I was actually in the garage doing something else when i seen this message on my phone so i thought while im here.... lol, pulled the master cylinder away from the booster and there is quite a bit of surface corrosion, im not sure if its been leaking at some point and dried up ? there is a little damp spot at the bottom but that will be from the wd40 i sprayed on the RH bolt as it was real real tight. I think anyway!





So if its not wet at the back i guess it isnt leaking then, the system is possibly just full of air as previously mentioned ? I think i might just replace it anyway if i need to try bench bleeding it, no sense using this old one. Im not sure if the booster is ok or not, can air leak into that part and mess the vacuum up where the push rod is ?

 

It looks really rusty. I'm thinking that your master probably isn't moving when you press the brake pedal. the center of the master should move in and out as you pump the breaks. try pressing it toward the master like the booster would and see it moves at all. it looks like the push rod is in the booster though.

 

you are probably going to need a new master??

 

I know it moves as when I started on the brakes ages ago I remember sitting in the car and pumping the pedal and I could hear the fluid in the master cylinder moving with it being in the garage and the hood open.

 

But yeah i will replace this regardless as it looks pretty nasty.

 

Describe the procedure you use to bleed brakes. Don't omit details.

 

I used my vacuum bleeder with my air compressor. Mainly because I work on the car on my own

 

You need to push air out of the calipers using the brake pedal. Slow and steady sweep of the pedal, hold still at about 3/4 stroke and close the bleed valve. Repeat until no air bubbles whatsoever. Attach a clear hose to the bleeder valve and have a loop facing upwards so fluid gets trapped in the hose. That way if anything is accidentally sucked back into the calipers then it will be brake fluid, not air.

A set of Russell speed bleeders make that a one man job. It is a a replacement bleed screw that has a check valve built into it. Earl's sells one too and might be easier to find in the UK. Problem with Earl's is the check valve is external to the bleed screw and can be damage or broken off. The problem with the Russell is..... well, it is Russell.

 

Yeah that's what I've done. Bled the brake calipers. But now it's looking like it could be the master cylinder if it's been off the car at some point and not bench bled.

 

I said don't hold back details.... and you held back details.

 

Lol. I bled the calipers....well all apart from the OH front as I couldn't get the bleed valve open. Fluid came out nicely from the other 3 corners though. There were bubbles but I kept pulling fluid and refilling it until I couldn't see any.

The brake pedal remained the same though. Good travel with a slight hiss noise but the pedal will not change with the engine running.

 

Sorry but seeing pics of that master and booster..I wouldnt think twice to replace both...that hiss sound still seems like booster leak noise to me.

 

a leaky master will cause the booster to fail. the leaking brake fluid damages the seals.

think i saw someone post something similar above somewhere.

 

New booster and master cylinder required then

 

Yup you should do both. I wouldn't bother wasting time making those current pieces work. As soon as you mentioned hearing a sound while braking I knew the booster was part to blame. I've been there. Had a leaky master...reppaces the master...only to have to replace the booster right after

 

Right then, i hadnt looked at the car for weeks as i just havnt had the time lately but tonight i decided to let it run for a bit and also decided to take off the under dash plastic for a look at the rod from the brake pedal, as soon as i got under the dash i could hear the whooshing noise of a vacuum leak, hmmmm.

dash plastic out the way it sounds like a vacuum cleaner under there ! i think ive found the problem for my lack of booster, im assuming there should be a rubber plug / seal in here ?!?!?

 

seals are part of the booster. replace it.

 

New booster already ordered. And a new master cylinder too. That was pretty corroded when I pulled it away from the booster so I might as well do both

 

Ok so new booster is fitted. Bench bled the new master cylinder. Fitted that. Bled the rear brakes and all is good.

Moved onto the RH front caliper and i just continuously get air bubbles. The pipes are fine, the unions are tight as I had a new pipe made. No leaks, plenty of fluid in the master cylinder which is going down as I draw it through the bleed valve with my vacuum operated bleeder but I just keep getting air bubbles. Wtf!

 

Air is probably leaking past the threads of the bleed valve. Just close the valve and see how the brakes work.

 

To really prevent air from getting sucked in around the bleeder screw threads, you need to elevate the waste fluid bottle above the level of the bleeder screw. This ensures above atmospheric pressure inside the bleeder screw and hence no air will be sucked in. If the hose is just run up a few inches and then down again below the level of the bleeder screw, the siphon effect could create a slight vacuum at the bleeder if the flow of fluid from the caliper is somewhat restricted. Or at least that is what I have been told

 

Actually my suggestion may not be worth anything. I forgot that I always finish off by pulling a vacuum with a Mityvac, or similar device, and that is when the air gets pulled pass the threads (little tiny bubbles). That should not be happening while bleeding by the brake pedal.

 

It's not that long since I bled the brakes when originally trying to find the source of the poor braking and it bled fine then. Pretty sure the bench bleed was fine. But even if it were air still in the master cylinder with the amount of fluid I was pulling through and then topping up it would of got rid of that air anyway.

I did tighten the bleed valve slightly and the fluid came through slower but still had bubbles in. I will try holding the breeder hose up then and see if that works and recheck all the bits are tight

 

Yes, you definitely want a column of fluid above the valve so that if the flow goes back you get fluid and not air.
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Done. Worked great ! Thanks guys.

It was getting late but I got the front bled and started it up. Idled really high ! I'm guessing because it had a huge vacuum leak from the old booster I've compensated for that when I done the timing. Now it's air tight the idle has shot up.

So I didn't test the brakes tonight apart from trying the pedal which now feels the same as in my 87. Good travel and feel. And more importantly when I switched the engine off and pumped the pedal it went really firm as it held the vacuum. Before it would just pump endlessly lol.

Gonna reset the timing tomorrow to get the idle down and try the brakes properly

 

Thats awesome news..I know it can be frustrating solving what should be easy fixes and nothing seems to go right the first time.Especially when you think you triple checked everything! But one thing for sure you can say is that majority of the parts are new now and you have that peace of mind for sometime to come because you have gone through the entire system.Plus you can dial the motor in now that the vacuum leaks are gone and it will stop when you hammer the pedal now.