Master Cylinder Question?

[KGM Racing]

I have a 97 stock full f150. We mostly run it in sportsman classes. Is there a heavy duty master cylinder some one recommends or should I just buy an original. Thanks

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[1wayne]

Are you running the stock booster? If you are the stock one should be just fine. I've found that you want to buy a name brand like Bendix. One more ? are you trying to get more stopping power. if so you could use a larger dia. master cylinder you have to a little homework as to which M/C would fit. Hope that helps.

[KGM Racing]

Yes we are running the stock booster. The reason Im changing the master cylinder where having brake issues. They just go away from me during the race. If I am on it hard for a long distance and then go to hit the brakes they go to the floor. So im pumping away and they will come back gets kinda scary though. We just put a new booster on and it still did it so Im on to the master cylinder. The reason I changed the booster cause when I would push down on the brake while it running the motor would idle down. Someone said it might be the booster having a vacume leak. Weve blead them and blead them but they seem good and then loose pressure after we run it. Any other recommendations someone can give me?
Thanks

[jonpfive]

Are your brakes getting hot? Maybe you are boiling the fluid. I was always told fluid needs to be flushed once it has boiled. Also use a high temp racing brake fluid if you are not already.

[KGM Racing]

No brakes are not getting hot. Cause the brakes will lose thier pressure even after the trailer ride to the race. So I back it off the trailer and have to pump them up to bring the pressure back. Ill still go ahead and flush the fluid though. Thanks for the info

[1wayne]

It sounds like your M/C is leaking down internaly, replace the M/C when you bleed the brakes bench bleed the M/C,install it then start at the right rear wheel, then left rear, right front,left front, when your bleeding the brakes only pump the the pedal once hold it down open the bleeder then close the bleeder, release the pedal wait 4 to 7 seconds press down on the pedal repeat till there is no air in the lines. Hope that helps.

[KGM Racing]

Thanks Ill give it a try!

[tltony]

Sounds possibly like the caliper pistons are being collapsed by movement, run-out or looseness of the rotors. Make sure all your wheel bearings are tight and that there is no more than 1 or two thousandths runout or thickness variation in your rotors.

Another possibility is that the brake fluid is being overheated for some other reason other than over-use. Check the routing of your lines around exaust, both proximity to pipes and actual hot gasses flow. At True Line we chased a similar problem on a work truck and found the cause to be a tail pipe that was dumping ahead of a steel line on a rear end housing. We pulled our hair out for a long time over that one.

Oh wait, you said it will happen on the trailer. Scratch paragraph 2. Paragraph one could occur, but only because of loose bearings/rotors.

Tony

[KGM Racing]

Thanks ill check them. Yeah its getting crazy trying to figure this problem out!