25 Master Cylinders

[LandCruiserSteve]

You could always do what one of the PO did to one of my 25s, convert over to early FJ40 brakes.

John, are you talking about a complete axle housing swap (front and rear) along with its brake components?

If you only knew how seriously I've been eye-balling the axles on my '78 FJ40 as a potential donor at this point. (But, then I'd have to track down replacements for it.)

 

[Living in the Past]

Quote: 1962fj40 Check out my Microfiche online, it should have what you are looking fir:

http://tlcfiche.dyndns.org:8081

Be sure to install the "AlternaTIFF ActiveX control"


Robert when I said early I meant early 1961 to mid 1963 with the centered pumpkin. The 69 to 80 are offset pumpkin. I'm been busy but I would still like to get together.





Quote: Landcruisersteve John, are you talking about a complete axle housing swap (front and rear) along with its brake components?


No Steve, on the front axle just from the front knuckles out and the back from the brake backing plate out. If you can work it out with early 40 axle parts only a few would know it's not stock. You could use your front axle housing with the front inspection cover and in the rear use your centered pumpkin. I just took the pumpkin out of a 66 front axle. The parts need a good cleaning but you can have them for the ride. On the back axle I don't know until I can get the early 40 axle part numbers to compare to the 25 part numbers. The 40 I brought back from Washington earlier this year has the centered pumpkin with the 40 brakes so it will work. The 25 that has 40 brakes has a Torsen limited slip with no C clips so if the axle line up so the C clips don't know. I don't have a 25 axle in town but I do have the 40 centered pumpkin in town. So if you can get me a measurement of the 25 axle housing between the backing plates I do the same on the 40. That will give us a start. If it's just the backing plate with a different offset it might be a easy change over.


John

 

[LandCruiserSteve]

No Steve, on the front axle just from the front knuckles out and the back from the brake backing plate out.

John, I'm a little confused.

You're saying that I'd only have to swap out the knuckles (and front backing plate) in the front . . . and just the backing plate in the rear, without having to change anything regarding the axles themselves??

And, that particular change would accomodate the early 60's FJ40 brake parts (i.e., shoes, drums, cylinders, springs, hardware, etc.)?

I just took the pumpkin out of a 66 front axle. The parts need a good cleaning but you can have them for the ride.

If I'm keeping the axle housings, axle shafts, the pumpkins and their respective offset that I've got already, why would I need to worry about the front diff?

 

[Cruiser_Nerd]

A couple of times, the wheels locked up after a few hours just sitting there in the garage after the adjustment/bleeding procedure without even driving the damn thing to get it warm.

This still happens? The only thing that will do this is expansion of the fluid or air in the system due to heat. In other words, expanding fluid must be able to escape, otherwise you make pressure. This is why I wanted you to drive without touching the brakes. If this is still happening you have a hydraulic problem.

Other than the brake lines (which appear to be okay), the only thing I have yet to replace are the three rubber brake hoses (two front wheels and the rear axle attach point). Is it possible that the interior of these hoses may've broken down on the inside to create some sort of "one way valve," so to speak?

It could. But, if you've cracked the bleeder at the wheel cylinder and the brakes didn't release something else other than hydraulic pressure is holding the shoes. By relieving pressure at the wheel cylinder bleeder you eliminate this possibility.

So,

If the brakes come on by themselves (you never touched the pedal).

Crack all the bleeders at the wheel cylinders to release the pressure.

If the brakes don't release something besides the brake fluid is holding them.

But whatever is holding them in place is not what caused them to come on. The expanding fluid did. You may be fighting two problems.

 

[Living in the Past]

Quote: Landcruisersteve John, I'm a little confused.

I wish I could say that I'm just a little confused.

I no longer have a 25 in town so I can't compare. If you look at the rear backing plate on 25 and the one on your 1978 FJ40 I'm "guessing" you'll see the the one on the 40 is offset toward the inside. If this is the case, the only difference might be the backing plate and brake parts. I now have a FJ25 parts manual but was out bid for the early FJ40 one on Ebay . That way we could compare all the axle part numbers to find out the differences.



