1970 FJ-40 SERIOUS brake issues. Needing Assistance

[JwSpeedWorkz]

Hello all. I work at a shop that works on just about any vehicle that fits in the door, hot rods, imports, anything. So this 70 land cruiser came in with a 2 page list of work to be performed. So I started with the most important part of the list, the braking system. This vehicle is kind of restored, body is like new, interior is done nicely. Most of what has been done to this truck has been done right. So first I find the front hub seals are leaking, the rear axle seals are leaking, and 3 of the 4 rear wheel cyinders were pouring fluid out. So I replaced all the seals, and replaced all 4 rear wheel cylinders with new replacements. Replaced the rear brake shoes, adjusted and bled the brakes. This is where things get frustrating. After bleeding the brakes thoroughly, I depressed the pedal, straight to the floor. So I pumped them up, rock solid. get off the pedal for more than 10 seconds, step back on, straight to the floor.This was the original complaint. So I proceeded to adjust and bleed the brakes again. No Dice. I then adjusted the brakes until i could no longer turn the drums, just to know that it wasnt a mechanical issue. Same issue. I replaced the master cylinder with a reman from a local parts house. Exact same issue. Its almost as if the master cylinder losses its prime if you let it sit. The only odd thing I found was that when I ordered the master cylinder, i had to order it for a '78 to get the same one that I took off of the car, the one with 2 reseviors and the outlets on the top. Has anyone ran into a simalar issue? I have wasted more time on this vehicle than my boss can tolerate. Thank you!
Jeremy
Reider's Service Station

 

[JasonH]

Is it still drums all around? The drum brake master has a check valve that keeps pressure on the drums. If you're running a disk brake master, you might be losing pressure on the front brakes.

 

[SouthBostonFJ40]

Sounds like it was not the original master on there. Have you checked the booster?

 

[FJforty]

Just guessing here. The return springs are not on right and the shoes are not pushing the wheel cylinders back together after the brakes are released. This could draw air into the wheel cylinders.

 

[GarageRat]

I'm thinking since it has a front disc master it's bleeding pressure due to having a residual pressure valve meant for discs (about 2 pounds of pressure) instead of drums (about 10 pounds of pressure) I'd try either installing an inline residual pressure valve in the front circuit or change to a dual reservoir drum master.

 

[Poser]

Welcome.

Get the correct master cylinder for that vehicle.



You have the wrong master cylinder on that vehicle.... residual pressure valves are part of it, but the different bore sizes make a significant difference as well...Drum brake master cylinders have a larger bore than the disc brake master cylinder on the 40 series from the factory.

 

[FJforty]

Brake pedal rod free play could be the problem. When the pedal is released the rod going into the master cylinder must have slack.

 

[zags]

JasonH and Poser have the only correct answers here.

 

[lostmarbles]

Who supplied the wheel cyclinders?

It might pay to read this thread which explains about how some aftermarket wheel cylinders are poorly designed with the bleed nipple unable to remove trapped air:

https://forum.ih8mud.com/40-55-series-tech/213410-master-cylinder-residual-valve.html

See post #28 in that thread

And drum-brake master cyclinders can have either one or two reservoirs. Having either type DOESN'T necessarily mean you have the wrong master. (But I agree that a master designed specifically for "discs up front" will move insufficient fluid for "drums-all-round".)

 

[lc69hunter]

Poser is correct.

 

[JwSpeedWorkz]

It does still have drums all around, and yesterday I checked to see if there is a residual valve in the front circuit, there was. Is there a 4 wheel drum master cylinder that has the outlets on top like the '78 master? and if so, where can I get one. I also checked the rod freeplay, it was adjusted the whole way back, but making any adjustments to it made no difference with the issue. I clamped off the lines to the front and rear axles, and it did the exact same thing, so I am 110% sure the issue has to do with the master.

 

[SouthBostonFJ40]

This is what a 1970 master should look like.

In 1971, it changed to this type below until ??

Do you have a 3 or 4 stud booster?

