I have a '79 F800 in which the brake fluid is quite old. It seemed to be kinda milky, full of contaminants, and just looked too old to be counted on. I want to change it, but don't know if bleeding the brakes will get it all out. Should I just keep bleeding the brakes until the reservior looks clean, and then bleed a little more to get the lines and drum cylinders clean, or is there a good way to drain the reservior and then bleed the brakes? I have bled brakes before on other vehicles, but the fluid was never this bad before.

 

I just did this on my 99. There are pressure units you can buy that connect to the master cylinder in place of the cap and then fill them with brake fluid and then pressurize. You then go to each wheel cylinder and open it and let the fluid run until it is clean close up and then proceed to the next wheel cylinder. I did it the old fashioned way. Had the DW pump the pedal as I opened and closed the bleeder screw at each wheel. Did this until each wheel would bleed clean fluid. All the time I was refilling the master cylinder to make sure it didn't get too low. Cheaper and really not difficult to do. Used about a large can and a half of new brake fluid. If you bleed each wheel until the fluid is clean you should get all of the contaminated fluid out.

John

 

So bleeding the brakes somehow a normal way until the fluid is clean will get rid of the contaminants. Thanks - that's what I needed to know!

 

I just flushed my brake system also - but I did it with a vacuum pump. I bought one of those handheld pumps with a tiny little plastic jar that connects between the bleeder screw and the pump. I replaced the little plastic jar with a big spaghetti sauce jar with a couple of fittings I put into the lid. That gave me a lot more capacity (much better than dumping out the little jar every five minutes). I could then pump up the vacuum to about 20 inches or so and crack open the bleeder. Then the vacuum dies off slowly, so I can keep tabs on the master cylinder. Another tip - take an old turkey baster and suck out some of the old fluid from the master cylinder and replace it with new fluid - there's no sense in going through all this effort to pull old fluid through. I went through a lot more fluid - close to a gallon before I was satisfied with what came out of the bleeders.

 

I would start out by removing as much fluid as possible from the resevior (turkey bastor) refill with fresh fluid.
I was advised to put a piece of 2x4 or a rewd brick under the brake pedal to limit it's travel. My brake guru said this will keep the pistons in the master cylinder from traveling into unused portions of the cylinder bore that can become corroded over the years.
He said that if they do they can become damaged and you will need to rebuild or replace the mastercylinder.
Good luck and let us know how you make out.

 

Thanks for the tips. I decided to take some of them and extend them to the level of "I'm a nerd and I have enough equipment to back it up." See I'm working here at college for the summer on this '79 F800 truck, so it's a beast of a truck. I decided that it would be easier to do the vaccuum style of bleeding cuz I'm the only one working on the project. The local parts store didn't have a vaccuum pump, so I took one of the old vaccuum pumps that we have here (the big kind that you normally evacuate a large chamber with) and hooked it up much like a handheld pump (the kind normally used for bleeding brakes) would be hooked up, but to a 5 gallon bucket. It works ok, but the bucket collapses quite nicely in less than 5 seconds first I'm in the process of tracking something down that will work a little bit better.

 

L.O.L. That's funny.

 

Is there any good way to clean bleeded screws, or is it not worth it and easier to get new ones? They're completely clogged from all the junk in the fluid, for the most part. Also with that, I am replacing the brake hoses up front and probably in the rear. Should I do more than that cuz there is so much rust-like looking stuff in the fluid (i.e. each of the wheel slave cylinders or the steel lines)?

 

The Super Suction Brake Bleeder Setup
How badly the bleeder screws are clogged

The new bleeder screws are on their way and should be here later today...gotta love NAPA deliveries direct to the university Maintenance garage Note on the bleeder system - the little connector on the top of the green tank (the new vaccuum chamber after I found out that the 5 gallon bucket would just collapse in a matter of seconds) is what hose to the bleeder screw hooks up to.

 

Check the steel lines for rust (leaks or soon to be leaks) and replace as necessary.

I'm impressed you even got the bleeders out. I would rebuild the wheel cylinders. $5.00 a piece for the rebuild kits. Cheap insurance and you are already half way into the process. Be sure to clean the bores well after you run your hone.

Brake failure is not an option! Especially on that big *****.

A regulater or restricter of some sort might be in order for your vacuum tool! Wouldn't want to collapse those new hoses or run the resevior dry.

Keep us posted.

 

a vacuum rig would be nice to have. i don't so i use place a plastic tube on the bleeder screw, run it up 3-4 inches then down into a bottle with a little fluid in it. i have big tires so i place the bottle on a block so the down is not to long. i pump until the fluid in the tube shows no air and looks clean. after all wheels look clean i would definitely replace all cylinders and do this again. if you have the proper hone and know how to use one you can rebuild them, if not you can get a headache or worst.

 

Well the brakes are kinda on hold right now... The jack for the truck has been taken and used for jacking a house up, and it would really help to get the brake lines on. My boss also said that I should get the truck able to be tested with drilling so that we can tell if it's even worth keeping as a drilling rig truck or just a huge truck. The truck will (hopefully) be used for a drilling rig to drill for oil around here, which will train students to drill for water in countries like Honduras and Guatemala. I might even get a CDL out of the project, cuz the truck is so big that you need one to drive it legally.