I'm not sure what causes this, but this is the third time I'm pulling this apart. Last time, which was a few months ago, I even purchased a brand new wheel cylinder and installed it instead of rebuilding the one in it. It seemed to be fine and didn't notice any leakage of brake fluid. Tonight I went in the garage and notice fresh brake fluid on the inner portion of my rims and the backing plate on the lower portion were wet with fluid. It's always on the passenger side rear wheel? Am I doing something wrong here? or what should I look for that may be causing the brake fluid to leak this way. I'm done with these drum brakes and may have to break down and put disc in the rear.

 

It's hard to say what would be causing it. Being an mechanic, I've seen leaking wheel cylinders on 3 year old vehicles and 30+ vehicles still on the original cylinders.

Also calipers are not immune to leaking pistons. They like to spray fluid at you when you check the boots.

 

Make sure your shoes are adjusted properly. Mine were to slack and would allow the cup to be pushed right out of the wheel cylinder. Brand new cylinders, old and very used owner.

 

Does your truck sit a lot? That's the worst thing you can do to your brake system. My truck sits from November to April due to the cold, icy, winters here in the northeast.. I got tired of rebuilding my brakes every two years due to leaking wheels cylinders and went with Dot 5 fluid. Presto! No more leaks. Dot 3 fluid will absorb moisture and become contaminated. Never leave the system open for longer than you have to and never use brake fluid that has been previously opened...

 

I have seen my new wheel cylinders leak also. This gets disgusting after a while. I know what you are talking about.......Soon to look at the problem,and have 2 boxes of new cylinders for other f600 and will use them if I have to. Bill

 

My truck does sit, but not for long periods, I make it a point to drive it on weekends and Wednesday nites to the local cruise night. Since I'm in CA, we pretty much have year round weather to be able to drive. I'm getting tired of the drum brakes and these wheel cylinders, plus they are a pain to work on. I was looking into this company who sell rear disc conversions for our trucks. They say they use a 1985-1989 Cadillac caliber (my guess is for the emergency brake) They sell the brackets and rotor for $220 and you buy the caliber. I wonder if a GM caliber will fit also? The kit without the emergency brake is $379 complete The whole kit with emergency brake is $499, that includes everything. NO WELDING REQUIRED! I may want to go this way. Anyone use this conversion kit before?
http://www.steeltechsolutions.com/

 

I'd bet on this or dirty (moist) fluid.

As for the conversion, spending all that money when all you need is perhaps an adjustment or a $20 part seems like an over-reaction!

 

How many years did that "brand new" wheel cylinder sit on a shelf? Rubber will dry out over time, and pollution in the air will not help.

Rule of thumb...when buying "new" cylinders, replace the cups and boots.

 

You may want to check the double flared brake line as well. My first mustang had a slightly twisted line that had cracked and was leaking with madening irregularity. Took me almost two months to figure out the steale line was bad and not the wheel cylinder.

 

I complete redid the entire braking system this summer, new MC, lines, etc. Fluid is new, lines are new. The only that isn't new is the wheel cylinders, except the passenger side that I replaced one month ago. I've been considering rear disc anyways because they are so much easier to work on and perform better. I hate pulling drum brakes apart and putting them together. I wouldn't be surprised if the cups are old. I'm just tired of having problems with the drum brakes. Maybe it's a sign that they need to go. I'll replace the cups and everything for now and see what happens, if it leaks again, they're gone!

 

I know where you are coming from....with the big trucks....driving them every day is not going to happen,and sitting is bad for the brakes. I am going to have to go over my brakes for leaks and hope to be done with that. I am so happy to start on a F100 and little brakes and master cylinders and not lifting 100 lbs every time I change a tire-haha!!!! I hate leaks!!!! Bill

 

i got the same problem and the left rear shoes will come " out " at the top when it does . i actually had to stop in a store parking lot and take the tire off and the drum and back off the brakes and pinch the line off to get it home once . have not got a clue as i flushed the entire system rebuilt the master cylinder and replaced everything else with new as i didn't wanna take chances . i just figured ol' murphy was following me around and slapping me with his law upside the cranium .

 

See my new post " now I'm really stumped!"