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07-08-2018, 09:00 AM | #21 | |
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Location: East Hartford, Ct
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Re: Any brake geniuses out there?
Quote:
I suspect that brake shoe material has a coefficient of expansion that is close to Zero.
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DON'T RECALL DOING SOMETHING FOR MYSELF BASED ON SOMEONE ELSE'S LIKES OR DISLIKES Last edited by 51 MERC-CT; 07-08-2018 at 09:12 AM. |
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07-08-2018, 09:11 AM | #22 |
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Join Date: May 2010
Location: on the Littlefield
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Re: Any brake geniuses out there?
what did you use for fluid in the brake system?? ---fluid contamination can cause the rubber cups to swell up causing your problem----when the brakes are locked up loosen the master cylinder bolts ,if they release it's the pushrod, if not look in the master cylinder
when you say "hydrovac" do you mean the booster run by the power steering pump? ----or is it a seperate vacuum booster plumbed into the line after the master cylinder (servo booster) |
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07-08-2018, 09:15 AM | #23 | |
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Re: Any brake geniuses out there?
Quote:
This is one REALLY good reason NOT to turn drums any more than the recommended dimensions, like 12.060" limit on our old Ford drums. The more meat in the drum, the less likely it is to distort in diameter. DD |
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07-08-2018, 08:06 PM | #24 |
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Join Date: Jun 2012
Location: North Aurora,Il.
Posts: 154
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Re: Any brake geniuses out there?
My humble opinion is that heat is the problem. Whether it be from something dragging or heat from the exhaust near a brakeline. Any heat is going to expand the brake fluid causing tighter braking. Since yours is a new problem, my guess something is hung up.
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07-08-2018, 09:57 PM | #25 |
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Location: NorCal
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Re: Any brake geniuses out there?
Maybe something to do with the Hydrovac unit, but I really don't know the internal workings of them
Last edited by Kahuna; 07-09-2018 at 09:03 AM. Reason: Info |
07-08-2018, 09:57 PM | #26 | |
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Location: MN
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Re: Any brake geniuses out there?
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Quote:
any update!!! 7 can be a lucky number being your post num to this point. Sounds like fluid expanding under heat or.... that sbc! ha ha ya I do that. |
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07-09-2018, 02:59 AM | #27 |
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Location: Solihull, England.
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Re: Any brake geniuses out there?
1ton said it is heat related. that's true. All brakes get hot when used. the fluid warms up and expands. When the brakes are released there is an open port (the recuperation port) that allows fluid pressure to equalise between the system and the reservoir. When you press the pedal, the very first part of the travel closes this port, allowing you to pressurise the system and apply the brakes. you might sometimes observe a little squirt of fluid into the reservoir as you apply the brake pedal, that is coming from the recuperation port.
If the pushrod is too long the port is already closed and the fluid can't equalise before the brakes are applied. The heat from the brakes further pressurises the system and applies the brakes even harder. I't's a vicious circle. If the pushrod is too short, you get a lot of lost motion before the brakes are applied. The trick (and I have done this) is to fine tune the pushrod length so you minimise the lost motion but still maintain an open port at rest. the other important thing is to ensure the brake pedal has a good return spring so it returns to the up position cleanly. If not, you could have a similar scenario where the recuperation port is not open. Mart. |
07-09-2018, 07:14 AM | #28 |
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Join Date: Jan 2011
Posts: 426
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Re: Any brake geniuses out there?
Very old rubber brake line hoses can act as a one way valve due to internal swelling.
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07-09-2018, 08:07 AM | #29 |
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Re: Any brake geniuses out there?
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07-09-2018, 11:32 AM | #30 |
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Re: Any brake geniuses out there?
I have seen new hoses that work as one way valves--- I have seen new wheel cylinders with holes drilled in wrong places--- if the edge of the cup covers the "in" hole just enough it can prevent return of fluid, I have had new master cylinders with the pushrod hole not deep enough, holes incompletely drilled and rubber that swells in brake fluid
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07-09-2018, 12:13 PM | #31 |
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Location: NorCal
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Re: Any brake geniuses out there?
Hydrovac units are powered by vacuum. Maybe it's located close to something & gets hot & upset?
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07-09-2018, 01:11 PM | #32 |
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Join Date: May 2010
Location: Mid coast Maine
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Re: Any brake geniuses out there?
Those rubber hoses will do that.
What some people do is pinch the line and this is NOT Good. |
07-09-2018, 11:11 PM | #33 |
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Location: Minnesota
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Re: Any brake geniuses out there?
Wide range of ideas here; but the original post says the brake lights were stuck on; kinda indicates the master cylinder was holding pressure; either by defect or misadjustment of the push-rod, most likely cause as previously mentioned.
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07-10-2018, 05:28 PM | #34 |
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Join Date: Dec 2017
Posts: 29
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Re: Any brake geniuses out there?
I'm getting closer...there seems to be a fine line between push rod adjustment and brake shoe adjustment that needs to be balanced. I should add that I've been driving this car for over 25 years; the problem only came up during this brake job...after finally getting new wheel cylinders that didn't leak, brake shoes that fit properly (relining the originals was the answer), and a U.S. made Wagner m.c. that didn't have to be pumped up for every stop. I appreciate everyone's expertise, experience and willingness to help!
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