Rear brake troubles, Why do they keep locking ? Options

[Thor]

Hello to everyone at 914world.com. I am a new member from Belgium and ready to post my first question ...

Fase 1: Summer of 2003 ... during a saturday afternoon trip, I suddenly felt that when rolling to a stop the car balanced diagonnaly. At a stop I got a burning smell going through my nose and soon discovered the rear left break was smoking and running terribly hot. I got the car home and my mechanic unlocked the brake.

Fase 2: While passing the annual technical control, the mechanic said there was still an imbalance between the rear brakes. So back to the shop (another - VW-Audi based) where I was told the brake pads were gone and they replaced them.

Fase 3: During an orientation rallye in november 2004 the rear brakes started to squeal and the burning smell was back. This time the right rear brake started to lock. A quick repair in a garage where some young mechanics wanted to have a look at it put us back on the road. We had some good moments but at some stops the right brake would still feel hotter then it's supposed to be.

Anyone an idea of what could be wrong ? Calipers are supposed to be replaced before I purchased the car.
What can I do to restore the balance and keep them from locking ?

Thanks guy's ! (IMG:http://www.914world.com/bbs2/html/emoticons/beerchug.gif)

[dlee1967]

If the car still has rubber lines, they could be breaking down on the inside and swelling/collapsing. They will let pressure through but not release. How old are the rear lines? Are they stock rubber or braided?

This seems to be a somewhat overlooked problem. Most are quick to blame the caliper and forget flexible line. David Lee

[cdmcse]

(IMG:http://www.914world.com/bbs2/html/emoticons/agree.gif)

Could be the hoses, or I had a similar problem plauge me on an MGB I had where once and a while one of the front calipers would not release properly. After re-building the calipers and replacing the lines it still occured. I rebuilt the master cyl and it got much worse, where the calipers would lock and not release at all till the bleed screws were opened.

I replaced the master cyl and all was fixed.

[Eric_Shea]

You're driving it. That's the problem (IMG:http://www.914world.com/bbs2/html/emoticons/laugh.gif)

Put it up on blocks and tear it apart like the rest of us (IMG:http://www.914world.com/bbs2/html/emoticons/smash.gif)

(IMG:http://www.914world.com/bbs2/html/emoticons/agree.gif) I had a 914 with swollen lines. Stopped just fine. Took about 5 minutes to get it rolling again. The MC has plenty of pressure to squeeze the fluid through the swollen line to the caliper. Once it's there it has a hard time releasing.

Be prepared... paying for the rear lines is the easiest thing you'll ever do. Putting them in with the engine still in the car is a B-I-T-C-H.

TIP: Gang... if you ever have your engine out and you're not sure about your rear rubber lines; Replace Them. For $30.00 you will be miles ahead of the game.

Next, it may be a stuck piston. These rear calipers are getting fairly grundgy these days and you may want to get in there and rebuild them.

[Eric_Shea]

Forgot. WELCOME TO THE CLUB (IMG:http://www.914world.com/bbs2/html/emoticons/smilie_pokal.gif)

[redshift]

It's GOT to be the soft lines...

Welcome, now tear your car apart, and turn to page one of the 914 club 10,000 step plan.

(IMG:http://www.914world.com/bbs2/html/emoticons/smile.gif)


Miles

[Eric_Shea]

One other possibility. If your venting clearance is set too close you will have them lock up when they get hot.

Remove the handbrake cable and reset the venting clearance.

[Gint]

Welcome to the Club! I resized your pic (I hate horizontal scroll bars). (IMG:http://www.914world.com/bbs2/html/emoticons/cool.gif)

QUOTE (Eric_Shea Posted on Feb 1 2005 @ 05:21 PM)

Be prepared... paying for the rear lines is the easiest thing you'll ever do. Putting them in with the engine still in the car is a B-I-T-C-H. TIP: Gang... if you ever have your engine out and you're not sure about your rear rubber lines; Replace Them. For $30.00 you will be miles ahead of the game.

It's a bitch even with the engine out. (IMG:http://www.914world.com/bbs2/html/emoticons/wink.gif) But Eric is right, definitely easier.

[IronHillRestorations]

QUOTE (Eric_Shea @ Feb 1 2005, 04:21 PM)

TIP: Gang... if you ever have your engine out and you're not sure about your rear rubber lines; Replace Them. For $30.00 you will be miles ahead of the game.

Another good tip for replacing the rear rubber brake lines: Take the engine lid drip pan drain line and grommet out of the engine shelf. Reach down through the hole with a 11mm flare crowsfoot on a long 3/8" extension. Use a visegrip on the end of the rubber line and orient it so it will hit and hold when you loosen the fitting on the brake line.

Eric's right though. The lines are best replaced when the engine is out.

Also if your brake fluid is more than two years old, replace it. The service interval for standard brake fluid is two years. Silicone lasts longer, but you don't really want to go that route.

[red914]

welcome to the nut house!

rebuild the calipers. Eric is right, they are old and cranky. rebuild! that way you can have your car on jack stands like most of us here, and we can come to this site (IMG:http://www.914world.com/bbs2/html/emoticons/type.gif) , drink beer (IMG:http://www.914world.com/bbs2/html/emoticons/beer3.gif) , and complain about 911 drivers (IMG:http://www.914world.com/bbs2/html/emoticons/slap.gif) !

