Bad Booster signs? (1 Viewer)

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Klunky Chris

Klunky Chris

Joined
Nov 5, 2003
Threads
77
Messages
1,063
Location
Shippensburg PA
Website
www.iluvrocks.com
How do you know if your booster is bad or going bad?

I've been browsing a multitude of threads about brakes and am wondering if my 74 booster is an issue.

History:
swapped the knuckles out off a 60 onto my 74 front axle. new 60 loaded calipers and new 60 rotors. New brake lines. pulled front resid-valve. 4 new wheel cylinders on rear with new brake goodies and turned drums.

Brakes were ok, but neede a lot of force to stop. Rears locked up real early.
Just installed proportioning valve and bled rear brakes. Brakes are horrible. (regardless of valve setting) mushy and take a pump or two to get good pedal. Can't say I didn't mess up the bleeding, but I've done it a bunch before.

I am going to try to re-bleed the rears, as it's the most obvious culprit, but this whole thing has me thinking about the booster. From what I've been gleaning in other threads, the booster can go bad slowly so that it's not noticed?

What is the best way to diagnose a bad or worn booster???

When I shut off my engine I hear a loud hissing sound as something lets air out (booster, or manifold?)

If I do need a new booster, what is the BEST replacement for more stopping power?

MC Q:
Been thinking about swapping out my MC. Just noticed mine has a '1' on it. I assume this means 1" bore? if so, what is the advantage of going with an FJ80 1" MC?

I assume everything is stock 74 but who knows..... here is a pic just in case:
P1010852.JPG
 
Bad booster

Hi,

I'm no expert, but I just replaced my booster this week. I too had a hissing noise in the cab when I shut down. Also, you mentioned that it takes a lot of force on the brake pedal. A good booster does not require much force at all. I would say your booster is bad. You can have it rebuilt, or get a different one. Search brake boosters and you can find that lots of different boosters can be used. I used one out of a 89 Toyota p/u 4x4. $45 for booster and m/c at the local junk yard. Don't forget the check valve. For the most part, it bolted right up. I did have to cut the push rod down about 1/2" to make it work. But now, what a difference! A new (at least to my 71 fj40) booster and m/c made a huge difference.

As far as your mushy pedal, that has nothing to do with the booster. Keep bleeding. Make sure that you don't have a leak anywhere.

Good luck!
 
OK, found in another thread that I *should* be able to hook a vaccum pump up to the booster and see if it holds vaccum?

got a hand pump that goes to 30 in Hg on the dial. I'm heading down to the hardware store to fab up an adaptor so i can use it.

If it holds vaccum it's still good?

I'm trying to decide between a 1 ton mini booster and an FJ60 booster. Does ANYONE know which boosters have the MOST boost?!?
 
Another easy way to test your booster is, with the engine off, press down on the pedal. Start the engine. The pedle should them move down more. Then keeping the pedal down, turn off the engine. The peddle should stay down with no additional force from your foot.. If it does not move down when you start the motor, or if it does not stay down when you turn it off, you need to replace the booster. I have not tried a rebuild myself, but I hear it is not worth it.

Shawn
 
no dice:mad:

maybe my vaccum pump is too small, but I can't get the dial to move at all.
I know I've got a good seal cause I can put my thumb over the check valve and pump the needle up to 25 in Hg.

I have no idea if this means I have a bad booster or not :confused:
 
interesting,
OK, pedal to the floor. start engine. pedal moves down slowly, after a few revs (500RM idle) it moves down a little more.
turn engine off. pedal moves back up!

I assume this is a bad sign..... :confused:
 
try vacuum bleeding your brakes. take it to a shop and they can suck every bit of air out of your brake lines that you may have missed with convential bleeding. If a new brake booster is needed a mini truck one is a direct bolt in application and easier to find. You can also adjust the booster. There is a shaft in between the master cyl. and the brake booster, you have to unbolt the four bolts and you can adjust the brake booster which may have something to do with it but i don't know. I ended up replacing my hissing brake booster with one from a mini truck...

i still think you shouldn't be needing that prop. valve on the back i think there is a problem with the front brakes because you should have more stopping force with those 60's brakes up front.

the master cylinder your using is it for a 4 wheel drum truck? or is it for a 40 with discs up front?
 
OK, update:
Bench bled the rear of the MC.
Re-bled the rear brakes.
Rear brakes should be totally separate from the front’s right? So since I have not touched the front system at ALL it should be OK. (unless the MC is leaking between the F & R maybe?)

