Front Brake Issue, 914 Pulls right when stopping Options

[PDXBob]

Hi All,
I just finished putting on rebuilt rear brake calipers done by PMB. Also, new braided steel brake lines and set of new Textar pads on all 4 wheels (1975 914). I took it out to do the “bedding” break-in process and I noticed it was pulling to the right.

So, (after doing cool down slow driving)when I got home I checked temperature of rotors. Both back rotors were about 125 degrees. However front right was about 240 degrees. BUT front left was only about 85 degrees. To a novice like me seems like front left is not working.

Any suggestions on diagnostic procedures or what to check out.
Thanks
PDXBob

[bkrantz]

I would jack up the front and have an assistant gradually depress the brake pedal while you spin both front wheels. See if the braking action is different from L to R.

Also more bleeding on the L?

[ndfrigi]

When you bled the left front, does it push brake fluid?
You can also try to jack the front and someone will turn the wheel and one person inside to push the brake. To check if left wheel will brake and compare to right side.

[PDXBob]

Good suggestions about bleeding again and spinning each front wheel.
Thx

[Krieger]

Recheck the venting clearance again on your rear calipers. Follow the proper proceedure and set at .004"

[PatMc]

Make sure you're bleeding from the uppermost bleed screw....bleeding from the lower screw will get you nowhere.

Once you're certain all the air is out, have someone run the pedal and make sure the caliper is actually clamping down on the front rotor. Very possible the pistons are locked up in the caliper.

[Eric_Shea]

Hey Bob,

Are the soft lines new? If not then I would recommend checking those.

https://pmbperformance.com/pages/frequently...-questions-faqs

About mid-way down on our FAQ page you'll see that old soft lines lines can swell from the inside. This often retains pressure on your front right (in your case). It will then lock up and pull to the right when you apply nominal pressure. It often drags as well then causing the heating issue you're having.

My rule is, if you don't know when your soft lines were replaced... replace them. Otherwise, every 10 years.

Hope that helps... give us a call if you have any other issues.

[PDXBob]

Hey Bob,

Are the soft lines new? If not then I would recommend checking those.

https://pmbperformance.com/pages/frequently...-questions-faqs

About mid-way down on our FAQ page you'll see that old soft lines lines can swell from the inside. This often retains pressure on your front right (in your case). It will then lock up and pull to the right when you apply nominal pressure. It often drags as well then causing the heating issue you're having.

My rule is, if you don't know when your soft lines were replaced... replace them. Otherwise, every 10 years.

Hope that helps... give us a call if you have any other issues.

Eric, when I had you rebuild the rear calipers I also bought a set of your braided steel brake lines. These were well worth the price, just in piece of mind compared to 40+ year old rubber lines.

No time to work on it until Saturday, but can’t wait to get brakes sorted. Also, my brother who’s a mechanic chastised me for not getting rotors hot enough during “bedding-in” process. It’s tough to drive 60 MPH and slam on the brakes in Oregon when the roads are wet 364 days a year!!!
Bob

[technicalninja]

Rear brakes are damn hard to get hot enough to "bed" in using street driving as the front do most of the work anyways.

Having the fronts operate as they are on your car would stop me from trying to bed anything.

Fix the fronts first and then worry about bedding pads.

All the suggestions have been good.

I have another...

Do the proper bleeding, make sure both sides squirt equal amounts out of the top bleeders. Re-check the rear pad adjustment, this does need to be correct.

Put both front tires up in the air and spin test them. Both spin free, have an assistant jam on the brakes and release. Both spin free- you have something way weird going on.
One stays locked up?
Break bleeder free.
Squirt like a bitch? You have a restriction in the system.
Old lines are a common culprit but yours are new.
If it's holding pressure against the caliper, you can slowly move up the system releasing each fitting until you find one that's not under pressure. Your restriction will be between the last pressurized fitting and the un-pressurized fitting.

No squirt from locked caliper? Send your front calipers to PMB for the same treatment you just had done to the rears...

[Eric_Shea]

Hey Bob,

Are the soft lines new? If not then I would recommend checking those.

https://pmbperformance.com/pages/frequently...-questions-faqs

About mid-way down on our FAQ page you'll see that old soft lines lines can swell from the inside. This often retains pressure on your front right (in your case). It will then lock up and pull to the right when you apply nominal pressure. It often drags as well then causing the heating issue you're having.

My rule is, if you don't know when your soft lines were replaced... replace them. Otherwise, every 10 years.

Hope that helps... give us a call if you have any other issues.

Eric, when I had you rebuild the rear calipers I also bought a set of your braided steel brake lines. These were well worth the price, just in piece of mind compared to 40+ year old rubber lines.

No time to work on it until Saturday, but can’t wait to get brakes sorted. Also, my brother who’s a mechanic chastised me for not getting rotors hot enough during “bedding-in” process. It’s tough to drive 60 MPH and slam on the brakes in Oregon when the roads are wet 364 days a year!!!
Bob

Let me know if you have any caliper issues. You have a 10-Year Unconditional warranty. (IMG:style_emoticons/default/wink.gif) (IMG:style_emoticons/default/beerchug.gif)

[Cairo94507]

@Eric_Shea - Holly molly- 10 year unconditional warranty!!!!

