So that's why my brakes suck!

Caffeine · Postby **Caffeine** » Thu Aug 21, 2008 1:32 pm

I have a basically unmodified 2001 NB8B. It has done 199000km, and has plenty of meat left on the pads (pads are newish bendix advance front and rear)

Only mod to the brakes is DBA slotted rotors on the front.

The problem I have is the brakes suck! I've bled them multiple times, replaced the fluid (with motul dot5 stuff) multiple times without fixing them. The handbrake is adjusted well.

The symptoms are that heaps of travel is necessary to engage the brakes, and often, if you haven't used them in a while, the pedal feels like it's going to hit the floor. Pumping the pedal once or twice brings back some pedal and the brakes work 'normally'

Once you have pumped the pedal once or twice, the brakes work well, they have no problems stopping the car.

I'm thinking the problem could be one or more of the following:

Stretchy brake lines, the pedal feel a bit bouncy when fully engaged (fitting new braided lines this weekend to remove that possibility)
Air in the ABS block (I'll bleed the lines at the ABS block this weekend also)
Dodgy master cylinder?
Vacuum leak?

Can anyone suggest another possible cause? Or point me towards which of the causes I've though of is most likely?

Thanks all!

RG.net · Postby **RG.net** » Thu Aug 21, 2008 1:42 pm

i also have this problem, i am not sure what it could be though. i have also bled the brakes and it was ok for a while but now its gone to S**t again. :frown:

GP14 · Postby **GP14** » Thu Aug 21, 2008 1:59 pm

Dot5 you say? that's the silicon stuff. Not good for our system. Dot5.1 is ok.

wun911 · Postby **wun911** » Thu Aug 21, 2008 2:01 pm

how do you bleed at the ABS bit?

Caffeine · Postby **Caffeine** » Thu Aug 21, 2008 2:08 pm

GP14 wrote:Dot5 you say? that's the synthetic stuff. Not good for our system. Dot5.1 is ok.

My mistake, it's 5.1, which I purchased from mania late last year

wun911 wrote:how do you bleed at the ABS bit?

I'm following this bit of info from mx5racing

how do you bleed the ABS unit

the pipes screw into the top of the unit - 4 of them - one for each wheel. Just crack the nut and gently press down on the pedal (obviously 2 people needed). Do them in the same sequence N/S/R, O/S/R, N/S/F, O/S/F. They are marked on the ABS unit.

If you are still lacking pedal feel then bypass/exclude one caliper at a time and see if the pedal regains a solid feel. Easiest way is to crimp of the flexible brake hose with hose tool or if you dont have them a flat faced pair of pliers - dont use vice grips!! If their is any air left after the crimpt of section the pedal should be better. Obviously you only do this in the garage on stands/jacks and never drive it this way

Garry · Postby **Garry** » Thu Aug 21, 2008 2:18 pm

How much play do you have in the slider pins Caffeine? Are the rubber bushes still attached to them? If there is a lot of play the caliper could be bouncing around over bumps knocking the piston back into the caliper?

Caffeine · Postby **Caffeine** » Thu Aug 21, 2008 2:25 pm

Garry wrote:How much play do you have in the slider pins Caffeine? Are the rubber bushes still attached to them? If there is a lot of play the caliper could be bouncing around over bumps knocking the piston back into the caliper?

No idea! Somthing to check though, thanks Garry!

wun911 · Postby **wun911** » Thu Aug 21, 2008 4:29 pm

Cool

Hey how long does the master last?

(clutch master went out at about 120 000 km)

Uncle Arthur · Postby **Uncle Arthur** » Thu Aug 21, 2008 8:57 pm

Do you have, or can you fit, a master cylinder brace?

manga_blue · Postby **manga_blue** » Thu Aug 21, 2008 10:46 pm

Dodgy master cylinder and slack old brake lines are definitely candidates with those symptoms.

Check for master cylinder leaks around the base of it where it joins to the vacuum unit. Check brake lines for signs of aging - perishing, cracking or noticeable bulging under pressure.

You haven't got fluid seeping out around the pistons in one of the calipers, have you?

Caffeine · Postby **Caffeine** » Thu Aug 21, 2008 11:21 pm

manga_blue wrote:You haven't got fluid seeping out around the pistons in one of the calipers, have you?

The fluid level hasn't dropped, and I can't see any seeping fluid. I'll try the other suggestions, thanks!

RG.net · Postby **RG.net** » Thu Aug 21, 2008 11:34 pm

would taking that black pipe running to the inlet manifold have anything to do with it, i did this and the brakes went crap, then bled them and they were ok (not as good as they were beforehand) but slowy went crap again

Postby **Boyracer** » Thu Aug 21, 2008 11:42 pm

Is the handbrake adjusted at the handle or at the caliper...sounds like they might be out of adjustment at the caliper....also check that all the wheel bearings are OK.

bigdog · Postby **bigdog** » Fri Aug 22, 2008 12:10 am

MXHEVN wrote:would taking that black pipe running to the inlet manifold have anything to do with it, i did this and the brakes went crap, then bled them and they were ok (not as good as they were beforehand) but slowy went crap again

That would be the vacuum line to the booster - without it your brake booster would not work, making the brakes much harder to operate. PUT IT BACK ON!!! :roll:

RG.net · Postby **RG.net** » Fri Aug 22, 2008 12:26 am

bigdog wrote:
MXHEVN wrote:would taking that black pipe running to the inlet manifold have anything to do with it, i did this and the brakes went crap, then bled them and they were ok (not as good as they were beforehand) but slowy went crap again

That would be the vacuum line to the booster - without it your brake booster would not work, making the brakes much harder to operate. PUT IT BACK ON!!!

it is back on, it was off for 5-10 seconds.