Both types are available on RockAuto Auto Parts

 

[Shawn Russell]

From the factory, 1970 had a single circuit brake system with 9mm fittings. Yours has been modified to handle the dual circuit of the 78 master. You can not use the 1970 master anymore. You have to go up in years for the dual circuit. Also, when they went to the dual circuit, they went to power brakes, and 10mm fittings.

Photos of the firewall would help also..

 

[SouthBostonFJ40]

From the factory, 1970 had a single circuit brake system with 9mm fittings. Yours has been modified to handle the dual circuit of the 78 master. You can not use the 1970 master anymore. You have to go up in years for the dual circuit. Also, when they went to the dual circuit, they went to power brakes, and 10mm fittings.

Photos of the firewall would help also..

And of the booster.

 

[Poser]

Is there a 4 wheel drum master cylinder that has the outlets on top like the '78 master? and if so, where can I get one.

No there is not.




Post up pictures of what you are working on.

 

[zags]

Pre 7/70 and older build dates had a single resivoir master cyl. 8/70 and up had a dual resivoir. (Mine was built 8/70 and has a dual resivoir) so yes, you can get a dual for 4 wheel drum. Toyota Part # 47201-60010

 

[lostmarbles]

If I understand him correctly, Poser/Steve (a well-recognised expert) is saying that there isn't any drums-all-round brake master with the outlets on top. (And I haven't seen any either.)

So now I agree that it looks like the wrong master is indeed being used.

But I think both "the number of reservoirs" and "the date of production/use of the master" are largely irrelevant (given that the vehicle is modified and that different markets got different things ..such as disc-front-axles .....in different production years).

Except of course that his master needs "two outlets" and "sufficient fluid movement for drums-all-round".

The purpose/effect of residual valves is widely misunderstood IMO. I believe they are there simply to provide residual pressure in the wheel cylinders while the pistons are moving back under the influence of the return-springs after a brake application. (This helps prevent fluid leakage by keeping the seal lips pressed against the walls.) If you accept this .. you can see why they are more important on drum brakes where pistons move further.....

Here are two masters I've used on my drums-all-round forty.

The original AISIN:



An aftermarket PBR unit:



Note that the AISIN unit looks like it has only one reservoir but in fact there are "two separate reservoirs within one" providing the same safety protection (of supplying a separate fluid reserve for each brake circuit).

 

[Poser]

Pre 7/70 and older build dates had a single resivoir master cyl. 8/70 and up had a dual resivoir. (Mine was built 8/70 and has a dual resivoir) so yes, you can get a dual for 4 wheel drum. Toyota Part # 47201-60010

No one was questioning that.....

so yes, you can get a dual for 4 wheel drum.

The question was about outlets, you know, where the brake line attaches.

The dual-circuit drum brake master cylinder that is for the USA 40 series has outlets on the left side of the master cylinder.

The dual-circuit disc brake front, drum brake rear master cylinder that is for the USA 40 series has outlets on the top, one in front of and one between the reservoir cups.








OP-

You make and progress on this yet?

 

[zags]

oops, I missed that part...

No one was questioning that.....

The question was about outlets, you know, where the brake line attaches.

The dual-circuit drum brake master cylinder that is for the USA 40 series has outlets on the left side of the master cylinder.

The dual-circuit disc brake front, drum brake rear master cylinder that is for the USA 40 series has outlets on the top, one in front of and one between the reservoir cups.








OP-

You make and progress on this yet?

 

[JwSpeedWorkz]

Good news! After reading your replys, I decided to get another 1978 master. I took the rear residual valve out of the new master and put it in the front of the other, and mysteriously, problem solved, easily locks all 4 up on dry pavement. the brakes are now surprisingly touchy, Im not complaining, and im sure the customer will be extatic! I thank all of you for your help on this issue. Im sure I will be posting here for other assistance because this customer will be coming back here for all repairs. He says we were the only shop within 75 miles that would touch his FJ.
Thanks again !
Jeremy