Brakes dry

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patUSMC
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Joined: Tue Sep 20, 2022 8:00 am
Location: Ennis TX

Brakes dry

Post by patUSMC » Thu Jan 12, 2023 1:51 pm

Howdy
I have a 1980 AM general M151A2. The problem is the master cylinder reservoir is dry I have taken off the brake lines at the hubs and they are all dry. My question is how do I know what type of brake fluid was in it? I do not want to assume what type of fluid it had in it. I do not want to put the wrong flavor in there and have it gum up if there is any left in the lines. also the brake pedal went straight to the floor and will not come back up.


Rickf
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Re: Brakes dry

Post by Rickf » Fri Jan 13, 2023 4:50 am

If there is no silicone residue anywhere from a leak then it probably had DOT 3 in it since that will wash away with water. But not matter what was in it there is nothing now. Any fluid in the lines can easily be flushed out with new fluid put in the master cylinder and run through the lines before they are hooked up. Then you have your favorite flavor in there and ready to go. You need to remove the wheel cylinders to get all the fluid out of them no matter what so when replacing them they will be filled with your new fluid. In this case you have a completely dry brake system it is best to replace at least the wheel cylinders since the cups will be dried out. The master cylinder should be replaced also for the same reason and also because you don't know where the fluid went. It is not on the shoes so it probably leaked out of the master cylinder. These are a single stage brake system so any failure at all and you have no brakes. I always replace all of the brake parts on any old vehicle I get. Peace of mind. As far as brake fluid, I use DOT3 since it is readily available anywhere and much cheaper than silicone. Moisture in silicone fluid will always migrate to the lowest points, the wheel cylinders. DOT 3 is hygroscopic so moisture is held in suspension. That way when you flush your brake system every other year you eliminate all moisture with the old fluid.
1964 M151A1
1984 M1008
1967 M416
04/1952 M100
12/1952 M100- Departed
AN/TSQ-114A Trailblazer- Gone

patUSMC
G-Civilian
Posts: 2
Joined: Tue Sep 20, 2022 8:00 am
Location: Ennis TX

Re: Brakes dry

Post by patUSMC » Fri Jan 13, 2023 2:34 pm

Howdy!
Thanks will do!

Fil Bonica
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Re: Brakes dry

Post by Fil Bonica » Tue Jan 17, 2023 7:08 am

Another opinion,
Do as Rick said,
Replace all components.
Use Dot 5 to fill the system.
Over the years it was all I used in the five A2s I had.
Has a mechanical brake failure.
I had to flush and fill the system after ten years.
The old fluid was as new.
No signs of moisture.
Have a military assessment of fluids and it showed the benefits of Silcone.
While more expensive it is more effective.
Your vehicle.
Your choice!

Fil Bonica


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