My latest '75 model from Oregon came to me in parts, but mostly complete. I built a 2056 with Elgin cam and twin Weber 40 IDF's and am quite happy with the results. She has a decent kick and gets 30+ mpg cruising over 70 mph. One rear caliper was missing, but I had a newly rebuilt one and changed it out. I used my shop air with about 5 psi to bleed and it worked for the most part. My pedal is about 80% of where I would like it.

Q: where is the brake fluid going? I recently sold my 356SC that had the same issue, but it had a drip in the rear circuit. This time I cannot see leakage anywhere

thanks

Check the front floor inside the pedal box.

I agree
M/C most likely

Pull the rubber boot to check

Thanks guys, at some point it must reach the ground, nothing yet

Negative

Well - I guess when the floor pan is sufficiently full with 10 or 20 gallons of fluid it might start weeping out to the ground somewhere.

Check pedal box under the plywood close out ASAP. Carpet absorbs the fluid. Likewise, the brake fluid then destroys the floor pan paint, leads to rust. Generally it’s a giant mess and a PITA to clean up.

Nailed it. Hoping maybe I can limp along until the winter season.

Thanks all

The good news is that since brake fluid is hygroscopic, it cleans up easily with water.

thats not a super safe choice...
you could potentially have a full failure of your brakes...
the initial failure is a warning sign

its yelling...... "do not drive a car while the brakes are beginning to fail"

I suppose the fact that you posted on a public forum could be used against you were anything bad to happen and any one to be hurt... you would be negligent and responsible for anyone's injuries for having chosen to endanger others...



also... yes brake fluid is hydroscopic....
but it also eats paint and promotes rust better than anything....
so leaving it to pool... is a sure fire way to create rust in your floor pan
it also is really good and seeping in between layers of sheet metal and starting rust from inside the layers where you can not stop it...

cleaning it quickly is a priority... waiting a month or two is a bad decision.

and some folks are afraid to drive their cars in the rain...
brake fluid is 99times worse for creating rust than any rain storm...

brant

yea, yea, yea, I know whats right. Just fix the damn thing.

Thanks for all the guidance and brake fluid does a number on any paint finish, the floor included.

I have read there is an easy and no so easy MC, and have a new one from Stoddard on the shelf, suppose I need to get off my lazy &*@ and just do it

That's not good news and that's not what "hydroscopic" means.

It means that it attracts water and is soluble in water.

What it also means is that it will act as an oxidizer (an electrical process) that will eat the raw metal whereever it finds it.

Besides being a safety issue which is first a side hazard to weaken an already vunerable unibody frame.

Agreed with all the above, I was checking another project that happens to be on the lift and sure enough an area about 6" x 6" was void of any coating due to the nature of leaking brake fluid. I bet this is common and also commonly neglected. I'm going to gamble and put this off until she comes off the road in another month or so. It's going to be a long winter here in Buffalo, how bout them Bills?

I have had master cylinders fail with no prior warning on 2 of my 914s over the years (one of them even had no parking brake). Not something you want to experience. You are lucky enough to have been given a warning, LISTEN TO IT. Brakes should be taken VERY seriously.

Yes, if it's soluble in water, it cleans up with water. It does other things too, but I was responding the "mess" comment.

Point taken, she is on the lift and I will be going after it this weekend.

Brake cleaner is best because it gets rid of both the water and the fluid. The solubility just adds to the oxidation. Not good on a teener....it just leeches more into the grains of the metal.

my most recent brake system failure was the actual reservoir bottle had a small crack under the strap-band...

small leak that went down the seam under the fuel tank area... penetrated all of the metal layers and then dripped out through the seam of layers into the pedal area...

confused me at first because the MC was dry when I pulled the rubber boot...
but boy did it do a number on the paint... and the seam... and likely rust that will accrue even after flushing and washing it out repeatedly....

big mess...

Yep...that same thing happend to me on my 73. On paint...safest thing there is to add an emulisifier like Dawn with water. If the paint is already stripped off you are screwed anyway, just use the brake cleaner.

