D2 rear left brake binding

[robertofollia]

Hi all,
Again, my D2 is turning me crazy.
Since 2004, when I bought it, I've changed and renewed brake fluid with good quality Dot4 ABS every 2 years.
Lately my left rear wheel began getting hot.
-Took caliper out. One guide pin was badly seized. Took it out, sanded, polished, greased and reassembled. 6 miles test drive and everything ok. Thought "done". How wrong I was.
Took a 30 mile drive and arrived almost smoking, smelling awful (burnt friction material)

-So took caliper out again. Checked guide pins-they were still ok and slided in and out like oiled spaghetti.
"Must be the piston" I thought. Took the biggest mole grips to grip the piston and turned it 180 degrees left and right, inserted and extracted it a little bit to see it was not binding. Pistons were a little hard to insert, could not do it by hand, needed a tool, but was not hard, went really smooth.
Went for a short test dirve (6 miles), braking many times as in a offensive driving (in ever do that). No problems. Wheels weren't hot. Thought "done". How wrong I was.

-Last weekend I took a 30 mile drive with almost no braking (only some times as it was mostly highway). Arrived stinking and almost with smoking pads.
Did nothing about it.
Yesterday I went to fill her up. 3 mile ride. Every 100 meters (so 0.06 miles I braked hard). Return journey from fuel station, same manouevre. All discs has the ssme temperature. If the brakes were binding I guess in 3 miles they would be scalding hot.
Pedal feel never changed

So if guide pins are OK and piston seems to slide well, what else do I have to look at? Hose? Maybe. But aninternally decomposing hose should fail always and brakes would be always on in the rear left corner of the car.
The same would be with a seized piston.

So, next step is to take caliper apart and renew rubbers and piston. I have only found (even I asked for another ones) the "blue box" rubbers. Is is true that some of them are 0.5 mm bigger in diameter? I can't find genuine or OEM ones, just blue box in Spain. Because reusing the old seals is out of the question.

Any help would be appreciated. I guess the easiest thing is go for complete new caliper, hose and carrier, but don't wanna follow the "easy" route.

Best regards

 

[stu454]

Just get a new caliper, for fuck's sake.

 

[riceybean]

Mine was doing this same thing last week. I just got a caliper and now its all better.

 

[discostew]

I think you should do a couple other things before you get the caliper . If its getting hot like that you should be able to lift the rear wheels off the ground and feel the drag as compared to the other side . Then open the bleeder or crack your line loose at the caliper if the bleeder is frozen . If the drag goes away its not the caliper . If it still has a noticeable drag with no pressure in it get a couple calipers . I would look for complete units with the brackets since your slides have already been a problem .

 

[robertofollia]

I guess it's not the hose as I cracked open the bleed nipple and drag was the same, no residual pressure either, only drips.
Checked it again after depressing and releasing brake pedal. no residual pressure.

I will be taking caliper apart and rebuilding it and might go for a new or recon caliper if binding persists.

But what I will never understand is how a caliper carrier/bracket, if pins are ok, can make brakes bind if it's not bent and everything apparently ok
Best regards

 

[discostew]

I guess it's not the hose as I cracked open the bleed nipple and drag was the same, no residual pressure either, only drips.
Checked it again after depressing and releasing brake pedal. no residual pressure.

I will be taking caliper apart and rebuilding it and might go for a new or recon caliper if binding persists.

But what I will never understand is how a caliper carrier/bracket, if pins are ok, can make brakes bind if it's not bent and everything apparently ok
Best regards

The pads move freely in there slides right ? If it is the caliper piston it wouldn't be a big surprise . But at least you know its not anything keeping fluid pressure in that channel . Just a free thing to check before spending the $$$ .

 

[The Fourth Amigo]

Just get a new caliper, for fuck's sake.

:smilelol:

 

[robertofollia]

Found! Solved!
Hose in perfect shape (so I'll save these for later on). I always renewed my fluid every couple years.
But... piston... f*ckin' seized. There was no way of pulling the piston out pumping softly the brake pedal. It always twisted and stuck. Had to come out with brute force.
Bore was ok, no scoring, no nothing. Lightly sanded it with wet-n-dry 500 grit paper embedded in brake fluid and cleaned thoroughly afterwards.
Piston was rusty but not corroded. Could not be saved as had a score mark due to sticking. Had a quality replacement piston.
But.. how about the seals?
wahahahahahahaaaaaaaaaaaaaaaaa blue box galore!!!
There were no OEM parts in stock, Gen-you-win ones out of stock and in backorder for 1 month, so no other possibility than dreaded blue box (so I ordered 3 sets just in case, luck I did)
The truck was being repaired in the garden of a friend and I had to remove it before dark (so it was a definite "i have to go back by myself, yes or yes).
So were the blue box parts:
-inner seal, 0,5 mm less in inner diameter. piston would not fit. So had to recicle the old one (was in perfect shape)
-Dust bellow: The old one was not fit for re-use, but the new one... would not fit. The part that fits into the piston fitted ok, but the part that should engage in the caliper's recess was 0,5mm thicker, so did not fit. 1st one ripped in the trial.
To fit the 2nd one, I Had to machine it, but how do you machine rubber? Easy. Turn it the other way round, find a suitable metal "doughnut" inside the seal and begin filing. Second bellow died in this procedure as I had machined too much.
Third one survived, the procedure and fitted after a bit swearwording.
Piston slid in no problems
Bleeding, no problems.
Pedal feel-perfect
Test-flying colours
Miles done so far: 200.
Problems: none
Braking performance: awesome: does not pull anywhere.
Brake temperature: perfect: no more burn-pad smell, all rotors at same temp

Here goes a pic of the piston as removed

Happy wed to everyone