yotarob2005

It has happened twice now, again on my way to work this morning and happens for no apparent reason. I can feel the front brakes starting to drag and my pedal will get very stiff. This morning I only had a mile or 2 more to get to work so I overpowered the brakes with the gas pedal and by the time I got to work I could smell burning brake pads. As soon as I pulled in I jumped on the forklift and picked up the front end to find that BOTH front wheels where locked up. I could not turn them by hand. Went back out 30 minutes later and checked them again and they where free, the pressure had bleed off. I have a hard time believing that both of my calipers are having the same problem so I am thinking master cylinder? Hate to just throw money at the problem so I am looking for any advise or reasoning to point me in the right direction. I have been all through my brakes trying to get them up to par but they still suck bad. They will not even come close to locking up my 33's. Here is a little history of what I have done to my braking system.

1) bought kits and rebuilt both calipers my self a few months ago
2) pads and rotors where replaced at the same time
3) LSVP removed and a universal prop valve installed near MC
4) MC swapped out with a larger 1" bore from a 97 Tacoma - used part
5) Dual Diaphram booster from 97 Tacoma - used part
6) Rear wheel cylinders and shoes replaced with new parts a few months ago.

I know I can still try installing the larger V6 calipers from a 92-95 4runner and possibly get better braking feel but I am not sure it will solve the problem.

Thanks for looking and for any advise on my problem.

yotarob2005

Some supporting evidence

Front brake stuff





Taco booster and MC




Prop valve





New wheel cylinders

mightymouse

iTrader: (6)

Bleed your brakes again, check the soft lines for any damage and replace if needed. Re-bleed and see what happens. Make damn sure the brakes are flowing properly when you bleed them. If they are flowing properly and the master cylinder is pushing the fluid then it seems as though you have narrowed it down to the calipers and cylinders. Get some stainless steel soft lines as well. Yours look old.

yotarob2005

Good idea as a place to start. I'll do that first. I bleed the snot out of them a couple months ago but it could never hurt. One more possible point of intrest is that one of my front hard lines is a bit kinked and I did order a replacement yesterday. I wouldn't mind spending the $80 for the stainless soft lines but again I am not sure it would help much.


Seems to me that after all of the brake work I have done this thing SHOULD stop on a dime. FML.

mightymouse

iTrader: (6)

if you think the master is going bad one of the first signs is pedal creep. The kinked line would be a first on the list to get replaced and the stainless lines will help if your old ones are week. How much have you messed with the proportioning valve? I would think the v6 calipers would help but then again you have a big master cylinder and small brakes that seems a little unbalanced if you ask me why upgrade half of the system and expect it to work like new.
With that said and if i was in your shoes i would replace the even slightly faulty stuff (kinked brake line and old old soft lines) then upgrade the rest of the system to match what you have done so far. It's kinda like having a big engine and a weak tiny transmission. One doesn't fit the other. This is obviously just an opinion as i don't have experience with the taco 1" master cylinder but what i do know is when pushing more fluid through the system the weak parts are going to get weaker.

yotarob2005

Sounds very logical MM. In true I have only upgraded half of the front brakes, I suppose that the V6 calipers should be soon on my list and I will get that kinked brake line replaced as soon as it gets here. I had already replaced the front brakes and did the MC and booster as an after thought. The proportioning valve is in line with the rear brakes only an has no effect on the fronts, for what it is worth I have it adjusted all the way out to allow the most braking in the rear possible.

Also funny you mentioned the creep. I do occasionally get a chirp when I push the brake pedal. I think I will start with the bleeding and replace the Master Cylinder since I got it used and then wait for my new brake line to show up. If I still have any issues then I will order a set of stainless soft lines and replace the calipers.

xxxtreme22r

I doubt the mismatch between the master/dual is an issue with the 4cyl calipers. I have the same type of setup on mine for quite a while now and no issues like that. Now of course I do have the factory LSPV there and not the wilwood style.

If the pads and rotors were old I would say maybe you over extended the pistons but that's not the case here either.

P.S> now that I think about it is that a 1" master or a 1 1/16 master from those? Mine is just a 1" master meant for a t-100. New from autozone BTW.