Quote: Landcruisersteve If I'm keeping the axle housings, axle shafts, the pumpkins and their respective offset that I've got already, why would I need to worry about the front diff?


You won't need to change the diffs. I'm just saying I have a complete front axle minus the diff and you could have any of the parts you needed, not that you would need the whole axle or diff.


Quote: Landcruisersteve You're saying that I'd only have to swap out the knuckles (and front backing plate) in the front . . . and just the backing plate in the rear, without having to change anything regarding the axles themselves??



You won't need to change the front axle housing with the inspection plate. The front inspection plate is something I would try to keep, the 25s and the very early 40s are the only one that came that way. That's what confused me about the 25 I have with 40 brakes. Still has the front inspection cover and a centered pumpkin. I know it can be done cause I have one. I guess my thought is if you have parts on your 25 brakes that won't stay adjusted and are worn out that this is the a way to keep the 25 axles but get your brakes fixed. If you had a dealer who still had the parts books you could try that too. I sure they wouldn't mind spending a hour or so with you just to have walk out without buying anything. So have I got you more than just a little confused now.

I will at some point do this conversion myself. The early 40 I have the front axle was changed with a later one with no inspection plate. So I'm going to covert a 25 axle to a early 40 axle.

Did you ever try one of those brake shops that say they can do all four wheels for $99

If we could find the 40 parts book I'm sure this would be clear as mud


Steve, let's just do this the easy way, ship the 25 out to my cabin and I'll fix the brakes

John

 

[LandCruiserSteve]

Steve, let's just do this the easy way, ship the 25 out to my cabin and I'll fix the brakes

At this point, that almost would be the "easy way." But, why do I get the feeling "return postage guaranteed" would not apply if I shipped it to you?

 

[LandCruiserSteve]

But whatever is holding them in place is not what caused them to come on. The expanding fluid did. You may be fighting two problems.

I heard that the 3-way junction box in the engine compartment (the one that splits the fluid to the two front wheels and a third line that runs back to the rear axle) also contains a proportioning valve in that little box. Is this fact or fiction? And if so, could that prop valve be gummed up or otherwise defective and keeping the fluid from returning?

 

[Cruiser_Nerd]

Fiction, the junction blocks are just that. cross drilled two ways with the fourth hole welded shut.

Steve, are you going to start applying a little scientific method here? ;p Really does sound like you're fighting more than one problem.

 

[LandCruiserSteve]

Steve, are you going to start applying a little scientific method here? ;p Really does sound like you're fighting more than one problem.

Yep, it sure does sound that way. I just wanted to cover all the potentially easier sources of problems before I think about jumping into a near complete under-carriage swap-out, which is something I really can't afford, nor do I have the expertise or accessibility to all the required parts (axles, knuckles, backing plates, etc.). Plus, I really don't want to deviate from stock if I can help it.

If the brakes on this beast managed to work nearly 50 years ago, they still should work today, as simple as they are. Seems like I've tried everything, but there still appears to be some hidden gremlins in the system that don't want to reveal themselves.

So, what scientific method could I apply here?

 

[foxfab]

have you tried a power bleeder?

 

[LandCruiserSteve]

have you tried a power bleeder?

No, haven't tried that yet.

But, if you've cracked the bleeder at the wheel cylinder and the brakes didn't release something else other than hydraulic pressure is holding the shoes. By relieving pressure at the wheel cylinder bleeder you eliminate this possibility.

Well, more often than not, cracking the bleeders DOES release the wheels. It's been some of those few ocassions where it's possible that I may've over-adjusted the shoes (just to get a good pedal during bleeding) that sometimes it doesn't free up. And, I am getting good solid stream of fluid out of the wheel cylinders when I crack them. No air burps or bubbles at all.

That possible over-adjustment also might contribute to the thing locking up before I even drive it, even though I'm getting a spinnable wheel (with a slight drag) during the adjustment when the wheel is up off the ground.

