Technical HOW TO RUIN A NICE SATURDAY

I am sorry to learn that your problem was caused by the use of Dot 5 fluid, but I am happy to learn that by just installing a new seal kit will solve your problem with the unit.
I also wanted to comment that I think your car shows superb workmanship.
Bob

 

Thank you Bob. That is appreciated.

 

I'm not sure if this belaboring the obvious, but I would suggest that while you have the unit apart for the rebuild that you check the bore of the housing for burrs where the ports enter or any other things that might score the O-rings.

 

Absolutely I will.

 

I've been reading along. Will you need to flush the Dot 5 out now before you put in the 3/4?

 

thoroughly. The tech suggested pumping a couple of reservoirs of DOT 3 through the M/C while the line is open prior to plumbing the bearing. He also suggested soaking the bearing in brake assembly fluid with the new o rings prior to assembly.

In case anyone is ever in my shoes and reading this post, here is the you tube video showing how to re-build the bearing.

 

good thing about the new urethane catalyzed paints they can handle getting a little brake fluid on them without softening up like the old lacquer or 1k products. if you get any on the paint just wipe it off then flush with water.
interesting [telling] that they posted rebuild instructions.........

 

I've been there before. A couple times actually. Now I always bench test the stupid things before I install them to also make sure travel & everything else is working correctly. I like to just hook it all up in the car externally that way I can include pedal travel into the equation (ask me how I found this out.) I recommend mechanical T/O bearings now!

 

52 Ford/Merc bell housing and a real throughout bearing, a fork and push pull rod and bellcrank will get it done with no leaks. Abunch of metal stuff that wont leak. Did it in a 38 Ford with flathead and Ford econoline 4 speed.

 

A bit late in the game for that.

I did push 3 reservoirs of DOT 3 through the M/C tonight. That should purge the DOT 5 I poured in initially. I should have the re-build kit tomorrow or Wednesday.

 

Sorry for the tough luck with the t/o, but thanks for the excellent posting and all of the suggestions and follow up. I planned on a hydraulic unit for my build for the clean look (hope to be at least half as uncluttered as you did......beautiful work)

Sent from my SM-G900V using The H.A.M.B. mobile app

 

It would be great if we could figure out why these seem to fail. I've had two of them leak first one was the cheaper one Speedway sells it was replaced with Ram lasted three months. Both were installed following instructions as to clearance, don't recall what type of fluid was used. System was replaced with a fork and cable been over a year and hasn't started leaking yet.. This car has a three finger pressure plate, I wonder if they will only work with a diaphragm style plate? Millions have been used as factory OEM without too many problems that I have heard of. It must be either aftermarket manufacturing is wrong or we are missing something in our installation / application. I would like to use one in my next project Cad 500 with a TKO 6 speed not much room left, but would like to drive it instead of tear it apart on the weekends.

 

Just a thought,but if available couldn’t you change out the seals to dot5 spec?
Are they lip seals or just o/rings?
I would of thought they are the only fluid sensitive parts in the throwout assembly.
You would have to consider your master cylinder seals and line as well though.
Just a thought.

 

If the dot 3 r 4 leaked what do you think dot 5 will do??

 

You need to go back and read... He was using dot 5 ..... McLeod recommends dot 3-4.

 

I read that you did the dimensional math; but the throw-out sure looks to be extended a long way in your picture, wouldn't hurt to go thru the numbers again.

 

Hose clamp. in frt.of t/bear. If you ever put 3 or 4 in any hydl. syst. NEVER PUT IN 5 OR SILICONE.

 

Still a killer build...we all make bonehead mistakes now and again. That's how we learn! Keep going. I want to see video of this thing rippin' up pavement!

 

That's some crazy ass short hand abbreviation happy stuff there..
I've read it 5 times and still not sure I understand what the hell it means and I don't care anymore

 

Bandit Billy, kudos to you for manning up, and telling us the reason the TO bearing failed. A lesser man would have blamed the manufacturer, or never told us why it failed. Good on you. Brian

 

I never understood why brake fluid is used at all. Why didn't they use hydraulic fluid? There are plenty of materials that can be used with it. It won't hurt paint. It doesn't absorb moisture and doesn't deteriorate over time like brake fluid does.

I don't know why they would use a seal that can't stand up to silicone brake fluid. Teflon seals would be a better choice. Did the master cylinder seals fail? If they had materials available for master cylinders that can be used with silicone fluid, why not use that same material in the slave cylinder?

 

I believe that it was the temperatures that a hydraulic fluid could withstand without breaking down.
https://en.wikipedia.org/wiki/Brake_fluid

Eventually, the new, synthetic hydraulic fluids may be a solution to this problem. They can withstand much higher temperatures before breaking down than the purpose designed brake fluids, but they still can't withstand the extreme temperatures that a modern brake fluid can.Bob

 

Hydraulic fluid will stand up to higher temperatures than the seals used in brake systems. The link you provided shows a high temperature of 260 for the modern silicone fluids while most hydraulic fluids can operate to at least 275 degrees. Hydraulic loaders use hydraulic fluid in their braking systems.

 

Possibly evaporation? I've spilled a lot of hydraulic oil, after a few days in the sun...it's gone. Never paid attention to brake fluid though, to compare.

 

Good point on hyd oil..Case in point: I have a Case skid steer [no pun] that is Hydro static drive..Uses 10-30 oil, engine oil, every where..In the drive system and the hydraulics all from the same reservoir.. There is an oil cooler in the system but operating temp is around 200°; have to let it run for 20 minutes to get temp up..So a 0-20w, I don't see why it wouldn't work..Trans oil in my car with 6spd runs at 160° so between the engine and the trans how hot can it get?

 

For over 50 years in the aviation industry, we used a product called Mil-H-5606 as brake fluid. It is a petroleum based fluid with a fire retardant. There recent upgrades to this fluid, but I don't think they matter for the purpose of this discussion.
Considering the fact that this fluid has been available for something over 50 years, is resistant to water contamination, and is cost comparable, there has to be some other reason that the automotive industry has not switched to the newer aviation type fluids.
The silicone brake fluid does overcome the water problem as well as the temperature problem.
Bob

 

I have a 720, into which I swapped a Cortina engine. I use synthetic hydraulic fluid, and although it is more expensive, there is absolutely no problem with immediate circulation when it is cold out. The synthetic engine oil I use, has a pour point of -60 F
Bob

 

I broke a steel brake line on a '57 chevy out in the boondocks once. Pinched the line off and filled the master cylinder with oil from my hydraulic jack and drove on with no problem.

 

It's an interesting topic to study.
For instance:
Almost everyone knows the brake fluid absorbs water right? Sounds sort of stupid and counter intuitive on the surface. But what that does is any moisture or water that does accumulate within the system never causes a problem. There will never be a drop or pocket of water or separation of water and fluid in the system. There will never be any water inside to cause corrosion. Yes it will draw moisture from the air too and that's why the extensive labeling on using a sealed container.
There's a bunch more too. Some is interesting and some rather dry.

 

Hygroscopic, except for DOT 5 which I am confused as to why it is on the market. WILWOOD says not to use it, McLeod says not to use it, not recommended for racing, etc.

I know, I saw that too. I will be re-working those numbers and adjustment as the bearing goes back together tonight after work.