Master Cylinder Probs

So i broke down and swapped out the master cylinder on my f1. I took out the stock one and swapped it with the one that was in my donor truck, a 81 chev truck. it was a power brake on there. now on the f1 its a manual. When i go to pump up the brakes i dont get any pressure... i can pump it all day and nothing... Do i have to get a manaul brake cylinder... is there a difference?

 

'81 should be for disc front, drum rear.. correct?

I ***ume you still have the 4 wheel drums on the F1.. If so, your 81 m/c is not going to displace enough fluid to work the wheel cylinders on the front.. possibly the rear also. Bore size may be a problem also.

Need more info on your setup.

 

Sometimes the manual ones have smaller diameter pistons/ bore so its easier on your leg..LOL..
But both work OK.
You have to bench bleed the new master before you install it.Or at least loosen the brake lines and pump until enough fuid comes out.Then hold the pedal down and have a second person tighten the lines..
That way you don't push endless air in the system!

Ollie

 

I have discs in the front and drums in the rear. Rear axle is outta a 74 nova. i have a Proportional valve and residual valves front and rear.

someone else mentioned bench bleeding it, but he thought i just had to do that if it were a new m/c. i even have to do it if i took it outta the truck? i guess it has been on the shelf for a few months... i suppose all the fluid drained outta it.

Thanks

 

Yes,it creeps out very fast!If you still can't get that air out try to loosen each connection one the way to the rear axle.Like working your way back,always til fluid pumps out.
An if your not shure about the 81 master:If its full and you push a screwdriver in,that thing should squirt a good foot.Thats how i test them,having 6tons of used old parts..LOL..
Always works!
Ollie

 

needs to be blead, it is leaking, or it is broken.

Not much else to really go wrong...

 

the power mcyl uses a different pedal ratio..
order up a mcyl from a 74 chevy 1/2 ton non power disc truck
Autozone lists it as # m1581..
good luck
Dave

 

Make sure your push rod to M/C has a bit of free play, the M/c piston MUST return all the way to the snapring in the bore of the M/C.

 

And have your helper pump the pedal very slowly and hold it down until you tell them to release it and pump again.
I've seen more issues with people pumping the brakes too fast or not doing the bleeding process correctly.<input id="gwProxy" type="hidden"><!--Session data--><input onclick="jsCall();" id="jsProxy" type="hidden">

 

So we ended up taking the m/c apart, and honed it good (some pitting inside) cleaned everything, put it back together and now it builds up pressure. so hopefully it all works good now. We did bench bleed it. broke my bracket studs off so that will be my next project..

Thanks for the help