Brake Bleed from hell - What's gone wrong
05-01-2010, 03:30 PM
#16
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Cliff,
Your C4 has the hydraulic brake booster instead of the vacuum type on the (non-RS) C2. Therefore you indeed need to bleed the accumulator ( 9mm spanner from the top of my head).
Turn on the ignition and let pressurre build until the booster pump shuts off, bleed the accumulator and repeat the process by turning on ignition, bleeding etc. until no more air is present in the flow of fluid.
After this has been done now turn your attention to the calipers....you should be able to get all air out in just a few pumps (3-5) of the pedal per caliper.
Good luck!
Your C4 has the hydraulic brake booster instead of the vacuum type on the (non-RS) C2. Therefore you indeed need to bleed the accumulator ( 9mm spanner from the top of my head).
Turn on the ignition and let pressurre build until the booster pump shuts off, bleed the accumulator and repeat the process by turning on ignition, bleeding etc. until no more air is present in the flow of fluid.
After this has been done now turn your attention to the calipers....you should be able to get all air out in just a few pumps (3-5) of the pedal per caliper.
Good luck!
Marc
05-01-2010, 03:32 PM
#18
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05-01-2010, 03:37 PM
#20
Nordschleife Master
05-01-2010, 03:42 PM
#21
Nordschleife Master
I crack open the bleeder before the pump runs .
I run a small tube from the bombs nipple to the top of the reservoir .
Then I power up the pump . The fluid runs at low pressure .
05-01-2010, 04:38 PM
#22
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05-01-2010, 08:30 PM
#23
Haven't read the entire thread yet, sorry if I'm adding to info already stated, but I've done a similar thing in the past letting air into my 91 C4. I bought 2 liters of cheap fluid and used that to rebleed. I used both liters as I was doing the entire system including the pump, bomb, valves etc.
After running the cheap stuff through I went back to the blue ate and bled that through until I saw it.
In the end I finally got the air out, but I was worried for a while there.
Hope you get it sorted.
After running the cheap stuff through I went back to the blue ate and bled that through until I saw it.
In the end I finally got the air out, but I was worried for a while there.
Hope you get it sorted.
05-01-2010, 09:38 PM
#24
Sorry, seems I jumped too soon.
As for amounts to bleed:
- how much to bleed when changing fluid
By measurement: the workshop manual says to bleed 250cc of fluid at
each wheel, and 100cc of fluid at the clutch to replace the fluid (if
you have a C4 add 250-300cc for the lateral differential lock, 200cc
from the longitudinal lock, then a couple complete drains of the
accumulator - a lot of fluid! - and solenoid block).
1000cc - 250cc at each wheel
100cc - clutch
300cc - lateral diff lock
200cc - longitudinal diff lock
?cc - couple of complete drains of accumulator and solendoid block
(a lot of fluid)
------
1600cc+ ~2 cans
As for amounts to bleed:
- how much to bleed when changing fluid
By measurement: the workshop manual says to bleed 250cc of fluid at
each wheel, and 100cc of fluid at the clutch to replace the fluid (if
you have a C4 add 250-300cc for the lateral differential lock, 200cc
from the longitudinal lock, then a couple complete drains of the
accumulator - a lot of fluid! - and solenoid block).
1000cc - 250cc at each wheel
100cc - clutch
300cc - lateral diff lock
200cc - longitudinal diff lock
?cc - couple of complete drains of accumulator and solendoid block
(a lot of fluid)
------
1600cc+ ~2 cans
05-01-2010, 10:58 PM
#25
Nordschleife Master
05-01-2010, 11:22 PM
#26
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After replacing my rotors about a year ago, and changing to SS brake lines, I had to push around 2L of cheap fluid through the system and then the ALTE Blue. I bleed all 8 caliper nipples, the clutch slave cylinder and the "bomb." You will be surprised where air can hide in the C4's system....
DO NOT drive to see if it gets better (although by now I am sure that you haven't)
I found that a lot of patience was needed, and it eventually worked itself out. I scared my dog a few times swearing so much in the garage.
Having done a full re-seal on my engine, IMHO I think that a brake bleed is actually harder.
On that note, good luck!
DO NOT drive to see if it gets better (although by now I am sure that you haven't)
I found that a lot of patience was needed, and it eventually worked itself out. I scared my dog a few times swearing so much in the garage.
Having done a full re-seal on my engine, IMHO I think that a brake bleed is actually harder.
On that note, good luck!
05-02-2010, 11:52 PM
#28
Three Wheelin'
Thread Starter
So here's how the story ends.
I also decided to change the pads while the car was up in the air before I sorted out the air in the system problem. I mean, how hard could it be? Every DIY states, that this is the easiest thing you can do. Well I'm here to prove otherwise.
I started with the front passenger. Unhooked the clamp - no probs, removed the wear sensor - no probs (didn't want to re-use them), pulled on the outer pad. Nothing. Stuck tighter than two coats of paint.
After some further Rennlist searchs, turns out the dreaded anti-squeal pad and mushrooms were baked-on, stuck-on in there. With some gentle prying, got the outer pad dislodged and out. Moved over to the inner. Followed same procedure. Got the pad clear from side to side, but top to bottom, it was jammed in. Not budging. Even hit it repeatedly with PB blaster.
