Brake Pedal Play

gunshow · 10-07-2013, 07:47 PM

Hello 911 brain trust. Got one for you to noodle on. I seem to have some excessive play in my brake pedal. It seems to depress about an inch before it meets any resistance and begins to slow the car. I thought it just might mean I need to adjust the rod that leads from the brake pedal to the master which just seems to lengthen or shorten the pedal. (Not going to shorten it, going to leave it as long a travel as possible from the threads I've been reading)

Take a look at the video I shot. Does this look normal to you? Any ideas would be appreciated. I want the pedal as solid and tight feeling as possible. it's just a little disconcerting feeling this loose when I get on them at speed.

Porsche brake pedal play - YouTube

chris_seven · 10-07-2013, 11:48 PM

'Play' in a brake pedal is difficult to define and I can't find the link to your video.

If it clearance between the operating rod and the master cylinder then you have an issue with adjustment.

If the movement is due to expansion of the rubber brake lines then you may be able to improve this aspect of the braking by either fitting new lines or PTFE lines.

Have you recently change pads to a new type?

It could also be due to slightly warped discs causing pad knock off.

is this a recent change or have you had this problem for some time?

If, however, you make the pedal too solid you could end up with very 'snatchy' brakes that will lock without much warning.

Slow911 · Slow911's Garage

Have you checked the bushings in your pedal cluster ? That was what was happening to my car and a rebuilt pedal cluster from DLewis did the trick.
Good Luck

gunshow · 10-08-2013, 05:49 PM

Sorry guys. Let me try that again with the URL. I thought it copied over the first time. I think this is really wither in the linkage but take a look.

Porsche brake pedal play - YouTube

gunshow · 10-10-2013, 11:45 PM

Bump. Any ideas would be helpfull. Thanks

proffighter · proffighter's Garage

There are 3 possible failures:

-Worn bushes of the pedal, not uncommon.

-Play at the uniball (can't see it good in your vid)

-crack at pedal (what I don't think is your issue)

To check bushes, just look at the pedal axxis when pushing, does it move out of clutch axxis (same center)?

gunshow · 10-14-2013, 10:42 PM

I'm pretty sure there was movement in the pedal axis. It didn't seem like much, but I'm sure it gets much more pronounced at the end of the brake pedal. I'll pull off the floorboard over the pedals again this weekend and take another look. Thanks for the ideas.

Norm Faustino · Norm Faustino's Garage

One problem with your video that makes it hard to T/S is that you are holding the camera with one hand while demonstrating the play with the other, making it hard to see any play occurring at the pivot points. If you could immobilize the camera and point it at the bottom of the pedal we might be able to help you better. Just from the clunking sound that I'm hearing I believe you have worn components, i.e. rod end bearings or bushings or both.

Jay Laifman · 10-15-2013, 09:22 PM

You didn't mention what year car you have. The earlier cars cars have softer/longer throws on the brakes. I believe it is the difference between single and dual circuit. I always have to adjust going between my '73 911 and '67 912 (I don't know when the 911 switched to dual circuit). But, once I get accustomed to it, they are still very strong, reliable and comfort building - by that I mean, they are always there when I need them and as much as I need.

thumbdoctor · thumbdoctor's Garage

I'd check the brake pedal return spring as they tend to break leaving a vague pedal feeling. I've just rebuilt a pedal cluster using bushings from our host and an OEM (ouch!) return spring. The cluster was very rusty and the brake pedal stop was almost gone. The bell crank bushings in the brake booster mount were worn out / replaced too. After media blasting, welding a new stop (new rubber grommet too), to the pedal cluster, the brake pedal feels normal again.

gunshow · 10-23-2013, 10:54 PM

Thanks guys, was too busy this weekend to check but am planning to pull the cluster in the next week or two. I'll check the return spring and hope I don't need a new one. I did not like the sound of that "ouch" in your post

. It's a 1984 930 FYI.

javadog · 05:31 AM

This is relatively easy to diagnose. First, try to understand how the system is laid out. You have a pedal that pivots on a pair of bushings. That's the first place you can have wear, although that won't cause your problem. Secondly, the pedal is attached to a pushrod. Grab the pedal with one hand and the pushrod with the other and move them. If you have relative motion between the two it should be obvious. It will occur at the rod end that attaches the rod to the side of the pedal. While you are down there, grab the brace that attaches between the pedal cluster and the brake booster and try to move it. It should be solid.

