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Discussion Starter #1
Brake load sensing valve/Brake pressure regulator has seized, so I have 'little or no effort' on the rear nearside and offside brakes.

I've drowned it in WD40 and belted it with various blunt instruments but can't seem to get it shifting, any 'tips of the trade' or have I got to shell out £70 for a new one?

J.
 

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I just failed the MOT on this very thing causing little effort on the rear brakes...(after advisories every year for the last 5)...bit the bullet and had the job done...so worth it.

63 odd quid plus vat from gsf. 90 quid labour at a "good but not very cheap" garage.

amazing difference to how the van stops now though...i didn't realise that the brakes could be as good as they are now.

wouldn't want to play around with the valve too much though...it's a safety critical part and could be the cause of the rear overtaking the front if it's done badly. :) :ILU:
 

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Discussion Starter #4
I bought a replacement from GSF got it home and compared it with the one that was 'seized' and it has exactly the same travel on the 'pivot' so I've greased it up and bled the rear brakes (A big air lock came out) so I'm hoping it's freed itself up with all the bashing I gave it.

Re-test tomorrow so we'll see! if it still fails I'll be off to get it done at a garage!

J.
 

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where is the valve located you got any pictures my rear brakes have seemed to stop working i assume i have the same problem....
 

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Discussion Starter #6
I'll try and get some in the light tomorrow...

Just reversed at speed (cul-de-sac, no traffic or pedestrians *pc correct disclaimer*) and slammed the anchors on and the back dipped sharply so I'm thinking the back brakes are definately working.. we'll see tomorrow.

J.
 

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Discussion Starter #7
it's right smack in the middle of the rear 'arms' with a T-peice going out to springs that are attached to the bottom of the arms (if that makes sense?)
 

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I know exactly what your on about never looked at it closely I always thought it was a handbreak cable.... I'll have a look at mine when the weather drys up a little
 

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Discussion Starter #10
It passed! Apparently it only has to move very slightly, I now have full brakes on the rear.
 

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The brake load adjusting valve itself is usually not the problem .It is the springs and levers that operate it that seize up .I spray the whole assembly weekly with WD40 which prevents it all from seizing .You can do this squirting from the side .Check tyres ,levels,and squirt each week.The valve does greatly reduce the brake effort when unloaded ,which is marginal for MOT reading .BUT there is nothing to stop you from loading the van for the test.I put half a tonne of sandbags aboard for the test and if the mechanism has been kept free with WD,you will get a good reading .Also ,as many will know, the rear caliper tend to freeze as they are in such a hostile environment .I service them every six months as follows .Remove caliper after undoing the bolts on the end of the slider pins ,wind back the piston with a winding back tool (ESSENTIAL),remove clean and grease slider pins with silicone grease,clean all contact surfaces of pads and caliper and lightly grease with copper grease ,taking care not to contaminate any friction surface with grease,reassemble .This is in no service schedule but I find, after six months, they are always getting sticky at the rear.The single piston calipers HAVE to float freely to work properly .Do this regularly and there will be no trouble with rear brakes .The load valve is a primitive ABS in fact,and made unnecessary by it .
 

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I squirt Fluid Film on mine every other year. Leaves a thick film on it.
 

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How does the valve mechanism work ?Well its a bit like the spring loaded safety valve on a steam engine .When the van is unloaded the spring in the valve is at its least tension ,so that when the brakes are applied most of the pressure is spilled back into system and little pressure reaches the rear brakes .Consequently there is little brake effort on the rear and they do not lock up and skid (also they tend to freeze since there is hardly any piston movement in the caliper ,hence the need to keep on at them to keep them working at all).When the van is loaded(rare for most t4s)the lowering of the body causes a system of springs and levers to press on the spring in valve ,loading it up and making it only release pressure at a higher psi .So the rear brakes then apply more effort to slow the vehicles increased weight .All quite primitive and because of hostile environment prone to seizing up.
 
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