jennrichard

I have a 1997 Toyota 4Runner with 285k miles. Over the past 8 months or so, I have had NON STOP wheel cylinder problems. I have replaced the rear passenger wheel cylinder at least 7 times. I've also replaced the rear driver wheel cylinder thinking it may have been causing the problem. Every time I replace the wheel cylinders, I also have to replace the brake shoes because they become saturated. Within a week or two of driving, the wheel cylinder busts again. Just this week, I replaced the wheel cylinder, brake shoes, and drum thinking maybe the wear caused the pistons on the cylinder to expand too far and caused the cylinder to bust. Two days later, I have a puddle of brake fluid under my tire so obviously the wheel cylinder is blown AGAIN.

The only thing I can think of is that the rear brakes are getting overpressurized causing the cylinders to blow so I started researching proportioning valve problems. I have read up on the proportional valve and it doesn't appear that is the problem because I haven't noticed my back tires locking up (that I noticed). Also, my master cylinder doesn't appear to be the issue because it holds pressure until the wheel cylinder blows. I have a hard time believing it's the back plate causing the problem because I haven't done anything to the back plate to cause the holes to elongate.

What do I do? I am so frustrated! Any input is appreciated.

Thanks,
Jennifer

wyoming9

iTrader: (1)

Pictures would be a great help .

Going back to the start do you recall anything that happened that might have led to this problem ??

At any time was there any Brake Upgrades done ??

I need to ask just what brand wheel cylinders your buying ??**** Are they the correct ones for your application ??

If they are incorrect that might be the cause

Just who is doing the work by the third time the cause of the failures should have been figured out.

Just how are they failing ?? I am guessing expanding to far allowing the seal to travel outside the piston

Has the New brake drum been measured ? Quality Control Problems ?? In this day it might even be the wrong Drum

Brakes not installed correct ??

With the tension spring and self adjuster installed correct Top of the shoes seated in the wheel cylinder it is almost impossible for a wheel cylinder to expand enough to blow the seals out.

Are you seeing any loss of Brake fluid between the new wheel cylinder and the failure ??

If for some reason that wheel cylinder is not contracting allowing the fluid to be pushed out that brake will be locking up is a few brake applications which you say is not happening

The more the wheel cylinder expands the tighter the brake shoes would get to the wheel cylindercame apart .

So your brakes keep failing I guess as of now you have been very lucky and have yet to hit anything.

Now the big question your sure your wheel cylinder is failing causing a complete loss of brakes ?/

That you don`t have a failed seal causing gear oil to saturate your brake lining??

Not being up close and in person these are just my best guesses .

I would love to be hands on

jennrichard

@wyoming9 - The first time I started having problems with the wheel cylinder was several months back. Nothing was done to the brakes at the time that the wheel cylinder originally started leaking. As for the brand, I have gotten wheel cylinders from 3 different auto part stores, all different brands, with the same outcome. There are 2 options for my make/model: one for a 15" wheel and one for a 16" wheel. My tire size is 225/75/R15 so I have been getting the 15/16" bore size made for a 15" wheel. I have been doing all the work myself with the exception of getting help to put the springs on the brake shoes. Nothing visible was wrong with the drum but there was some slight wear and I wasn't sure if the previous owner had gotten them skin cut so I just went ahead and replaced it out of desperation. I don't think it even needed replacement as the new one and the old one measured the same. At no point in time have I lost brake pressure so my brakes are not failing per se. What's happening is, brake fluid starts leaking out the backside of my tire and leaving a puddle on the ground and saturating the brake shoes. It's definitely brake fluid leaking and it comes out pretty good just sitting idle after driving it for a little while. It doesn't appear that the old wheel cylinder pistons are over extended.

