I searched but did not find the answer to this simple question---
How much brake fluid is there supposed to be in my reservoir?
I have a 1993 Breakaway with a Spartan chassis. I found the reservoir on the fire wall behind the generator compartment door. It is about half full. The markings and writing on it are not legible. My brake warning light is starting to flash on every once in a while, especially if applying the brakes on an uphill or downhill stop. Doesn't seem to come on on flat land. It did flash on once when I was holding the brake and pulled the parking on. Read in one of the search results that it could be a low brake fluid level.
If it isn't that, then what?

The reservoir should be nearly topped off. Now that doesn't sound too helpful!

But the brake reservoir should have the fluid completely sealed off from air becuse the common DOT 3 fluid will absorb moisture, which is undesirable. To accomplish this the reservoir has a gasket with an expanding section or two.

The general procedure is to partially collapse the expandable sections of the gasket, fill the reservoir nearly to the top, and install the gasket forcing as much air out as possible.

The expandable sections can compensate for the fluid expansion as it heats, such as after prolonged braking. That feature also compensates for a reduction in fluid level as the pads/shoes wear without ingesting air; the gasket expansion fills the void.

BTW, brake fluid is an excellent paint remover; modellers have used it for years.

Thanks Rusty. Your input is what I normally find in my cars. But the Breakaway has a "canister" for the brake fluid and I do not see an expansion gasket. I guess it still should be filled to the top.
Now I have to start figuring out where the fluid was/is going if it is emptying the canister...

Also make sure the master cylinders are full. Crawl under and bleed them. Cured my light flashing on.

Not sure this is related to the brake system or not, but I need to know just what this drain is in the Genset compartment of our '93 breakaway. I drained about a cup of fluid out of it to remove some moisture and it appears to be brake fluid but I'm not sure:



Here's a closeup. Note the drain tube below the blue faucet:



The liquid is dark brown and I'm happy to say it bears no aromatic resemblance to the black water tank...lol

Lou

That's the drain for the heater core. Can also be used to bleed the heater lines after a coolant change. There may be another such fitting on top (bleeder); look above this one.

Rusty to the rescue..

OK, so what is the liquid....Coolant? Should it be dark brown? If not, should it be completely drained/Flushed? (It originally had moisture in it.) Where does it get refilled?

Coolant. The color signifies nothing, as you don't know what went in there.

Change the coolant and the Cummins filter, which has additive the engine needs.

Rusty---I stand corrected. There is an expansion gasket in the cannister. I just did not notice it because it did not expand down to take up the empty space in the cannister. Could that also lead to air getting into the brake lines/master cylinders?
I filled the reservoir to the top and it is still full after making a couple of trips with the coach. But I am still getting the brake fluid warning light to come on at times.
I plan to bleed the master cylinders and brakes, at which time I will also be "changing" the brake fluid to new. Any special way I should do this? If this does not work, then I would assume I might have a bad master cylinder...

I can't be sure about the brake light; my system is entirely different from yours. However, the sensor is usually in the reservoir.

On some coaches, the brake light is also activated if the parking brake is engaged. Mine doesn't have one.

Since we were heading to the mountains this past weekend, I figured I better have the braking system checked by my mechanic. Well, we found the problem which was causing the brake fluid light to go on in the coach. The rear brake master cylinder was leaking fluid into the booster. I had no real back brakes on our last trip pulling a trailer. Must have been using the brakes on the trailer to help stop with the front brakes on the Barth. Having a "jake brake" on the coach certainly helped....
Since I had the trip planned, a call to Spartan and a FedEx next day delivery resolved the problem. We got the correct part and did an R&R and away I went with a full braking system again. I replaced the complete booster/master cylinder unit, which cost $669.72 plus $59.08 NDA charge. They might not be the cheapest guys selling parts, but Spartan does know what you have and what you need. And if you have a Spartan chassis, they stock just about everything your Barth may need to repair it. I haven't found anything they didn't have yet. But you have to be smart about what you NEED to buy from them and what you CAN buy from them. Sometimes it doesn't make good financial sense to purchase certain items from them. But I'm a happy and satisfied customer on this transaction

Spartan's prices are very competitive (not so for Gillig, I understand) and the service is unsurpassed.