Re:Re:Jimny Front Brakes Seizing

Hello all – I have been a reader of this site for years, but have just registered as I am stumped by this. I had my last Jimny 10yrs, did 132,000miles and it never gave me any problems, but I replaced it a couple of years ago with a 2012 SZ3, and months ago the front brakes started binding soon after setting off on the first journey each day. I have freed off the callipers, cleaned and re-greased the pistons, polished and re-greased the sliders and replaced the pads.
After reading just about every post on here about brakes, I see that some others have experienced similar problems, but nobody has confirmed what the cure was. Following suggestions made in these posts, I have run it with the servo disconnected; with the fuses removed from the ABS pump and with a replacement (2nd hand) ABS pump all with no change. The problem appears to be a build up of hydraulic pressure, but does not seem to affect the rear, only the front, backed up by the unchanged rear shoes still being in good condition, but the new front pads already being worn down. When they seize, there is very little travel in the pedal, and it always affects both sides, suggesting it is not a flexi pipe issue. Relieving the pressure by cracking a nut on the ABS pump instantly releases both callipers, suggesting the callipers are working correctly. As I don’t get increased pedal travel and it only affects the front, it suggests the master cylinder is working OK. If there is a problem with the ABS pump, it would mean a problem with both the original and the replacement, and is still an issue with the fuses removed, so I am guessing it is not this, either. It still happens with the servo vacuum disconnected, suggesting the servo is not the cause.
The front brakes get very hot and seize so much that hills are a problem, the top speed is reduced to 40mph and the mpg is down to less than 2/3 what I used to get. When stationary, it is impossible to push it or roll it downhill, yet when left standing with the engine off for an hour or so, the brakes have released and the same journey can be done with the brakes working perfectly with no seizing or heat build up, no matter how much I pump the brakes. Also, it can sometimes release itself during the journey – you can feel the performance increase and the pedal travel return to normal. There is a connector/splitter (pressure differential balance valve?) between the master cylinder and the ABS pump that I am thinking of replacing as I cannot see what else can cause this, but I am really clutching at straws – any ideas (especially from those who had this problem in the past)?
Thanks for reading.

Welcome to the forum. I haven't had this myself on Dreadnaught, just the usual slider seize problem occasionally. So somehow you're getting excess pressure in just the front system? I'd expect a fault code if it were abs related. Have you examined the hard lines forensically from master to caliper for and sign of deformation or damage including the fittings?

Thanks, Lambert. It's as if there is a sticking valve, allowing pressure to build up in both front callipers but not releasing it. I've looked at the pipes and they're all in good nick. The only part of the system with any corrosion is the around the outside of the aforementioned splitter (bolted to the inside of the n/s wing just below the ABS pump). I've ordered another, but if this is just a connection block with no valves inside then I can't see it being that.

Has one of the flexible pipes collapsed internally, acting like a one way valve

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I had this problem on a 2009 Swift. I suspected the master cylinder so got a used one from ebay and a new seal pack ( total cost about £60). Never any trouble after that.
Chris

What would be the position of your breaking pedal in each case?

It sounds like the break is applying pressure without pressing the pedal.