Gave up for the time being, moved to driver side front. Same thing. Outer came out with no probs, inner was completely baked in. No movement or slack at all. Frozen.
Gave up again. Moved to the rears. They came out as expected. Popped new pads in with some gentle tapping with a hammer (its damn tight with new pads) and repeated on the other side. Took less than 10 mins per wheel.
Moved back to the first brake. Pulled and pulled on the pad, but no joy. Final decided to loosen the 19mm hex bolts and slide the caliper up off the rotor enough to tap the bad out sideways. Worked perfect. There was enough slack in the hard line to make it work.
So far 75% of my brakes are replaced! Went back to the last wheel. Figured that popping the caliper up would work again. Tried it, and cleared the rotor. Tapped away at the stuck pad - nothing. I then thought the only thing left to do is completely remove the caliper by unhooking the hard line and hammering the stuck pad out. Remember I still have to flush the brakes to get rid of the air, so if I unhook the hard line I can just re-fill the entire system and be done with it.
So I began to loosen the 11mm nut at the caliper end. Because of years worth of sludge and build up, the nut didn't loosen, instead the hard line started to twist. Urgh. So now, on a Sunday afternoon, I'm really going to bugger things up by breaking the hard line. I retightened the nut, slipped the old brake pad in and buttoned up the brake.
I also found out that the driver front suspension coil is turning on its axis (still on original Boges with 165k kms). It's not fully secured at the top of the mount. Not very comforting, so I think I should consider a new suspension or just get the shop to re-secure it. The rubber boots up there have all cracked any way, so it's time for a change.
I re-bled the system and got the required pedal pressure back and went out for a test drive. Works perfect except for the one brake with old pads. I'm going to take it to the shop, have them replace the hard line, remove caliper and hammer the snot out of the sticking pad.
I tried valiantly to fix it all myself but fell at the last hurdle. But learned a heck of a lot about the car. Thanks in no small part to everyone here on RL and my neighbour Chris. Oh year and my battery is dead too.
Still grinning after my test drive. Even after all that cursing and bruised knuckles (ego). Happy motoring and thanks for all the advice.
Cliff
I also decided to change the pads while the car was up in the air before I sorted out the air in the system problem. I mean, how hard could it be? Every DIY states, that this is the easiest thing you can do. Well I'm here to prove otherwise.
I started with the front passenger. Unhooked the clamp - no probs, removed the wear sensor - no probs (didn't want to re-use them), pulled on the outer pad. Nothing. Stuck tighter than two coats of paint.
After some further Rennlist searchs, turns out the dreaded anti-squeal pad and mushrooms were baked-on, stuck-on in there. With some gentle prying, got the outer pad dislodged and out. Moved over to the inner. Followed same procedure. Got the pad clear from side to side, but top to bottom, it was jammed in. Not budging. Even hit it repeatedly with PB blaster.
Gave up for the time being, moved to driver side front. Same thing. Outer came out with no probs, inner was completely baked in. No movement or slack at all. Frozen.
Gave up again. Moved to the rears. They came out as expected. Popped new pads in with some gentle tapping with a hammer (its damn tight with new pads) and repeated on the other side. Took less than 10 mins per wheel.
Moved back to the first brake. Pulled and pulled on the pad, but no joy. Final decided to loosen the 19mm hex bolts and slide the caliper up off the rotor enough to tap the bad out sideways. Worked perfect. There was enough slack in the hard line to make it work.
So far 75% of my brakes are replaced! Went back to the last wheel. Figured that popping the caliper up would work again. Tried it, and cleared the rotor. Tapped away at the stuck pad - nothing. I then thought the only thing left to do is completely remove the caliper by unhooking the hard line and hammering the stuck pad out. Remember I still have to flush the brakes to get rid of the air, so if I unhook the hard line I can just re-fill the entire system and be done with it.
So I began to loosen the 11mm nut at the caliper end. Because of years worth of sludge and build up, the nut didn't loosen, instead the hard line started to twist. Urgh. So now, on a Sunday afternoon, I'm really going to bugger things up by breaking the hard line. I retightened the nut, slipped the old brake pad in and buttoned up the brake.
I also found out that the driver front suspension coil is turning on its axis (still on original Boges with 165k kms). It's not fully secured at the top of the mount. Not very comforting, so I think I should consider a new suspension or just get the shop to re-secure it. The rubber boots up there have all cracked any way, so it's time for a change.
I re-bled the system and got the required pedal pressure back and went out for a test drive. Works perfect except for the one brake with old pads. I'm going to take it to the shop, have them replace the hard line, remove caliper and hammer the snot out of the sticking pad.
I tried valiantly to fix it all myself but fell at the last hurdle. But learned a heck of a lot about the car. Thanks in no small part to everyone here on RL and my neighbour Chris. Oh year and my battery is dead too.
Still grinning after my test drive. Even after all that cursing and bruised knuckles (ego). Happy motoring and thanks for all the advice.
Cliff
05-03-2010, 08:24 AM
#29
Nordschleife Master
Cliff, sounds like you have the classic symptoms of caliper plate lift. It's corrosion behind the spring plates that is forcing them inwards which means it's hard to remove old pads and usually even tougher to put new ones in. You really don't want to be tapping new pads in place with a hammer. The temporary solution is to grind the sides of the pad backing plates down. The proper solution is to refurb the calipers to remove the plate lift.