Brakes will not pump up

[DeanG]

After sitting for a couple of months I wanted to go for a short drive to warm things up before starting to do some maintenance items. I don't have any brakes:
1. The brake peddle goes to the floor with very little effort
2. Pumping them (20+ applications of the brake) doesn't make any difference
3. The reservoir is full
4. If I shut off the engine the peddle seams to firm up but once the engine is restarted the brake peddle goes to the floor again
Does anyone have any ideas about this?

[Brit-Car-Nut]

Look under all 4 corners just to make sure you don't have a caliper or hose leaking.

If no leaks, sounds like the master cylinder has failed. Remember, the LHD cylinder is DIFFERENT from the UK cylinder.

[wayne]

Bad master cylinder????

SJ's do a replacement cylinder for about £50 but it has a steel body instead of aluminium. It will fit the LHD RoW cars
so will probably be ok for the US cars.

I think you have to just fit plugs in the ports not being used....

[Brit-Car-Nut]

The UK uses different size threads in the master cylinder from the FED.

There is a US cylinder that has the right bore but has odd threads due to having proportioning valve attached at the cylinder. Some people get that and swap the innards. I believe it is from the 1988-90 Pontiac Lemans With 2.0L engine, NOT the 1.6L. Most refer to it as the "Second Generation". Needs to be 7/8" bore, not 13/16"

I don't know about the ROW/LHD cylinders.

[DeanG]

Thanks guys. I started going around the car starting with the LR. I adjusted the wheel bearings which took way too long in today's heat and humidity. I will do the RR tomorrow and hopefully around the car this week putting refreshed front calipers from Steve. I was guessing that it was the master cylinder. I'll report back ASAP.

[steve matthews]

Dean, sorry to hear about break cylinder.
I do have a auto bleeder and the possibility of extra time on my hands next week.
Looks like with the overflow tank out of the way access not to bad.
Let me know.
Steve

[DeanG]

Still no brakes.

Today I finished installing the front hubs except for torquing the big expensive nut that holds everything together (which needs brake force to pull the 170 ft-lb). Bled the brakes with a vacuum bleeder. I can't get them to pump up. I tried both with and without the engine running. I have rebuilt calipers and master cylinder.

What do I do next?

[superbad]

There are really only a few possibilities:

1. Very unlikely to be your problem, but verify that the brake pedal is actually moving the master cylinder rod. Then:
2. You could have a leak somewhere that is preventing you from building pressure. Easy to check. Mark the fluid level, pump the brakes a bunch, see if the level has dropped. There are several junctions that could leak, you could also have a split in one of the hard lines. A brake hose could have rubbed on something and failed. After checking that:
3. The rebuilt master cylinder could be bad. Your initial post sounded like it was leaking into the vacuum booster. Check that it's actually displacing fluid. Open a bleed valve or disconnect a brake line, run a hose into a cup, see if fluid comes out when someone pushes the pedal. Another test- try capping the two ports exiting the master cylinder and see what happens. Pedal should be solid.
4. You have a large amount of air in the system somewhere that your bleeding didn't eliminate.

[dapinky]

Following on from superbads advice (which i agree with!) - having re-built the master cylinder, did you prime it with new fluid? Sometimes a new pump will not displace anything unless it is full with fluid.

It is easy to rectify by simply removing any exit pipe from the master cylinder (or evn just losening it a bit) and operating the brak pedal until fluid seeps out of the loose connection - that way, at least you know the master cylinder is pumping, then re-bleed the brakes in the usual way.

If you have all pipes full of air at the moment, then i'd start with the front brakes as they are the easier ones to bleed - then with them full of fluid, the rear ones are easier to 'pressurise'.

[DeanG]

All is well. Today I drained the coolant (again) and loosened the a brake line on the master cylinder. A friend came over and in just a little bit we had success. I was able to torque the wheel hubs and put the car on all 4 wheels for the first time in months. This week I will get all 4 corners bled and start the rebuild on the CAS. Thanks.