Brake fluid, somewhat Backdraft specific

[JayBar]

Ok, hear is the story. Dot 3 fluid in the clutch and Dot 5 in the brakes.

Well I have cooked my clutch fluid many times. Now with Ed's heat shield I think the problem is solved.

My brake fluid (Dot 5) has heated up at track events and gave me a very soft pedal.

Now in my reasearch on Mustang web sites nothing good has ever been said about Dot 5 fluid except it does not hurt paint. On the other hand there are some very high temperature Dot 3 -4 fluids.

So I purchased a supply of high temp Dot 3 -4 (purple stuff) and want to first put it in my clutch system. Then I want to change the Dot 5 out and replace it with the DOT 3.

My question is... is there a problem with the DOT 3 in the inter-workings of the BMW barke system?

If not, and it is ok to change, what is the best way to make a complete fluid change. Hopefully I won't have to take all the calipers appart but I want to do it right so, suggustions please.

[BUCKEYE COBRA]

Jay,
Running Dot 4 with no problems and no heat sheild. Worked great at the Mid-Ohio/London event.
Wrapped headers seem to make a bid diff in under-the-hood temps.
John

[jim ccc]

Jaybar

I dont know if you get the same products as us here in OZ.
I have had a lot of sucsees with Castrol SRF brake fluid.
Its not cheap but has worked.

You are obviously exceeding brake fluid temp.
I have seen temp strips that adhere to the calipper body that change color at different temps ,the same as disk temperature paint it may give you an idea of how hot it is actually getting.
It can tell you if your pads are suited to there designed temp also.
Because if they are getting torched the excessive heat will pass from the pad to the calipper pistons & into the fluid.

I built a turbo car that had a similar clutch problem the SRF & a heat sield fixed it.

Another thing that tends to get over looked is when you come in the brakes are hot dont sit with your foot one the brake as it boils the fluid because of the heat transfere and no air flow.

Hope I havnt over answered your question.
Just passing on what I have experianced

Jim

[Tommy]

Jaybar -
A similar question was addressed on the Corvette Forum recently. The answer simply stated was DO NOT MIX DOT 5 fluid with other fluids. Here's the link: Click here. Pay particular attention to comments by SWCDuke. He's a very knowledgable retired engineer from GM.

[JayBar]

Tommy,
Well I read it, and it is not really the same thing. First of all I said "Backdraft Spicific" because I have to know if the BMW components can handle Dot 3-4.

The part about taking apart the entire system does make sense.

[round_midnight]

The BMW components in the system (master cylinder, calipers) are designed for DOT-4 fluid. I have three BMWs, and run Motul RBF 600 racing fluid in them. It is great. No soft pedal ever. The only reason I don't run it in my Backdraft is that I don't know how to get the DOT-5 fluid out.

[JayBar]

Ok, that's the answer I was looking for.

On the removal of the Dot 5, maybe pump some cheap Dot 3 through the system, then pull the calipers, open them up, and clean out the remainder. I guess while they are open you could rebuild them but I assume most Backdrafts have less than 5,000 miles on them so there should not be much ware on them.

I just to be safe if "Mister Lucky" would chime in and tell me two things.
First: is the master cylinder a BMW unit?

And secondly if so what is the reason for the Dot 5 fluid.

Jay

[Tommy]

Jay -
More info for your consideration: Click here.

[MrMagoo]

Great article Tommy. If Jay is using DOT 5 in the brakes, you can see why he is suffering from mushy pedal feel: it's prone to the formation of large air bubbles whereas DOT 3/4 fluid allows for the breaking down of air so large bubbles don't form.

The important point for Jay: "If you have already changed to DOT 5, don't compound your initial mistake by trying to switch back. Just change the fluid regularly"

[tony martin]

HI GUYS,

WE HAVE JUST COMPLETED A I HOUR RACE OUT HERE IN SA.

WE ENTERED THE RACE TO TEST AND EVALUATE CERTIAN COMPONENTS,ONE OF THESE BEING BRAKES.

WE RAN HEAVY (FULL ROAD WEIGHT CARS) ON RACING SLICKS.

THE CAR I DROVE RAN FERRODO PERFORMANCE CERAMIC PADS(ON A FERRODO SCALE OF 5 THESE PADS ARE 3, ROAD RACE PADS) AND CASTROL SRF BRAKE FLUID.WE DID HAVE A SMALL HEAT SHIELD UNDER THE MASTER CYL.