[SirAndy]

QUOTE (Eric_Shea @ Feb 1 2005, 04:21 PM)

Next, it may be a stuck piston.

(IMG:http://www.914world.com/bbs2/html/emoticons/agree.gif) could be as simple as sticky pistons ...

time for a rebuild!
(IMG:http://www.914world.com/bbs2/html/emoticons/smash.gif) Andy

[Joe Bob]

Scared this guy away too....

Welcome to the club...if ya post back.... (IMG:http://www.914world.com/bbs2/html/emoticons/biggrin.gif)

[bd1308]

hehe....welcome guy! and while your at it, i'll make you a offer...$350 for a turbo-tail

[Thor]

Thanks allready for the many responses !

@bd1308
Are you making an offer for mine or offering one for my car ? Mine is one with two grilles, and since we don't see them very often I want to retain this one. Probably I will have to replace him because the rubber lid is broken as is the base for the lock ... but I'm still breaking down the car, so not in scope for the moment. If you can get a very good one (the same type), I'll get back to you later !

Rebuilding the calipers and stuck pistons: these are "supposed" to be fairly new. They look rather unblemished too. I'll keep this as a last solution.

Replacing the lines: I allready considered replacing them. Would there be a benefit in replacing them with braided ones ?

Venting clearance: I must be honest ... never heared about it. If it's to close would the brakes lock up on one side only ? I'll check this when replacing the lines. I allready got drilled rear rotors in stock. By the way ... a set of two for the rear at 100 Euro, about $ 106, I thought this was a good price ...

As you can see still a lot to do, but not a 10.000 step plan. I'm allready there with the 911. (IMG:http://www.914world.com/bbs2/html/emoticons/rolleyes.gif) I've got to keep one on the road !

Anyway, I'm delighted to have gotten the tip to take a look at the forum ( thanks to Craig from Camp914). You've got some great stuff going on here !
And thanks to Gint for resizing the picture. I couldn't find the Edit button.

[Eric_Shea]

QUOTE

Venting clearance: I must be honest ... never heared about it. If it's to close would the brakes lock up on one side only ? I'll check this when replacing the lines.

I would replace with factory rubber lines. Cap'n Krusty likes Stainless Lines for sure! (IMG:http://www.914world.com/bbs2/html/emoticons/w00t.gif)

Yes the venting clearance would cause the brake to lock up on one side only, the side that is not adjusted properly. You have two adjusters an "inner" marked (I) and an "outer" marked (O)

(I) (O)
--| || |-- <---------Adjusters
----||
----||
----||||-
----|||| <---------- Rotor
----||||-
----||
----||
----||

They both operate with a 4mm hex wrench. The outer adjuster has a 13mm lock nut on it. Loosen the 13mm nut before you begin to adjust. Use a feeler gauge and set the clearance of the pad to rotor at .004. Do this by removing the parking brake cable. Then turn the outer adjuster "counter clockwise" to move the piston and pad toward the rotor. The inner adjuster will have a cover that probably has a 4mm hex slot in it. You need to go through the access hole on the control arm to get to it. Remove this cover and you will access the 4mm adjuster. Again, set the pad to rotor clearance to .004. This time the adjuster will turn "clockwise" to get the pad closer to the rotor. Once you have the clearance set, reinstall the parking brake cable.

If you have drilled rotors they may be "irregular". Spin them to make sure they're not hitting the pads once you've set the clearance. If they are, this is probably your problem. Make sure the mounting surface on your hubs is clean as well. You may have a piece of rust (what's that?) or other misc. item under the rotor causing a slight wobble. The rubbing on the pads can cause heat and heat can cause a lock up on that side.

My guess is those two things (new lines and venting clearance) will solve the mystery. If not... rebuild.

[Thor]

QUOTE

My guess is those two things (new lines and venting clearance) will solve the mystery. If not... rebuild.

Your guess is my hope, Eric !
Great explanation, now I've got something to work with !

QUOTE

If you have drilled rotors they may be "irregular"

They're still in the box, brandnew. I'm gathering all bits and pieces. If you look at my reply to the members pictures section you'll know what I mean ...

QUOTE

I would replace with factory rubber lines

What would be the difference with the braided ones ? After a reply like this I would allmost immediatelly go for the originals, but I just want to know.

[Eric_Shea]

Any luck?

The integrity and usefulness of braided lines has been questioned here and on other forums at length. I think the factory lines are less expensive and more trustworthy than the "standard" braided lines. That being said, you can get some decent braided lines, they're just more than most people want to spend on them.

[JmuRiz]

QUOTE (Eric_Shea @ Feb 1 2005, 04:43 PM)

One other possibility.  If your venting clearance is set too close you will have them lock up when they get hot. Remove the handbrake cable and reset the venting clearance.

I agree, that can be another cause. I need to check mine. At a local HPDC, my right rear was locking and my fronts were not (not something that should happen with stock rears and Boxster fronts!). Someone suggested checking my venting clearance. Just haven't gotten around to it yet, just been normal street driving since.

QUOTE

By the way ... a set of two for the rear at 100 Euro, about $ 106, I thought this was a good price ...

That's about $130 these days, the euro is kicking the dollar's ass (IMG:http://www.914world.com/bbs2/html/emoticons/sad.gif)