Bleeding brakes....

964RS · Jun 14, 2008

Advice needed please.

Car: 1993 RS Lightweight LHD.

I needed to replace the brake fluid as the brake pedal was going to the floor at the track and the diagnosis was that the brake fluid had boiled and needed replacement. I do not know when it was last changed. The existing fluid is 'normal' brake fluid colour.

I bought a Gunsons Eezibleed kit and 2L of ATE Super blue fluid. Following their instructions I:

Clamped the brake fluid reservoir vent tube at the flexible section. Connected the Eezibleed to the tyre at 20psi. I drained all 4 corners under pressure (is this where I went wrong?) in the order: Right Rear, Left Rear, Right Front, Left Front.

Filled the Eezibleed canister with ATE brake fluid. Re-pressurised the tyre and bled the brakes in the order: Right Rear, Left Rear, Right Front, Left Front until old brake fluid and then blue brake fluid came through and no air bubbles - didn't take long.

Problem: the brake pedal goes straight to the floor and there is little or no braking effort. If I pump the pedal: the effort builds up (I can hear the pump whirring) - then the pedal goes solid after about 5 cycles but only for a second and then the pump (or a pressure relief valve perhaps) starts whirring, the brake warning light illuminates and the warning buzzer beeps about 5 times. I take my foot off the pedal and after a few seconds try again but the brake pedal goes straight to the floor. Brake fluid is also pouring out through the ventilation tube onto the road during all this activity. If I go round to the front the pump is running and running and then eventually stops.

Help!

By clamping the flexible pipe have I starved the pump of fluid? Do I need to bleed the pump too? Where have I gone wrong and what do I need to do?

rs phil · Jun 15, 2008

you are best doing it with two people,furthest away first and then front on same circuit,diagional,so right rear first then left front,then left rear, right front, get someone to pump pedal until hard,then bleed off from caliper,also you have to bleed the inside and outside nipples on each calliper,inside first i think,do this process for the rest of the callipers,i find you need 2 litre of fluid, i usually just use a small ammount of the second can, this way works every time, throw that easy bleed away,get the wife out of the kitchen and get her pumping that middle pedal,hope this helps..also get castrol srf brake fluid,expensive but never any problems

rs phil · Jun 15, 2008

just spotted what you said about claping tube,when you do it with two people you dont have to clamp anything just keep topping up fluid, by the sound of things you have clamped the wrong tube for the easy bleed,it should be the tube that comes out of the top of resivoir,the one that lets the fluid go on the ground behind the drivers wheel,you can put a small self tapper into the pipe where it comes out rather than clamp pipe,i would still do it with two people

harry · Jun 15, 2008

ORIGINAL: 964RS

Advice needed please.

Clamped the brake fluid reservoir vent tube at the flexible section. Connected the Eezibleed to the tyre at 20psi. I drained all 4 corners under pressure (is this where I went wrong?) in the order: Right Rear, Left Rear, Right Front, Left Front.

Filled the Eezibleed canister with ATE brake fluid. Re-pressurised the tyre and bled the brakes in the order: Right Rear, Left Rear, Right Front, Left Front until old brake fluid and then blue brake fluid came through and no air bubbles - didn't take long.

Help!

By clamping the flexible pipe have I starved the pump of fluid? Do I need to bleed the pump too? Where have I gone wrong and what do I need to do?

I don't think you are supposed to empty the brake fluid reservoir. When I did my 993RS, I clamped the venting hose and used a pressure bleeder (Motive power bleeder) I had mailed from USA. You can buy it in UK also under a different brand name. I bled the caliper furthest to the reservoir 1st then the next furthest etc. but I did not let the reservoir fluid level go below minimum - I kept disconnecting the reservoir and topped it up with fresh brake fluid until all 4 calipers were bled so I think you made a mistake. I don't know if you keep bleeding it will resolve but you may need to take it to a professional to get it bled? I suggest you go to Rennlist to search their archives and if nothing turns up ask how you can resolve your problem. Good luck.

Harry

harry · Jun 15, 2008

ORIGINAL: rs phil

you are best doing it with two people,furthest away first and then front on same circuit,diagional,so right rear first then left front,then left rear, right front, get someone to pump pedal until hard,then bleed off from caliper,also you have to bleed the inside and outside nipples on each calliper,inside first i think,do this process for the rest of the callipers,i find you need 2 litre of fluid, i usually just use a small ammount of the second can, this way works every time, throw that easy bleed away,get the wife out of the kitchen and get her pumping that middle pedal,hope this helps..also get castrol srf brake fluid,expensive but never any problems

Yes, SRF will make it extremely expensive if he is doing it incorrectly and he will have to bribe his wife with some goodies [

]

Harry

Steve Brookes · Jun 15, 2008

Like Harry said you are supposed to bleed one caliper at a time and not let the reservoir fluid go below the minimum at any time. i.e. you should have bled the right rear until it got to the min mark then stopped and added your new fluid to the reservoir and bleed bottle. It looks like you've now got an air lock and need to start over. Here's what I would do:

1. Go get at least 1 more litre of brake fluid (Halfords do normal dot 4 or dot 4 racing which is the same spec as ATE blue/gold).
2. Fill the reservoir to just below max mark.
3. Fill the gunson bleed bottle and attach it to the reservoir. Clamp the vent hose.
4. Attach the air hose to the tyre.
5. Bleed the right rear caliper through both valves. Outside valve, then inside valve. Stop bleeding when the Gunson bleed bottle gets to the min mark.
6. Undo the air line, refill the bleed bottle and do the left rear the same way.
7. Do the front right caliper the same way.
8. Do the front left caliper. At this point you can let the bleed bottle empty and can stop bleeding when the fluid in the reservoir gets just below the max mark.