I am telling you guys, those that do not already know, if you need brake work, Eric (PMB Performance) is your man. Additionally, almost anything Porsche related, and Eric is still your man. They are turning out beautiful cars. (IMG:style_emoticons/default/beerchug.gif)

[Eric_Shea]

Thank you Amigo!

[PDXBob]

So, after performing several of the tests listed above I came to the conclusion that something was blocking one of the right front brake pistons. Making it chronically drag. I had a conversation with one of the people at PMB (which had recently rebuilt my back calipers) and they had a number of good suggestions. I decided to have PMB rebuild my front calipers as well, so shipped to SLC on Monday.

It will be nice to have 4 rebuilt calipers, new steel brake lines and new pads- Now just have to bleed (again). Thanks to all for your advice!
PDXBob

[930cabman]

So, after performing several of the tests listed above I came to the conclusion that something was blocking one of the right front brake pistons. Making it chronically drag. I had a conversation with one of the people at PMB (which had recently rebuilt my back calipers) and they had a number of good suggestions. I decided to have PMB rebuild my front calipers as well, so shipped to SLC on Monday.

It will be nice to have 4 rebuilt calipers, new steel brake lines and new pads- Now just have to bleed (again). Thanks to all for your advice!
PDXBob

Having great brakes is near equal to having great tires. Glad you are on the road to safe driving (IMG:style_emoticons/default/smilie_pokal.gif)

[PDXBob]

So, an update:
Had my front calipers just rebuilt by PMB. This solved my problem with pulling to the right. However I still don’t have good brakes, i.e., pedal goes nearly to floor before the car stops. Can’t come close to locking up wheels.

So far, I’ve had front and back calipers rebuilt by PMB. Also, replaced rubber brake lines with PMB braided steel. Bought 4 new Textar pads. Adjusted (vented) the back brakes to within specs. I have a Motive Pressure Bleeder and have bleed brakes using it at least 3 times. Just today did the 2-person brake bleed procedure on back brakes. Will do 2-person brake bleed of front’s tomorrow. Master cylinder only about 3 years old. I’ve pumped about 2 quarts of fluid through system and each time get pure, clean fluid and virtually no air bubbles. I’m Running out of ideas on what else to do.

Any thoughts or wild-a$$ guesses greatly appreciated.
PDXBob (1975 914)

[technicalninja]

The rear adjustment can be difficult to gauge.
Just for testing adjust the rears until you have no clearance and see if that helps.
Don't drive the car like this but by taking all of the adjustment out you eliminate one variable.
If this works, then back the adjustment off just a bit. .004 is maybe 10-15 degrees of swing from contact.

I recently rebuilt a MSM Miata rear caliper set. It has one adjuster exactly like the 914 on the inside. Set it up as Mazda suggested and had low pedal. Adjusted the clearance more by "feel" than with gauges the second time. Worked fine after a much tighter adjustment than the service manual suggested.

[rjames]

So, an update:
Had my front calipers just rebuilt by PMB. This solved my problem with pulling to the right. However I still don’t have good brakes, i.e., pedal goes nearly to floor before the car stops. Can’t come close to locking up wheels.

So far, I’ve had front and back calipers rebuilt by PMB. Also, replaced rubber brake lines with PMB braided steel. Bought 4 new Textar pads. Adjusted (vented) the back brakes to within specs. I have a Motive Pressure Bleeder and have bleed brakes using it at least 3 times. Just today did the 2-person brake bleed procedure on back brakes. Will do 2-person brake bleed of front’s tomorrow. Master cylinder only about 3 years old. I’ve pumped about 2 quarts of fluid through system and each time get pure, clean fluid and virtually no air bubbles. I’m Running out of ideas on what else to do.

Any thoughts or wild-a$$ guesses greatly appreciated.
PDXBob (1975 914)

Virtually no air bubbles isn't good enough. You need to bleed them until all of the air is out of the system. Try the long hose method (bonus, only 1 person is needed). I couldn't get mine properly bled until I switch to speed bleeders. Good luck!

[Olympic 914]

Just ran through this myself.

Adjusted rear brakes just until they let the disc turn free. no feeler gauges. You will gain air gap as the brake pads wear in anyways.

Also used Motive pressure bleeder.

The proportioning valve is at a high point in the system. Very hard to get a wrench on the top of the banjo bolt. Try pumping up the motive to 15 lbs and loosen each of the lines from the banjo union to each side, one at a time. Then follow up with another round of bleeding the rear calipers.

I would crack the bleeder on the rear caliper then reach inside the car and press the brake pedal slowwly 3-4 times, the pressure from the Motive should keep fluid moving out.

[Superhawk996]

Raise the rear of the car to help move air through the proportioning valve and up to the rear calipers.

[brubou]

I would start at the beginning of the system. Throw some barb fittings in the outlets of the master cylinder, run tubes from those over the fender into the brake reservoir. Then pump the pedal until not even a rumor of bubbles is present. Sitting in the driver seat gives you a great view. These master cylinders looks small but I swear mine had an oil barrel amount of air trapped in it. Once there were no more bubbles I bled the rest of the system as normal and now I can lock my brakes if I'm not too careful.