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Old 05-09-2019, 05:17 PM   #1
R-Pow3R3d
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Default Temporarily Frozen Front Caliper?

Background: Foam cannon and pressure washed the 745 on Monday. Left parked since then until this morning.

Story: When I left this morning, I backed up to turn around and the brakes were very squeal-y. Didn't seem unreasonable since I had sprayed them with water days before. About 3/4 of the way through my ~20 mile drive to work it felt like the car was dragging and then I started getting a shake in the steering wheel that felt like a flattening tire but there was no pulling. Couldn't hear any strange noises. Stopped the car, checked the tires, nothing seemed out of place, so I finished the drive. When I got to work, I went to back into a spot in a gravel lot. I stopped in the loose gravel facing up hill, then tried to move further up the hill and it didn't want to go (tire spin). This is when it occurred to me the brakes were likely sticking. Got out and found the front wheels to be emanating a great deal of heat (both of them). I left it to sit for the day and then came back when it was time to leave. When I got in, I tested it on the gravel and on some asphalt to see if it felt like it was sticking anymore and it wasn't. Drove the whole way home with the windows down and radio off. No signs of problems. Once home, checked the wheels and there wasn't any heat coming off of them.

Question: So, what gives?

Follow-up Questions: What should I check? What is the likely culprit? What should I plan to replace in short order?
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Old 05-10-2019, 03:41 PM   #2
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If it was me I'd get the front up on jack stands, and get the wheels off. I'd put new pads if they look thin...At least remove the pads and press the caliper back and see if the cylinders compress as they should. Put it back together and lube everything properly.
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Old 05-10-2019, 03:47 PM   #3
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Old brake hosing can disintegrate internally, shedding flaps that act as one-way check valves that allow the high pressure fluid from the MC to the calipers but not the relatively lower pressure fluid to return.
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Old 05-10-2019, 04:16 PM   #4
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Quote:
Originally Posted by tintintin View Post
Old brake hosing can disintegrate internally, shedding flaps that act as one-way check valves that allow the high pressure fluid from the MC to the calipers but not the relatively lower pressure fluid to return.

My guess too.
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Old 05-10-2019, 07:09 PM   #5
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Quote:
Originally Posted by intothelabyrinth View Post
If it was me I'd get the front up on jack stands, and get the wheels off. I'd put new pads if they look thin...At least remove the pads and press the caliper back and see if the cylinders compress as they should. Put it back together and lube everything properly.
Pads & rotors were done less than a year ago by the previous owner, so hopefully that's not to blame. I think tearing them down just to verify condition and lubricate is a good plan.

Quote:
Originally Posted by tintintin View Post
Old brake hosing can disintegrate internally, shedding flaps that act as one-way check valves that allow the high pressure fluid from the MC to the calipers but not the relatively lower pressure fluid to return.
Quote:
Originally Posted by alschnertz View Post

My guess too.
Interesting. This sounds like it could definitely be a culprit. I have no records of the hoses being replaced, so that will be on my replacement list.

Last edited by R-Pow3R3d; 05-10-2019 at 07:14 PM..
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Old 05-10-2019, 10:14 PM   #6
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I am pretty sure this is just how a 740 tells you it is crusher time...
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Old 05-10-2019, 10:48 PM   #7
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Originally Posted by NotSoFresh View Post
I am pretty sure this is just how a 740 tells you it is crusher time...
I assure you, it is not.
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Old 05-10-2019, 11:22 PM   #8
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Quote:
Originally Posted by R-Pow3R3d View Post
I assure you, it is not.

Joking aside, one of my 240s did this and it was bad brake lines as said by others. In my case, a small piece of the line made it into one of the calipers.
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Old 05-11-2019, 12:34 AM   #9
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Line are cheap. Just replace them if you're going to tear it all apart. Probably throw a rebuild kit at the fronts as well. You're going to have to bleed the system anyways if you pop out the caliper pistons for cleaning...

Which front calipers do you have? If you got the dual piston Bendix calipers with the single guide/slide pin, swap them out for the big 940 ones.
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Old 05-11-2019, 12:43 AM   #10
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Quote:
Originally Posted by NotSoFresh View Post

Joking aside, one of my 240s did this and it was bad brake lines as said by others. In my case, a small piece of the line made it into one of the calipers.
Seems like a pretty consistent response. If my half-developed plan comes together, maybe I can get these done at the end of the week.

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Originally Posted by gottarollwithit View Post
Line are cheap. Just replace them if you're going to tear it all apart. Probably throw a rebuild kit at the fronts as well. You're going to have to bleed the system anyways if you pop out the caliper pistons for cleaning...

Which front calipers do you have? If you got the dual piston Bendix calipers with the single guide/slide pin, swap them out for the big 940 ones.
Yeah, assuming they are original makes me want to replace them regardless of whether they are the issue. I've been on a rampage of replacing anything under the hood that looks worn out. Probably due to flush the brake fluid anyways.

In the few months I've had the car, I haven't pulled the wheels off yet. I would assume the 740T would have the bigger calipers, but perhaps not. I'll have to wait and see.
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Old 05-11-2019, 12:53 AM   #11
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It's a two man job. One guy on the brakes calipers other guy pushing the pedal. Caliper bro pushes calipers back, then pedal bro pushes pedal in and pads go tight at caliper. Do that open close the calipers 40 times, that will fix the sticking caliper problem. Put new brake fluid in first or not..

One side of the caliper pistion at a time if you got two opposing piston calipers. You can take the shoe out and replace it with a big plyers breaker bar screwdriver thing and use that to push piston back real quick. It doesn't take that long with a true bro helping. Work that rod, in, out, in, out.
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Old 05-11-2019, 12:59 AM   #12
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^^

I have done what Simon suggests above and it was successful. You are essentially breaking loose all the crap in the caliper bores and flushing it out. It is time consuming and there is no 100% guarantee of a long term success.

I have had many calipers stick and then release. I doubt this has anything to do with your brake lines. A 240 I fixed up and sold last year did that twice with the same front caliper. The second time it got so hot I could barely get the car to go over 25 mph. I stopped at the car wash and cooled the rotor off and then drove it home using the e-brake only. I replaced the caliper the next day. I've had this happen on several 2-7-9 series cars and it was never the brake lines. Just old calipers that have rust and crud in them from countless years/cycles of use.
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Old 05-11-2019, 02:01 AM   #13
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Quote:
Originally Posted by 2manyturbos View Post
^^

I have done what Simon suggests above and it was successful. You are essentially breaking loose all the crap in the caliper bores and flushing it out. It is time consuming and there is no 100% guarantee of a long term success.

I have had many calipers stick and then release. I doubt this has anything to do with your brake lines. A 240 I fixed up and sold last year did that twice with the same front caliper. The second time it got so hot I could barely get the car to go over 25 mph. I stopped at the car wash and cooled the rotor off and then drove it home using the e-brake only. I replaced the caliper the next day. I've had this happen on several 2-7-9 series cars and it was never the brake lines. Just old calipers that have rust and crud in them from countless years/cycles of use.
To that end, I'm very much considering just doing the whole deal. Starting fresh. Lines, calipers, pads, rotors. Need to see what condition the pads and rotors are in (should be good since they are pretty new and haven't seen much use).
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