Brakes hard as a rock

This site may earn a commission from merchant affiliate
links, including eBay, Amazon, Skimlinks, and others.

Sep 29, 2007
I'm still working out the bugs on my newly acquired 91 FJ70. I got what looks like 5 years of grime washed off today :) and took pics too, tomorrow will get a couple up. Also, had it aligned and the exhaust fixed.The brakes down below are new, but obviously something else is amiss cuz they are super hard and no stopping power. Also, my e brake is very weak, but I imagine that is just adjustment and stiff cables. Anyway, nfortunately I'm thinking my booster is shot. There is not a vacuum pump around to do a proper test but really that's about all it could be right? I'm down here in no man's land and new toy parts are stupid expensive if you can even find them, can these be rebuilt? Otherwise, would like to know if anyone has a good source for used and or new parts for a 70 series? I'm also needing a vacuum advance for my dist, mirrors, door a door lock, I put a wanted add in the classifieds but nothing yet, any help appreciated, thanks.
Check the vac pump by removing the pipe of the booster, you should a little whoosh of air when you take it off(with car running of course).
Poor braking could be the adjustment of the LSPV, if has minor adjustment by undoing the bracket on the dfff and moving a little.
Major adjustment is done by sliding the body of the LSPV.
As the brakes are so poor, I would try sliding the LSPV body on the chassis the opossite way its at now, rememer to mark where it was orginally, providing you can see it between the dirt and grime ;)

Well I got a good 50% of the d and g removed, but tell me please what does LSVP stand for? thank you.
Tapage I'm in Peru, I found rebuilt unit's in the US for about 200, even I can afford that lol
Well I got a good 50% of the d and g removed, but tell me please what does LSVP stand for? thank you.

Load sensing ( or sensitive ) proportioning valve ..
The booster is original (hell I think the air filter was original), and though it's only got 120K miles on it, it's 20 years old, rather suspect it's bad so have one on the way. I'm going to feel like a fool if I get the new one in and find that it really was just the LSPV. I just can't imagine (though that doesn't mean much) how the proportioning valve could get so far out of adjustment as to basically make the brakes inop? I mean how could that happen unless some idiot got under there and moved it for the heck of it? Are there internal changes that could take place to the valve over time that would require a movement of position to compensate? Like I say I'm going to feel real silly if it does turn out to be the valve I just was really skeptical that it was causing the problem... think I was too hasty?
Depends I suppose on how you treat your vehicle.
We replaced everything on my friends land cruiser to try and resovle poor braking, Booster, cylinders and pads, all rubber pipes.
Took two years to finally get there :), even replaced the LSPV with the same results.
Only when we read the manual properly did we realise the Body of the LSPV slides up and down as well for major adjustment. Once we slid it the other way, he almost went through the windscreen when applying his brakes, so we roughly set it right and his brakes works like a charm now :) Do the non cost options first or you will end up replacing everything and kicking yourself when you realise what it was...
Check the rear drums as well?
booster test, is pump the brakes with engine running, with a hard pedal and foot pressed down, turn the engine off, your foot should go down a bit. This is the vacuum being used up in the booster and should check if its working.
Also check your drum brakes...
"The brakes down below are new"

Unless the pistons were cleaned before the new pads were installed your cylinders may be seized.
Pull the pads replace with some wood and try the brakes...if the caliper cylinders move freely then the problem is upstream. be sure to check all four.

If you bled the brakes yourself you will know if the fluid is new/clean if not crack the bleeders one at a time and make sure fresh brake fluid is showing. If this works again the problem is upstream

If a caliper is seized then it will be nearly impossible to crack unless you take it off and bench clean and your brakes will be nearly immpossible to apply.
My 2 cents, brake booster is shot, based on past experiences. MIke
I had a similair problem last year...I have documented all the process I did to find the source of the problem in the post called (bj70 brake problem: on and off stiff pedal). I turns out my master cylinder was leaking in my brake booster.

The solution I have opted for was to replace the Brake booster and master cylinder from a 92 4runner. Early ninties brake booster from toyota mini pinkup and t100 are supposed to fit on your truck

Good luck
DieselDen, very useful information thankyou. Though I have an original booster on the way, I will certainly get myself an MC too to prevent a repeat due to a leaky MC. So... will the MC from a T100 fit on an original FJ70 booster? Thank''s again.
Not sure...look at the bolt pattern be very carefull of rod lenght (the one that goes from your MC to your BB). If it long then your original, you might damage you BB.

If you want a really cheap solution, bring your BB with you to a scrap yard where your removed the car pieces yourself (you could get the MC and BB for about 50$). Once there, spot some late eithies or early ninties tacoma, t100 or 4runner. Make sure of 2 things: 1. The BB bolt pattern is identical to your original BB and 2. There rod that goes from your BB to your brake pedal had the same lenght. If these two conditions are met, you can remove the BB from the truck you found (keep the MC attach to it) then swap these two parts to your truck. By doing so, even if your MC rod is longer then your original MC Rod, it will not matter since you kept it attach to the BB it was designed for.

I can't remember if i had mentionned in my post but the 92 4runner BB rod (the one that goes to the brake pedal) was a little bit shorter then the original so I had to weld a little piece of metal to make it longer and i also turn the BB upside down cause even if the BB pattern was similar the BB wasn't center like the original.

Aside from these 2 small thing every thing fit alright

By the way, My cousin, who have a BJ74 swapt his BB and MC for and early tacoma and didn't have these 2 small mismatches

Good luck : )
Hey all, just reporting that rock hard pedal was indeed BB, have great brakes now! It's never anything like adjusting the LSPV in my case :rolleyes:

Users who are viewing this thread

Top Bottom