Troganin Posted May 13, 2009 Report Share Posted May 13, 2009 I am over hualing the brakes on my '48 plymouth. Both passenger side drums are leaking fluid. When I disambled the cylinders there was alot of rust on the inner bore. Is there any methoid to preventing rusting and subsquent failure of the piston seal? I have been looking into the possible switch to DOT 5 fluid. What are some issues that I would encounter with the swap? Quote Link to comment Share on other sites More sharing options...
TodFitch Posted May 13, 2009 Report Share Posted May 13, 2009 There have been many, many threads on this topic on this forum and on every other old car forum which I frequent. At the risk of being repetitive, my opinion -- and I stress the word opinion, is as follows: Changing from DOT3 to DOT 5 (or the other way) is best done when all components are replaced. Most of the horror stories are from times when a change in fluids in an existing system is attempted. Two hypothesises are typically given: 1) The fluids are incompatible despite official information to the contrary. 2) One of the suggested procedures is to use alcohol to flush the old fluid out and that the alcohol damages the rubber components. DOT5 foams a lot easier, so any agitation of the fluid while filling gets more air into the system. This can make a DOT5 filled system much harder to properly bleed. For racing, DOT5 apparently results in a soft pedal when the brakes get really hot. So those are the negatives that come to mind. For DOT3 two big negatives for me in a collector car: 1) It damages paint. 2) It absorbs water from the air and results in corrosion failure of components where water can collect. Quote Link to comment Share on other sites More sharing options...
desoto1939 Posted May 13, 2009 Report Share Posted May 13, 2009 I converted my 1939 DeSoto to Dot 5 back in 1988. I have not had any problem, nock on wood. You did to use denatured alchol to flush the old dot 3 fluid from the system. Do this several times. If you then flush via the blleder screw into a clean jar you will notice that the two fluid will float at differnt levels. Keep flushing untl there is only one type of fluid in the jar. Put on new fresh hoses, cwheel cylinder cups and internal cups. Make sure the brakes are adjusted properly. Do not tamper with the eccentrics if you have the Lockhead brakes. Pour the fluid in slowly to the MC do not shake the fluid maybe even let it sit over night then start the bleeding of the lines. I assume you willnot be racing with the old car. At least every month go out to the car and pump the brakes this will also insure that the entire system is functionaing and keeps everyhting moving. I do this during my winter months. Rich Hartung desoto1939@aol.com Quote Link to comment Share on other sites More sharing options...
oldmopar Posted May 13, 2009 Report Share Posted May 13, 2009 Dot 5 gets my vote I have used in 5 vehicles over the 5 or 6 years sold 2 of the cars to friends still no brake problems. However as Tod pointed out they were all in vehicles where every part of the brake system was replaced or rebuilt Quote Link to comment Share on other sites More sharing options...
George NU Posted May 14, 2009 Report Share Posted May 14, 2009 One other Option is to go stainless linners in All Cyls , and Put your filler reservior up in engine compartment out of dirt and Moistures way ,as the cap is where the Air goes in every time you push the pedal ,and where is it ? Under the floor with all that nasty stuff you drive thru ! LOL ! To Me, this, along with the Fluid change out is The best of the best! Nu Quote Link to comment Share on other sites More sharing options...
1949P17BC Posted May 16, 2009 Report Share Posted May 16, 2009 DOT 5, replace all parts at the same time and/or really clean the existing system Quote Link to comment Share on other sites More sharing options...
Troganin Posted May 16, 2009 Author Report Share Posted May 16, 2009 Thanks for all the advice that everyone has offered. When I get to the frame up resto I'll replace all of the lines and rebuild the master and cylinders. For now I just like to get it back on the road for my summer driver. As it has been sitting all throughout college. I'll just have to go out and pump the brakes every once in a while when it sits and hope that will fight off the rust. Thanks again. T Quote Link to comment Share on other sites More sharing options...
Plymouthy Adams Posted May 18, 2009 Report Share Posted May 18, 2009 one thing to conside when using dot 5 is the dye..not so much an issue with these cars and tucks but newer ones with plastic reservoir and maybe someone here has a remote plastic style reservoir..bea careful..it will stain the body and make it appear at quick glance to still be full of fluid when in fact it could be at empty....have seen this a few times..just be aware is all.. Quote Link to comment Share on other sites More sharing options...
Troganin Posted May 18, 2009 Author Report Share Posted May 18, 2009 Thanks for the tip. Thats one of those things that doesnt occure to you untill its to late. That would be more eciting then the burr I had in one of my cylinders that caught the pistion. Quote Link to comment Share on other sites More sharing options...
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