Okay, So first i would just like to say that i have read i swear pretty much every post that has to do with a 4x4 89-95 toyota pickups brake system. To start with i just finished replacing the front two cv shafts cause the boots were ripped and not knowing if they were the originals with the 340,000km on them it was just a better call. I also replaced the rotors, calipers, and pad cause they were pretty grinded into tin foil and needed replacing. I also replaced the shocks all around with bilstein HD´s.

Now comes the evil that has possessed my brake system. I bleed all the lines starting with the RD, RP, FP, FD and the LSPV. Gone thru 2 bottles of brake fluid and have no air coming out of any of the bleeders. I also replaced the front two brake lines cause they snapped into two pieces. I have bench bleed the Master cylinder on the truck and there is fluid coming and no air. The problem is the brake pedal will fade very very very slow with the truck off and slightly quicker with the truck running. If i push the brake and feel the fade i let up and then press again it will brake okay for a bit but then start to fade once again.

From everything that i have read on the forums it seems the problem would be with the master cylinder letting fluid slip past the seals. This would make sense to be me as i have no idea if this is the original master cylinder or not. So from what i gather when people replace their older calipers with new ones the MC always seems to not be up to the task. Is there anything else i can try before i have to go spend the $79 + core charge for a new one.

Oh and yes i check to see if there was air in the LSPV and it looks to be working correctly. I am about ready to firebomb the dam thing.

Please help interweb truck gods

 

Do yourself a favor & order an Aisin from MarlinCrawler or WabFab.

don't know what else to tell you. Unless your emergency brake is not adjusted properly....

 

Your master cylinder might be the culprit, but you will also get brake fade with a failure of your power brake booster. Have you noticed any hissing or a change in engine RPMs when you hold your foot on the brake and the fade occurs?

 

i went through 2 refurb MCs that were bad out of the box from orielly's before i went to AZ and got a working one

 

I'll check out the rpm and see if it changes. If there is no change I am going to guess the booster is okay. I havnt heard a hissing noise. So guessing a new master cylinder is the way to go. Sounds like the reman ones are more pain then they are worth.

 

You say nothing of the rear brakes!!

Are these adjusted up and the drums within specs??

It is the use of your emergency brake that keeps the rear brakes adjusted.

If your E-brake is not working it is easy for the adjusters to seize up this can give you the soggy pedal feel. From to much movement of the shoes.

It is also possible you have a connection sucking air and only a tiny amount of fluid.

 

Wyoming9 is correct, but in your case I think that your adjustment is fine as you have firm pedal, but then it just fades. I've never had a problem with the re-manufactured master cylinders, but it's like everything else, if Buddy who is rebuilding it has a bad day...you may get a dud!
As far as adjustment, I've seen procedures where you have to use a spring scale to measure pull of the cables and other complicated procedures that would make your head spin, but when I used to have Ford trucks I had an old manual that gave a procedure for brake adjustment. "Put your emergency brake on 2 clicks and adjust your brakes up until they are just scraping on the drums." I've used this method on every vehicle I've worked on since. You may have to fine tune it if your drums are out of round but all in all this works pretty well.

 

Old bump...

I have the similar issue with my 4Runner. abourgeois, did you ever get the problem resolved? If so, what was the culprit? Need to know, gotta get my truck back on the road.

 

"Fading" is almost always a master cylinder issue (unless you have a leak, which is really easy to see). Air in the system doesn't manifest itself that way (think: spongey pedal).

 

I had to pull my rear axles a while back to replace the diff seal. Could not knowing what you're playing with on the drums cause this? I think that I might have adjusted a wheel and not got it back to where it should be. I just wonder if that might be the cause of this.