This LRO reader emailed LRO.firstname.lastname@example.org to ask our experts for help with a brake bleeding problem on his Land Rover Defender 130.
I can’t get all the air out of my Defender 130 V8’s brakes. Before starting the engine, the pedal is firm. Once started it goes down about halfway and needs pumping for full braking power.
I’ve tried new front calipers and master cylinder, a rebuilt Zeus rear disc conversion, stainless steel brake pipes and a new balancing valve on the bulkhead. With the actual bleeding I’ve tried: pressure bleed from the spare tyre; syphon feed from the bleed nipples; and pushing the brake pads back in. I’ve also tried the standard bleeding procedure, and jacking up the front and jamming the pedal down overnight.
The local garage has tried pressure bleeding from the nipples back, bleeding the master cylinder and bleeding from the balancing valve. So – quite a few things tried but no luck! Any thoughts?
Philip Pearce-Smith, Southampton
There are a number of things you could do on a braking system with this sort of problem – and you’ve already covered most of them.
So now you have two things to look at. First, check that the piping is correct on the bias valve, I don’t think this would cause the pedal travel problem but it’s worth looking at. You need to check on a similar-age vehicle to get some idea.
Not that? Well, by the process of elimination (as you’ve changed absolutely everything else on the system) it must be a fault in the servo.
There’s an adjusting rod in the servo that mates to the master cylinder piston when it’s bolted to the servo – but this is factory-set and a great deal of care must be taken when adjusting it. It can feel fine in the workshop and then when everything gets warm in the braking system you can find yourself in the middle of the road with seized on brakes.
I think the best thing to do is try a different servo.
This workshop advice appeared in the December 2015 issue of LRO. Back issues are available to download on digital devices here.