going from dot5 to dot 4
Thread Starter
Burning Brakes
Joined: Aug 2005
Posts: 801
Likes: 1
going from dot5 to dot 4
Well just don't seem to have much luck with bleeding out the dot 5.I'm going try it a couple of more times.If I still can't get a decent pedal I'm thinking about changing to dot 4.Here's the thing.Everything in the system is new within the the last few months.I know the two ain't compatible with each othere.Should I replace all the seals and flush out all the lines or just flush out the mastercylinder and calibers and lines,blow them out with compressed air and call it good.
Le Mans Master
Joined: Sep 2004
Posts: 5,116
Likes: 5
From: Livonia MI
Problem with dot 5 is doesn't absorb anything, and when crud gets in the system, just lays at the lowest point and builds up. Blasting the lines with compressed air's a good idea, but running some solvent through, like brake cleaner's probably the next step.
Race Director
Joined: Jan 2000
Posts: 13,015
Likes: 2,260
From: Corsicana, Tx
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I've used DOT 5 forever with no issues getting a solid pedal. Has to be some air somewhere, rotor runout or something?
In fact just swapped calipers and rotors a couple of weeks ago for new aluminum ones and it bled quickly and had same great pedal.
JIM
In fact just swapped calipers and rotors a couple of weeks ago for new aluminum ones and it bled quickly and had same great pedal.
JIM
Melting Slicks
Joined: Aug 2008
Posts: 2,200
Likes: 3
From: Lehigh county Pennsylvania
I agree with JIM. Your problem is something other than the silicone brake fluid. I had all four corners of my brakes apart this spring while doing other improvements. I put them back together and bled them with my MityVac vacuum pump and topped up with new DOT 5 fluid...once and done...no problems. Don't blame your brake fluid.
Thread Starter
Burning Brakes
Joined: Aug 2005
Posts: 801
Likes: 1
I found a tiny seep right at the front brake line going into the mastercylinder.I hate cranking down hard on the fittings but it seems you have to to get the lines to seal properly.It wasn't dripping.I had to take a mirror and a bright light to find it.I have more fun with the brakes on this car than anyone should be allowed.I have owned over 20 vehicles over the years and worked on all of them.Never had this much fun getting the air out of them.That's why I kept thinking it was the fluid.I even boiled the junk and just pressurized the power bleeder instead of filling it up with fluid.This stuff dosent drip with just a small leak you really have to look for it.I will go at it again in a few days.It's time to walk away from it for a while.
Le Mans Master
Joined: Sep 2004
Posts: 5,116
Likes: 5
From: Livonia MI
Yea, doubt it's much to do with the type of fluid used, except the crud build up problem with non glycol based types. Dont know of any modern manufacturer using DOT5 in their product line, but some of the old school guys seem to love it. A buddy of mine with a 65' 396, wont use anything else.
Thread Starter
Burning Brakes
Joined: Aug 2005
Posts: 801
Likes: 1
Everything in its new.I doubt if there is any sludge in it.It's been flushed more times than I care to think about.Let it never be said I didn't have a lot of patients but it is starting to get old.
Melting Slicks
Joined: Nov 2001
Posts: 2,668
Likes: 43
From: Eastern US XX
I agree with JIM. Your problem is something other than the silicone brake fluid. I had all four corners of my brakes apart this spring while doing other improvements. I put them back together and bled them with my MityVac vacuum pump and topped up with new DOT 5 fluid...once and done...no problems. Don't blame your brake fluid.
Prefer the Pressure bleeder route, however - didn't have much success with the MightyVac. Haven't had any problems in years.
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