75w90mantraN

I would check again how the shoes are installed against the wheel cylinder. Like Wyoming said, if the tension spring and adjuster are correctly in position, the wheel cylinder would be right up against both top ends of the shoes. The fact that the issue followed from one brake job to the next leads me to suspect there's possibly an error with the install. Its easy to mix up which shoe opening takes the tension spring...
Do you have pictures of what it currently looks like with the drum removed?
It be hugely coincidental that all 3 aftermarket parts are duds right out the box.
My only other thought is whatever the wheel cylinder is connected to as far as the brake line system may be loose/overtightened/corroded...I dont have wheel cylinder removal experience so that be my guess.
Hope this gets sorted out.

jennrichard

I will take pics when I get home from work. I hope it's as simple as an incorrect install but I doubt that's the problem. My dad replaced the brake shoes the first time and I still had the same problem with the wheel cylinder busting. I really think there's a problem with over-pressurization of the rear brakes but I don't know why only one side is giving me the problems. The driver side has never leaked. I just replaced the cylinder and shoes on that side because I read somewhere that the differential pressure could cause one side to over-pressurize to compensate for the loss of pressure on the failing side.

akwheeler

Just what do you mean by "busting"?
"Within a week or two of driving, the wheel cylinder busts again."
"My dad replaced the brake shoes the first time and I still had the same problem with the wheel cylinder busting."
Just where is the fluid coming from? Inside the drum, or from where the tube and bleeder are?
Do you have one of the old ones still to show us pictures?
Having a lot of brake repair experience, but not knowing how yours are set up, I would make sure you are not missing something like the forward shoe and rear shoe will sometimes have thinner/thicker linings, so if you put both of the thick ones on one side and the thin ones on the other you might get issues.
Some of the wheel cylinders I have replaced in the past had a short "pushrod" that popped into the rubber boot on both sides that you needed to reuse from your old one, are you missing something?
I have a fire system exam in a couple of hours, but I'll look up the schematic of your brakes when I get a chance if you tell me it's from inside the drum.
please post pictures of both sides and forget about pressure being lower on one side making the other side overpressure, if there is one flexible brake hose going to the center of your rear axle and it tees off to either side there is no way for pressure to be different from side to side.

75w90mantraN

http://www.4x4wire.com/toyota/maintenance/rearbrakes/
For reference, just in case. System was bled and topped off, right? Brake line by the backing plate isn't leaking brake fluid?
Assuming install is good, axle leaks can also get all over shoes and tires.

wyoming9

iTrader: (1)

This confuses me the Wheel Cylinders are Failing but you have never lost your Brakes ???

I wish you were close I would love to see this in person !!

This will have my thinking till this is figured out

If it is leaking out the back it means the bleeder is leaking or the line into the wheel cylinder .

I have seen such poor quality that no matter what they don`t seal

Then How are the brakes getting coated in brake fluid??

If it is leaking inside the drum it can only be the cylinders are of such poor quality they fail within a short time.

Poor Quality made in China Wheel cylinders is why I spend the Extra Money and use only Toyota

This whole Bursting thing is confusing !!

Since we really don`t know your Driving Habits Yet are you hard on your brakes?? Getting things much Hotter then Normal

jennrichard

Here are a couple of pictures. You can see the brake fluid leaking out from the back side of the wheel. The brake line and bleeder valve were both bone dry so that's not where the leak is coming from. By busting (sorry for the southern slang) I mean that brake fluid keeps escaping from the wheel cylinders after replacement. Sometimes after I replaced the cylinders, I didn't have any problems again for several weeks. This time, I "fixed" it on Tuesday, drove it back and forth to work that night and Wednesday and by Thursday afternoon I had a puddle again. Maybe the wheel cylinder isn't the problem but if that's not what's leaking, I don't know what is.

@wyoming9 - I don't smoke the brakes on this car. I mean I hardly even get to drive it because of the brake fluid, plus it was down for several weeks with a bad U-joint.

