Recently bought a '84 Ford F350 truck with utility bed. Got it for hauling stuff to/from the house & family property a few counties over.

Truck has some cab rust near the bottom and a tick probably from a lifter, but seems to run OK otherwise.

Went to run an errand today and noticed that my brakes felt unusually soft. Got my errands done and came home. Went out again a few minutes ago, again soft brakes. I tried pumping the pedal a few times (not stomping it, just pressing it in) and the brake light came on in the dash.

Came home, opened the master cylinder cover and found that the front compartment was completely empty. On the F-350, the front compartment (the smaller of the two) controls the rear drum brakes. The larger compartment is for the front disc brakes.



Without pulling any of the wheels I visually checked for dampness around the rear and front brakes and couldn't spot anything leaking.

I filled up the front half and started the truck.. brake light is still on (even with a few more pumps on the pedal).

Two questions.

1) What is the brake light trying to tell me?

2) Why are there two compartments in the master cylinder?

 

Brake light is saying there is a problem in the system.
2 chambers~ 1 front 1 back brakes. Not sure off hand which goes to which. Just follow the lines.

If you cant find a leak feel around the top of the floor mat. Might be leaking back through the plunger inside.

 

Anyone know what component of the braking system the brake warning light is hooked to?

I have a feeling I am going to replace the master cylinder and possibly both calipers and rear cylinders. The MC is pretty rusty on the outside and the fluid looks pretty nasty.

It would help if I could find out what exactly the brake light is warning me about.

 

The brake light is turned on by the proportioning valve that sits on the frame below the master cylinder. If it senses a large differential in pressure between the front and back brakes, such as when one side runs out of fluid, it will turn the light on. And the way the book says to turn it back off, after fixing the problem, is to stand on the brake pedal hard with the vehicle stopped. However, the valves are sometimes gunked up and don't like to reset once triggered.

I do agree that you should replace the MC, calipers, and wheel cylinders as your fluid shows there is rust in the system. And you should also replace the hoses - two in front and one in the rear. They are surely in bad shape by now.

 

Ok so new brakes all the way around. Fun.

I am having major buyer's regret on this vehicle. Spent way too much for it. The motor ticks but at least it doesn't belch smoke.

Thanks for the help/tips.

 

The brake warning light indicates a difference in pressure between the front and rear brake systems. If you follow the two lines from the master cyl they will come to a distribution block with the brake light warning switch with two wires attached.

When the rear brake fluid reservoir (smaller front most one) went empty and pushed air, that lowered the pressure in the rear brake system and triggered the brake light warning switch turning on the brake warning light.

Two failures that the brake warning light would indicate are one empty reservoir or a big leak in the front or rear system.

Edit: You guys type faster than I do.

 

What's the consensus on remanufactured master cylinders? They are half the cost of a new one. Are they as reliable and safe as the new part?

 

I would say to check the brake line that runs along the frame rail. That seems to be the first line to rust out around here, and mine is bad. I don't know where you're located, but up here in NY road salt just sits on that frame rail and chews up brake lines and fuel lines.

And I've heard horror stories of going through 3 or 4 remans before finding a good one. I'd recommend buying new, and if you go with reman, staying away from Cardone.

 

I'm running a re-manufactured one with no problems. But I got the best O'Reilly's had.

 

it its made by cardone, you don't want it! if its made by anyone else, it can be expected to work fine for you, just follow the instructions about bench bleeding it

 

I would say if it is not the flex hose going from the frame crossmember to the axle breather, it is likely the steel line running along the drivers side frame rail.
Unfortunately these seem to rust out behind the midship gas tank.

Fix the line and get your brakes back before you start throwing all kinds of parts and $ at a truck you're not happy with anyhow.

 

With it empty like that, you have a leak. You need to find and fix the leak before wasting money on a master you likely don't need yet. Get that nasty fluid out too. Little known maintenance item is flush the brake fluid every few years. I am also guilty of not following that maintenance... Be warned that the rear bleeders may not come out, or break off. Nice thing is that wheel cylinders are cheap. For those, don't bother with rebuilt, new is still cheap. They are generally not worth the effort to try to rebuild yourself either, they run many times under $10 each.

Did the pedal all of a sudden go down and the light come on? If so, you blew a line somewhere. The rubber hoses are generally suspect. If I recall though, the smaller portion of the reservior is for the rear. The point of having the reservior divided is so that at least half of the braking system still is able to work in the event of failure like that. The pre-1966 systems had one, and if you blow a line, you will lose ALL brakes. All cars and trucks post 66 are required to have two sections to the master like that.

 

i put in a rebuilt master cylinder two years ago. cost me like $20. I couldn't believe how cheap they are. That's without any discounts and from Advance Auto. Rock auto or another online supplier might be less. but watch shipping. They're cast iron and "heavy" in comparison to an aluminum one.

Anyway, regardless of my M/C i too have a mystery leak. It's not at the calipers, lines, or drums but my resevior seems to be low every so often. I still can't find it and constantly looking. Maybe this ford is as hungry as mine for some Dot3. Mmmmmm dooooot 3.

good luck, keep looking for that leak and let us know. OH on a side note, I have a feeling mine might just be a gasket leak at the cover. Still not 100% sure and even if so I still check for leaking fluid. Can never be too careful with brakes. That's one thing I don't like to "cheap" out on. My powerstroke rig just cost me $90 for two front calipers. I was hoping to just rebuild them but the piston in one of them was just trashed.

 

As the front pads wear, the fluid space inside the caliper gets larger, so some fluid will go there and stay there. Depends how much and how often you have to add if it is simply the calipers taking it up.

 

While I am usually on the side of "find the problem and fix it and it alone", in the case of brakes I deviate from that approach. In other words, I don't agree that you should find the leak and fix only it. That is because the nasty fluid shown in the picture indicates there is moisture in the fluid which has caused things to rust. And, those "things" are surely going to be everything the fluid touches.

You could spend your time finding and replacing the leak, which may be a hose or a line as has been suggested since you didn't see fluid at the wheels. But that is the tip of the iceberg and I believe you will be back to replace other components very soon - if they don't fail at a very in-opportune time. So, if you are going to use the truck I recommend fixing the brake system, meaning replace the M/C, calipers, and wheel cylinders. And, while you are there I'd look the shoes and pads over closely as well.