has replaced / refurbished their calipers and the reason?

[Panamax]

Flat Six Pete said:

As the 993 is approximately 25 years old and the calipers on that car have never been touched I wondered who here has replaced / refurbished their calipers and the reason?

It tends to depend on how the car is used and also where it's parked.

Typically the problem is salt and crud getting past the rubber boot seal and into contact with the steel piston, which then starts to rust. The rust forms a crust on the piston which causes it to jam in the caliper bore. Back in the day you could often refurb a caliper at modest cost by buying a new piston and a seal kit.

These days, depending on the car, new calipers aren't very expensive whereas labour rates are high so most garages will just fit a complete new caliper. It has the added benefit of the fix being "right first time" as opposed to "might work or might not".

Whether expensive calipers are still worth a refurb I can't say because I've never had a problem with one.

[ras62]

Calliper refurb is a common job on a 993/964. They suffer corrosion behind the steel plates which causes them to lift and stop the pads moving properly.

[Flat Six Pete]

Thanks for the reply. I will take them off for a look see.

[Orangecurry]

ras62 said:

Calliper refurb is a common job on a 993/964. They suffer corrosion behind the steel plates which causes them to lift and stop the pads moving properly.

This.

OP - taking the pads out should be really easy, but it isn't. Obviously you need to move the pistons off the pads, but once you have, each pad has two 'spiders' glued (probably) onto the back face - these spiders fit into each piston.

So IF the pads have worn down enough, you'll be able to manoeuver them out.

When you fit new pads you are supposed to glue new spiders on the back.... procedure is probably
1 - put spider into piston
2 - put glue on pad
3 - slide pad in...

I say 'probably' as I don't glue the spiders to the pads, and therefore I can slide pads in and out with ease.

So - to the point of all this faff....
The stainless steel plates that sit in the calipers are at each end of the pads - once the spiders are out of the equation, if you can't slide the pads in and out of the caliper, the steel plates have started to lift, jamming the pads.

Picture 1000 words thing. Plates are the dark metal - pistons with recess for spiders (different sizes)

Good luck.



ETA and if the owner, or the garage fitting new pads, doesn't want to deal with the plate-lift, they can just file away the edges of the new pads, that's the metal part of the pad not the friction material, in order to slide new pads in. So you won't know for sure with your own calipers until you come to fit new pads. Who fitted your current pads?

Edited by Orangecurry on Tuesday 25th July 22:52

[supersport]

1987 3.2 not touched the brakes in 15 years, beyond fluid changes.

Done 80,000 km in that time. A handful of track days and many spirited drives.

I guess they just don’t make them like they used too.

[Bobley]

I had particular manky 87MY 944 Turbo calipers refurbed back in 2009. Cost about a grand using many new and a lot of used but clean pistons and new seals. The bent steel plates were all replaced too.

I've got my eye on the present 94 993 Calipers. Someone has painted them red... badly... and put the decals on wonky... nice job for the winter I think!