Next, go in the trunk and decide if you want to keep screwing with this. The next link in the system is a lever that pivots inside the brake booster bracket. The pushrod from the brake pedal pushes on one end of this lever, it pivots and then pushes on the rod coming out of the brake booster. The main possibility for play at this end is in the clevis connection between the end of the push rod and the lever. This connection is has a fair bit of clearance, as does the connection at the other end of the pushrod, at the brake pedal. It was never designed as a close tolerance fit. There is also a clevis at the lever-to-booster joint, which can have the same play as the clevis at the end of the pushrod. (Earlier boosted 911s don't have a clevis at the booster end of the lever, just a cup that pushes on a ball on a rod protruding from the booster). You might also have a little play where the lever pivots in the booster bracket.

The bad news is that you can't see much of anything on this end without taking it apart. That is a bit of a pain in the rear. The other bad news is that you can't improve it much. You can replace all of the parts that wear with new ones, which might help a little. You can refit the joints with parts of your own making to reduce the clearances.

Or you can realize that this is pretty normal (call it tolerance stack-up), made to seem worse by the leverage ratio built into the pedal geometry and go find something else to screw with.

JR

DRACO A5OG · DRACO A5OG's Garage

Sorry to bring this old thread up but OP, have you figured out your symptoms? I have the exact same slop on my brake pedal and I am thinking of welding my slot on the rod to take up the slop in my pedal as yours.

Jim

DRACO A5OG · DRACO A5OG's Garage

I guess, not too many sloppy pedals out there, eh?

Okay will document my repair for the unlucky like me :-(

axvel · 09:54 AM

Quote:

Originally Posted by DRACO A5OG

Sorry to bring this old thread up but OP, have you figured out your symptoms? I have the exact same slop on my brake pedal and I am thinking of welding my slot on the rod to take up the slop in my pedal as yours.

Jim

Had the same problem, it was a brake booster that was bad. I narrowed it down, after i changed the cluster bushings and tried to adjust the rod, when you adjust the rod it brings the pedal out closer to you and make it uncomfortable. If you open the front trunk you will see the brake booster there, it has a plastic cover in front, take it of and pull on the rod inside, if there is play, than you need to replace it.

DRACO A5OG · DRACO A5OG's Garage

Hmmm? you mean the booster, right?

axvel · 12-16-2014, 09:53 AM

sorry right booster

DRACO A5OG · DRACO A5OG's Garage

Interesting, will take a look.

I guess our PO's slammed on the brakes too much, eh?

Thanks Brother!

axvel · 12-16-2014, 10:08 AM

Quote:

Originally Posted by DRACO A5OG

Interesting, will take a look.

I guess our PO's slammed on the brakes too much, eh?

Thanks Brother!

Probably, but my booster on my car was never changed from 77 so for me when i saw that was a no brainer, with a new booster the feel is much better, i enjoy the car more now. I checked everything, first, the bushings, replaced, then i thought maybe bigger brake calipers will do it, no. Then after i replaced all the lines, fluid and etc. I looked where the booster was. Like i said, when i adjusted the pedal with the rod in the back, there was no play after and it braked horribly. Plus the pedal stuck out by a lot. So the booster it was.

DRACO A5OG · DRACO A5OG's Garage

Ah ha, that makes sense.

Too bad it is NLA. Will need to look into a good used one or do something to take the play out like welding???