Spongy brakes???

[GTS]

I fitted new brake pipes the suggested way (front res to rear & rear res to front) and the only advantage I gained was the back brakes dont seem to be locking up anymore.

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?

[ozbox]

so you still have spongy brakes?..did you re bleed them back to front this time?

[GTS]

so you still have spongy brakes?..did you re bleed them back to front this time?

Bled twice the right way round.....still hittin a sponge.

--- Updated ---

If you have fitted a master cylinder off a different model, never mind the reservoirs and pipes being back to front, but also bear in mind that diameters may be different between models or break points in production also.

I bought it from Autopro and they said it was the recommended replacement.

Did you over haul your front calipers and replace the pistons?

I put a seal kit through them and everything seemed to be OK. I used the original pistons.

Another thing to t is the bleeding technique, where you have an assistant pump the pedal vigourously and then have them count 1! 2! and on three,snap open the bleeder before they stomp hard on the pedal. This can often dislodge air pockets in some systems.

I did a gravity bleed to the l/h rear then got Mrs GTS to pump the pedal. I'm confident we got all the air out of the system.

All other advice offered by other members has been good too, assuming you have adequate knowledge on brake systems fundamentals.

I've been in the automotive and earthmoving equipment spares business since 1978. I've rebuilt more cars than I care to remember so I'm pretty confident that I have adequate knowledge....although this current problem really has me stumped.

as a matter of course, did you bleed the new master on the bench before installation?

I did it when I installed it 12 months (or more) ago and did it again tonight while I had the pipes off it.

I don't mean to sound condesending, but sometimes the most simple things may be the cause. I hope this helps too.

No problems there....I'll take any suggestions at this point.

--- Updated ---

BTW are you anywhere near Sydney? I can give you the name of an absolute guru as far as things with brakes, clutches and heads go......

I'm in NSW near Canberra. I've got a few mates in the brake industry...time to give them a call. I didn't ask them before because they are going to take the piss outta me soooooo bad.:errf::errf::(

Thanks for the suggestions anyway.

--- Updated ---

So back to my question......is the pushrod between the booster and master cylinder the same length from model to model?

[mckackie]

I seem to remember something somewhere about the push-rod or master cylinder piston cup.......the more I think about it the more it seems to cause a brain spark, a bit like a bug zapper not quite zappin that bug. Eventually though, it may come to me, as I can re-call issues with brake parts on HJ's thru to HX being somewhat interchangable, but also needing to be very careful.SO......
Give Jim at Sydney brake and clutch exchange a call on 02 9663 2556.....he may remember better than I can, as he is still hands-on and 50 years(I think) owner of the shop. I will also talk to a mate who woked on H series Holdens for quite some time and see if we can help before you tear all your hair out or develop a drinking problem
If Canberra is closer, try Commonwealth Motors spares dept, as there may still be a bloke there with excellent knowledge about them too. oldholden.com in the holdepeadia might help too, if not contributors on there might know too

[RodneyHZ253]

Gts I 'am not a mechanic but are the rear brakes adjusted up.maybe you could adjust them up to tight check bleeding and see if this makes any difference.if this help maybe you need to use the brakes and let them bed in a little.mind you builders don't give real good mechanical advice.

[wbute]

If you pump the pedal and the brakes come back its the rear shoe adjustment, if not, its air in the system. But if the rears were locking then they must be adjusted.

It has to be air somewhere. Spongy means you are compressing air in the lines somewhere. If its as bad as a front master cylinder on a motorbike then the air can sometimes be next to imposible to get out.

[GTS]

Thanks again people. I'm getting a vac bleeder today and give that a try. I agree that there must still be air in the system somewhere......even after being bled 4 times.
The rears are adjusted up.

--- Updated ---

I made 2 new pipes last night and fitted them they suggested way. When I was bleeding the master cylinder I noticed that the front res (rear brakes) squirted out first then the rear res (front brakes) didn't squirt until the pedal was almost at the floor. Methinks this is a problem.....shouldn't the front brakes come on first?

[mckackie]

I would like to share some things worth consideration also......
If you have fitted a master cylinder off a different model, never mind the reservoirs and pipes being back to front, but also bear in mind that diameters may be different between models or break points in production also. Did you over haul your front calipers and replace the pistons? We went bonkers once with an XC ford until we discovered the new pistons were concaved, and the old ones were flat. subsequent lunch room raves over the years also had comparable things like that with holdens, just as suppliers like Repco were becoming involved with replacement brake parts. Another thing to t is the bleeding technique, where you have an assistant pump the pedal vigourously and then have them count 1! 2! and on three,snap open the bleeder before they stomp hard on the pedal. This can often dislodge air pockets in some systems. All other advice offered by other members has been good too, assuming you have adequate knowledge on brake systems fundamentals. as a matter of course, did you bleed the new master on the bench before installation? This too can cause hours of needless fun. A messy job, so do it well away from any vehicles. I don't mean to sound condesending, but sometimes the most simple things may be the cause. I hope this helps too.

--- Updated ---

BTW are you anywhere near Sydney? I can give you the name of an absolute guru as far as things with brakes, clutches and heads go......

[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.