Brake Pedal Not Returning Fully

Post Wed Oct 23, 2019 4:55 pm

I recently fitted an M52 to my E30 and therefore also fitted a Clio servo. However, this issue has been around since before the engine swap.

When the car is running, more often than not my brake pedal doesnt return fully to the correct resting position after I've applied the brakes. As a result my brakes bind for a few seconds each time I use them and it gets a bit annoying.

I'm guessing I need to make some adjustment on the rod that connects pedal to servo but I can't get it right in my head whether I need to lengthen it slightly or shorten it? The only other thought I had is I need a return spring or something to get the pedal back where it needs to be?

Can someone enlighten me before I start a trial and error approach ??

Cheers
Joe

Post Wed Oct 23, 2019 7:57 pm

Assuming you've got things right at the master cylinder end, you need the lengthen the pull rod that goes across the car. It has a reverse thread on one end and a normal thread on the other, so rotating it one way (after loosening the locknut) will shorten it, and rotating it the other will lengthen it.
Raise the pedal to just short of its stop.
As things are at the moment, your brake lights are either on all the time, or flashing on and off as you go over bumps and potholes.
Reading your post again, from what you say about the brakes binding, it looks like you may not have got things quite right at the master cylinder, so sort that first.

Post Wed Oct 23, 2019 9:49 pm

Thanks Brian. How can I get things right at MC end first, do you mean in terms of bullet spacer etc?

It took a few attempts to get the spacer right, pedal feels good other than the last bit of return travel and brakes bite nicely.

I did have the issue you described about lights flickering on and off.

I’ve been out tonight and found that the pedal was quite high and definitely making strong contact with the rubber stop. I’ve backed it off a bit so that it just about activates the switch when at highest position. Have I got that bit right now ?

Post Wed Oct 23, 2019 10:06 pm

If the brakes bind slightly when releasing them, I'd guess that the spacer is marginally too long.
The pedal being low doesn't affect the operation of the brakes at all, other than the lower down it starts, the less travel you have before the pedal hits the floor, which may suddenly become important if one of the two brake circuits fails when you're driving, but the pedal height does affect the brake lights, so it should be adjusted up to the stop.

Post Thu Oct 24, 2019 12:55 pm

Ok so I think the pedal is in the correct place now, it just rests on the rubber stopper.

Brakes only bind whilst the pedal is in it’s ‘not fully returned’ state. Pedal eventually gets back to where it needs to be and the binding stops.

I shall try a slightly shorter spacer and see if that sorts things out, thanks Brian.

Post Thu Oct 24, 2019 1:17 pm

Bell cranks at either end of the pull rod aren't partly seized by any chance? Not something I've ever seen, but there's always a first.

Post Fri Oct 25, 2019 5:46 pm

I will check but don’t believe so, although it would explain why I had the issue long before the engine swap / servo change.

The previous owner originally switched the car from auto to manual so he retro fitted the pedal box. Could he have missed something ?

Post Wed Nov 27, 2019 6:23 pm

I took the car out after checking that the pedal rests just off the bump stop. It is a lot better now but there is still a very slight drag on the brakes for a moment or so. Not sure that this is a spacer issue as it did it well before I swapped out the engine / brake servo etc...