Ever since I converted my 37 Chevy p/u to a dual master cylinder sometimes the brake pedal will go to the floor while going slow like trying to back in or leaving from a parking spot,now once I get the truck moving the pedal goes back to normal and did not do it when it had the original style master cylinder. I made a bracket to adapt the newer master cylinder to the original pedal assembly and it now sits out past the bracket and does have two exhaust pipes right under it,I am thinking its getting hot from the pipes and going to look into a aluminum shield to put under the master cylinder but if anyone has any other ideas I would like to hear them.
If you're looking to make a heat shield, stainless is much more effective than aluminum, whether it's for brakes or anything else. Good luck.
I wouldn't think heat from the nearby exhaust pipes would only affect the brakes when you're parking. A heat shield is an easy enough experiment.
I'm sorry I'm not help but what master cylinder are you using and do you have drums all around? What type? Thanks..
Boiled brake fluid is useless and dangerous, if that is what is happening. You will need to bleed out that fluid as it is breaking down. Repeated overheating will just cause it to become less and less effective. Once you get your heat shield on, bleed the brake system. For a temporary fix you can use a starter heat blanket to protect the MC, might have to modify it for the brake lines but otherwise it should fit. At the track if there is a boiled fluid issue with a car, after it comes in we bleed the system. Usually it's just the rotors/calipers that cooked the fluid so we bleed enough to clear the calipers. But in your case the problem seems to be at the MC itself, which will require complete bleed.
I used a heat sheild on a part of my braking system, it looks like "Woven" aluminium with some goop in between. I don't remember the name, but it is real handy, thin, (1/8"), and can be cut and worked like sheetmetal. You should be able to get some from the "Go fast" stores.
I think the master cylinder is a from a late 70s Ford truck with discs up front and drums in the rear,the same exhaust system was on the truck with the original master cylinder but never done it but the truck was sitting higher off the ground too at that time. The pedal assembly has like a shelf cast in it where the master cylinder mounted to so it most likely deflected the heat where its sitting a few inches back now,going to see what I have laying around this week and try to make something.
It sounds like you need to put a residual line pressure valve in the system. If it is an under floor unit you may have fluid bleeding back and the first application results in a low pedal.
It does have residual valves,it will not do it under normal driving and only while creeping very slow with almost no air flow going under the truck.
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