Spongy brakes???

[HK1837]

The only other issue I have had that is similar is with a UC. Not sure if the older metal cylinders have the same thing. This damn UC had all sorts of issues when I bled the brakes after changing the cylinder. I tried 5 x different cylinders, all had spongy brakes. What it turned out to be is these boosters (that suit the UC/WB/Commodore cylinders) have a reaction pad in the booster that sits around/on the pushrod. It had fallen into the booster. An old hand at a brake place diagnosed it. Fitted a new pad and it was sweet as. I've never had this issue with the metal cylinders, but no-one had heard of it in the plastic ones either until the old guy at the brake place remembered it happening to him.

[mckackie]

yes! definetly check the reaction pad hasn't fallen. I remember being an apprentice, and pressing the pedal when the master cyl was off, and the resulting calamity ended up being one of my monumental phuque ups. if thats not it, does yours have a proportioning valve that may be U/S?
Clarify 'bleeding master cylinder...." when we installed a new master on any car, we would prime the master on the bench. vital proceedure to say the least, most of the time you can get away with not doing it, but it does make life easier. otherwise, it could well be a dodgy new master.hope this all helps.

[GTS]

When I removed the pipes from the proportioning valve I bent them back up so they would refill the master cylinder when the pedal was pushed. I had to make new pipes anyway and figured that was the easiest way to do it. I primed it on the bench when I originally installed it last year and thought I'd give another go while I had the pipes off.

[Rico]

This is why I pay a brake specialist....they can do it, and give me some sort of guarantee!

[RodneyHZ253]

Sometimes when you cannot sort it out you need to start again and start replacing parts but there must be still air in line

[GTS]

The left hand caliper is/was the problem. Got it sorted last night, thanks for the replies

[playwme]

Good stuff. Was it a dodgy seal or something?

[GTS]

Massive air lock ......I'm surprised at the amount of fluid that still came through the nipple (with no air bubbles) when trying to bleed it with sooooo much air trapped inside.

[GTS]

If the new master cylinder, which is arse about face to the old one, is off a later model then my question would be "is the pushrod between the booster and master cylinder the same length????"

I have come across this before where as little a 3mm makes a huge difference. Can anyone confirm one way or the other?

I know, I'm replying to my own question....but the scary part is that my suspicion was right....for a change.


After I got the air out of the l/h caliper it turned out it didn't make any significant difference.

Today, after sitting in my, now well worn, pondering chair last night killing off some excess brain cells with my favorite brew I made a 3mm spacer to go over the end of the push rod out of the booster. The result was instant...full, hard pedal. It still needs a little tweak but I had to start somewhere.....I reckon a 2.5mm spacer will be on the money so I'll trim this one down in the morning.

Prior to this, after clamping off all 3 hoses and getting full pedal, all I had to do was remove either 1 of the front 2 caliper clamps and the pedal crept to the floor. I knew it couldn't be the calipers full of air anymore so I started looking at the master cylinder. I figured that the pedal was creeping because the seal hadn't gone past the little vent return hole and was bleeding internally....almost as much as I was after spending 2 weeks trying to find the problem. The pedal sunk to the floor as if I had a slightly open bleeder nipple...there was a bit of pressure there but it still went to the floor.

So theres yet another solution to a brake problem....although I guess it'll only ever come up when you make 1 van out of 3 then start using new and old parts. BTW, the only old part of the braking system is the booster and the pedal. Lesson learned.

[GTS]

I checked out a different brand master cylinder today only to find it had the exact same casting numbers etc as the one I bought. The brake guy said they are all made in China these days and reboxed into whatever brand. I'm guessing this problem is going to pop up every now and then if this is the case. I also contacted PBR Australia......they only supply the Chinese cylinder so I guess most/all of them will be too deep in the piston area as well.