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09-09-2012, 12:00 AM | #1 |
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Location: Anaheim California
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Hydraulic Brakes
I know I should post this on the V8 or Hot rod forum but I thought I would ask among friends first.
A prospective new member to the club told me he had hydraulic brakes and after driving some miles they build up so much pressure they lock the wheels. I had a little experience with hydraulics 50 years ago but never ran across anytning like this. Is this something common? Is there an easy fix? I already offered a complete set of mechanical brakes but he turned me down. Thanks, Richard Anaheim CA |
09-09-2012, 12:30 AM | #2 |
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Re: Hydraulic Brakes
There's something radically wrong with his master cylinder if pressure does indeed build up.
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09-09-2012, 12:31 AM | #3 |
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Re: Hydraulic Brakes
Adjust the link between the pedal and master cylinder.
It sounds like the piston is not coming back far enough to clear the port. |
09-09-2012, 12:32 AM | #4 |
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Re: Hydraulic Brakes
It is possible that there is a problem with the residual (check) valve, if there was one installed. The purpose of the residual valve is to keep a little hydraulic pressure on the wheel cylinders when the brakes are not applied. This prevents the wheel cylinders from "sucking" air back into the wheel cylinders. If the residual valve is faulty or is not the correct one for the application then it could cause the brakes to drag or even lock up. It could also be some foreign matter in the system that plugs up the system that blocks the fluid returning back to the master cylinder.
Just my 2 cents. Bob |
09-09-2012, 12:53 AM | #5 |
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Re: Hydraulic Brakes
Can't hurt to post on both of the other sites as well.
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09-09-2012, 01:14 AM | #6 |
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Re: Hydraulic Brakes
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some play in the pedal to give the fluid a place to expand. If all that is ok I would suspect bad front brake lines colapsing on the inside and acting like a one way valve causing the brakes to drag. |
09-09-2012, 02:26 AM | #7 |
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Re: Hydraulic Brakes
If all 4 brakes lock up, it has to be master cyl. related. Check all the things that the others have posted. Bill W.
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09-09-2012, 09:17 AM | #8 |
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Re: Hydraulic Brakes
dot5 i'm told with it's silicon may heat up and expand.
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09-09-2012, 09:39 AM | #9 |
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Re: Hydraulic Brakes
Dot 5 silicone is the only thing I use on my old cars that have hydraulic brakes. I don't know that it expands with heat, but even if it did, it would simply raise the level in the reservoir. I'd bet the problem is the master cylinder piston isn't coming back far enough to uncover the hole.
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09-09-2012, 11:53 AM | #10 | |
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Re: Hydraulic Brakes
Quote:
Charlie Stephens |
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09-09-2012, 12:09 PM | #11 | |
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Re: Hydraulic Brakes
Quote:
Pete's post nailed it! The piston is not returning far enough to uncover the port and as the heat builds up and expands the fluid it applies the brakes. Shorten the pushrod until the piston uncovers the port allowing the fluid to return. Bill |
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09-09-2012, 12:44 PM | #12 |
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Re: Hydraulic Brakes
Thanks everybody. Thats great information and reallly quick.
I have printed all the replies out and will deliver them to him this morning Thanks Again, Richard Anaheim CA |
09-09-2012, 01:37 PM | #13 |
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Re: Hydraulic Brakes
The guys got it right. A car I owned for a short time did that. In my case the bleed back passage in the master cylinder plugged. When the piston retracted the passage was at least mostly uncovered. That car hadn't been driven for a couple years.
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