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seized front brake D2


steve_a

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Had a carp end to the afternoon. Had been driving about through the day, starting and stopping and then final house viewing (well it turned out to be the final house viewing) started to move off and noticed the D2 was not as perky to go as it normally was.

Felt like the brakes were binding.

Went around the corner and was certain there was an issue, so stopped the car, pumped the pedal a few times, started it, reversed in case something was stuck in the calipers.

Still nothing. It was just getting worse.

Made a decision to scrap the rest of days viewings and limp home (about 10 mins away) but the binding got very, very bad. Basically I limped it to the main road and stopped as the pads were smoking at that point.

Checking around it looked like only the front right was hard on, the rear left also seemed warm, the other two brakes were normal.

Called the RAA to get recovered and by the time the flat bed came, the brakes had released.

I've been in the garage and taken the two wheels off and the only things I can find:

1) Front Right did get v hot, but plenty of meat left on pad, no sign of anything caught.

2) tried to compress the pistons to check for a seized one and they wouldn't move.

3) tried them one at a time and they both move without fuss

put the front back together and popped the back wheel off.

Seemed maybe a little heated, but not so sure, the same burn smell as the front was very faint, but the same on the other side

Again, couldn't press the piston in.

I'm edging towards the ABS unit playing up. I have the ABS/ETC/HDC lights on (and have for ages) so I got no hint about that. I saw the handbrake/general brake error light come on a couple of very brief times in the last few weeks. But I thought the first one was low fluid so topped it up.

I also saw it briefly after startup today.

Any hints - I'm thinking i have done all I can and need to take it to a garage to be testbooked, which is needed for the ABS modulator.

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Yes I think you have done all you can - never heard of the ABS being responsible for sticking the brakes on though, its normally dormant unless triggered - could you hear it chattering at all? If it thought (perhaps due to a dud sensor) that one wheel was not moving and was trying to brake the others to "stop wheelspin" then that might do it but you would hear it clearly.

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Not a noise - usually get a bit of an ABS like noise on start up, according to Rave it's supposed to that as an ABS test. Though with the three Amigos showing, I thought ABS was off.

About the only thing I can think of is that the outlet solenoid has decided to die, stopping the caliper from releasing. I pulled the cable block off the abs and ran the engine up without it, as expected extra lights on dash, then reconnected and restarted. It would fit with no symptoms followed by buggered, followed by OK.

It's a killer, if the flatbed had been a bit quicker i might have got it in the garage while still seized and had the chance to burn myself / look at the issue, especially if the diagonal wheel was locked, that might suggest master cylinder issues, but again, upstream of ABS mod and you have to garage it :(

I think I preferred my simple 90 and series 1 disco... anyway, good to know I'm not giving up prematurely

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Got a call from the garage. They want to:

replace the complete caliper on each side, on each axle, i.e. 2x front and 2xrear

new discs on back

new pads on back

new master cylinder

new servo

A$6500

WHAT!

The master cylinder, servo, discs and pads are legit (I reckon) the pedal has had some creep and they reckon it has leaked into the servo. Not impossible.

The discs are now needing doing.

But replacing the WHOLE caliper on each wheel???!? Bear in mind this thing doesn't know what rust is, I think there is still a factory sticker on one of the calipers.....

On top of that there was labour for replacing the master cylinder, and labour for replacing the servo. Erm. That's charging twice for the same bit of work.

Glad I went the main Adelaide dealer, a fly by night place would have been terrible....

Needless to say I explained the the parts bill was about 2-3 times the size it needed to be and that I would just do any work myself. I've instructed them to flush the brake system to see if that gets rid of the current problem and I'll go from there.

Bear in mind I told them I had had the caliper off and had seen the pistons moving freely (when operated separately) and that the problem was very much 'instantaneous' it didn't kind of build up. If they did the work they might have fixed it just as a by product of flushing.

That's restored my faith in asking garages to do work on my cars.

Oh well, of out at the weekend to buy a Suzuki jimny :)

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i dont get why you cant push the pistons back together... this is a normal procedure that you'd do if you were fitting new pads, so if it doesnt work it indicates an issue imo.

One possibility is the rubber flexi hose could be breaking down inside stopping the fluid moving back correctly

The garage dont have a clue whats wrong with it, and are just trying bore you a new ass hole.

MC and servo i find highly suspect.

All four calipers? well only 2 of them were acting odd, so thats completely made up

disks and pads, well fair enough.

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I agree with Aragorn: it might be the rubber hoses colapsing. However, If you can't move the pistons back with the caliper off the truck, they are seized. They need to be replaced or rebuilt. New parts for my DI were like 170 USD for the front. I went ahead and bought the rears at the same time because I figured eventually they would need to be replaced too.

If the caliper was seized you need to replace the pads and either replace or resurface the rotor because it has most likely warped with the heat. You should always replace the pads in sets so you should definitely do pads all around and see how the rotors look.

MC, Servo and ABS control unit probably won't buy you anything.

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The front calipers are dual piston. I couldn't push both in at the same time, but I could see-saw them, showing that they are free to move.

There is the ABS block up from the caliper, it has solenoids which control both inflow and outflow of fluid from the caliper, as well as having to push fluid back through the convoluted path in the block if nothing else.

Have a look at a dis-assemble of the block here Hummer Forum ABS modulator pdf to see what I mean.

I have checked Rave, because I wondered if there was instructions to open the bleed nipple when pushing the pistons back when fitting new pads. However... the front pads have a decent amount left, so it maybe that the pistons are already all or most of the way in.

Good point, I'll have to check the run out of the front disc and make sure it's OK.

As I said, I noticed some pedal creep when I was firm on the brake stopped in traffic and had noticed a little fluid loss, I wouldn't be surprised if the MC and servo needed doing, there was no sign of any fluid loss anywhere else and I had been over everything, just forgot about trying to check the MC/servo.

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Well, I'd better fess up, and perhaps it can go in the tech archive for fault finding....

Got the car home and took the master cylinder off - no sign of leak into servo, so if anything probably a leak past the seals in the M/C

However, started searching around the garage for some brake fluid to put the M/C back on and start flushing/bleeding. I couldn't find any. What I could find was a bottle of power steering fluid, clear/yellowish in color, bottle identical to brake fluid.

I also found a bottle of ATF power steering fluid, color red, bad news for rubber products.

I topped the cylinder off about 2 weeks ago after seeing a brake warning light going around a corner. I also parked the car on the car port (which has a good slope to it) with the nose up.

I can only assume I picked up a mislaid bottle in the auto part shop and got power steering fluid. I never noticed because of the color and during the last two weeks it has presumably been causing issues for the M/C rubber seals, and the up hill parking would suspiciously be towards the secondary circuit, with the front RH caliper on.

Costly accident, as it appears that I can take a chance and flush the hell out of the system and have a cost of M/C, brake hose and piston seals, though it may have affected more on the way through.

Or do the right thing and replace all the rubber items:

M/C (£170 at least D2 one doesn't seem rebuildable)

Seals for calipers x 6 (£40ish)

flexible hoses x 6 (£35 ea ish so £200 ish)

plus one servo one way valve (if I can get one) since the bugger broke as I was taking M/C off.

If I'm lucky the ABS block is OK, if not that will add a good amount the bill. I'm planning on doing it decently, and see what the ABS block is like afterwards.

The garage didn't pick up on the issue, even though I had a note in with the car explaining I'd topped it up, and searching on the net showed that the calipers locking on like this was a common indicator. I could also see some swirling mixing in the resevoir, which was probably the two fluids mixing together.

doh!

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