d21 86 4xd D/cab brakes looking up

d21 86 4xd D/cab brakes locking up

hi guys i need your help ive got a bug in my brakes and its playing hard to get...
all started back when i got the truck - the front brakes were on just a little on a big drive they would get hot and pull on ..
was told to look at ...
1 brake flush...done
2 flush brake lines with air.... done
3 try new calipers... done fixed for few months...
now.... same thing going on...
things ive fixed this run...
new master cylinder... pulled caliper apart... flushed.. re greased pins.. all good...
10 mins ago ... front hub spin free... bleed the brakes ......... hubs dont spin front brakes on....
crack nipple on caliper ... hub spins free....
so come to net for help....

looking for my brake set up online.. looks like its the 2wd setup as i dont have a load sensor on the diff.... only odd thing on mine is a piece under the driver seat .

here is a drawing of the bit...


when i bleed the brakes i start at the back work to the front all 5 nipples
any ideas????? please help

No, you don't have the 4x2 setup - no 4x4 D21s in Australia received a LSV, they're all exactly as you describe.

Question - when you climb under the dash, and try to move the pin that attaches the brake pedal to the master cylinder push rod, does it slide freely with no pressure on the pedal?

hi mate..thanks for that..hard to find info on the aus d21..
i got a cd of ebay its got a different setup..
looked at the d22 info on here its the same no good...

would you know the name or function of the mystery part...

I don't think the d21's had a bias valve on the diff.Check your brake booster.The round black thing that the master cylinder bolts to.Did d21's have a booster?Also check the block that the brake lines go into from the master cylinder.

billy_bob said:

would you know the name or function of the mystery part...

Click to expand...

That's something I've been trying to work out for a while, but it's no good. The local manual even states that there is an LSV but I call bullshit: an LSV requires some mechanism to sense the ride height and this just isn't present. I'd say it's an external Proportioning Valve, as the drum brakes require different pressure to the disc brakes. As for the split point or ratio, I don't know, there are values in the book but they don't apply to an external PV.

scottybobcat said:

Check your brake booster.The round black thing that the master cylinder bolts to.Did d21's have a booster?

Click to expand...

Yes, but there's no obvious proportioning valve there

scottybobcat said:

Also check the block that the brake lines go into from the master cylinder.

Click to expand...

It's just a block, no valving.

Great drawing by the way, it made your question very clear

hi guys. today's update...
called brake guy.. told me
1..pump brakes till calipers lock on.. then break nipple... if ok pump up brake till locks undo next joint in brake line till you find block..

no good keep getting back to M/C

2..unbolt Master cylinder from booster see if brakes release..

yes brakes release..GOLD getting some where....

3.. got online to find how to adjust brake booster push rod..
no good ..the clearance is fine....???
link to some good info... http://www.autoshop101.com/forms/brake05.pdf

4.. start car to see if booster leaks.....

brake booster rod pushes out 3mm...

so after all this on and on booster is engaging brakes when car starts.............

i got an old booster there ill put in see if it fixs it..

.... brake guy was vague on what the part under driver seat is.. call it proportioning valve..his word if its not working ya brakes will be S#@T !.....