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#1 |
71 DELUX
Join Date: Sep 2003
Location: Northern CA / Sac
Posts: 1,056
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proportioning valve... bad ?
OK,
The more I think about it, the more I realize that there are three areas that could be causing my brakes to stick... Screwed up-old and deteriorating brake lines (maybe this is it). Bad master cylinder (but I don't think so). Screwed up proportioning valve (leaning more this way). Here's my problem. I have new spindles, new pads, new fluid and yet the first couple stops are fine, but the following ones get worse and worse until both front brakes feel VERY tight. If the truck sits for a while, the brakes will be fine for another 2-3 presses of the pedal... then everything is stiff again. What are the thoughts out there, proportioning valve, or lines? JT |
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#2 |
Mike
Join Date: Jan 2003
Location: west chester pa
Posts: 2,474
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I would change the lines first.When I changed mine they where around 40.00.
__________________
70'c/10, 71 suburban4x4 402bb, 72suburban 4/6 drop, 72k/5 4x4 blazer 4" lift 35 tires |
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#3 |
Registered User
Join Date: Sep 2003
Location: Tyler
Posts: 575
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Are your brakes sticking all around or just in the front?
Do you have disc brakes in the front? If so your calipers may be bad. If they have gotten real hot sometimes it will warp the piston and cause the brakes to drag or lock up. Also how old are your brake lines? I don't think they are the cause of your problem but if they are craked or worn they need to be replaced.
__________________
1969 Chevrolet SWB Stepside 1959 Chevrolet apache * Sold 1967 Prostreet Chevy SWB Fleetside *Sold 2014 1/2 ton Crew Cab Chevrolet 4x4 |
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#4 |
71 DELUX
Join Date: Sep 2003
Location: Northern CA / Sac
Posts: 1,056
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Great... a fourth option, yikes.
I am hesitant to go with the caliper option at this point, since when they've gotten tight I've simply babied it home and was never more than 2-3 miles from home. Yet I'm not sure how hot they'd have to be to get warped. And really, the calipers looked to be in very good shape when I took everything apart. OK, more to investigate. |
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#5 |
71 DELUX
Join Date: Sep 2003
Location: Northern CA / Sac
Posts: 1,056
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My guess is (even though the ball joints and many other parts have been serviced or replaced) the brake lines are 32 years old. They look old, not cracked...but old.
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#6 |
Registered User
![]() Join Date: Feb 2000
Location: Georgetown, KY, USA
Posts: 631
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I think (dangerous I know) that I have read about that kind of problem and it was the linkage rod not allowing the master cyc to return all the way. Like you held the brakes part way down. This kept the fluid from returning to the master cyc.
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#7 |
71 DELUX
Join Date: Sep 2003
Location: Northern CA / Sac
Posts: 1,056
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YES, that is exactly what the problem feels like.
It is as if the fluid is not returning to the master cyclinder, but simply pumping to the front brakes...continually. Then, when the truck sits for a while, the fluid just "migrates" slowly back to where it is supposed to be. What linkage rod are you talking about? Is it something IN the master cyclinder? Should I get a rebuild kti for the MC? |
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#8 |
Keepin an eye out
Join Date: Feb 2003
Location: So.Cal
Posts: 3,921
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Yikes, cant wait to see what kind of problems I will encounter when im done with my DB conversion
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1970 Chevy C10 SWB 5.3 1996 Toyota Tacoma SR5 4x4 2007 Vespa GTS 250 Scooter ZIP 91351 |
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#9 |
71 DELUX
Join Date: Sep 2003
Location: Northern CA / Sac
Posts: 1,056
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My problem is not yet resolved. I put the new brake lines in which was a good thing to do. I do not sense the valve is the issue...master cylinder is my next matter to explore.
Boraxman- I spoke to a friend who converted the drums on the front of his old chevelle to disc. He picked up a prop valve from and old nova or something similar at a wrecking yard, bolted it in and had no problem. Imagine that! |
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#10 |
Registered User
Join Date: Jan 2003
Location: Santa Fe, Texas
Posts: 250
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You did replace all the rubber lines? Sometimes they collapse inside, but they look good on the outside. My Sub lines collapsed and it would feel like the brakes weren't releasing in the front. The line lets fluid thru so your brakes work when you press but when you release the pressure the line collapse inside and it acts like a oneway valve. It does bleed down over time.
Mike |
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#11 |
Registered User
![]() Join Date: Jul 2000
Location: Hampton, Ga, USA
Posts: 217
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Master cylinders for drum brakes have residual pressure check valves in the outlet ports. Disc brake should not have the check valves in the front outlet. Check valve could cause tight brakes.
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68 Short Stepside, 350, quadrajet, 700r4, 3:73 posi, power front discs, HEI, Factory Air, Tilt, Tach, accelerator cable instead of rod, sway bar. 96 Impala SS 97 Monte Carlo |
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#12 | |
Registered User
Join Date: Mar 2002
Location: Agua Dulce, Ca. usa
Posts: 179
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Quote:
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Ed ke6bnl Agua Dulce 70 S.E. Los Angeles 70 Chevy short bed 1948 F3 ford pu 1949 F1 stock V8 flathead 3 on floor 1950 F1 pu street rod 1948 F6 Ford Dually/350sbc no bed stock trans&rear 1972 El Camino 4" chop 1953 Chevy 3100 2b daily driver 1970 SB 4X4 400ci 6in lift |
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