Dot 5 brake fluid and leaking wheel cylinder’s

B

Bruce Newbery

Member
Dot 5 brake fluid and leaking wheel cylinder’s

In the past five years,I have been constantly having wheel cylinders leaking. The first set of wheel cylinders were offshore . I then purchased Raybestos wheel cylinders about two years ago and today,both rear cylinders are leaking and have contaminated the shoes. To my knowledge made in USA wheel cylinders are not available. I have been thinking of all new hoses,master cylinder and wheel cylinders and changing back to Dot 3. Do any of you have had similar problems. I am getting exasperated
 
Re: Dot 5 brake fluid and leaking wheel cylinder’s

I’ve had dot 5 in one of my 40s since 1995 with no issues. I’ve had it in my other 40 since 2006 with no issues. Both cars have all new steel lines , flex lines , wheel cylinders and master cylinder.
 
Re: Dot 5 brake fluid and leaking wheel cylinder’s

Same with mine Ken. 20 mears more or less. (I tried to use the plus over minus sign but won't let me do it here on the barn. Go figger.) Maybe it is not politically correct or somethin'nuther.
 
Re: Dot 5 brake fluid and leaking wheel cylinder’s

Lawson Cox said:
Same with mine Ken. 20 mears more or less. (I tried to use the plus over minus sign but won't let me do it here on the barn. Go figger.) Maybe it is not politically correct or somethin'nuther.
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Works here. Hold the alt key down, type 241 on the keypad, then release the alt key.
 
Re: Dot 5 brake fluid and leaking wheel cylinder’s

Have you tried to put residual valves on brake lines ? They will keep slight pressure in cylinders and seals seated. I had that same problem in my ´40 Stude. Not brake fluid related.
 
Re: Dot 5 brake fluid and leaking wheel cylinder’s

Lawson Cox said:
Kicks me off every time. Okay on emails, etc. Go figger.
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OK, "figger" this! Make sure your "NUM LOCK" key is illuminated. Coop


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Re: Dot 5 brake fluid and leaking wheel cylinder’s

±±± Well whadda you know. Y'all taught this old fart sumptin. Now, on to posting pictures. LOL
 
Re: Dot 5 brake fluid and leaking wheel cylinder’s

What are the right residual pressure valves for drum brakes? Brand / part numbers, etc..

I might add them in the future. Also, given that I have a single piston master cylinder, my guess is that I would only need a single residual valve (depending on how the brake lines are routed).
 
Re: Dot 5 brake fluid and leaking wheel cylinder’s

the original master cylinder has a residual pressure valve
 
Re: Dot 5 brake fluid and leaking wheel cylinder’s

I have new residual valves but noticed when I removed the. rubber boots on the wheel cylinders, I see leaking fluid and it looks like a black dust in the leaking fluid. It’s like the rubber in the piston cup is failing.Could the piston cups be defective. Rubber that is not compatible with dot 5 ?
 
Re: Dot 5 brake fluid and leaking wheel cylinder’s

Bruce Newbery said:
I have new residual valves but noticed when I removed the. rubber boots on the wheel cylinders, I see leaking fluid and it looks like a black dust in the leaking fluid. It’s like the rubber in the piston cup is failing.Could the piston cups be defective. Rubber that is not compatible with dot 5 ?
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Don't remove the rubber cups. All kidding aside, why are you removing the rubber cups> Is the fluid leaking THAT badly?
 
Re: Dot 5 brake fluid and leaking wheel cylinder’s

Yes some wheel cylinder/master cyl cups are non compatible to DOT 5. With that being said I have used very old kits with no bad results with DOT 5 years ago. I know for some time new and rebuilt master cylinder had a warning not to use dot 5 as it was not compatible. With the quality of parts all over the place now a days its hard to tell. Steve
 
Re: Dot 5 brake fluid and leaking wheel cylinder’s

I still use DOT 3 for all the old stuff. I've had similar age problems with both fluids so I use what ever was originally used by the manufacturer. I've noticed no real advantage of one over the other but they are not always interchangeable. The type or rubber used in cups & boots is not always crystal clear.
 
Re: Dot 5 brake fluid and leaking wheel cylinder’s

look for kits with cup expander attached to the springs, they were used on disc brakes/ drum brake cars without residual pressure valves——
My permanent fix to the hydraulic brake problem was to sell the car, got a 36 because it has reliable mechanical brakes
 
Re: Dot 5 brake fluid and leaking wheel cylinder’s

I measured all bores on wheel cylinders and they were exactly on spec. I found that the cups were soft and pliable. I took a new Raybestos cylinder apart and found that the new cups were very rigid and the fit was perfect and much stiffer. There is definitely a problem with a reaction of this brake fluid to the cup rubber. I bought new hoses, residual check valves ,wheel cylinders,shoes. I am changing to Dot 3 . I am also removing and flushing the lines with brake clean and alchol.
 
Re: Dot 5 brake fluid and leaking wheel cylinder’s

simply science dot 1 thru 4 are basically organic [ vegetable oil compounds] where as dot 5 is synthetic [not necessarily silicone ] the dot rating relates to boiling piont and water hydrcopity [the ability to absorb water ] and the same goes for brake rubbers they are not pure rubber but rubber compounds some later one actually contain no rubber at all so you need to check compatability or at least ask whoever supplies these parts what is the best fluid to use miss match is a ticking time bomb
 
Re: Dot 5 brake fluid and leaking wheel cylinder’s

I tend to go for dot 4. In my mind it is 1 better than dot 3.
 
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