Thanks to all who replied, One more question: I have a new ATE M/C appears to match the failed unit to a T. I have the M/C on the bench, installed the rubber seals onto the steel tube ends, installed the new "washers" ( had to tap them in) and pushing, pushing pushing the new rubber seals into the M/C. I watched Ian's video and he mentions a "pop" sound when the seals are seated. I am unable to get a "pop". Is there another way to know if the seals are properly seated?

Measure and mark the tube with a marks-a-lot. I didn't feel it snap in either.

There is a much much much better alternative for brake fluid: silicone brake fluid. Among other things, it's not hygroscopic. It has a higher boiling point. It won't harm your paint or promote rust.

It's best not to mix with "conventional" types of brake fluids as it can creates so called "worms" when the different fluids interact. One of my projects this winter is replacing the 914's front suspension and rear trailing arms with 911 stuff along with the MC, all brake lines, pressure regulator, etc. A perfect time to upgrade to silicone brake fluid.

I've done the same upgrade to another vehicle of ours and it works as advertised.

Thanks Jack,

The jury is out for me with regards to silicone brake fluid. I need to do a bit more research.

Victory.

I had a new ATE master cyl on the shelf and got it in yesterday. Not too bad of a job.

Firm pedal, no leakage, reset the push button on the warning light switch.

On the road again

Silicone brake fluid can be problematic. It doesn't absorb water, true. But that means any water that gets in just sits in its own layer in the system. Not great for whatever it's sitting in. I've also heard stories of stuff growing in that layer of water!

In general, regular DOT4 brake fluid is more than good enough for our cars.

--DD

Thanks Dave, I have heard/read the same. I will stick with conventional for now.

Use what you want of course. For my money (and time), it's silicone brake fluid when appropriate.

Track car or street car? OK, don't use silicone brake fluid in your track car.

But, (and be honest) do you really flush your brake lines every 12 to 18 months?

"Water contamination also leads to corrosion of brake pipes, wheel cylinders, calipers, and master cylinders, resulting in pipe leaks, “frozen” cylinder pistons, accelerated seal wear, and the formation of sludge. Silicone fluids avoid these problems by being non-hygroscopic (not moisture-absorbing), while glycol fluids can absorb as much as 6% water just by being in a “sealed” automotive hydraulic system for a few years. This moisture is generally absorbed from the air. Some moisture even works its way into brake hoses. Most comes from master cylinder cap vents and resultant condensation in the air space above the fluid, and from allowing cans of brake fluid and master cylinders to remain open to the atmosphere for too long."

Being truthful, I have never changed brake fluid in any vehicle I have owned in 50+ years and never a failure I know of. I understand what the recommended cycle is, but always been lax in this department. Changing engine oil every 3,000 miles has been my mantra for the same time period. Call me old/stubborn it's ok

Uhmmm. Weren’t you the guy that started the thread with a failed master cylinder ?

Correct, it may have been the original. If so, I can hardly have an issue with anything close to 50 y/o

Could be a candidate for

I should have noted that previous post as being a sarcastic

Agree hard to complain if it was original. If it was an OEM 17mm part - don’t toss it. 17mm getting hard to find. So are 17mm rebuild kits but they are out there.
Measure it before you toss it. 19mm are dime a dozen so toss that if bad.

Has anybody tried this? I guess Summit is selling refurbished parts??

https://www.summitracing.com/parts/agb-mc39...l/914/year/1973

Has to be refurb. It's a 17mm.

I have used Summit with some success, but be careful with this one. Claims to fit our 914 with power brakes??

I had an ATE unit on the shelf

Their description infers it is new but the pictures are of an ATE 17mm cylinder.

Jim

From their website:
Raybestos PG Plus Professional Grade brake master cylinders are manufactured from precision castings for an exact match to your OE design. Their casting design features a reduced weight that does not stress the brake booster mounting. Raybestos offers more than 1,600 replacement models for vehicle dating from 1947 and up. Order the size and specs recommended for your application. When using PG Plus Professional Grade brake products, you can be certain that your replacement brake components will perform as well as your original equipment.

I would like to rebuild my old one, but cannot find a rebuild kit?

thank you

They are not easy to find but they are out there. Keep an eye on Ebay, and some of the parts houses that sell NOS parts.

I believe the NOS ATE part number is 3.0370.1517.2

That Summit part would be super interesting if it really is a rebuilt 17mm.

Thank you, if i can find one, I will post it for future users