cleaning the brake lines and master cylinder

[Promise]

My M35A2 had no brakes, I added fluid to the master cylinder, still not brakes. I opened the master cylinder and found sand inside the master cylinder. I am going to replace it with a new one. But, I wonder about how to clean the rest of the system. I would like to clean the whole thing real good but I wonder if I need a special fluid to clean it or should I just blow it with and airgun. Any suggestions would be greatly appreciated. This truck is going from Chicago to Florida and then on a boat to Panama.

 

[stumps]

There is only one way to clean a brake system, and that is to disassemble all of the brake cylinders (master, air assist, and wheel) and wash them out. The brake lines can be flushed with brake fluid.

However, it is fairly unlikely that the sand in the master cylinder got into the rest of the system. Not all that much fluid moves when the pedal is pushed. Cleaning the master cylinder is probably adequate.

However, there isn't a deuce alive that could come from surplus without needing the brake system being completely overhauled. You have no way of knowing how it was treated in the past.

-Chuck

 

[roger-wilco-66]

When you swap the MBC and have things open anyhow, you could check the system for sand or crud step by step, e.g. first open the airpack cylinder and see if crud is inside (most likely, if the airpack has been bled for example), then dismount the first brake line and flush it with alcohol - check what's coming out here. If it's clean, your brake lines and whatever is further down the line is most likely not affected by the dirt in the MBC

However, I agree with Chuck, there is no way knowing how the brake system was treated, how long it has been sitting around collecting rust in the wheel cylinders, and so on.


Cheers,
Mark

 

[bsorcs]

This thread is just what I was going to start. There's no substitute for blind luck!

I'm in the process of changing or re-packing bearings, replacing all seals, and re-building the wheel cylinders. Rears done; fronts next [also new boots there]. I'm going to change the fluid as well...DOT5.1 to DOT5. Wheel cylinders are not being re-connected until lines have been flushed with alcohol and new fluid is in the MC.

The only brake issue so far has been slight leaks at the cylinders on the rear rear. So, the questions are:

1-Do I need to re-build the MC and the older-version air pack while I'm at it? I note that a re-build kit is about 37% of the cost of an NOS new-style pack.

2-If no to #1, can I just drain the MC and fill the pressure bleeder with alcohol [?denatured from HD/Lowes ok?] to flush the MC and lines? Re this, I do not want to run the alcohol through the cylinders unless absolutely necessary. I'll plumb all of the lines together with Tygon tubing to a single discharge point, but I have no idea if this would get me a complete flush. We'll see.

I need to get this beast on the road asap for a long boat 'recovery', so I prefer to defer anything that can be deferred until later, like the MC and air pack re-builds.

Comments/suggestions?

bs