Brake woes

[kriswaatch]

Hey everyone;
I could use a hand here.

I bought an 87' BJ70 a few weeks ago. Since then, I have started noticing the trucks braking abilities, or lack thereof.

(Disclaimer. My nomenclature for parts and mechanical terms may be lacking, so please bare with me.)

I brought it to the fella who sold it to me, as he's much more mechanically inclined that what I am. Turns out a few months ago, he changed the pads on the front brakes, and they were working perfectly. Since then, the truck hasn't been driven.

He thought that the rear cylinders needed changing. So, we bought some Aisin one's. After changing them, and trying to bleed the brakes, we noticed no juice was coming out. None. Zero. I was sitting in the cabin doing the brake pushing, while he was opening and closing the valves. Obviously, when I press the brake pedal, the rear wheels turn freely.
As soon as we moved to the front brakes for bleeding, it was working perfectly, the brake pedal went to the floor and juice came out. But, each time we went to the back brakes, nada.
So, we thought about loosening the master brake cylinder and doing the same thing, pressing the brake pedal and see what happens. He said when he loosened the front brake valve, juice came out and it was fluid, while doing the rear brake valve on the master cylinder, it wasn't fluid.

Do you fellas think it's time to change the master cylinder? Or is it possible it's the booster? Or, perhaps something else. I have yet to crawl under the truck to see if one of the lines was crimped, but, I will do that this afternoon.

Thanks

 

[kriswaatch]

Oh
I forgot to mention something.

I've been checking into purchasing a master cylinder from several places. But, I'm not really sure what to look for. There's always options to make things more confusing.
For example, at toyodiy, they have 2 options : (cylinder kit, brake master), or (cylinder-sub-assy, brake master).
Locally, at a napa dealer, I also have 2 choices, a generic master cylinder for a 112$ CAD and a remanufactured master cylinder for a 144$ CAD.
May I ask, what are your opinions?

 

[clintnz]

Could be a master cylinder issue. If you strip it down you'll be able to check it out & see if a seal kit is all it needs. For a generic replacement, if the bolt pattern, cylinder internal diameter & fitting types are the same then you should be able to make it work.

Also check that fluid is getting through the LSPV ok: Load sensing proportioning valve - which your Cruiser probably has. A valve on the chassis in the rear brake lines with a lever connected to the rear axle housing. Designed to bias the braking to the back more if the suspension is compressed.

Brakes are kinda important so if it's your 1st time working on them take plenty of pics as you disassemble so you can put it back together the right way, & read up on the the principles of exactly how your braking system actually works.

Cheers
Clint

 

[kriswaatch]

Thanks Clint.
Someone suggested to me yesterday to remove the rear brake line from the master cylinder, and plug that line into a bottle with brake fluid. Then remove one line from a rear cylinder and use suction to see if I can get fluid out of that line. Sounds like a sound idea. I'll have to do that tomorrow, as I don't have any tubing (it's a holiday here today).
Thanks for your suggestion Clint. If the vacuum test doesn't work out, I'll give your idea a shot.
Cheers

 

[jblueridge]

When I put in a new master cylinder (meant for early 80 series models) I "bench bled" it first to get air out of the MC.
I searched in this forum to gather info on what MC's bolt right into a BJ74.

 

[kriswaatch]

Hey *jblueridge
thanks for the info.
Not to be lazy or anything, but, would you by any chance have that particular link you searched for?
I have searched, and I really haven't found anything.
Thanks

 

[clintnz]

If you can't find an exact part listing for your truck, chances are something out of another Toyota will cross over.

The first thing you need to get right is the Master Cylinder internal diameter - usually stamped on the casting in fractions of an inch. This can be different depending on discs vs drums etc & there are a few variations across Landcruiser models.

The next thing is the booster mount bolt pattern, AFAIK Landcruisers have just 2 variations: 2 bolt or 4 bolt pattern.

If it's Toyota the fittings should be M10x1 thread.

Cheers
Clint

 

[jblueridge]

I remember reading good stuff posted by Hulsty and AlbertoSD. If you do go with the 80 series MC you need to make an extension for the rod that connects to the pedal.
Sounds like you should check your lines and hoses first.

Read


Read Post #353 and more

 

[Squash]

Start with the LSPV.
Try bleeding first, disconnect the arm and manually open/close the valve....fluid needs to get past the LSPV