Gasket genius: We need you now!

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cruiser

cruiser

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Hi All: How many of us have owned a MOPAR product that DID NOT have a leaky brake master cylinder? Go to any junkyard full of vintage Mopar cars. Pretty much all of them show a great deal of firewall corrosion around the master cylinder, because they all leaked corrosive brake fluid onto the paint. The leaks are almost always from the master cylinder lid gasket. No matter what I do, I cannot stop my lid from leaking. And yes, I've tried all the tricks listed in this forum, short of replacing the master cylinder which I don't want to do because its original to the car. A local and reputable brake shop overhauled my original MC, and it works great but still leaks. We need a genius level designer to create a new gasket. Not rubber. They always leak. It needs to be made of some new material that fills the space between the lid and the MC body. Something that cannot leak. Maybe something thicker. We've solved problems like this before. If you're that genius designer out there, you can really help out the hobby with this decades - old problem. Lets solve this once and forever, and maybe you could make a lot of money doing this. Thanks for reading.
 
Remove m/c and belt sand the casting so its dead flat. Find a new oem gasket and cut up the old one. 1/2” wide seal ring off old gasket should work. Then put new one on and install cap. Will be a fight to get it locked in place but should work.

forgot, you have to wash the resevoir before re installing.

drive car. Realize it was a waste of time and upgrade the bloody thing already. If you are a purust, why the hell are you driving it?
 
New parts, then install Silicone Brake Fluid In the complete system.

Silicone Brake Fluid does not draw moisture and create corrosion like conventional brake fluids do.

Especially good for vehicles that sit for long periods of time.

Especially good for the multiple piston calipers like Kelsey Hayes and the Corvettes. Keeps them from seizing up from non use and corrosion.

Screenshot_20220109-194128_Firefox.jpg
 
The DOT5 fluid is a good choice if you don't want the paint hurt. That's DOT5, not DOT5.1. They're different.

Also, it's not good to mix DOT5 with DOT4 or DOT3 as the seals will swell and become useless. So that means you either have to flush the HECK out of the system, OR you could replace all the rubber parts. Kinda a pain if the system is already together.

It is also true DOT5 does not absorb moisture. That does not mean moisture doesn't get in the system. It does. It just does not mix with the fluid. So, it gathers "wherever it is" and accumulates. I'm not sure which I prefer in that situation.

I've always used DOT3 and just "dealt with it". But you're right. I too have never seen a master cylinder that's completely leak free. One reason is, they must have a vent in the cap "somewhere" and that normally is where the small amount of fluid comes from.
 
RustyRatRod said:
The DOT5 fluid is a good choice if you don't want the paint hurt. That's DOT5, not DOT5.1. They're different.

Also, it's not good to mix DOT5 with DOT4 or DOT3 as the seals will swell and become useless. So that means you either have to flush the HECK out of the system, OR you could replace all the rubber parts. Kinda a pain if the system is already together.

It is also true DOT5 does not absorb moisture. That does not mean moisture doesn't get in the system. It does. It just does not mix with the fluid. So, it gathers "wherever it is" and accumulates. I'm not sure which I prefer in that situation.

I've always used DOT3 and just "dealt with it". But you're right. I too have never seen a master cylinder that's completely leak free. One reason is, they must have a vent in the cap "somewhere" and that normally is where the small amount of fluid comes from.
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I bought a master cylinder once from I believe Master Power Brakes, and it had a label that said pretty plainly: "Do Not Use DOT 5 fluid". I have since seen others tagged that way as well. Any idea as to why?
 
dustertogo said:
I bought a master cylinder once from I believe Master Power Brakes, and it had a label that said pretty plainly: "Do Not Use DOT 5 fluid". I have since seen others tagged that way as well. Any idea as to why?
Click to expand...
The only reason I could possibly imagine is, they're afraid someone will mix the two fluids and cause them a warranty situation. Other than that, I got nothin.
 
DOT5 doesnt absorb moisture so this will cause rusting as the moisture isnt absorbed (kinda doesnt make sense but its still in there) DOT5 used to not play well with OEM rubber. That was the myth when it came out, but others have made the switch and not had issues. DOT5 is also (reportedly) more spongy when it comes to brake pedal firmness (cant be used in anti-lock brakes with fast modulation) . 5.1 is still glycol based, just the best temperature rating. I dont know, never used it but going to a remote reservoir Neon type MC is a plus as they dont leak (why not?) and they dont seem to corrode as they are plastic where they may vent (at the caps). Magnums went to a machined gasket rail and rubber gaskets on the valve covers, this was an expensive operation when trying to save a buck but they did it anyway....wonder why. Cast gasket surfaces suck!
 