ChefYota4x4

iTrader: (5)

Have you tried adjusting that valve, Rob, to see if you're putting too much to the rear, etc?

Brandon, ... did you just install the T100 Master onto your existing booster?

xxxtreme22r

no I pulled a dual from a 3.0 truck. I had it setup with the factory single but the pedal felt too hard. And not really hard but caught too far up I guess you can say.

ChefYota4x4

iTrader: (5)

So, it's a custom thing, using a T100 Master and 3VZE Booster? Just checking, cuz the T100 was the 3.4, right? Sorry Rob, ...... just curious.

xxxtreme22r

t-100's also had the 3.0 I believe as well, but should still be the same booster.

yotarob2005

I wouldn't think the mismatch would be a problem either but good to know that you are running the same thing and do not have issues.

I have not messed with the valve, but don't see how it could have any effect on the front brakes either.

It's odd because this just started happening, I did just get it street legal and all but I have taken it to the Off-Road park and wheeled it for 8-10 hours and never had any problems. I'm off to buy a new master cylinder I guess. Keep the ideas coming and I'll let you guys know if the new MC helps.

ChefYota4x4

iTrader: (5)

Thanks, buddy, as always!

Best wishes, Rob, ....... hope that solves your issue. Just curious though... what if you don't need the new Master? Not trying to second guess ya... just wondering, what if it's just the kinked line, causing strange pressure variations, thus, locking you up? I guess having a new Master is better than a used 97 one, ....just wondering(cuz I store all this data in my cranial basket and keep it for when I have an issue..... And yes, since my memory is NOT QUITE as great as it used to be, .....I do bookmark it in Firefox with special tags, too! hahaha) Is your master leaking at all inside, etc? Just seems to me that it would be getting softer and softer, not locking up more and more.....????? lol. Sorry, I'll stop throwing things atcha! lol.

Another reason I'm throwing things out with abandon, I suppose, is because, well, I'm thinking of doing SOME brake mods, ...and want to know whether I should just go new on the master, used on the booster(I've heard the boosters can go over 500,000 miles and still work fine, ...whereas, the Masters.....not so much, yah? lol)

yotarob2005

Well Mark if the master cyl doesn't help then I am out $80 but have a little more piece of mind in knowing that it is not a 14 year old part. I already bought one and will get it installed in a few hours, I'm tied up at a kids b day party right now, trying to post from my wife's stupid phone.

ChefYota4x4

iTrader: (5)

Hahaha, ...Oh trust me, I wasn't trying to steer you into anything, either way, bud Just invoking deep thought in ya! lol. Deep thought....great for lil kids Bdays! hahaha.

Hope it's the solution, first thing tried!

rworegon

Ok....this probably won't help much, but to my eye those caliper pins do not look like they have any caliper grease on them. I'm thinking that once the pads are heated up they are binding on the pins, thus seeming to lock the wheel. Then, as you say, 30 minutes later they had freed up....hmmm, because they had cooled down and were no longer binding??? Pull the pins, clean off the rust, put thin layer of caliper grease on the pins and give it a go.

yotarob2005

LOL, yeah right, fixing it on the first try never happens

Good in site, I'll pull them apart again and grease the pins.....couldn't hurt right.

The new MC is installed, I still need to bleed the brakes but my Mighty-Vac is out on loan and I don't have a helper to do it the old fashion way at the moment. Will update as soon as I get that done and make a test run.

ChefYota4x4

iTrader: (5)

Suweet, let us know. U gonna grease the pins while waiting for the bleeder assistant/tool?

rworegon

Doing the simple, easy things never can hurt unless they are the wrong things to do.

corax

before you replace the master cylinder, adjust the pushrod - if the master cylinder pistons aren't coming back all the way it will hold residual pressure in the system. Brake pedal should have a slight amount of play (not related to the MC push rod), but also make sure you're brake light switch isn't holding the pedal down.

The pushrod adjustment trick I learned was to put a dab of grease on the end of the shaft and then put the master cylinder in place. Remove the master cyl and look at how much grease is left on the end of the shaft. If there is zero clearance when assembled, the grease gets completely squeezed off the end of the shaft.