Dragging Brakes
12-21-2018, 09:16 AM
#16
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12-21-2018, 11:32 AM
#17
Drifting
There's no line of sight so it's very easy to damage the allen key head
Apparently the best way to undo them is to heat the machine screws with a oxy acetylene torch first
That's beyond my skill set so I send the calipers off for the machine screws to be removed, and then I do the rest of the work myself
Apparently the best way to undo them is to heat the machine screws with a oxy acetylene torch first
That's beyond my skill set so I send the calipers off for the machine screws to be removed, and then I do the rest of the work myself
12-21-2018, 02:54 PM
#18
Drifting
The original description of the brakes unlocking after a few hours doesn't seem to fit the 'plate lift' theory.
But agree with Ukkid that if the brembos have never been attended to, then there will be plate lift present to some extent.
Whatever the brake drag problem turns out to be, I think one of the best projects I ever did on my car in terms of constant payback in driving was going through the entire brake system. Replaced all flex hoses, all calliper plates with new, replaced all piston seals and dust boots, and checked all pistons for corrosion (actually they all looked like new). Oh and new bleeders for good luck. Flushed fluid, new discs and pads all round The result is a lovely braking feel — pleasure to use on every application.
Those plate screws put up a fight, but subsequently reading this forum I found my approach may have been wrong. I believe the correct advice is to try to get heat into the callipers, not the screws. At any rate only 3 or 4 were too damaged to come out conventionally, but came out very fast with welding a nut onto them and turning this out.
But agree with Ukkid that if the brembos have never been attended to, then there will be plate lift present to some extent.
Whatever the brake drag problem turns out to be, I think one of the best projects I ever did on my car in terms of constant payback in driving was going through the entire brake system. Replaced all flex hoses, all calliper plates with new, replaced all piston seals and dust boots, and checked all pistons for corrosion (actually they all looked like new). Oh and new bleeders for good luck. Flushed fluid, new discs and pads all round The result is a lovely braking feel — pleasure to use on every application.
Those plate screws put up a fight, but subsequently reading this forum I found my approach may have been wrong. I believe the correct advice is to try to get heat into the callipers, not the screws. At any rate only 3 or 4 were too damaged to come out conventionally, but came out very fast with welding a nut onto them and turning this out.
12-25-2018, 01:40 AM
#19
Burning Brakes
Thread Starter
So, work is proceeding. I am now using Stan's advice from another thread. Just reposting as it seems like a really good procedure. Thanks Stan!
https://rennlist.com/forums/928-foru...l#post14658687
https://rennlist.com/forums/928-foru...l#post14658687
This is how I clean them out , this lets the tank look like new.
NOTE use ATE brake fluid the new version is Gold type 200
.Note - Ate Super Blue Racing Brake Fluid is no longer available. The blue fluid did not comply with US DOT Federal Motor Vehicle Safety Standard for brake fluid color. The federal standard requires motor vehicle brake fluid to be colorless or amber in color. Typ 200 has all of the same properties and performance as Super Blue but in the correct amber color.
Tank cleaning....
First spray some brake cleaner from a red can shake the tank then drain, repeat.
Next spray simple green into the tank add a few OZ of hot water shake tank drain, repeat, till its clean
Final rinse the tank with hot water, shake dry.
I clean the outside of the tank with simple green and a toothbrush.
Last pour about 1 oz of alcohol into the tank and shake vigorously, drain it out ,
Then get a hair drier and blow warm air into the tank till you dont smell any more alcohol .
This will remove the last traces of water.
NOTE use DC111 on the tank grommets and the metal grommet bores of the MC,
this will prevent water migration into the MC inlets, and prevent corrosion from damaging the grommet bores.
NOTE every time the car gets wet water runs down the MC tank and then coats the master cylinder.
the water will migrate into the bore and rust .
Also use the DC111 on the test plunger rubber boot thats on the top of the tank,
this will restore its flexibility and preserve it.
NOTE use ATE brake fluid the new version is Gold type 200
.Note - Ate Super Blue Racing Brake Fluid is no longer available. The blue fluid did not comply with US DOT Federal Motor Vehicle Safety Standard for brake fluid color. The federal standard requires motor vehicle brake fluid to be colorless or amber in color. Typ 200 has all of the same properties and performance as Super Blue but in the correct amber color.
Tank cleaning....
First spray some brake cleaner from a red can shake the tank then drain, repeat.
Next spray simple green into the tank add a few OZ of hot water shake tank drain, repeat, till its clean
Final rinse the tank with hot water, shake dry.
I clean the outside of the tank with simple green and a toothbrush.
Last pour about 1 oz of alcohol into the tank and shake vigorously, drain it out ,
Then get a hair drier and blow warm air into the tank till you dont smell any more alcohol .
This will remove the last traces of water.
NOTE use DC111 on the tank grommets and the metal grommet bores of the MC,
this will prevent water migration into the MC inlets, and prevent corrosion from damaging the grommet bores.
NOTE every time the car gets wet water runs down the MC tank and then coats the master cylinder.
the water will migrate into the bore and rust .
Also use the DC111 on the test plunger rubber boot thats on the top of the tank,
this will restore its flexibility and preserve it.
12-25-2018, 10:42 AM
#20
Team Owner
looks like new
12-29-2018, 05:01 PM
#21
Burning Brakes
Thread Starter
SOLVED
Well, y'all thanks a lot for the help!
Just as a recap here:
1.) After sitting for about a year a low mileage car with regular flushing with ATE fluid had brakes that would gradually seize/drag more and more when used. Only way to fix it was take wheels off and pry open the front calipers.
