Thread: Need to pump up brakes

If I understand correctly, you are saying you still need to pump the pedal with all three hoses clamped.

If this is the case -

1. Pedal pumps to rock solid
Either the free play on the master cylinder pushrod is incorrect or -
Faulty cylinder or the wrong cylinder

2. Pedal is spongy not solid
There is air in the system. Bleed by loosening unions until you have it solid.

I expect the issue to be 1. above. Fitting a swb cylinder to a vehicle with lwb wheel assemblies will have this result, as you need to move six cylinders not four - and they are bigger.

John

Hi John,
1. describes the situation I have. It will pump up to a very solid pedal, but needs to be pumped to get there.

Would the way to test the master cylinder be to check the free play and if that is correct then it is time to remove it and have a look at it's internals?

How do you set the free play? Is there a nut on a rod that gets adjusted until the pedal has a certain amount of travel?

Thanks,
Rex

G'day Rex,

John has given you great advice to follow.

However, if it were my vehicle and road driven I would replace the master cylinder first up. Is your life only worth $50?. The wheel cylinders have leaking rubbers and dirt. Most probably the dirt has got into the system by way of the master cylinder so will be scored as well.

Before you buy a new master John has indicated you need to get the correct one, 4 wheel cylinder on 6 wheel cylinder type. Also CB and CV types.
Once the master has been replaced start again and all should be good to go.

A service manual and parts manual is the way to go here. You will no doubt be using both before you finish your project.

Hope this info helps.

Chris

Originally Posted by rexhunt

Hi John,
1. describes the situation I have. It will pump up to a very solid pedal, but needs to be pumped to get there.

Would the way to test the master cylinder be to check the free play and if that is correct then it is time to remove it and have a look at it's internals?

How do you set the free play? Is there a nut on a rod that gets adjusted until the pedal has a certain amount of travel?

Thanks,
Rex

The manual clearly shows how to get the correct free play, although it is not all that critical. Roughly, if you remove the cover plate above the pedal where the top of the pedal arm connects to the pushrod, you will see the trunnion on the pedal is between two locknuts on the pushrod. These should be adjusted so that the pushrod moves 1.5mm before it pushes on the piston. Prior to that adjustment, check that the pedal is 158mm from the floor when against the stop.

Note that if the pedal return spring is missing, this may also cause this problem.

John

@ Chris
You do make a very good point and I certainly will replace the master if I feel it has been compromised. However in the past I have been very guilty of throwing parts at a problem that didn't really need them and if a part is still serviceable then I would rather use it then having to wait until I can buy it.

@ John
Thanks for that. I will have a look and see if that helps at all.

If I do need to replace the master, is it worth looking at replacing it with an improved one? Perhaps a dual circuit one?

Thanks,
Rex

go get s selection of ball bearings.

remove the lines out of the MC and put a ball bearing in, put the line back and bleed it up.

if you get a stiff pedal straight up, its not the MC, if the pedal creeps down the MC is recirculating and a DIY over haul is on the cards, if the bore is scored replace it or have it sleeved.

then proceed to move the ball bearing down the line, bleeding as you go.

remember the II MC doesnt flow a huge amount of fluid and if you haven't done it just right a combination of small things that seem ok will add up to a lot of pedal movement.

usually if you can pump it up and hold it without creeping it turns out to be the wheel adjustment, if it pumps up and is spongy its air in the front cross pipe and left rear lines.

Originally Posted by rexhunt

.......

@ John
Thanks for that. I will have a look and see if that helps at all.

If I do need to replace the master, is it worth looking at replacing it with an improved one? Perhaps a dual circuit one?

Thanks,
Rex

There is something to be said for changing to dual circuit brakes - but it is not as simple as replacing the master cylinder. The whole brake pedal assembly is different, you need to either do significant panel modifications to the RH mudguard or replace it with a Series 3 one, and you need to fit a proportioning valve and modify the pipework plus warning light and wiring (without this there is no way of knowing one circuit has failed). As far as I know all dual circuit M/Cs are power assisted, so you have the vacuum piping as well.

In my view, for most people, the cost and complication is not worth it. I have driven vehicles with single circuit brakes for sixty years and have never encountered sudden brake failure due to loss of a hydraulic circuit (either mine or anyone else) - and remember that most cars on the road had single circuit brakes probably until about the end of the eighties.

Other brake improvements I think are worthwhile include upgrading 88 to 109 brakes and probably on a 109 from 4cylinder to six cylinder wider front brakes. I like the disc conversions, but would have trouble justifying the cost unless the vehicle is doing a lot of miles (or you have unlimited funds and time!).

As suggested, it is worth getting the master cylinder SS sleeved.

John