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Brake woes! Hard pedal and seizing calipers

Neoparoykos

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Long story short, my 1972 Bavaria is experiencing some brake issues. If you are in the E3 Facebook group you have likely noticed my constant whining over the issue.

I have replaced most of the system at this point.
-New reman'd from calipers with new seals, etc
-Refurbished the rear calipers with new seals, etc
-Replaced all soft rubber lines with the stainless steel
-All hard lines (excluding the four from the MC to the front calipers) have been replaced
-New check valve
-MC was replaced then reinstalled original as new unit did not resolve issue
*Booster and rear proportioning valve are original

Between me and an experienced mechanic I would say the system has likely been bled 40+ times at this point, both using a power bleeder and the traditional method.

Here is the issue, the car will drive with a period of time without issue. Proper pedal feel, stops adequately, blah blah... Then after some time, either precipitated by normal use or hard braking, all four calipers will begin to lock (like smoking) and the pedal will firm significantly (rock hard). Pressure is obviously building to a high level and won't release. Not surprisingly, if I allow the car to sit for a period the pressure will release and the brakes will return to normal. There doesn't appear to be any vacuum leaks unless I am missing something. I have noticed, just yesterday, that the car is seeming to idle more poorly than when this issue began. This, of course, leads me back to vacuum, but I don't even know where to begin in that regard. Besides, the issue began well before the idle issue.

I can see from searching the site that E9 owners have very similar symptoms, but they never return to describe how they resolved the issue. Hoping enough E3 owners peck around in here to help. I am over a month on trying to solve this, and other brake issues and just want to drive Cherry (as well call her) issue-free again. :(

Any help would be tremendously appreciated.


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adawil2002

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You may have a bad booster check valve from the manifold to the booster.

How long ago were the flexible lines changed to Stainless wrapped ones?
 

Neoparoykos

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You may have a bad booster check valve from the manifold to the booster.

How long ago were the flexible lines changed to Stainless wrapped ones?
Thanks for the response! Check valve was replaced with a new unit. I replaced the original ATE unit to see if that would have any effect. None. Flex lines were changed during the overhaul this past month.
 

bluecoupe30!

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Have you noticed a loss of brake fluid? Have to top up but cannot see any leak? It may be the brake fluid is accumulating inside the booster. A seal has gone internally, and causing your symptoms. If it is what I think it is, entire booster must come off and unit must be rebuilt. There are several specialists who can remanufacture brake boosters. Good luck!
 

sfdon

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Sounds like the actuating shaft in your booster is staying in too far into your master and keeping constant pressure in your master. The pressure never releases the brake fluid all the way and as your brakes are used pressure builds up the clearances disappear and you come to a stop with smoking rotors. Odd but common problem on e23 models when DYI folks would replace their masters with a later version and accidentally mix up the shafts which had different shapes and thus different lengths.
I think the problem is in your booster or in your brake pedal linkage.
Measure the distance from brake pedal to gas pedal faces- should be at least 1 inch.
 

Neoparoykos

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Have you noticed a loss of brake fluid? Have to top up but cannot see any leak? It may be the brake fluid is accumulating inside the booster. A seal has gone internally, and causing your symptoms. If it is what I think it is, entire booster must come off and unit must be rebuilt. There are several specialists who can remanufacture brake boosters. Good luck!
I haven't noticed this thus far, but will keep an eye on the fluid. Thing is, everything functioned properly before the calipers and lines were overhauled.

Sounds like the actuating shaft in your booster is staying in too far into your master and keeping constant pressure in your master. The pressure never releases the brake fluid all the way and as your brakes are used pressure builds up the clearances disappear and you come to a stop with smoking rotors. Odd but common problem on e23 models when DYI folks would replace their masters with a later version and accidentally mix up the shafts which had different shapes and thus different lengths.
I think the problem is in your booster or in your brake pedal linkage.
Measure the distance from brake pedal to gas pedal faces- should be at least 1 inch.
I have seen this issue floated and wonder if it may explain my issue. At present, the brake pedal seems to be significantly higher than the gas pedal (see picture). The MC at this point is an ATE unit that was functioning properly. It was changed for another ATE unit (which did seem to have a different rod length and diameter) which presented the same problem and so we reverted to the original.

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Neoparoykos

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It could be the brake booster Piston rod is adjusted poorly. Your pedal appears to be farther from the firewall than it should be.

9.65 inches or 245 mm is correct.