2.) Letting fluid out of the front calipers didn't unlock them. So changed calipers and front brake lines.
3.) Problem became better because the brakes didn't start dragging as badly, and they would magically unlock after a certain amount of time.
4.) Changed brake MC and rear brake lines.
5.) Problem seems gone. At least after 40 miles of driving, and I could not repeat the problem.
Don't yet really understand how the failure mode described in 3.) above, was really due to a brake MC. I'll have to think about that some and better understand some basic hydraulics.
Now: is there any place I can have those calipers rebuilt and keep them on stock for a rainy day?
Just as a recap here:
1.) After sitting for about a year a low mileage car with regular flushing with ATE fluid had brakes that would gradually seize/drag more and more when used. Only way to fix it was take wheels off and pry open the front calipers.
2.) Letting fluid out of the front calipers didn't unlock them. So changed calipers and front brake lines.
3.) Problem became better because the brakes didn't start dragging as badly, and they would magically unlock after a certain amount of time.
4.) Changed brake MC and rear brake lines.
5.) Problem seems gone. At least after 40 miles of driving, and I could not repeat the problem.
Don't yet really understand how the failure mode described in 3.) above, was really due to a brake MC. I'll have to think about that some and better understand some basic hydraulics.
Now: is there any place I can have those calipers rebuilt and keep them on stock for a rainy day?
Last edited by Red Flash; 12-29-2018 at 07:59 PM. Reason: Imprecise wording...
01-03-2019, 10:13 AM
#22
Rennlist Member
Thanks for the update. My holidays were tied up doing engine and transmission mounts on a 996, so my 928 MC project got delayed. I'll try to do the MC replacement this weekend and HOPEFULLY report back similar results.
01-03-2019, 04:54 PM
#23
Team Owner
Lets put it another way,
the master cylinder is a wear Item.
if you still have an original MC it would be wise to install a new one after 30 years.
NOTE if the MC was leaking fluid into the booster then also replace the 30 yo booster at the same time
the master cylinder is a wear Item.
if you still have an original MC it would be wise to install a new one after 30 years.
NOTE if the MC was leaking fluid into the booster then also replace the 30 yo booster at the same time
01-03-2019, 07:13 PM
#24
Drifting
That was an interesting read, glad you solved it!
06-10-2019, 11:46 AM
#25
I first read this thread after experiencing similar braking issues that were actually related to the rear calipers, and I'm now re-reading it after noticing the issue become much worse.
Last summer was fine with my '83. I could drive the car all day without issues with brakes and engine overheat. Now, only a year later, I can't drive 15 minutes without having to fight the brakes to get where I'm going, and then wait 10 minutes for the brakes to free up. I also noticed on one occasion, the brake lights were still on after I parked it (I left the key on and fan running, hoping it would cool it down faster). I'm on a very tight budget, so it might be a while before I can get anything to fix it.
Last summer was fine with my '83. I could drive the car all day without issues with brakes and engine overheat. Now, only a year later, I can't drive 15 minutes without having to fight the brakes to get where I'm going, and then wait 10 minutes for the brakes to free up. I also noticed on one occasion, the brake lights were still on after I parked it (I left the key on and fan running, hoping it would cool it down faster). I'm on a very tight budget, so it might be a while before I can get anything to fix it.
06-10-2019, 07:47 PM
#26
Burning Brakes
Thread Starter
Are you sure it is the rear calipers? Did you jack the car up, crack the hydraulic line at the rear caliper to see, if the rear caliper freed up?
I would try that first before replacing the rears. The rears are quite pricey. The brake MC is in comparison really only pennies... And, they really do seem to exhibit strange behaviors when they start to fail.
I would try that first before replacing the rears. The rears are quite pricey. The brake MC is in comparison really only pennies... And, they really do seem to exhibit strange behaviors when they start to fail.
06-11-2019, 10:29 AM
#27
Are you sure it is the rear calipers? Did you jack the car up, crack the hydraulic line at the rear caliper to see, if the rear caliper freed up?
I would try that first before replacing the rears. The rears are quite pricey. The brake MC is in comparison really only pennies... And, they really do seem to exhibit strange behaviors when they start to fail.
I would try that first before replacing the rears. The rears are quite pricey. The brake MC is in comparison really only pennies... And, they really do seem to exhibit strange behaviors when they start to fail.
The problem I have now is with all the brakes getting stuck. I measured the temp of all four rotors after test driving it one day and all of them were between 250F and 380F. I was having to use a bit more throttle to get moving.
Like the original post, though, the brakes are just fine at the start of the drive, but 10-15 minutes later I notice the brake pedal getting very hard and not too long after, feeling the brakes dragging.
05-02-2020, 06:08 PM
#28
4th Gear
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I'm experiencing the exact same issue described here on my 82 928. I've read through this thread twice, but it does not seem like anyone has found a definitive solution to the problem. The MC was replaced, but this did not fix the issue. After driving for 10-15 min, the brakes begin to stick, and they don't unstick unless they cool down for a few hours. Does anyone have the definitive fix for this issue?
05-02-2020, 08:25 PM
#29
Rennlist Member
Not sure I have the definitive fix, but I had the exact issue last year on my 83. I replaced master cyl. and booster because they were the originals. I also made the adjustment (wider) to pedal/ booster rod gap. I think the brakes would drag after they got hot and eventually begin to lockup as fluid expanded. Of course it didn`t help i was in Phoenix in summer. I havn`t had any issues since then.
Last edited by Hold On; 05-02-2020 at 08:30 PM. Reason: spelling