DOT4

[wrighthm]

I have been having brake issues for a while now and today I decided to finally get to the source of my problems when I believe I caused an even bigger problem. So my rear drums had been sticking and last week I took them apart and replaced the shoes, springs and drums. When I tested the pedal it was very sticky and did not return to its original position. Today I thought I would bleed the system and see how that would affect it. I noticed the rear flex line was very worn and when I bled the right rear cylinder dark fluid and bubbles came out. The fluid looked like it had come into contact with old rubber so I immediately thought I would replace the rear flex and see how that changed things. I knew I had a spare flex line so I went to get it and found it to be newly broken at the threaded part. I then came inside to the computer and brought up roversnorth to order a new one when I stopped by the forum. I then found that everyone was saying to use dot4 but not the petroleum based dot4. I had always understood that I was to just simply use dot4. I am almost certain I have used petroleum based dot4, not only today but also 6 months ago when I replaced all of my wheel cylinders and the front two flex hoses. I always thought my best rover buds were being snobs when they would say that they only used "such n such" brake fluid.

How bad did I screw up and could the rubber in my master cylinder be screwed as well? Is that why my pedal won't return to it's resting position? Should I replace my entire braking system when I get a better job??

I'm devastated, should I be?

[Apis Mellifera]

Read this: http://mgaguru.com/mgtech/hydraulics/ht115.htm

"D.O.T. 3 and D.O.T. 4 brake fluids are glycol-based, while silicone-based fluids are classified as D.O.T. 5."

Everywhere it says "MGA" read Series II and where it says "MGB, read Series III.

The bottom line is the rubber in braking systems is no longer actually rubber and thus it doesn't matter what fluid you use as long as what you add is compatible with what's in the MC already. I have used Castrol GT LMA, but have since switched to Valvoline Synth Dot 3/4. Despite the old wives tales, I've never had any type of fluid-mixing-related problem. I've used a variety of fluids in my oldest cars (MGA) to the newest ones (MGB and SIII). I think a lot of the stories about the catastrophic nature of using the "wrong" fluid or mixing DOT 3 and 4 are just that - stories. Heirlooms of the old days; not actually fact.

I suspect you have a collapsing flex hose(s). As the inner layer comes apart, it can act as a one way valve, holding pressure with the pedal off. The outside often looks perfectly fine. That's pretty common and as the old material degrades, it contaminates the fluid too, turning it black. That's normal when dealing with old components. Even new parts, if manufactured from sub-par materials, can degrade quickly. I've been particularly uneasy about the recent Chinese-made master cylinders for old British cars. I just replaced my SIII MC and the brake lines. The reservoir already has a few black particles in it.

Buy a new, quality flex hose from RN or have one made locally (it's generally cheaper and you can get it steel braided) and flush the black fluid out.

[cedryck]

Black contamination brake fluid.

Just a quick note,
You most surely want to purge the system of foul (black) brake fluid, It is contaminated, and will do the same to the rest of the fluid. It is a pain, but it must be done.

[bpj911]

brake fluid

I use regular whatever from the store. have never seen lma brak fluid anywhere for sale and after being in the brakes there is certainly no special rubber anywhere that i see

[wrighthm]

Thanks to all of you. I have ordered another flex line for the rear from our host. Should be here Friday and I'll be getting the exposed fluid out of the lines asap. I am very excited to finally get to drive the truck without feeling like I'm pulling a camper !

It is nice to know I can count on the forum in my most naive moments, thanks again