M52/Clio Booster issue.

Post Thu Mar 10, 2016 1:26 am

Hi All,

Recently completed an M52 swap, with Clio booster, retained E30 master.

Wound out the push rod a little, added the 20mm shot of steel into the master cylinder (as per the wiki here). Bled brakes, new fluid. All seems OK.

Driving last week the rear right locked on, and enough to create a nice plume of smoke from the disc when I pulled over to examine a couple of hundred meters down the road.

Callipers were dry for 6-9 months during build time.
I've got new guides and seals inbound to refresh however, looking for any other lines of investigation.

Ideally I'd like to be able to lower the height of the brake pedal, too.

Anyone had a similar issue?

Thanks in advance,
DB

Post Thu Mar 10, 2016 9:54 am

Length of spacer for the servo has to be determined by measurement, but if one rear brake locked on and the other was fine, then the problem is at the rear of the car - there's only one brake line to the rear of an E30.
Rubber brake hoses can delaminate internally and form a one way valve that locks brakes on, but of course it can be a caliper fault as well.
Lowering the brake pedal will cause issues with the brake light switch. Pull rod has to be adjusted so that the pedal is against its upper stop. The switch and stop could be modified and the pull rod wound in, but don't forget that this will come off of available pedal travel.

Post Sat Mar 12, 2016 8:18 am

Thanks for the advice.

I've just replaced the rear seals and guides, and the fronts.
Issue still persists.

Lines are in good nick and the brakes bleed just fine.

The pedal feels a little high compared to the clutch and accelerator.
Should I be looking closer to the booster, if so am i needing more or less overall length in the rod spacer included) from the booster to the Master.

Post Sat Mar 12, 2016 10:27 am

If the problem affects one rear hub and not the other, then near the hub is where you should be looking.
Have you considered that it may be the handbrake at fault?

Post Sat Mar 12, 2016 7:04 pm

Brianmoooore wrote:If the problem affects one rear hub and not the other, then near the hub is where you should be looking.
Have you considered that it may be the handbrake at fault?

Does sound like hold-down pin failure.