Series 3 brake issues

davidpurton · Nov 10, 2022

Hi, would be interested in some opinions based on other's experiences!

Always had great brakes on my S3, even with the 10" drums. I had replaced the servo, master cylinder, pipes, shoes, drums, cylinders and the twin circuit valve a few years back.

But I have a problem. At first the brakes work as they should with a short travel on the pedal before it becomes solid. The brakes lock on instantly and evenly .

The "servo" test light on the dash illuminates when tested with the ignition on...

But a second application of the brakes and the pedal, travelling the same distance as before, becomes hard as expected but the brakes are virtually ineffective, certainly not bringing the vehicle to a stop despite putting my full weight on the pedal.

Once the pedal is released, a further application and they work fine again until the "second" time they are used again and the "hard pedal/no brake" experience is repeated.

I am thinking servo/non return valve problems or break failure twin circuit valve but anybody on here had the same problems?

Thanks!

kermit_rr · Nov 10, 2022

I'd miss read your original post in the intro section as your pedal going hard and the brakes sticking on. Oops
Not aware of a servo test light, do you mean the dual circuit light? That comes on if there's an imbalance between the 2 circuits, indicating a leak.
There's a piston in the valve which i guess could be jamming, does the warning light come on/go off with the brake pedal?

Turboman · Nov 10, 2022

davidpurton said:
Hi, would be interested in some opinions based on other's experiences!

Always had great brakes on my S3, even with the 10" drums. I had replaced the servo, master cylinder, pipes, shoes, drums, cylinders and the twin circuit valve a few years back.

But I have a problem. At first the brakes work as they should with a short travel on the pedal before it becomes solid. The brakes lock on instantly and evenly .

The "servo" test light on the dash illuminates when tested with the ignition on...

But a second application of the brakes and the pedal, travelling the same distance as before, becomes hard as expected but the brakes are virtually ineffective, certainly not bringing the vehicle to a stop despite putting my full weight on the pedal.

Once the pedal is released, a further application and they work fine again until the "second" time they are used again and the "hard pedal/no brake" experience is repeated.

I am thinking servo/non return valve problems or break failure twin circuit valve but anybody on here had the same problems?

Thanks!

I don't remember the servo test light either, although that could be because it is many years since I had a Series 3.

But I would suggest you remove your postcode from your location, or you might not have a Land Rover at all shortly.

davidpurton · Nov 10, 2022

Hi,

There's a test switch/light on a panel in the centre of the dash which checks the servo.

The instrument warning lights all extinguish on engine start up. Pretty sure the two way valve brake switch isn't actually connected to anything!

kermit_rr · Nov 10, 2022

The test switch is for the dual circuit failure valve

kermit_rr · Nov 10, 2022

The only electrics near the servo is for the brake lights

Turboman · Nov 10, 2022

davidpurton said:
Hi,

There's a test switch/light on a panel in the centre of the dash which checks the servo.

The instrument warning lights all extinguish on engine start up. Pretty sure the two way valve brake switch isn't actually connected to anything!

That sounds like earthing issues.

There probably isn't anything wrong with your brakes at all.

tottot · Nov 10, 2022

I think one of your brake circuits is losing some pressure as per Kermit's post above. Could be a master cylinder problem. Try slamming on, on some loose gravel and see which wheels are not locking, could give clue as to which circuit is noy working.

Wildefalcon · Nov 11, 2022

What brand hoses did you use on the rebuild?

steve2286w · Nov 12, 2022

I have the warning light on my 84 series 3 although. not seen it lit for years
I have dismantled and cleaned the pressure differential valve a while ago not too difficult, if there is a leak then the piston moves and shuts off one side , agree with tottot test brakes on gravel see which wheels lock, are you losing any fluid.
Is brake shoe springs on properly and the master cylinder pushrod got the correct free play
The NRV easy to test just suck and blow but don’t swallow
Does yours have the vacuum bottle as may diesel , the vacuum system in mine is airtight and a day later the bottle still has vacuum stored , perhaps you have a loss of vacuum on the 2nd brake press?

Series 3 brake issues

davidpurton

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kermit_rr

Very

Turboman

Mab An Gov

davidpurton

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kermit_rr

Very

kermit_rr

Very

Turboman

Mab An Gov

tottot

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Wildefalcon

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steve2286w

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