Laurence Gibbs · Jun 18, 2008

sounds to me as if you have a secondary problem causing your lack of pressure. I would doubt that you would loose all pressure in your brakes from boiled fluid (certainly whilst it's still hot, but not when it's cooled back down) I would have thought some pressure should have remained after the fluid cooled. Certainly draining the fluid completely was a no no and you've now compounded your problem as you don't know if it's your bleeding or you have another problem.
First off the high pressure side of the circuit is completely seperate (the electric boost pump and high pressure reserviour (ball) if you've not bled that yet leave it or you will confuse yourself more (further the pressure from the ball is HIGH and there is a specific way of bleeding it!!
From what you describe the boost side is trying to create boost (the motor werrs and stops once upto pressure) your frantic pumping of the pedal then depressurises the boost pump circuit and the pump then tries to boost again.Having just read your description again it's also possible that the boost circuit is trying to pressurise and can't which leads back to the prv at the bottom of my post(does the pump whir then stop then you have pedal pressure which goes after five presses of the pedal or does the pump just keep trying and pressur is only built when you pump the pedal?) . You have no presure on the low pressure side of the circuit. Either because you have introduce a shed load of air in or something has failed. Your mention of fluid coming out of the breather may be a clue to your problem . One further thing to note, if you drained the reserviour empty you may have got air into the high pressure pump too but only if allowed the pump to run whilst empty at the reservoir. There is a PRV in the high side though i am not sure without checking if this would cuase the symptoms you have if it failed. my guess is that you have more than just air in the system.

RSGulp · Jun 18, 2008

ORIGINAL: 964RS

Advice needed please.

Car: 1993 RS Lightweight LHD.

I needed to replace the brake fluid as the brake pedal was going to the floor at the track and the diagnosis was that the brake fluid had boiled and needed replacement. I do not know when it was last changed. The existing fluid is 'normal' brake fluid colour.

I bought a Gunsons Eezibleed kit and 2L of ATE Super blue fluid. Following their instructions I:

Clamped the brake fluid reservoir vent tube at the flexible section. Connected the Eezibleed to the tyre at 20psi. I drained all 4 corners under pressure (is this where I went wrong?) in the order: Right Rear, Left Rear, Right Front, Left Front.

Filled the Eezibleed canister with ATE brake fluid. Re-pressurised the tyre and bled the brakes in the order: Right Rear, Left Rear, Right Front, Left Front until old brake fluid and then blue brake fluid came through and no air bubbles - didn't take long.

Problem: the brake pedal goes straight to the floor and there is little or no braking effort. If I pump the pedal: the effort builds up (I can hear the pump whirring) - then the pedal goes solid after about 5 cycles but only for a second and then the pump (or a pressure relief valve perhaps) starts whirring, the brake warning light illuminates and the warning buzzer beeps about 5 times. I take my foot off the pedal and after a few seconds try again but the brake pedal goes straight to the floor. Brake fluid is also pouring out through the ventilation tube onto the road during all this activity. If I go round to the front the pump is running and running and then eventually stops.

Help!

By clamping the flexible pipe have I starved the pump of fluid? Do I need to bleed the pump too? Where have I gone wrong and what do I need to do?

Yep, this is where you went wrong. You are meant to fill the easibleed with new fluid at the start then bleed each caliper until all the old fluid is pushed out and new fluid can be seen. Never let the easibleed run out of new fluid. You shouldn't have used air-pressure to drain (empty) the system. I would guess you still have air somewhere in the system.

You did clamp the correct tube - the brake fluid reservoir vent hose. If you don't do this the easibleed will push fluid under pressure through it and it will drain all over the floor.

Rich

964RS · Jun 18, 2008

Repeated with more fluid as Steve said. There was just a little air left in the callipers but enough to make a BIG difference. Now a solid pedal after only an inch of travel. Warning light was on because fluid level was on minimum after pressing brake pedal (thanks Dave F). Big difference compared to before. Previous fluid was regular fluid and I have no record of when it was last changed. I'm hoping there is no heat soak through on track days now that I'm using RS29s and ATE Super Blue (disclaimer - other brake products are available [

]). In future - I am going to bleed a little out of the callipers after every track day. Is there any benefit in going to Castrol SRF anybody?

Pagid yellows squeal like crazy at urban speeds unless I give them a firmer push and then they are silent. Haven't bled the clutch circuit - I'll leave it for another day when I feel like hugging the gearbox!

Next I'm going to clear out the holes in the brake disks - 5.5mm diameter rear and 6mm diameter front?

Steve Brookes · Jun 18, 2008

Glad to hear you're all sorted and now good to go at Croft. [

]

964RS · Jun 26, 2008

Brakes were superb at Croft! ABS did not kick in once. Did brake-free cool-down lap after every session. Going to bleed them a little and clean out the holes in the disks.