75TS brake problem

[sslim]

hi all,

i am new here, i am having brakes problem with my RHD 1989 75 2.0TS for the longest time and i can't seem to solve the problem, i hope somebody can help me.

my brakes set up:
1. brand new bendix master cylinder
2. steel braided hoses all round
3. tarox front disc and fast-road pads with stock 2-pot brembo calipers
4. tarox rear fast-road pads and OE discs with stock bendix calipers
5. manual frt/rear brake bias adjuster
6. Tutela Extreme 5 (DOT 4) brake fluid

problems that i am having:

1. pedal travel - i can't seem to get rid of the first 2-3 inches of pedal travel before it starts to bite. no matter how many times i have bleeded the brakes, i still have this problem. could it due to a loose linkage cuz mine's a RHD? or i need a bigger master cylinder? or something else?

2. not enough braking power on track - it is fine driving on the streets, but once i hit the track i just don't get enough biting power to slow the car fast enough. initial bite is ok but it does not kill enough speed and when i press harder, the pedal is a little spongy. i can't get the weight to transfer to the front fast enough for turn it, hence it understeers quite a bit. front calipers have been serviced, does this means i need more braking power in front? but i want to run 15", which means i can probably just upsize the calipers and not the discs, will this work? any suggestions?

3. brake fade - after 3-4 laps i start to get some brake fade as the pedal gets a little spongy. i suspect it is the rear brakes heating up, and also the exhaust manifold heating up the brake fluid reservoir. anyone running air ducts on the rear brakes?

somebody HELP!

ss

[75evo]

SS,

Gravity bleed the system. Just open the reservoir cap, then open one bleed screw at a time, and the the fluid flow out on its own. It'll take about 2-3 minutes per side. Make sure the fluid doesn't drop below min. level in the reservoir. Don't pump it or anything. Just let it flow out on its own.

Use the front fog light opening as brake ducts to the caliper

Wrap the rear exhaust section close to the caliper.

Also check the linkage for RHD cars for play.

[BigSwede]

Air in the rear brake line.

Raise the rear as high as possible and bleed the system once again, if it doesn't work, leave the rear elevated over night with pressure in the system. jam the brake-pedal down with a piece of wood between the seat and pedal or similar.
Where did you mount the bias adjuster? you didn't create a new "high point" in the system did you?

[sslim]

hi 75evo,

this gravity bleed technique, does it apply to both front and rear brakes?

[sslim]

hi bigswede,

i mounted the adjuster right in front of the master cylinder, pretty much same level as the master cylinder in the engine compartment. when the hoses are ready next week i am gonna move it into the glove compartment (my car's RHD), or somewhere in car.

so you suggest i re-bleed just the rear brakes using your method? or both front and rear brakes?

[75evo]

Quote:

Originally posted by sslim hi 75evo, this gravity bleed technique, does it apply to both front and rear brakes?

[BigSwede]

Front are easy and straight forward, usually the rear is the problem.
How do you bleed them? I suggest that you put a friend in the driver seat and he/she puts a foot on the pedal and give it som gentle pressure and when you open up the pedal is pushed down in a not too fast steady motion, not too fast as it may cause cavitation and give you more air...
Try to close before the pedal hit the floor so no air sneaks back in through the threads. Repeat until the fluid is clear and no air comes out.

About the high point, I just checked to see that you hadn't put it betwen the front seats or similar, that would be a beatch to bleed becaus of the air getting trapped in the highest most point.

[sslim]

hi all,

tried all methods, can't seem to solve the problem.

- checked all the linkage and everything's fine. problem is not from there.
- used gravity method, tested brakes, still the same.
- used big swede's method, same thing.
- paid a workshop for their brand spanking new suction bleeding machine, same thing.

bleeding 3 times over the weekend and it is still the same. i am very sure there is no more air in the system (there can't be!?), my next question is, what else?

could it be master cylinder/master pump, do i need a bigger one? anyone tried fitting a bigger one from another car before? am i not getting enough fluid fast enough to the calipers?

ciould it be some flex in the system? could it be the aluminium brembo caliper flexing due to metal fatique after so many years?

servo? or anything else?

i would very much like to just plonk the money down to upgrade the front calipers, and hope all the problems go away ..... but don't want to have the same problem after spending the money.

have been at this problem for almost 5 months and still can't seem to nail it, HELP!

[75evo]

Hmm I've never had this problem except when the wilwoods were installed. But the problem was the wilwoods I originally had pistons which were too large. Then I swapped to wilwoods with smaller pistons and 24mm MC.

For your problem, what are the chances the the brake bias adjuster is the problem? Can you try using the original brake line routing without the adjuster?

Or maybe it is your MC.... but I think you should try removing the adjuster first. Stock MC is more than adequate for stock calipers.

One thing I did do when installing the 24mm 164 alloy MC was to do some MC bleeding while it was still on the bench. I think what I did was to install the reservoir on the MC, fill it up with fluid, connect used hard brake lines to the MC, and bend them all so they flow back into the reservoir. Then I slowly pumped the MC (while it is on the bench) about 6-7 times.

Can you check if the caliper pistons are moving when you are the pedal is 1/2" into the travel?

[BigSwede]

Not to diss you or anything but you do know that there is two bleedscrews per caliper in the rear? Are you sure you have adjusted the handbrake properly?

[75evo]

Good point BigSwede. In case you haven't done so, check the pad to caliper-piston clearence in the back.

[nizam]

... and don't forget to disconnect the emegency/hand brake when you adjust the pads.

I used to use a feeler gauge. Eventually, I followed my mechanic's method of tightening the pads until the wheel doesn't turn anymore, then backing it off little by little until the wheel is free, with a slight hint of resistance from the pad/rotor.

Works great.

Once that's done, put back the e-brake cable.

[sslim]

hi 75evo,

the problem was already there before i put in the bias adjuster. i had tried removing the adjuster and it is still the same.

i re-bleeded the brakes, also bleeded the MC, there is slight improvement in pedal firmness. went to track again and after couple of warm up laps and 1 hot lap, the brakes starts to fade slightly again. and by the end of the 1-hour session, the pedal has sunk closed to the floor, and i don't ride the brakes ... after a few days of regular driving, the brakes will slowly come back to normal.

i still can't get rid of the 2-3inches of free play before the brake bites, linkage ok, nothing is loose. the pad does not touch the disc for the 2-3inches free play at the pedal. could this an undersized MC?

do you happen to have the part number for the 24mm MC from the 164? i checked through the bendix catalogue and it shows i am running 22.3mm MC, same as the 164 v6 ones, so i am not sure where to get the 24mm MC.

bigswede,
yup, bleeded all 4 rear nipples and adjusted the handbrake to 5 clicks on max locking.

nizam,
yes, i use the same method to set the rear brake pads/discs clearance, works well.

i believe my rear brakes are not getting enough cooling on track, that is causing it to fade. i am going to wrap the rear exhaust and try to find a way to put in air duct for the rear brakes, has anyone done that before?

thanks all for help!