Rear brake fluid reservoir empty - refill? Bleed?

[stuartrubin]

I just noticed that the rear brake fluid reservoir is completely empty. I don't know how long it's been like this. (The FIAT owners manual tells you to check it every 300 miles!) I'm not sure what to do next.

Intuitively, I'm thinking that if it's empty, just fill it up, but I suspect it's not that simple.

Do I need to bleed the system?

Anything else I need to look out for?

Thanks!

Stuart

[kilrwail]

Check under the master cylinder for a leak. Also around the rear calipers. There's a good chance you need a new M/C.

[RRoller123]

+1. That is where mine started leaking. The seal goes on the Master Cylinder, where the plunger from the Vacuum Booster pushes in. Needed a new Master Cylinder. In my case, it ran down the inside of the lower fender and suspension parts and even down the inside of the wheel. Take a look there. It also could be leaking anywhere along the brake line going to the splitter in the rear too, or at either rear brake. Check those spots as well. At any rate, have to fix the leak before refilling and bleeding.

[stuartrubin]

Thanks for the responses. As you said, I guess I have to find the source of the leak first. Here come more stupid questions:

Can I just pour brake fluid in the reservoir, pump the brakes, and look for the drips? Is it that simple?

And even stupider questions:
If the hydraulic brakes are a closed system, and obviously when you actuate the brakes, fluid doesn't squirt back into the reservoirs, how does the fluid flow, when needed, into the master cylinder? What allows the fluid to flow in, but not out?

Thanks for indulging me. I'm the eternal noob here, but I'm trying! (I also don't want to find myself driving with no brakes!)

[RRoller123]

Yes, to your first question, and the fluid volume that actually moves is very small. It can flow back to the reservoir, as evidenced by the air bubbles that flow back in there when it is being primarily filled. It needs to have some small ability to flow somewhere for thermal expansion too.