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Get all the air outta the systems, so the fluid doesn't forcefully "geyser" back into the reservoirs
Yeah, I know, - " it's bled" ! . . . Is it ?
 
pishta said:
DOT5 doesnt absorb moisture so this will cause rusting as the moisture isnt absorbed (kinda doesnt make sense but its still in there) DOT5 used to not play well with OEM rubber. That was the myth when it came out, but others have made the switch and not had issues. DOT5 is also (reportedly) more spongy when it comes to brake pedal firmness (cant be used in anti-lock brakes with fast modulation) . 5.1 is still glycol based, just the best temperature rating. I dont know, never used it but going to a remote reservoir Neon type MC is a plus as they dont leak (why not?) and they dont seem to corrode as they are plastic where they may vent (at the caps). Magnums went to a machined gasket rail and rubber gaskets on the valve covers, this was an expensive operation when trying to save a buck but they did it anyway....wonder why. Cast gasket surfaces suck!
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Right, but you still don't mix DOT5 with any of the rest. That's not a myth. So if you're gonna use it the system either needs to be new and dry or flushed to the nth degree....how you would do that, and get all the DOT3 out, I don't know.

DOT5 is good stuff. "They say" it gives better pedal feel and all.....I've never noticed it....maybe my foot ain't sensitive enough. Matter of fact, Matt just called me recently askin about it, thinkin about changing to DOT5 on his builds for the paint reasons. All of his builds have seriously nice paint work so he has an interest there.
 
Please help me with this.....
How does one correctly flush the system of DOT3 and changeover to DOT5?
Appears to be the same issue/question in flushing out old OEM antifreeze and replacing with new OEM antifreeze.
Seems to me that you're always going to have some type of cross contamination.

Please educate me.... Thanks
 
Danny Boy said:
Please help me with this.....
How does one correctly flush the system of DOT3 and changeover to DOT5?
Appears to be the same issue/question in flushing out old OEM antifreeze and replacing with new OEM antifreeze.
Seems to me that you're always going to have some type of cross contamination.

Please educate me.... Thanks
Click to expand...
Right. It's a conundrum for sure. IMO, the only sire fire way to do it is to replace anything with rubber seals, flush the lines with DOT5 and refill the system with DOT5. IMO, DOT5 is really made for vehicles that either come with it from the factory, OR custom builds where it is originally installed. Pretty tough to get DOT3 out of everything such as distribution blocks, proportioning valves and residual valves. At least, that's my opinion.
 
Single pot master cylinders caps are not sealed look at the gasket inside the cap it has vent holes in it. Now look at a split system master cylinder it has a diaphragm gasket in the lid to allow the system to be sealed but still allow for displacement of fluid as it is lost to leakage or brake pad wear.
 
cruiser said:
Hi All: How many of us have owned a MOPAR product that DID NOT have a leaky brake master cylinder? Go to any junkyard full of vintage Mopar cars. Pretty much all of them show a great deal of firewall corrosion around the master cylinder, because they all leaked corrosive brake fluid onto the paint. The leaks are almost always from the master cylinder lid gasket. No matter what I do, I cannot stop my lid from leaking. And yes, I've tried all the tricks listed in this forum, short of replacing the master cylinder which I don't want to do because its original to the car. A local and reputable brake shop overhauled my original MC, and it works great but still leaks. We need a genius level designer to create a new gasket. Not rubber. They always leak. It needs to be made of some new material that fills the space between the lid and the MC body. Something that cannot leak. Maybe something thicker. We've solved problems like this before. If you're that genius designer out there, you can really help out the hobby with this decades - old problem. Lets solve this once and forever, and maybe you could make a lot of money doing this. Thanks for reading.
Click to expand...
 
cruiser said:
Hi All: How many of us have owned a MOPAR product that DID NOT have a leaky brake master cylinder? Go to any junkyard full of vintage Mopar cars. Pretty much all of them show a great deal of firewall corrosion around the master cylinder, because they all leaked corrosive brake fluid onto the paint. The leaks are almost always from the master cylinder lid gasket. No matter what I do, I cannot stop my lid from leaking. And yes, I've tried all the tricks listed in this forum, short of replacing the master cylinder which I don't want to do because its original to the car. A local and reputable brake shop overhauled my original MC, and it works great but still leaks. We need a genius level designer to create a new gasket. Not rubber. They always leak. It needs to be made of some new material that fills the space between the lid and the MC body. Something that cannot leak. Maybe something thicker. We've solved problems like this before. If you're that genius designer out there, you can really help out the hobby with this decades - old problem. Lets solve this once and forever, and maybe you could make a lot of money doing this. Thanks for reading.
Click to expand...
I used some make it yourself gasket material and made it the size of the MC and cut the inside out hollow. It was just thick enough with the rubber gasket the lid comes with to really make the MC lid tight enough not too leak.
 
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