steveplym Posted September 22, 2007 Report Posted September 22, 2007 I'm working on a friends '65 chevy shortbed. Front drum brakes, just replaced both front wheel cylinders, shoes, and front brake hoses. Continuing to have a problem when once you drive the truck 30-40 miles pressure starts to build and the front brakes lock up. The only way you can get them to release is to open the bleeder valves on both front wheel cylinders. We went ahead and replaced the master cylinder and that did not help. This is a single reservoir master cylinder. I purchased these at Napa and wondering if there possibly could be a defect in these wheel cylinders as both front wheels lock. Anybody ever had a problem like this? Wondering if I should just take the wheel cylinders back or purchase a set from someone else? Quote
Lou Earle Posted September 22, 2007 Report Posted September 22, 2007 That usually means air inthe system. If you let it sit overnight and it unlocks I would bet the farm there is air somewhere I have had that headache on several cars Lou Quote
Normspeed Posted September 22, 2007 Report Posted September 22, 2007 I've had that happen when the return port in the master cylinder is blocked but if it was happening before and after you replaced the MC, that's unlikely. Maybe air in the lines like Lou says. Quote
Niel Hoback Posted September 23, 2007 Report Posted September 23, 2007 Check into the brake pedal return, it has to come all the way back. Also check the pushrod between the master cylinder and the booster to make sure it is not holding the master cylinder piston down, there should be a small amount of play between them. Quote
BobT-47P15 Posted September 24, 2007 Report Posted September 24, 2007 Did you replace all the rubber hoses in the system?? My car would work ok for a while, but eventually the rear brakes would lock up and had to bleed them to relieve pressure. Reason.....the inside of the rear hose was collapsed. It would allow fluid thru when you applied pressure with the pedal. But, it did not want to return to the system. Hose looked perfectly fine on the outside. Just a guess on your problem. Quote
steveplym Posted September 24, 2007 Author Report Posted September 24, 2007 I'm going to try to bleed the brakes again this week to make sure all the air is out of the system before I pull the wheel cylinders. I've replaced all the hoses on the front. Haven't replaced the back hose as it was ok and the rear brakes didn't lock up. Will need to readjust the brakes too just to rule out everything. Thanks for the help. Quote
kencombs Posted September 24, 2007 Report Posted September 24, 2007 Just to second the suggestion to look at the pedal free play adjustment. That has been the source of every one of these I've seen, probably 8 to 10. Quote
Young Ed Posted September 24, 2007 Report Posted September 24, 2007 Wouldn't that lock all 4 wheels? Quote
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