russman7549

Hello,

This is my first post. If this has been covered before, I apologize.

I have a 1986 SR5 4x4 pickup. Recently, the passenger rear wheel would lock up sometimes when I applied the brakes a little harder than normal. Since the drums haven't been off since I replaced the axles shortly after I got the truck (2006?), I decided it was time to take a look. There was a lot of brake dust, buildup on everything but mostly on top of the wheel cylinder. The brake shoes looked to be about half worn down (compared to the new ones). I did notice a little moisture or leakage from the wheel cylinder but not a whole lot. It wasn't dripping onto the backing plate but I decided to change the wheel cylinder and brake shoes. I cleaned everything the best that I could, replaced the wheel cylinder (lost more brake fluid than I wanted), and replaced the shoes. I had to order the other wheel cylinder as there was only one auto parts store that had a lifetime warranty and they only had one in Knoxville. I put both drums and tires back on and proceeded to bleed the brakes.

This is where my trouble happens. I have a power or pressure bleeder that connects to the master cylinder and you pump the handle to generate pressure. I did this but stupidly, didn't add any fluid inside the pressure tank like you are supposed to so you don't pump the master cylinder dry. I let too much fluid out without checking the reservoir and got air into the master cylinder/lines. I bled the master cylinder then filled up the master cylinder then added about a pint to the pressure reservoir. I couldn't get any pedal pressure and then I remembered the proportioning valve needs to be bled also. I did that and got a little air out but still no pressure. I ran a lot of fluid through the passenger rear bleeder and kept getting air bubbles. I then remembered that the last time, I used teflon tape or plumbers tape on the bleed screw threads. This stopped the air bubbles.

Long story short: I ran 16 oz (a water bottle full) of fluid from all 4 wheels and the proportioning valve and still no pedal pressure to speak of. My logic was that there couldn't be any air in the lines so it must be a bad master cylinder. I thought that I may have pushed the pedal down too far when I was bleeding it and damaged the master cylinder. Since I have a lifetime warranty, no problem just get a replacement so I put that on today after I bench bled it according to the included instructions. The new master cylinder and had the same low or no pedal pressure. No I didn't bleed the lines since I didn't see any fluid come out of the lines when they were off (kind of like when you take a straw out of a drink with your finger over the end, nothing comes out until you remove your finger - suction).

I'm at a loss. I should also say that there are no leaks. I'm not loosing fluid as the level in the reservoir doesn't go down. Just for the hell of it, I looked at the lines and all four corners and can't see any leaks.

The only thing that makes sense to me is that there is a pocket of trapped air somewhere. Logic says it has to either be the proportioning valve or the new wheel cylinder.

I thought that I would ask some fellow truck people in case someone else had a similar issue and might be able to shed some light on my situation.

How could there be any air in the lines after over 16 oz of fluid at all four wheels and the proportioning valve have been run through? I should also say that during those 16 oz of fluid, I never saw any air bubbles at any of the bleed screws.

Any help or suggestions would be greatly appreciated.

I guess my next step would be replacing the wheel cylinder with the new one on order when it comes in if no one has any suggestions?

Thanks in advance,

Rusty

Vman455

FWIW, the factory service manual for 1991 says to bleed all 4 calipers and then the proportioning valve last. I would bleed the calipers again and proportioning valve (since you didn't after replacing the master, if I'm reading this correctly), see if that changes anything, check that the parking brake adjuster is working correctly, and then look at wheel cylinders.

snippits

Bleed it all again by the book. I have resorted to cracking the lines open and shut at the master cylinder. Of course you will need a helper to work the brake pedal, and some rags to catch the brake fluid. A good line wrench will make it easy.

wallytoo

iTrader: (1)

skip all the power bleeding and pump bleeding. use gravity bleeding instead. i've used this on my 4runners every time, and in any high-firewall mount application.

it takes longer, but as long as the master is kept half full or better, no air can get in. i do one bleeder at a time. no helper needed; this is a solo operation.

russman7549

Ok guys, I got it working. When I tell you what I did to fix it, you're going to think that I'm an idiot so let me preface that by saying that I haven't worked on drum brakes other that early Volkswagen since I got the truck in 2006 (I think that's when I got her).

After I got the brake shoes and hardware off and got everything cleaned off, I turned the threaded "star" adjuster all the way in to make it easier to get everything back together (so you don't have to stretch the springs farther to get them connected). I never turned the adjuster back out to take up any of the slack either before putting the drums on or after they were on my using the "sight hole" from the backing plate. This means that there was enough distance from the shoes to the drums for the shoes to expand out farther than normal before touching the drums (if they ever did) and making the pedal go down almost to the floor making me think there was a problem.

Tonight, I took the plug out of the sight hole and used a small chisel and turned the adjuster until there was a slight drag when spinning the wheel (obviously had axle on jackstands). The direction was up to expand the shoes and down to make them come back in. The adjuster will only turn one way unless you press on the retaining lever.

Having said all of that, in my defense, VW doesn't use a threaded adjuster. They use a tapered piece of metal with groves and pulled down by a spring. When you put on the brakes and the shoes expand, the spring pulls the tapered metal shim/adjuster downward (getting increasingly thicker as it goes down). Since there is nothing to adjust manually, I wasn't used to doing that and I didn't do it on the truck.

That is something that I won't forget for the next time no matter how long it is until I do the next one.

I wasted close to three quarts of fluid and about a whole Saturday of time.

I appreciate the suggestions on how to fix this issue.

I wanted to say what fixed this issue just in case someone made the same mistake that I did.

Thanks again everyone.

Discombobulated

No judging here dude!!!! A thread helps someone else for years and bonding with your truck is always a fun time…..even if you cussed at it a few times, thought about cheating on it with a new truck, looked at it with disgust, but in the end job well done and you still love your truck!!!!! Thanks for reporting back!!!!

HSHSURF

Oh man, you're my hero! I'm working on this very project right now, along with rebuilding the LSPV system. If I hadn't read your posts I probably would do the same thing. You saved me some major headaches with this reminder. Thanks!

russman7549

I'm glad that my situation was able to help someone from hopefully not making the same mistake.

Thanks for the kind words.