RenoHuskerDu Posted October 28, 2019 Share Posted October 28, 2019 After a couple months of being driven not-quite-daily, I found the brake fluid low. Because we'd never done the rear brakes, I figured it was time and expected to see a leaky wheel cylinder. No, they were dry. We did the rear brakes anyway. But now I'm scratching my head. This is a new master cylinder, just this year. How does this dual reservoir system work? It's not front and rear, is it. It's primary and secondary, I seem to recall. If there's no brake fluid traces on the wheel cylinders or calipers, no smell of brake fluid down on the driver floor area, and no traces of fluid leaking out of the dual reservoirs or master cylinder, then where could it have gone? I saw another thread out here where it was leaking out right at the cap, but as you see in the photo, that lip area looks solid on my brake MC. Link to comment Share on other sites More sharing options...
reamer Posted October 28, 2019 Share Posted October 28, 2019 out the exhaust? MC leak in to the booster, booster vac. in intake? Link to comment Share on other sites More sharing options...
Gary Lewis Posted October 28, 2019 Share Posted October 28, 2019 out the exhaust? MC leak in to the booster, booster vac. in intake? Yes, it can go out the exhaust. Or down the firewall, either inside or out. Or, out under the cap, maybe on the engine side where you can't see it. I had this on Big Blue. Link to comment Share on other sites More sharing options...
grumpin Posted October 28, 2019 Share Posted October 28, 2019 Yes, it can go out the exhaust. Or down the firewall, either inside or out. Or, out under the cap, maybe on the engine side where you can't see it. I had this on Big Blue. Did you check your front brake pads? As they wear the fluid will go down. Link to comment Share on other sites More sharing options...
reamer Posted October 28, 2019 Share Posted October 28, 2019 Did you check your front brake pads? As they wear the fluid will go down. That's an awful lot of fluid loss from pad wear, ….. Link to comment Share on other sites More sharing options...
RenoHuskerDu Posted October 28, 2019 Author Share Posted October 28, 2019 Did you check your front brake pads? As they wear the fluid will go down. I will check them. But there are reasons why we don't wear its brakes much. 1) We live in the country 2) We don't have big hills 3) It's a manual tranny 4) It's a 420 with only 160hp lol Link to comment Share on other sites More sharing options...
RenoHuskerDu Posted October 28, 2019 Author Share Posted October 28, 2019 Yes, it can go out the exhaust. Or down the firewall, either inside or out. Or, out under the cap, maybe on the engine side where you can't see it. I had this on Big Blue. OK, I'll bite. Out the exhaust? Link to comment Share on other sites More sharing options...
Ray Cecil Posted October 28, 2019 Share Posted October 28, 2019 OK, I'll bite. Out the exhaust? If the master is leaking fluid into the booster, the vacuum inside the booster can pull fluid into the intake of the truck, where it gets burned and goes out the exhaust. Link to comment Share on other sites More sharing options...
85lebaront2 Posted October 28, 2019 Share Posted October 28, 2019 OK, I'll bite. Out the exhaust? If the master is leaking fluid into the booster, the vacuum inside the booster can pull fluid into the intake of the truck, where it gets burned and goes out the exhaust. Diesel engines have a external vacuum pump, belt driven on Ford's that provides the vacuum for brakes, HVAC and transmission sinal on the C6. The two reservoirs are, small for rear brakes and large for the front brakes, the reason is the caliper pistons keep moving out until the pads are exhausted. I would look at the steel lines under the truck, in particular where the line turns from down the frame to go inward for the rear brakes, there is a low area that collects dirt and water and will cause the line to rust through (ask me how I know). Here is the best picture of the area I could find, red line is the brake line to the load compensating valve. Link to comment Share on other sites More sharing options...
RenoHuskerDu Posted October 29, 2019 Author Share Posted October 29, 2019 Diesel engines have a external vacuum pump, belt driven on Ford's that provides the vacuum for brakes, HVAC and transmission sinal on the C6. The two reservoirs are, small for rear brakes and large for the front brakes, the reason is the caliper pistons keep moving out until the pads are exhausted. I would look at the steel lines under the truck, in particular where the line turns from down the frame to go inward for the rear brakes, there is a low area that collects dirt and water and will cause the line to rust through (ask me how I know). Here is the best picture of the area I could find, red line is the brake line to the load compensating valve. That is good to know, and I thank you for it. But the larger of the two was the low one, which is for the front brakes. So I don't see how a leaky line to the rear could pull down the front brake fluid level. This truck was from central Cali before it moved to Central Texas, so it's about as rust-free as one could hope for. Link to comment Share on other sites More sharing options...
Recommended Posts