THE BRAKES WERE STD. BDR EQUIPMENT WITH THE FERRODO OPTIONAL PADS AND BRAKE FLUID.

THE MASTER CYL WE USE(STD BDR EQUIPMENT) IS FROM ATE.IT IS MANUFACTURED FOR USE ON NISSAN VEHICLES.THE REASON THAT WE DO NOT USE THE BMW UNIT IS BECAUSE OUR CAR WEIGHT BIAS IS FAR DIFFERENT TO THE BMW.

THE CAR RAN FAULTLESSLY FOR 54 MINS. UNTIL A BACKMARKER TURNED INTO ME!! WE WERE LEADING THE GT CLASS COMFORTABALLY AT THE TIME.

TO GET BACK TO THE BRAKES.

PART OF THE RACE WAS IN DARKNESS AND THE DISCS WERE GLOWING RED.

THE PEDAL NEVER CHANGED AND THE CAR STOPED PERFECTLY,IN A STRAIGHT LINE, ON EVERY LAP.

THIS TELLS ME THAT THESE BRAKES ARE MORE THAN A MATCH FOR THE JOB.

IF U WANT TO RACE I CAN ASSURE U THAT THIS SET UP IS PERFECT FOR THE AVERAGE SPORT RACING.

LOOKING AT THE SPEC. I ALSO BELIEVE THAT MOTUL RBF 600 FLUID WOULD WORK AS WELL.

SHOULD U REALLY WANT TO RACE SERIOUSLY WE HAVE SOME EXCITING STUFF COMING.

AS TO MIXING THE FLUIDS,THIS IS SOMETHING THAT I HAVE NEVER DONE.WE NEED A SPECIALIST TO ADVISE WHEATHER WE NEED TO STRIP THE BRAKE SYSTEM OR NOT?

I AM SURE THAT THE SEALS WOULD NOT NEED TO BE REPLACED EVEN IF U STRIPPED AND CLEANED.

AN HOUR OF SPIRITED RACING SURE SHOWS WHAT YOUR SNAKES ARE MADE OF!!

NOW IF U GUYS WILL TELL ME HOW,I WILL TRY TO POST A FEW PICS OF THE CAR AND HEAT SHIELD.

DONT LAUGH,I AM JUST A CAR SALSMAN WHO TYPES WITH 1 FINGER AND JUST ABOUT KNOWS HOW TO TURN A COMPUTER ON!!

DRIVE SAFELY

PS. OUR SECOND BRD WON THE GT CLASS.

[thunder1]

[IMG][/IMG]
HI Jay,
hope to see you at the round up. Glad to hear the sheild helped you with the heat problem. I know it has helped my car.

[thunder1]

jAY
here a link I thought you and others might like. look how they did the cooling to brakes.
http://www.svtperformance.com/forums...t=Anthony+Dail
ED

[ROUSHAC]

Tony,

PM sent regarding posting pics/vids on Club Cobra.

Cheers!
Dave

[Nor Cal Al]

I was under the impression that Dot 3 and Dot 5 were not compatable and that you had to a teardown and flush if you wanted to switch? I am running Castrol in the clutch and I put a heat wrap around the clutch cylinder. Prior to that, I did cook the fluid once and have a replacement clutch cylinder and rebuild kit for the throwout piston to put in. The fluid was black like it had piston material in it.

[rdorman]

3&4 are not compatible with 5. You need to tear the system down and start from scratch to change. Valvoline synpower is about the best bargain on the planet and Wilwood 570 works for just about everything at a decent price.. both DOT 4 if I recall correctly. DOT5 is not generally recommended for performance applications.

[JayBar]

Ed,
Funny you should mention that thread on SVT forum. I bought that exact package from Anthony several weeks ago. I installed them. Pretty straight forward, and ran at Sebring. AS far as I could tell they worked well. But then I had the other issue with the brake fluid.

[JayBar]

Well I bit the bullet and changed from the Dot 5 to Dot 3. I ran 2 quarts of inexpensive Dot 3 through the system before I filled the system with ATE Super Blue. Seems to work ok.

[Capt H]

Does anyone know where to buy the heat sheild for a BDR.

[ROUSHAC]

Originally Posted by Capt H

Does anyone know where to buy the heat sheild for a BDR.

Check out this thread:

http://www.clubcobra.com/showthread.php?t=67979

Cheers!
Dave

[Capt H]

Thanks Dave!