Anyway, my pedal is back to where it was before. Much better breaking. Also I adjusted the Summit proportioning valve to 7 turns. It has approx 11 turns to full lock. @ a total possible of 57%. This should make it about 37% less pressure for the rear stock drums. This has made a big difference, as I can now get on the brakes harder w/o the rear locking up. Stopping is dead straight :D

However..... I still feel I'm not quite there. As stated above, I think I have booster problems as it still takes a lot of pedal pressure. I also get a little more pressure after one pump of the brakes. Anymore, I'm not sure what this means.

I'm leaning toward a used Tundra booster. I don't know, but it seems like it might have more power than a 60, or 1 ton mini.
Amazingly, this whole 'best booster' thing is not decided in this forum!?! :confused:

Plenty of "this will work" but no definitive "this has more power" anywhere!

Maybe we need a forum project where we tear apart bad boosters to see how much surface area is in each. This would give us a pretty good idea of stopping power of each booster...
 
bandy rooster said:
i still think you shouldn't be needing that prop. valve on the back i think there is a problem with the front brakes because you should have more stopping force with those 60's brakes up front.

the master cylinder your using is it for a 4 wheel drum truck? or is it for a 40 with discs up front?
Click to expand...

MC came with the truck. truck had 4 drums so I assume it's stock. it does have a '1' on the side which in other threads I've confirmed means 1" bore which is bigger (more stopping power) than the later 40's.

Many I trust told me that my rears locking up is normal as the discs take a lot more power to clamp. Therefore the rears lock up. I have a soft top also which means less weight in the rear.
As you can see in my above post, the proportioning valve did it's job in this regard. If I had rear discs I would probably be OK or at least need a lot less proportioning. (someday I might go the disc route)

Thanks for the help!
 
Best Booster?

This could probably be debated, but the mini truck booster that I put in does a great job. It takes very little pressure on the pedal to lock up the brakes. I'm not saying it is overly sensitive, it just doesn't take a lot of pressure. I would imagine that any booster in good working order would accomplish the same thing.

Also, "best booster" could mean different things to different people. Do you want one that bolts right up? Does it have to be a stock Land Cruiser booster? Cheapest?

For me, a bolt on, working booster, that was relatively cheap was the best booster for me. JMO.

Again, good luck getting it figured out!
 
I just replaced mine earlier this week.

I would check your check valve on the booster...

Also, a funny idle is another sign your booster is going out.

SOR has a write up on how to test the booster. Search under my name REZARF and booster and you will get the link for the testing proceedure.

FWIW, I bought a 86 mini truck booster and MC for 40 bucks at the local yard, just make sure to get the check valve off of the firewall that runs to the engine or you will make two trips like I had to :D

I had to cut the rod down about a 1/2" but everything bolted right up easily after that.

Hope that helps.

Rezarf <><
 
guys!
thanks for all the help and ideas!

FREAK, I agree that there is a different *best booster* for different people.
My point was, which booster gives the most assist, for a minimal amount of modification (and of course this means different things to different people)

It's well known that you can put a mini booster on, or a 60 booster on. Also, different people say they've put other boosters on as well. (Trecel, Tundra, etc... even hydro:eek: )
However, no-one has figured out what (if any) difference in assist/boost any of these give.
If we knew this, we could decide that it's silly to pay and mod anything other than a minitruck. (or some sedan for that matter)

Or.... if you want the MOST boost possible, go route 'X' but it's more expensive and takes some modification. Being well informed, one could make a decision.

If I'm going to buy a new booster, I want to get the one with the most assist. If there's little difference, it's silly to hunt something special down and do a bunch of mods.

REZARF:
I read that thread :D

Also, I swapped the check valve off the 77 I have with no effect. So unless they are both bad (and how do you check them?) it's something else.

As for the SOR check. I think I'm showing signs of a bad booster, but not 100% sure... :rolleyes:

SOR said:
7/70 - 9/75 When pressing on the brake pedal a hissing sound, a rapid change in idle or a rough idle are signs of a brake booster malfunction.
Click to expand...
this doesn't help me as I have a K&N that will out hiss anything the booster could produce. It does hiss loudly after shutoff. Idle wise, I have a very strong 1 1/2F that idles smooth at 500RPM. idle seems a little affected, but not consistantly. Hard to say if booster is having an effect in this regard.
SOR said:
To Check Your Booster: Engine Off - press the brake pedal several times, pedal travel should not change.
Click to expand...
my pedal will pump up *firmer* w/ the engine off = probably bad
SOR said:
Start engine, pedal should move down a little and the pedal pressure will get softer.
Click to expand...
pedal moves down, but slowly over time (see above post) = probably bad
SOR said:
Press the brake pedal all the way down, shut off the engine, the pedal should not change position.
Click to expand...
pedal moves back up against my foot = BAD
SOR said:
Restart the engine, run for a minute and shut off, press the pedal several times, the pedal pressure should get harder each time.
Click to expand...
pedal gets firmer after first pump, but no real difference after that
SOR said:
If your booster does not work this way its time to rebuild or replace it. Before buying the repair kit please refer to the factory Chassis/Body manual for the repair procedure.
Click to expand...
 
