MC Bleed

[Bookseeb]

Does anybody know the correct proceedure to bleeding the master cylinder on my 86'LC.

 

[Spook50]

You can either bench bleed it, or bleed it while it's in the truck. Disconnect the lines from it, and make up a small pair of hard lines that go from the fittings back into the reservoir. Fill the reservoir with fluid and just start pumping away until no more bubbles go into the reservoir. I already had mine out, so it was easier to bench bleed it (I put it in a vise and used a large philips screwdriver to actuate the piston). Also remember to depress the piston all the way to ensure that the entire MC is bled properly.

 

[Bookseeb]

Thanks Spook, I put that info to good use. Not exactly the way you described it (on the vehicle), my way required a lot more of a mess, but it got the job done.

Thanks, Brad

 

[schaats]

I want to suggest you buying of small hand pump kit from auto shop such like Autozone or Checkers.
It's not expensive tool but helps very much when you bleed your brake or clutch system alone because it have many useful adapters as well as hose and pump itself.

Oh, Min Seok

 

[muddogbob]

The easiest way to bleed the MC is to mount it up to the truck, fill it with fluid, and with the lines disconnected slide a large ziplock bag over the cylinder. push your fingers tight against the ports (on the out side of the bag). Keep them pressed tight while someone pumps the brake. This will allow the fluid to slide past your fingers into the bag when the pedal is depressed, and when it is released, your fingers and the bag will keep air from entering the cylinder. Fill the resivoir and repeat as necessary.


This is how I did mine and it worked well. Ez clean up too.

 

[Bookseeb]

Thanks guys, great info for future reference.

 

[sandcruiser]

Whatever you do, here is what *doesn't* work

Don't: try to use your fingers to block the holes while you tell your wife to pump the pedal Gently. It'll spray fluid all over the damn place.

When you do get a face-full of fluid but manage to keep your fingers on the holes, preventing air from entering...

DON'T say anything that your wife might hear as "again"

Because if you do, she'll pump again, and you won't be ready. This time you **really** get brake fluid everywhere. Including on your lips. That burns.

Of course, the pain and surprise will probably make you take your hands off of the master cylinder, so in addition to all the discomfort, you'll have made no progress at all.

Then you'll go ahead and fab up the short tubes into the reservoir and start over, doing it right.

Which is a better way to do it.

 

[muddogbob]

Whatever you do, here is what *doesn't* work

Don't: try to use your fingers to block the holes while you tell your wife to pump the pedal Gently. It'll spray fluid all over the damn place.

When you do get a face-full of fluid but manage to keep your fingers on the holes, preventing air from entering...

DON'T say anything that your wife might here as "again"

Because if you do, she'll pump again, and you won't be ready. This time your **really** get brake fluid everywhere. Including on your lips. That burns.

Of course, the pain and surprise will probably make you take your hands off of the master cylinder, so in addition to all the discomfort, you'll have made no progress at all.

Then you'll go ahead and fab up the short tubes into the reservoir and start over, doing it right.

Which is a better way to do it.

There is a lesson here somewhere.

I have never had a problem with the ziplock bag and finger plug method. When done properly it works, ez as pie.

 

[Pluton]

I just replaced the brake hoses on my mini truck, and bled all 5 locations and the pedal action was still soft. Then I noticed an easy M/C bleeding procedure (I think it was in the Haynes manual): Have someone put moderate pressure on the brake pedal. Wrap a rag around the brake line fittings on the M/C. Loosen the fittings to bleed into the rag. Do it several times for each fitting. I didn't see any bubbles come out into the rag, but it fixed the soft pedal and did no harm otherwise.