Prime master cylinder

[J90rdn]

During the engine conversion my master brake cylinder drained down. Bleeding the brakes has not been possible, so I assume the cylinder needs priming. As I don't have a priming kit, is there any way of doing this? I've just removed the cylinder from the car.

Is an alternative to buy something like a bleed ezy kit and force the air out?

[maxfield]

Cylinder shouldn't need priming.

Are you certain you have all the air out the system?

If the master cylinder had been emptied and the brake pedal has been pressed while empty, it's possible to flip the seals in the master cylinder.

[J90rdn]

How do I check for this?

[J90rdn]

And if so how do I fix?

[maxfield]

Get some clear pipe on bleed nipples and make sure all the air has gone.

If it has clamp all your flexi hoses. If the pedal is hard, still air in the system. If it goes to the floor master cylinder.

[J90rdn]

That's the problem. When I was trying to bleed the brakes I was not getting any fluid coming through. The master cylinder worked fine before coming off for the engine conversion.

[maxfield]

How are you bleeding the brakes?

It does take a while before fluid comes through.

[J90rdn]

Old school 2 man pumping the brake pedal.

[maxfield]

I'd keep trying, even with a duff master cylinder you get fluid through. It does take a while to come through.

I always use clear pipe and a bottle. That way you can are air bubbles coming out of the caliper

[Andyboy]

Try to avoid pedal pumping on old iron body master cylinders as the seals will rub against the inevitable rusty bits and ruin it - not an issue on alloy cylinders but as brake fluid is hygroscopic (it absorbs moisture), rust on the unused sections of the master cylinder bore is going to happen on a 25 year old cylinder. That's why I use a pressure bleeder, just a cheapo Gunsons one that uses air pressure from a spare wheel.

[e30rapidic]

bench bleed the master cylinder before you install.

[J90rdn]

Bench bleed as best I could and put back on. Immediately got fluid to the calipers so must have been an air block in the master cylinder.

One thing I have noticed is with the passenger front caliper. When trying to bleed the caliper, loosening the bleed nipple, which is brand new as they all are, has the fluid coming out of the threads of the nipple rather than the hole in the nipple. Tried another nipple (again brand new) and got exactly the same. Any ideas?

[kam-325i]

how much are you turning the nipple to undo it ?

[J90rdn]

About 1/4 turn, same as all the others

[kam-325i]

sounds like the thread has been poorly cut.