It does sound like your booster is bad. Mine too would hiss loudly after the rig was shut off. You could always hook up a vacuum gauge to your system (not the booster itself) and see if you are losing vacuum somewhere. Then you might be able to narrow it down some as to where it is hissing. Just a thought.

Rezarf - thanks to your thread, I remembered the check valve. I also got the advice from your thread to cut down the push rod. It worked beautifully! Thanks! :) :beer:
 
yea.... I'm now hunting the internet furiously for more info on boosters :D
amazingly..... there isn't any....

I did find a great link to exactly how they work!
How Stuff Works

Anyway, SSBC says you need 18 in Hg for your booster to work properly. Gave me the idea to hook the hose up to my pump gauge and see what I got. I'll try it tomorrow.
 
It takes a LOT of pumping with a minipump to build up vacuum in a booster because the cans are so big. 100 or 200 pumps wouldn't be unheard of.

If changing boosters get the smallest one you can find that bolts up. Makes working around the carb a lot easier.
 
FF LC FREAK said:
It does sound like your booster is bad. Mine too would hiss loudly after the rig was shut off. You could always hook up a vacuum gauge to your system (not the booster itself) and see if you are losing vacuum somewhere. Then you might be able to narrow it down some as to where it is hissing. Just a thought.

Rezarf - thanks to your thread, I remembered the check valve. I also got the advice from your thread to cut down the push rod. It worked beautifully! Thanks! :) :beer:
Click to expand...

No Problem, I am just passing information that was passed on to me.

Glad your working.

Rezarf <><
 
Fixed!!!!!!!

OK, for future search help, I wanted to post my findings:

I finished my booster swap tonight.
:eek: OMG!!!! :eek: holy brakes Batman!!!:eek:

I don't think my old booster could have been doing much.... :rolleyes: I never did try to drive it with the vaccum hose plugged because I didn't have an easy way to do it. I get the feeling I was stopping solely on my 1" MC w/ no assist.

I put a junkyard FJ62 booster on and just went for a spin. WOW!!!! I have HUGE braking power now!!! These are the brakes I've been looking for :D

For future reference, A Tundra Booster will NOT work!!! It uses a 2 bolt MC pattern and the edge of the booster interfears with the clutch MC. Don't do like me and go get one..... for $75.... :rolleyes:
I tried to swap it for a 98 Tacoma booster but when i got there, they said it was bad. They didn't have another. At this point the junkyard guy asked me what the heck I was doing because now I'm asking him for a T100 booster :D
Turns out they HAVE an Fj62 in the yard so I get the booster off it.

However...... for whatever darn reason, Toyota decided to switch the FJ62 to the external check valve.... I didn't know this, DIDN'T ask for it, didn't get it..... and had to pay Toyota $50 for it :mad:

In the end, this whole mess of shennanigans has cost me right around $150-$175 all told. This of course doesn't include all the time put in as the junkyard is 1hr45min from me.


I could have bought a re-man Taco booster from Advance Auto for around $200-$250 depending on which brand I wanted.
Even has the right @$#! check valve....
532791.jpg


Anyway, I'm not 100% sure that the 98 Tacoma booster would work, but I've been told it will. If I have to give advice, I'd tell someone to just go get the re-man if they can't find a Tacoma in a junkyard.
 
heh. sorry man.I told you to get the Tundra one :doh: I was told the one I had was that, but I should have confirmed before spreading misinformation :)

The Taco booster works awesome. Do be sure to grab the spacer if you pull it from a junker, or you will need to space it about 1/2" from the firewall some other way. I used nuts because I am cheap :)

Glad your brakes are working!!!

cheers-
Dustin
 
no prob Dustin :D
I just wanted to make sure no one else makes my stupid mistake. Pretty obvious when it's only got 2 MC studs :rolleyes: but not if someone's buying it sight unseen.
 
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