Front Disc Rotors are hot to the touch! (2 Viewers)

[Josie'sLandCruiser]

Hi All:

Just swapped in a '89 mini-truck brake booster (to replace a dead drum brake booster) along with the brake master cylinder from a V-6 mini-truck last night on my '74 FJ40 with a '78 disc brake frontend.

Just took the rig for a short neighborhood test run, starting out slowly on side streets then getting up to 40 mph on an arterial to test the stopping of the rig. Route was not more than 1.5 miles I'd guess.

The truck is stopping much better than before, but I noticed a bit of "drag" when coasting in neutral; i.e. the truck was slowing-down while coasting sooner than it would before the parts swap last night. When I got home I touched the rear brake drums; they were perhaps slightly warm to the touch. The front disc rotors however were very hot to the touch (can we say "third degree burns!)

Any opinions about this condition? I'm assuming something needs to be adjusted.

Thanks in advance!

Alan
Seattle

 

[camcruiser13]

maybe a slight adjustment need i notice when i change the pads mine will drag for a little while then its stops, but yes the rotors will get hot

 

[Rice]

You mean burn to the bone and fry the veins shut hot?

That'd be about normal.

 

[nat]

It could be vacuum creep with your booster. Did you adjust it so there was a little play in the vaccuum booster pushrod when the brake pedal is not engaged? I think about an 1/8" is good.

 

[Poser]

Nat has it...


Adjust the acctuation rod between the master and booster...there is a little threaded piece on the end...turn it in...it is likely pressing on the master cylinder piston, creating pressure on the system, and the heat your are seeing and feeling at the drums and rotors....When you put the master onto the studs on the booster, you should not feel anything trying to push the master away from the booster....


Make sure your pedal freeplay is correct also... 1/4" or a little more will not hurt....



Good luck!



-Steve

 

[numtel]

I had the same thing happen to mean when I put on front discs. I just adjusted that pushrod all the way back in and haven't had any problems since.

 

[cruisertom]

They make a tool for this adjustment. Not sure where to find one (maybe Napa) but it is made out of about 1/4" steel and is in the shape of an H with an adjustable rod that slides through the middle of the H. Works very well.

 

[Josie'sLandCruiser]

Hi All:

Thanks for the responses!

I have since adjusted the brake pedal attachment to the booster rod. The "drag" seems either gone or greatly reduced . . . but don't know if that solves the problem . . . . the brake rotors still get fairly warm to the touch; I drove my 1991 Isuzu Trooper today that has the *original* factory rotors and aftermarket brake pads (installed at 124,000 miles) and they were cool to the touch after driving around!!

So, what do you guys think?

thanks!

Alan
Seattle

 

[Poser]

I have since adjusted the brake pedal attachment to the booster rod.

Ok-



But did you unbolt the master, and shorten the acctuation rod inside the booster, that presses on the piston inside the master cylinder?


If you have not done this, you need to.



Good luck!


-Steve

 

[Yoda]

Alan,
When I put the 4runner booster/master into my 71 (79 FJ axle), I had to build a 1/2"spacer to put between the booster and the body. Also adjusted the inner pushrod between the booster and master.

 

[Josie'sLandCruiser]

Hi All:

Steve, how does one adjust the length of the rod that goes into the brake master cylinder?

My friend who helped with the install tried to loosen the "lock nut" on the end of the rod that goes into the master cylinder but was unable to; he was afraid of breaking it, so he "eyballed" it comparing the rod length to that of the original drum brake booster.

Any thoughts?

Thanks!!

Alan
------------------------------------------------------------------------------------
"Poser" wrote:

Ok-

But did you unbolt the master, and shorten the acctuation rod inside the booster, that presses on the piston inside the master cylinder?

If you have not done this, you need to.

Good luck!

Steve
----------------------------------------------------------------------------------
Originally Posted by Josie'sLandCruiser

I have since adjusted the brake pedal attachment to the booster rod.

 

[Poser]

I had to build a 1/2"spacer to put between the booster and the body.

Why?


What was in the way?

 

[camcruiser13]

even when your brakes become adjusted correctly they will still get hot, i dont advise touching them. the front brakes take the brunt of the weight and are the main stopping source, on my dodge ram 03, i can rost marshmellows on the rotors if i wanted too.

 

[Poser]

even when your brakes become adjusted correctly they will still get hot, i dont advise touching them. the front brakes take the brunt of the weight and are the main stopping source, on my dodge ram 03, i can rost marshmellows on the rotors if i wanted too.

Yes brakes get hot cam, no one is questioning that....they should not get smoking hot, going around the block.....


Something is not adjusted properly with the master cylinder and the linkage to acctuate it, that is why there is pressure in the system applying the brakes when they should be released...

 

[camcruiser13]

tru

but i thought it was downhill both ways?

 

[Poser]

Alan-


Is this piece similar to what you are having troubles with adjusting?


This is a 1987 booster that I had at the shop, with a disc brake master cylinder from JTO...

 

[WhiteKnight]

Hello all,

New here and this is my first post. I had a similar experience when I changed the power booster on my 78 FJ40. I had to put a power booster off of a later model Toyota truck. The front brakes dragged like crazy after that. I ended up having to shorten and adjust the rod from the brake pedal going into the power booster. Haven't had a problem since. Hope this helps.

John Milligan,
Albuquerque, NM.

 

[Poser]

Welcome John.


Thank you for this post. I have installed the Mini booster into earlier 40's that require the spacer to clear the support rib on the early firewalls, but you need to lengthen the rod that connects to the pedal, not shorten it, like in the later trucks.




-Steve

 

[WhiteKnight]

Thanks for the welcome Steve,

The booster I used just required a set of washers, one for each stud, to clear everything, though it was real tight. I had to shorten the shaft from the pedal about 1/16 to 1/8 of an inch to free everything up under the dash. Not much, but it made a huge difference. I don't have a digital camera yet, but taxes will be in soon and thats at the top of my list. Will post some pick of the installation then.

John Milligan,
Albuquerque, NM.

 

[Josie'sLandCruiser]

Hi All:

First off, thanks very much to everyone for their suggestions and comments! Greatly appreciated!

Steve, yes! That is exactly the piece we had trouble adjusting. Thank you for going to the trouble of taking pics!

I want to clarify the first post of this thread; yes, I burned my fingertip touching the brake rotor (third degree burn) but the front brake rotors were NOT "smoking hot," just very hot to the touch! I did not state in the first post that I had done several "panic stops" in that 1.5 mile circuit (zoom up in speed, then slam on the brakes!)

So, I adjusted the rod where it meets the brake pedal; also noticed that no return spring was present so installed one. Afterwards I did some testing; I drove my 1991 Isuzu Trooper, got it up to 40 mph, then used the brakes to pull-over in a safe, controlled manner. Touched the front brake rotors - hot! Then went home, parked the Trooper, hopped into the FJ40 and took it for a drive. Got it up to about 40 mph, coasted down a slope, and using transmission braking slowed-down and turned onto a side street; was able to get the rig stopped without ever touching the brake pedal. Got out and touched the front brake rotors - they were stone cold!

So, everything appears to be in order! Thanks again for all the help!

Regards,

Alan
Seattle