Warning, long post!

Here's a problem I hope some of you experts can help out with: Original brakes on my 97 4runner were shot, so after reading on here and other sites I figured while I was replacing parts I might as well upgrade to the Tundra rotors and calipers. I bought a set of reman. 99 Tundra calipers (the shorter of the two options, I believe, 193mm?) and DBA slotted rotors, put them on a few months ago and tried to bleed the system, but could never really get the pedal to feel firm. The brakes seem to have enough power, they just feel mushy and you have to stomp the pedal down to the floor to get the truck to stop.

SO...recently we decided to sell another vehicle, which means my wife will be driving the 4runner, which prompted me to quit messing around and take the truck in to the dealer to have the brakes power-bled. Now, they just called and are telling me that the Tundra calipers are "incompatible" with the 4runner, but can't give me any more detail than that. They're saying that if I put stock calipers back on, all the problems will go away. Being an engineer, this doesn't make much sense to me. The caliper is just a "dumb" slave cylinder, so if the system is fully bled of air, it shouldn't even matter what the physical configuration of the caliper is, correct? It should still compress and release just like any other, even if it doesn't physically bolt on to the vehicle (which these Tundra calipers obviously do).

So I'm thinking there's another problem here, maybe the vacuum booster or some sort of ABS valve acting up? Any suggestions before these guys try to charge me $110 for doing nothing?

Thanks,
Desmond

 

I call BS.

The 4Runner caliper and the Tundra caliper are identical for all important purposes as I have done this swap on Rockslide's 4Runner and it was a simple bolt on swap with little bleeding. We just powder coated his calipers.

The key to swapping out calipers is to use vacum line caps over the removed brake line so you have to bleed things very little and loose little fluid.

You just need to rebleed the lines probably.

Did the MC get empty? Did you bleed the whole system in the proper order?

 

Well first off, the dealer is going to tell you Tundra calipers are "incompatible" with the 4runner, simply b/c they did not come standard on 4Runners. The Dealer sees a change in stock configurations and assumes the change is the reason for any and all problems you incur from it.

Where did you purchase your reman calipers from? Oh and the original calipers where 199mm. The larger ones that were released in the TSB, are the 231mm calipers.

 

Thanks for the quick replies guys! I got the reman. calipers from Rockauto.com, if I remember correctly. Also, I just replaced the master cylinder as well, thinking that might have something to do with the problem (it didn't seem to change anything). All in all, the whole system has been bled probably 6 or 7 times now (in the proper order, and the MC was bench bled before being installed), including twice by the dealer yesterday, with no change in the pedal feel, which is leading me to think there must be something else wrong in the system.

What does a bad vacuum booster feel like? And what can I tell the stealer to make them actually do their job and diagnose the problem?

Thanks again

 

hmm... i have this same problem stock, mushy feel, can take a "release and push again" movement on pedal to get firm feel... new stainless brake lines didn't seem to help. I haven't replaced anything else yet, but was thinking maybe MC... I'm curious as to what you figure out, sounds like the same things I have gone through (bleeding repeatedly, correctly, still mushy)

tell them the problem was there before the new calipers... also, someone I talked to said air bubbles can get trapped in upper cavities in caliper, and said caliper has to be loosened and rotated to remove bubbles... not sure if this is true

 

http://www.aa1car.com/library/pwrsteer.htm seems like a good amount of info,
and there is a nice pdf at this link describing the entire system... www.autoshop101.com/forms/brake05.pdf

 

Have you checked the REAR brakes for wear?

 

Was the pedal firm before the conversion? I know that you said the brakes were shot, but that doesn't tell us much. If the pedal is the same as it was before the conversion, likely the culprit is something else entirely.

 

good call, can't forget those guys. I will have to check those tonight... I need to find the specs on drum dimension too, to tell if they need replacement

 

Rear brakes are new as well, and I adjusted them very tight to the drums which did help with the engagement, but it still feels crappy. Before the conversion, the pedal did feel soft too, but not as bad as it is now.

Wabbit - Thanks for the links too. If I'm reading the pdf correctly, it seems like my vacuum booster is operating normally, so I'm not sure what the next troubleshooting target would be. Isn't there some sort of solenoid valve that "pulses" the fluid for the ABS? Where is that located on the truck?

 

I will take a guess that because you are just now checking the rears that you did not truly bleed those out as well(?)

How new is the fluid? sorry if I missed that detail....

 

No, unfortunately I've tried it all! When I swapped in a rear axle with a locker just recently I put in new rear brake shoes, replaced one leaking wheel cylinder, and replaced all the flex lines (front and rear) with stainless. Fluid has been fully exchanged, probably a few times by now (Valvoline synthetic). I'm really at a loss, but the dealer just called me and after much arguing, they at least agreed that the Tundra calipers probably aren't the cause of the problem. They're looking into it further, so maybe there will be some resolution by the end of the day.

 

When I did the the swap to the tundra calipers I started by getting new drums on the back first. It was a cheap upgrade and made a major difference in the pedal feel. It seemed like even with adjusting the rear brakes, the drums were worn down enough that the pedal didn't feel good and solid (I drive from 9000 to 5000 feet every day).

Once I put on the actual Tundra calipers I can't say I felt a huge difference in stopping distance or pedal feel. It really was the rears that were considerably noticeable.

Just something to consider.

 

some ways the front could be incompatible is if the
rotor is not the same width as the tundra rotor, making the
piston reach too far to make the pads hit the rotor

or

if the volume of brake fluid in the caliper internals is too big
and you can't get the proper action with your master cylinder

both situations would feel like an air bubble


but peeps have done this swap successfully so I reckon you has air bubble

 

sorry to hijack with my problem... but except for the swapping of parts, my situation was exactly the same... just (tonight) adjusted rears A LOT, made an incredibly huge difference. Pedal feel is better than it has been in the last 1.5-2 years, I wish I had caught this sooner, so much time with crappy brakes. Brakes are firm, engage soon (as should), and lock-up if needed.... thanks to those who mentioned the stuff that helped me too

 

Wow, that's good to hear. Can't believe the dealer owned up to that. Let us know what you find out. Just hope the problem is not within a faulty caliper or something of the sorts.

Off subject, but how much work was involved in swapping in the elocker and other needed parts? I know you swapped in the axle too, but how hard was the wiring and other misc stuff? I'd like to have one of my own someday

 

rears should auto adjust if you reverse, then nail the handbrake, and do this several times. that makes the automagic take-up ratchet click

 

but you should still check and adjust manually... unless you stomp on gas and then brake each time you reverse it won't do any good, most people just coast slowly in reverse. Mine hadn't been adjusting themselves, and were quite a bit out of adjustment, very mushy pedal and basically only using front brakes.

Additionally, my e-brake is completely frozen/rusted, so I couldn't adjust that way either, hooray for rust

 

Well, they kept the truck overnight and said that they had bench-bled the MC again, which helped the pedal feel a lot, but they wanted to check some other things today, so we'll see how that goes.

I bought a complete used axle with the e-locker from a local junkyard (is the PC term "recycler"?!), which made the physical install very easy. Just got that in last week, so I haven't had a chance to tackle the wiring yet, but when I do I'll be using the stock toyota switch and ECU (also from the junkyard), and following this writeup:

http://www.sonoransteel.com/phong/re...ic_locker.html

Doesn't look to difficult, but we'll find out...

 

EDIT:
DJ, I've moved this discussion over here: CLICK ME


I'm assuming your 4Runner is 2WD correct?

I was just skimming over the write up a little while ago...was your 4Runner somewhat prewired for the elocker so the install will be more of a plug-n-play install or are you going to have to do a full wiring job?