Spongy brakes, is it a vacuum issue?

The vacuum will not cause a spongy feel to the pedal. That would only be caused by air in the hydraic brake line. I have seen master cylinders go bad during bleeding and the first thing you should have done was bleed the master.

All the power booster does is reduce brake pedal effort. The pantera needs about 14 inches to operate the booster as designed. It will give you boost at 12 inches but at a reduced amount.

Thanks, any suggestions on bleeding the master as there are no bleeding nippels in it


#1154

quote:

Originally posted by suburb:
Thanks, any suggestions on bleeding the master as there are no bleeding nippels in it


#1154

Yes. You need to disconnect the tubes coming from it and fabricate temporary tubes that circle back into the reservoir.

You may be very surprised to find that is the source of the air in the system.

It's ok to disconnect those temporaries and re-connect the permanent supply tubes. The air you are introducing to the system is outside of the master but you will need to rebleed the front and rears to get that little amount you just let in completely out.

If the pedal doesn't get high and hard then the master has a leak in one of the o-rings and needs to be replaced.

Ok, will do

Hey Panteradoug I did like You said, but there is only oil coming from the niplle closet to the windshield, push for about a minute. Does this mean the cilinder is shot ?

quote:

Originally posted by suburb:
Hey Panteradoug I did like You said, but there is only oil coming from the niplle closet to the windshield, push for about a minute. Does this mean the cilinder is shot ?

I think so? I would change it for safety.

Still, why would it fail just now you've been working on the calipers only?

Just wondering...

Hey Kid ,good point also how does this relate to the losing of brake pedal pressure on starting the car

#1145

quote:

Originally posted by Kid:
Still, why would it fail just now you've been working on the calipers only?

Just wondering...

Often a master cylinder that goes through this procedure of pumping the brakes in the process of rebuilding the brakes, fails during the procedure or shortly after.

I have seen this many times on many cars.

Using a vacuum pump to suck the air out of the system is less traumatic to the master itself BUT you still need to bleed the master first for it to work.

The vacuum pump will not bleed the trapped air out of the master.

Maybe you can just think of it this way, the master was just hanging on the edge and the stress of pumping the brakes, especially if there was air in the master and it was pumping dry as a result, just pushed it over the edge.

Incidentally, I have had new masters fail right after installation BECAUSE they weren't bleed first.