Guess I need to just take it to a repair shop. I am a mechanic (not on cars) in my day job and replacing a wheel cylinder isn't exactly rocket science so I guess pride has kept me from taking it in. I am at a loss though... Brake fluid leaking out the back side of the wheel
Assembled brakes

75w90mantraN

You say you did the driver side shoes and cylinder and no leaks, so what's weird is why only one side? I'm leaning towards trying OEM, though it would make me wonder is there anything different about the driver side you did that perhaps you may not have done with the passenger...
Dot 3 fluid right? I know its obvious but just to be safe. Not too sure if these brake systems take dot 4 kindly.

jennrichard

That's what has me so confused too... why only one side is giving me trouble. The driver's side wasn't even leaking. I just replaced it because I read you should replace both if you replace one. And, yes, I use Dot 3 fluid

akwheeler

I think Wyoming was onto something here, I think you mentioned not loosing your brakes. If your master cylinder is still full and you still have a solid brake pedal your rear axle seal is leaking gear lube, not your wheel cylinder leaking brake fluid!

jennrichard

I bet both of you are right. That makes perfect sense and also explains a few other unanswered questions I had. I'll pull the rear axle and let you know what I find. If that's the culprit, you are both my heroes!

wyoming9

iTrader: (1)

Now brake fluid and gear oil smell nothing alike.

If you have been losing gear oil or not I sure would check the level in your differential You don`t need the expense of replacing a differential .

While Brake fluid leaking on the outside can only leak from the bleeder valve or the brake line connection .Yet your saying both are dry!!!!!!

There are always the strange and different exceptions but having this many wheel cylinders that had flawed castings would be quite a long shot

To back up if the Wheel cylinder had failed when you broke the brake line loose there may have been a few drips of Brake Fluid coming out not the normal amount you get from the gravity bleed because the Master cylinder is much higher then The Wheel cylinder

Gear oil will leak on both the outside and inside and make a big gloppy mess on the brake shoes

This is a learning Experience

Where you having any vibrations or noise coming from that side ??

Many times a bad bearing will cause a seal to fail .

Another good thing to check is that the differential vent is not clogged the build up of pressure will push gear oil out past the seal

Please keep us updated on what you find .

big red 95

i have an 04 tacoma i just replaced the lspv with a used part had to cut the lines and mak new was wondering if it matters were the feed lines go because i am getting fluid to it where i bleed it but i am not getting any through it to the brakes i am pretty sure it is hooked up right because i marked them befor i cut them any thing els i could check or did i get a bad valve

wyoming9

iTrader: (1)

Wow maybe your own thread would help.

Does your used valve have a guarantee??

You did check it worked before attempting to install??

Perhaps the lines going to the front brake tee are full of dirt or even disconnected

The tee on the differential might also be full of rust

akwheeler

jennrichard, did you get this figured out?

Noil

I've actually had both the wheel cylinder and axel seal problem ... My experience with the axel seal is that you will smell the grease when it starts getting hot when you walk around the back of the 4runner. My issues with the wheel cylinder popping came from the wrong size wheel cylinder, when I replaced the original I didn't realize that I was give one for a 15" tire size when I needed 16" tire size one. Both bolted up but the smaller one did not last long before it popped the plungers. This took a few changes / parts exchange to figure out. Check make sure your replacement is the right one.

fierohink

Sorry to bring up this older thread, but I think some people are looking for a resolution on the issue. Plus I want to add my observation.


If you are leaking enough fluid to cause a puddle and you have no need to top off the brake fluid, it isn't brake fluid you are leaking. Which in that area leaves gear oil coming from the axle as your only other option. Please check your fluid level and add as necessary. You don't want to starve those bearings off lubrication. The parts inside your axle can rack up like a cash register very quickly. I think you are leaking from your axle seal. Now whether that is a result of the seal failing or a bad bearing causing the axle to wander will require some additional investigation.

akwheeler

fierohink, there is no investigation required in that case, replacing the seal requires replacing the bearing since it's all pressed onto the axle shaft. I don't ever remember anyone getting the wheel bearing off without damaging it, let alone re-using it.