34331103601
Piston rod

The irony is, it was never changed since the system overhaul. Could it go from properly adjusted to otherwise on its own? Is that measurement what is recommend from BMW?

Great photo, looks like some clean threads on that piston rod may explain things. Perhaps an adjustment to where the oxidation begins again will produce a different result?
Thanks! See my comment above to the other user. I like your observation though! Trying to find out if the mechanic adjusted it at all.
 

Neoparoykos

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Some success to report (albeit sprinkled with a little disappointment). The push rod length was indeed modified by the mechanic who worked on the car. He was attempting to solve the brake issues. Of course it inadvertently caused the calipers to begin seizing after a period of driving. I backed it off and gave it a test drive.

Drove it some more.

And then some more.

Calipers never seized.

I adjusted it to the spec detailed in my Haynes. After some driving, brakes felt a bit squishier than previously. I adjusted it further away from the fire wall. Drove some more. Still squishy. Adjusted. Squishy.

Good news is it is safely stopping, but not as much as I know it should be. I'm going to give the pads/ rotors some time to break-in and then bleed the system once more if it remains squishy. No fluid appears to be leaving the MC so this is certainly positive. I thank you all for the tremendous help and time to explain things thoroughly. After leaving the Honda/ Acura forums many years ago it's nice to come back around to a group of enthusiasts who are knowledgeable and willing to help without reservation.
 

sfdon

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Your pads are ruined in my book. Most likely glazed to death and so are your rotors.

I would look at your rotors- if they are blue throw them away.

Don’t let people work on your car and do things that make things worse.

I have to ask- what do you possibly imagine that adjusting a brake pedal distance would have anything to do with braking effort?
Wipe the Koolaid that your mechanic has been giving you off your chin and find a real wrench that can help you. You deserve better!
 

Dick Steinkamp

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That was my first of the two most common reasons front brakes stay on that I posted when you asked for input on your problem on May 9...

Screen Shot 2020-05-18 at 5.58.26 PM.png


On Facebook, it is easy to disregard some (much?) of the input since there are a lot of posters that have no idea but have the need to post anyway. Stick around here. You'll get valid input.

And I agree with Don. Your mechanic isn't one.

Beautiful car, BTW. :cool:
 

Neoparoykos

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Your pads are ruined in my book. Most likely glazed to death and so are your rotors.

I would look at your rotors- if they are blue throw them away.

Don’t let people work on your car and do things that make things worse.

I have to ask- what do you possibly imagine that adjusting a brake pedal distance would have anything to do with braking effort?
Wipe the Koolaid that your mechanic has been giving you off your chin and find a real wrench that can help you. You deserve better!
Tough words, but I hear you. It seemed reasonable to assume that the pedal distance would influence the pedal feel as the increased distance led to the extremely stiff pedal and seizing calipers. I have done all of the work myself (suspension overhaul, brakes, lines, bearings, etc.), but after 35+ attempts bleeding the system I was at my wits-end. I took it to him (he is also a very close friend) and he seemed to resolve it. Unfortunately, adjusting the pedal length had unintended consequences. Nevertheless, I appreciate your encouragement. ;)

That was my first of the two most common reasons front brakes stay on that I posted when you asked for input on your problem on May 9...

View attachment 93426

On Facebook, it is easy to disregard some (much?) of the input since there are a lot of posters that have no idea but have the need to post anyway. Stick around here. You'll get valid input.

And I agree with Don. Your mechanic isn't one.

Beautiful car, BTW. :cool:
I apologize, Dick. I suppose I ignored the first part after reading the second part knowing that I had changed the lines to SS. At that point, I hadn't yet taken it to him either so the rod length had not been changed in any way. Thanks for your patience! Looking forward to sticking around and thank you for the compliment. Hope to put faces to names at Vintage for those that attend.

And I agree with the Facebook comments, some are just incredulous! I don’t know why anyone would post there.
Noted. Ease of use is def a benefit versus the forum model, but this is clearly where knowledge resides. I should have known this after poking around Honda/ Acura forums for almost 15 years.
 

dang

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Funny how your description of what's going on with your brakes is the same with my coupe. The difference is, it all worked pretty decent before suddenly starting to have binding calipers. I've parked my coupe because of it and will go back to it after finishing up my E3. I wish mine was as simple as adjusting the push rod but I think it may be the master cylinder going. On the bright side, I've completely gone through the brake system on the E3 so working on the coupe should be easier when I get to it.
 
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