 

[madoc1]

steve just astrong thought. if hoses are original they need to replaced anyway--even if the are just 20yrs it would be a good idea. have seen bad lines on a76 fj40. east to check. just pulloff and blow both ways. or try a redneck check with a coat hanger.

foot pressure will make the hose expand, but spring pressure often is not enough, at least immmediatly.

good luck on this, its only mechanical-i think jim

 

[LandCruiserSteve]

if hoses are original they need to replaced anyway--even if the are just 20yrs it would be a good idea.

Yep. Good idea, madoc1. I'm going to check those this weekend.

By the way, thank you everyone for not just the great ideas for troubleshooting this damn mess, but also the emotional support. (That's about as warm and fuzzy as you're gonna get out of me. ;p ) I've never had anything that's driven me this crazy with a truck before.

 

[Cruiser_Nerd]

Alright Steve, I had to take a brake , but I'm back.

I thought you had tried a power bleeder in the past.

Anyhow, take a look at the brake line, if it's like mine it leaves the M/C then goes up and across the firewall. This was my first thought with mine, that air was trapped there heating up and expanding. Even had insulating wrap on it for a while.

Mike is right, try the pressure bleeder. A big volume of fluid moving at once will get out a lot of air you never thought was there. I made mine with an old M/C plug. Just let me know and I'll pop it in the mail to you. After you pressure bleed it, you can at least be sure there's no air in the system.

Oh yeah, brake hose part #'s are in the parts thread (available new from Mr. Toyota). May as well replace them if you're bleeding it again anyhow.

 

[LandCruiserSteve]

I thought you had tried a power bleeder in the past. :

That originally was going to be my next step had I not bought the new Toyota MC and got sidetracked with the leaky wheel cylinders.

Anyhow, take a look at the brake line, if it's like mine it leaves the M/C then goes up and across the firewall. Even had insulating wrap on it for a while.

Yep, mine's the same layout. And, I tried the very same thing with the insulation back when you suggessted it earlier.

Mike is right, try the pressure bleeder. A big volume of fluid moving at once will get out a lot of air you never thought was there. I made mine with an old M/C plug. Just let me know and I'll pop it in the mail to you.

That makes a lot of sense. (I think my local Auto Zone has a power bleeder on their "borrow a tool" program.) Thanks for the offer on the loan of your adapter, but since I'm running the newer style MC without the threaded reservoir cap, I believe the universal adapter just clamps over the plastic ones. Does using the power bleeder eliminate the need for bench-bleeding the MC?

Oh yeah, brake hose part #'s are in the parts thread (available new from Mr. Toyota).

Got it . . . thanks, Jim!! Any idea if the hoses would any cheaper from Toyota (dealer or CDan) than they would be from $OR?

 

[LandCruiserSteve]

I just checked SOR's site and it lists the two front brake hoses as 086-30-FJ25 ($24.09 each). But, the only listed rear hose is 086-32A ($55.42).

According to your parts list, Jim, all three hoses are supposed to be the same. (Either that, or Marv is still labeling parts for "1958-62 FJ40s.")

 

[foxfab]

The rear hose is slightly longer, but Jim says its not an issue. Just get three of the fronts.

I have the Toyota P/N here somewhere if you want to try Cdan.

 

[LandCruiserSteve]

I have the Toyota P/N here somewhere if you want to try Cdan.

The part number Jim listed in the Parts thread is 90947-02006. I'm assuming that's the one?

 

[foxfab]

should be.

 

[Cruiser_Nerd]

Yep, I just used the same hose for all three, it was plenty long in the rear, even with my massive lift. There are adapters that are stock on the front hoses at the wheel cylinders. Don't lose them, you'll need new copper washers there.

As far as the power bleeder goes just fill the M/C reservoir slap it on and let it rip. Just don't bleed out too much without checking the cylinder. It really sucks to pump air into the whole system if you run out of fluid.

Oh yeah, my homebrew tool would just fall right in wouldn't it?