Flushing Brake lines

[TJFred]

New to the site. Got an M151A1 from one of the regular posters here and am finally working on it. Brakes dont work and wanted to get them fixed before I tear it down. Looking in the master cylinder and the fluid looks like oatmeal. Was thinking about removing the master cylinder, cleaning it and blowing out the brake lines with air, after the lines are disconected from the wheel cylinders. Then flushing the lines with some type of solvent, MEK? Any thoughts out there. Thanks

[rickf]

If you are going to flush the lines with anything at all it should be alcohol but if the master cylinder looks that bad it is best to replace it, blow out the lines and then just run the fluid you are planning to use through the lines instead of any kind of flush. You are still going to have to remove the wheel cylinders and rebuild or replace so this is a good time to do a fluid conversion if you plan on doing so. It sounds like someone mixed DOT-5 and DOT-3 hence the oatmeal. The wheel cylinders will look the same.

[TJFred]

I do have a replacement master cylinder so I'll go that route. As to the wheel cylinders, is there a standard rebuild kit the can be bought a any auto parts store, or is this typical military stuff?

[SturmTyger380]

Not sure how often it gets updated, but I got this from clicking on the G838 Wiki at the top of the page:

9. Brakes

Brake Hose Clip CarQuest PN: BRK W72
Brake Hose Clip Napa PN: 80742
Brake Shoes for 1964 AMC American Oriley's p/n #433
Brake Hardware Kit Wagner PN: H7037 (Has all hardware as NAPA PN: 2215 to include the adjuster spring. 1 kit = 1 axel)
Brake Hardware Kit Napa PN: 2215 (All Springs, Hold-downs, and Backing Plate Rubber Plugs except Adjuster Spring: For 1 Axle)
rear 3/4 brake cylinders: Brake Best part number WC251660 or WC16535 (at O'Reilly Auto Parts)
brake shoe holder springs Brake Best # HDW1156
Wheel cylinder kit Napa PN: 127 (Includes 2 ea. boot, piston, cup, and 1 spring)

[Hambone]

If your bore is still good in your master cylinder, you can buy a rebuild kit for about $30 vs. $80 for new master cyl.

[rickf]

I do have a replacement master cylinder so I'll go that route. As to the wheel cylinders, is there a standard rebuild kit the can be bought a any auto parts store, or is this typical military stuff?

If you have an old time parts store where there are guys that still know how to use parts books then finding rebuild kits by cylinder size is not a problem. If you do not have that then it is better to just buy new cylinders. The A1 should have 3/4" wheel cylinders all the way around. If you take them apart and they are not rust pitted and the cups are soft and pliable then you can clean them up with clean fluid and reassemble them. Would not hurt to run a brake hone through a couple of passes. Spray cylinder clean with brake cleaner, coat with brake fluid and good to go. If you use new parts be sure to coat all new parts with brake fluid as you assemble them. And before you ask, DOT-3 or DOT-5, either will work just as well. Just be sure to only use one or the other and mark the master cylinder fill as to which is in there for future reference.

[Fil Bonica]

A couple of things to consider:
While doing all this work , consider inspecting all the flex rubber and replacing as necessary.
Removing and replacing the master cylinder is one of the most frustrating jobs on a 151
Patience and dexterity are essential.
Small children and people with sensitivity to foul language should be excluded from the work area while perfoming this task .
In any event
Good Luck

Fil Bonica

[raymond]

If your brake lines still have the fabric loom covering them, consider removing the fabric and inspecting the lines. The fabric holds in dirt and water and the lines will be more corroded where it is still intact.

Raymond

[m3a1]

I'm a fan of NEW. I've done quite a few brake jobs over the years and new wheel cylinders and new master cylinders can be had at a price that far outweighs the extra time invested and the risk of doing a rebuild improperly. Reading about it here and doing it are two different things.

Frankly, your health, safety and welfare and the health safety and welfare of the people you share the road with far outweigh the savings garnered by rebuilding parts that are fairly cheap to purchase brand new in the first place.

If you are new to rebuilding but want to learn, install new parts, save your old stuff and try rebuilding it when some extra money comes along.

Your Mutt's hydraulic brake system only works properly when everything is 100% because there is only one reservoir servicing all four wheel cylinders.

Any leak anywhere compromises the brake system's ability to keep and hold pressure.

As for the lines, I'm in favor of a good flushing and by that I mean making disconnects where there are disconnects and flushing those sections independently of one another. If you do it in that way, this job is a good time to replace those old flexible lines.

As for replacing the master cylinder, I don't agree that removing and replacing the MC is all that difficult because, as with most jobs on this truck it's pretty straightforward, with the notable exception of one particular bolt that is fairly well hidden and is best accessed by removing the headlight switch.

You will be miles ahead if you consult the TMs and this group before getting into it.

Cheers,
TJ

[halftracknut]

my 2 cents ...It's brakes.....replace it all..........

[Barlow L]

As for replacing the master cylinder, I don't agree that removing and replacing the MC is all that difficult because, as with most jobs on this truck it's pretty straightforward, with the notable exception of one particular bolt that is fairly well hidden and is best accessed by removing the headlight switch.

I would agree, 25 years and a hundred pounds ago. Not so much now,

Lee

[Fil Bonica]

The last few we have done we removed the the whole pedal assembly to remove and replace the master cylinder .
It sounds like a lot more work but I think it makes it easier in the long run..
If money allows a complete replacement makes a lot of sense.

Fil Bonica

[m3a1]

That's how I did it...removed the whole pedal assembly which provided an opportunity to clean everything up, inspect the bump-stops and have a good look at the condition of the brake light switch.

Not a thing wrong with rebuilding components (as one might have gotten the impression from my earlier post) but new parts vastly reduce the possibility of problems and in all, makes for a much quicker turnaround time on the job.

[TJFred]

Thanks to all. The master plan is to get the brakes working, drive it around to check out everything, it drove when I got it but had it parked for a while. (What are you going to do with that thing in the backyard. I think it would make a great flower pot.) Anyway its now parked in my shop. Then to do a restore. Its uncut and not a lot of rust. There is some post military modifications like a steel plate welded on the back and diamond plate on the floors. Holes drilled for a roll bar on the back fender tops and both front fenders damaged and rusted. As I progress I'll post pics as I know I get great ideas, tips and tricks from those who do the same. If it runs ok, it will save an engine and drivetrain rebuild. Not driving it at the Indy 500, so I'm not concerned the engine letting loose. Most likely will trailer it to events.

[m3a1]

Am I missing something or are there still no pics?