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LJ70 Brakes are BAD! Is it normal?

Si LJ70

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Jan 5, 2021
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great_britain
Hi. Are the brakes on the LJ70 known to be a bit rubbish? I have checked the discs and pads and the piston movement and all good. Could it be the servo? Cheers
 
No, not normal. Quite the opposite, in fact.

Sometimes the proportioning valve at the rear rusts solid so you end up with hardly any rear brakes and all the action on the fronts. You'll know if that has happened because if you need to stop in a hurry the front locks up you end up with brown trousers:openmouth: That doesn't sound like your problem.

If the discs and pads are good then it sounds like you need to get the calipers off and pull out the pistons to make absolutely sure there's no rust in there. If the servo wasn't working you would need a right leg like Hercules to stop, there wouldn't be any doubt about is it or isn't it working. When the servo goes most people think the brakes have failed completely, you have to shove so hard to slow down you think the pedal is going to fold in half.
 
I checked the calipers and on one side one of the four a pistons is jammed. I will try a rebuild kit if I can get it out. Cheers
 
Repair kits with piston seals, dirt covers and clips are readily available online, but there are kits for piston diameters of 43mm, 48mm and mixed 34/43mm for the LJ70. If yours is not a daily drive it would pay to measure the diameter to be sure before ordering. I did mine last year and got the wrong size to start with.
 
I put new calipers on the 120 few weeks ago, like you only one piston actually seizing and whilst the brakes were superb before the bite now with new calipers is amazing, hope the rebuild goes well.

I recall playing around with the rear proportioning valve on my KZJ70, when i first got it too prone to locking the fronts, adjusted slightly too far which led to premature locking of the rears, not nice, but eventually found the sweet spot.
 
I felt my 90's brakes were pretty good until i decided an overhaul was due , new disks and pads all 4 corners and calipers rebuilt by http://biggred.co.uk/ was a night and day shockingly good difference .
 
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I just took my LJ out for the first time in weeks as been replacing the rusty rear wheel arch. The brakes are bad. Even when I press hard. Any way I will measure the pistons and get a repair kit.
 
I have done a basic brake servo/ vacuum test. Where you pump the brakes engine off. Then start the engine and the pedal sinks towards the floor. This seems ok. But it's not holding vacuum long. I am trying to work out where the vacuum pipe to the servo goes to. The alternator has a vacuum pump. Is this user for the brakes?
 
I have seized piston in front left caliper. Another is cracked from the heat of uneven braking. The truck was manufactured in 1989 do had the thinner solid discs. Any ideas on where to purchase?
 
Has anyone tried fitting the later 1990< vented 20mm discs, calipers and pads onto an 1989 LJ70? These parts seem much easier to get hold of.
 
I have refitted the brake with the new pistons. The brakes are just as bad. Dangerously in effective. Any ideas on what it might be? I think next I still try to bleed the whole brake system
 
You definately need to bleed the whole system and make sure all the flexible hoses are good. they sometimes collapse on the inside where you cannot see and thus stop fluid flowing and returning. If they are old change them.

Graeme
 
Hi Graeme,

Thanks for the advice on the brakes. Will try a full brake bleed. Definitely feels like something is not right so will check the rubber pipes too. Never knew they could collapse inside.
 
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