Early 90 brakes

What does it brake like with the servo vacuum pipe disconnected?

I'm going block off pipe and drive it see if it makes any difference.
I've ordered new pipe and one way valve this morning just incase its collapsing inside.
Thanks for all your suggestions I'll try a few things over next few days.
I want to sell it .
Well I say want but more like need.

I fitted my 90 with the 110 callipers as per landowners post, an easy bolt on upgrade. Most early 90's came with little 205's as standard.

If I've no luck with servo I'm going fit some 110 calipers mine are original ones still as far as I can tell so I suppose 30 odd years old

Some early ones were imperial, keep that in mind when replacing them, but , your brakes are faulty, upgrading them may not fix the problem.

nobber said:

Some early ones were imperial, keep that in mind when replacing them, but , your brakes are faulty, upgrading them may not fix the problem.

Click to expand...

Yeah I'm going try fix the suspected servo problem first.
I've ordered new pipe and non return valve just to rule that out.

I've replaced servo pipes.
I'm getting vacuum at servo that's for sure.
Brakes are still not good.
I can hear servo "working" air moving around when I push pedal.
I pumped brake pedal with engine off to dispel air.
Then started it up and pedal goes down a bit ie it's easier to push.
So I think servo is working.

Am I right in thinking rear brakes are activated first limited by g valve then front or are both done at same time.
Is that why length of push rod is so critical?

Just remember brake performance is mostly the work of the front wheels where as it is the job of the rear to stabilize the vehicle. Length of master push rod is critical for the release of fluid to and from the reservoir. The g valve will only work to limit the pressure at the rear once the front brakes have started to slow the vehicle and produced some gee.

I'm sure I checked rod length when i rebuilt landy.
I've never managed to lock brakes.
I think front calipers are my next thing to check.

double check the rod length on the MC
This wont be the G valve

are you sure the servo doesnt have a crack and is holding pressure and also are you drums at the rear?

Did you pipe up the master correctly? You didn't get front and back mixed up did you?

Good one nobber, would not be the first.

This is how my 85 Ninety is piped up.

I'm sure pipe size is different front to back on master cylinder and I reused the pipe to g valve.
Yeah drums on back, I've check adjustment.
Over weekend I'll check push rod length.
I replaced every thing in braking system apart from g valve. Avoiding britpart for shoes pads and cylinders.
Bearmach drums if I remember I think mintex pads.
The servo looks like new still I know that means very little but it is behaving like it's working fine.
It's got its mot soon I might book it early and see what happens on brake tester.

Okay could be your drums are over adjusted. Did you replace them all? It’s possible to put the Limoges and springs in the drums on wrong and rather than hold them away they pull them into the drum. Double check the drums as poorly adjust can feel ‘okay’ but give a weird pedal.

Is the mc he right one for your callipers? They are different. Deffo set the rod as per the factory guide. It’s fairy important lol, I still think it sounds like the rod is over adjusted and bringing the brakes on ‘too soon’.

You can stick a ball of blue tack on the end of the rod then actuate the pedal and then look at the blue tack to get approx clearance - I can’t remember what it should be but it’s in the book. I can look later

Have you plumbed the g valve the right way? It’s not a part that fails.

The brake system on a defender is simple, it won’t be anything ridiculous, Just needs methodical approach to go through it all.

Ok I'm fairly certain I've got springs right as this has been going on for around 18 months.
I replaced shoes and drums then as I had a "lumpy pedal" when braking I remember double checking I had it all right.
I'm doubting now if I've got right master cylinder i replaced it like for like but brakes were terrible before.
I'm sure g valve is correct as i left it on bracket during refurb.
Over weekend I'll have chance to check rod length.

Ok I think I've got wrong master cylinder after looking through mountains of invoices from my rebuild.
Looks like I've got a 110 master cylinder part number BR3235

Okay so
2 options,

You can either change the master cylinder for the 90 one (the 110 one moves more fluid as 110calipers have bigger pistons)

Or you can change the 90 callipers for the 110 callipers that have larger pistons.

It’s horses for courses tbh, the 90 callipers are perfectly up to the job so MC swap is probably easier.

I *may* have a 90 MC on the garage spare I will look tonight

Yeah looks like I need NRC9529.
If you could that would be great thank you.