Brakes Sticking

[Oaktown 986]

Hey,

My MY99 is having an unusual "problem". Sometimes, usually when the car is just starting up as well as when I've been driving in stop and go for a while, the brakes stick. The pedal goes down, I brake, then upon release of my foot off the brake pedal, it does not fully return to its original position. There is still braking pressure being applied, as I live in a hilly region, and I can rest at an incline in place without rolling backwards.

I've never had this problem before, but the brakes are in great condition, have plenty of power, are not scored, and the brake fluid level is at a perfect point. I'm doing some maintenance next week (spark plugs, oil change, air filter) and would like to fix whatever it is ailing me at the same time. Any suggestions?

jon

[eightsandaces]

Have you checked the brake/clutch fluid level? I'd bleed the entire system, might as well change the fluid when you do, I'd bleed the clutch too. If that has no effect it could be in the master CYL, hope this helps...

[Oaktown 986]

I hate to sound inexperienced since I've done some semi-advanced work on autos before, but I've always outsourced brake work to one of my buddies. We now live nowhere near each other... so I have to learn.

Can you explain how I'd go about doing that? Or a link to help?


Thanks!

[Lil bastard]

Sounds like the MC to me.

[eightsandaces]

The easiest way I have ever done it is with a power bleeder, which is a pressurizing device that you screw onto the fluid reservoir. Once attached you pump up to manufacturer spec pressure then open the bleeder screws on the caliper one at a time and run the fluid out till you see no air bubbles. (should only be a very short period of time). Then repeat the same with all four calipers and for good measure with the clutch bleeder under the car on the drivers side, see bentley for a good pic.


PS If you don't have a power bleeder have an assistant pump up the brakes and maintain pressure on the pedal when you open the bleed screws. Do each wheel, two bleeders per wheel one at a time, if that doesn't fix it then I'm with lil B prolly a master cylinder.

[Oaktown 986]

Originally Posted by eightsandaces

The easiest way I have ever done it is with a power bleeder, which is a pressurizing device that you screw onto the fluid reservoir. Once attached you pump up to manufacturer spec pressure then open the bleeder screws on the caliper one at a time and run the fluid out till you see no air bubbles. (should only be a very short period of time). Then repeat the same with all four calipers and for good measure with the clutch bleeder under the car on the drivers side, see bentley for a good pic.


PS If you don't have a power bleeder have an assistant pump up the brakes and maintain pressure on the pedal when you open the bleed screws. Do each wheel, two bleeders per wheel one at a time, if that doesn't fix it then I'm with lil B prolly a master cylinder.

So I bled the brakes, and the problem disappeared for about 10 minutes. It then returned; I jacked the front end up, and checked the wheels while a buddy braked. It looks like the passenger side front is spraying a small amount of brake fluid out when braking from behind the caliper at the attachment point of the brake line and the caliper.

Thoughts?

Jon

[extanker]

it looks like you have been working on this car for 8 mos. perhaps a flatbed to a repair shop would speed the process along.

[Oaktown 986]

Originally Posted by extanker

it looks like you have been working on this car for 8 mos. perhaps a flatbed to a repair shop would speed the process along.

Well, it's not a huge problem. I have 3 cars, but I drive the Porsche 2-4x per week. I've put 30k on it in the past year, and the little irksome things are starting to pile up...

[extanker]

its squirting brake fluid....thats a HUGE safety issue for other people on the road if you are driving it

[Oaktown 986]

Originally Posted by extanker

its squirting brake fluid....thats a HUGE safety issue for other people on the road if you are driving it

not squirting, and it's been about 10k like this. It's merely fizzing some aerated dribble. not enough to even lower the MC readings at all.

[extanker]

the brake line maybe held on by a 'banjo bolt' it can have 2 crush washers that are supposed to be used once. they can be leaking or the bolt can be loose. the line where it swagged can be old and leaking. i dont know what year it appeared in but does this car have "hill assist" ? on the dragging brakes : fix leak first then jack up each wheel ...apply brake then release...look /feel for one wheel dragging...if so maybe stuck caliper/stuck pad/ crushed [inside] brake hose...if all 4 wheels drag...back track system.....if just fronts drag...back track..if just rears

[Oaktown 986]

Originally Posted by extanker

the brake line maybe held on by a 'banjo bolt' it can have 2 crush washers that are supposed to be used once. they can be leaking or the bolt can be loose. the line where it swagged can be old and leaking. i dont know what year it appeared in but does this car have "hill assist" ? on the dragging brakes : fix leak first then jack up each wheel ...apply brake then release...look /feel for one wheel dragging...if so maybe stuck caliper/stuck pad/ crushed [inside] brake hose...if all 4 wheels drag...back track system.....if just fronts drag...back track..if just rears

it's def. one wheel dragging (front passenger) and it's a 99, no options. I think the seal from the line to the caliper is bad.... any thoughts?

[extanker]

doulbe check the dragging...loosen pass. front brake line and make sure its still dragging. if so get 2 front calipers,2 front brake hoses,front pads w/ALL hardware and 2 front rotors...call me oct. when your ready

[stephen wilson]

I agree, if one wheel is dragging, pull the brake pads and check for a sticking caliper piston. See if the pistons can be retracted with reasonable effort, as if you were installing new pads.

[eightsandaces]

When you say it's leaking behind the caliper is it leaking right where the line connects? IMO, you need to remedy any leaks before you can assess the function of the caliper.

[insite]

do repair any leaks & bleed the system prior to making this next assessment.

here's a quick primer on calipers. the caliper seals are made of high durometer EPDM. they are square rather than round in profile. when you press your brakes, the pistons don't slide through the seals in a normal braking situation. instead, the pistons extend and the seal STRETCHES a bit. this elasticity is important, as the secondary function of the seal is to actually RETRACT the piston.

EPDM is pretty durable, HOWEVER, if it gets overheated, it will soften. when it softens, it will no longer retract the piston, causing brakes to drag. this, in turn, causes more heat which futher softens the seals & the cycle repeats itself. it is possible that this has or will happen to you. if you fix the system leaks & bleed the system & service the master cylinder and you are STILL having this problem, you may need to replace the caliper seals in one or more calipers.

[Oaktown 986]

Originally Posted by insite

do repair any leaks & bleed the system prior to making this next assessment.

here's a quick primer on calipers. the caliper seals are made of high durometer EPDM. they are square rather than round in profile. when you press your brakes, the pistons don't slide through the seals in a normal braking situation. instead, the pistons extend and the seal STRETCHES a bit. this elasticity is important, as the secondary function of the seal is to actually RETRACT the piston.

EPDM is pretty durable, HOWEVER, if it gets overheated, it will soften. when it softens, it will no longer retract the piston, causing brakes to drag. this, in turn, causes more heat which futher softens the seals & the cycle repeats itself. it is possible that this has or will happen to you. if you fix the system leaks & bleed the system & service the master cylinder and you are STILL having this problem, you may need to replace the caliper seals in one or more calipers.

Solid advice: Will be investigating the second week of May, and will update accordingly. Much thanks for all the advice.

[Oaktown 986]

Ok, so had it checked out by www.abauer.com Porsche, and it was discovered to be a bad booster. Ordered the new part from Pelican ($170 overnighted), and now have to figure out how to actually install it. Any insights? (I've bled the brakes on this guy before, and I've replaced many pads/rotors in my days)

[Oaktown 986]

bump

any advice?

[insite]

this really isn't hard. just dig in, & if you hit a hiccup, we'll help you through it.