Hydraulic Leak Between Brake MC & Booster

[amcordo]

Is there a seal or something between these two that may need replacement? Thanks!

[NickDawson]

If there is fluid then your master is shot. I think this is universally true, it was true with my rig...it should not be leaking behind the seal inside the MC itself. I just replaced mine - assuming everything else is in fine enough shape it should be a pretty simple job.

[amcordo]

Thanks nick! Did you have to remove the wing to do it, or is it just the two bolts I see. And will I need to bleed the brakes?

[bmohan55]

Mine looked just like that also, you need a new MC. Do it soon before the fluid degrades the diaphram in the booster as they are $$$. Yes you will need to bleed your brakes afterwards...it helps if you "bench bleed" the MC before you install as that cuts down on the air. Now I have "one pump brakes"!

I did not have to remove the wing (left hand drive), it was one of the easiest things I've done on my truck. Use a flare wrench on the connectors (brake lines going into the MC) to avoid rounding off the nuts and causing alot more work.

FWIW, I was told to avoid the rebuild kits for the MC as you really need to know what you are doing to get it right...and I don't.

[NickDawson]

Like Bmohan55 said, it was one of the easiest things I have done as well. Did not have to remove the wing on my RHD 88" either.

Now...bleeding the brakes was another thing... but I ran into a bad cylinder during the process.

I did not catch mine in time and lost my booster as a result... been living without it just fine actually but its on my list of things to fix soon.

[amcordo]

Ugh. I had no problem just dealing with it for a while, but you're telling me it'll destroy an even more expensive thing if I just leave it. I definitely don't want to spend $250 to replace the MC, but looks like I'll have to do it after the new year.

I wish RN or one of the parts companies offered a buyback program where they'd buy the old MC and refurbish it or something - it would soften the blow a little. Hint. :)

[NickDawson]

Ugh. I had no problem just dealing with it for a while, but you're telling me it'll destroy an even more expensive thing if I just leave it. I definitely don't want to spend $250 to replace the MC, but looks like I'll have to do it after the new year.


Not only will it damage the booster, but that fluid is nasty stuff (and inflammable!) - it ate through the paint and metal of my wing - fortunately the underside above the tire so it is not visible.

Give RN a call - I think they have a proline option that is a lot less - thinking I paid about $100

[siii8873]

my MC was leaking also. I purchased a rebuild kit but the problem was with the MC bore so it didn't fix the problem. I ended up buying a new one also.

[amcordo]

Can someone describe to me how to bench bleed the dual power mc for the 109? Thanks!

[NickDawson]

Can someone describe to me how to bench bleed the dual power mc for the 109? Thanks!

It was one of my first mechanical endeavors (read: verify these steps with someone who knows what they are doing)



keep the plastic "bolts" covering the outlets in place
Clamp the MC to something sturdy like a work bench or outdoor table.
Pour some brake fluid in the cup
remove the plastic bolt furthest from the plunger end of the MC
using a long handled screw driver or something similar, push in the plunger on the MC, repeat until you are covered in brake fluid
replace plastic bolt, remove the other plastic bolt
repeat step 5

Note, do not, as I did, stand so closely (for observation purposes) that you end up with brake fluid in your face.

you might even be able to cover the outlets with your finger, that worked for me when I lost one of the bolts....its like priming a pump, you are just getting the fluid into the outlets.

Its a 2 minute job - good luck and keep us posted!

[Terrys]

Not just because I am a Scot, but simply because properly rebuilding a Cltuch, or Brake MC, and wheel cylinders also, I only resort to new when the offending part is beyond honing. Lockheed, Lucas and Girling hydraulic components too expensive to just roll over and reach for the wallet. A wheel cylinder hone is all you need in the way of tools, other than a drill press or hand electric drill. If you have fingers like a gorilla, get someone to help, but, otherwise, all that remains is patience and a clean work area.
The easiest ones to rebuild are the cast iron ones. The aluminum ones tend to gall more easily, and as a result, many have grooves too deep to hone out. The worst ones are the old cast iron ones which have been sitting for years. Brake fluid is very hydroscopic, and the moisture acumulates in the bore, water being heavier than brake fluid, and eventually will pit the bores.

[amcordo]

Amusing and helpful. Thanks Nick!


It was one of my first mechanical endeavors (read: verify these steps with someone who knows what they are doing)



keep the plastic "bolts" covering the outlets in place
Clamp the MC to something sturdy like a work bench or outdoor table.
Pour some brake fluid in the cup
remove the plastic bolt furthest from the plunger end of the MC
using a long handled screw driver or something similar, push in the plunger on the MC, repeat until you are covered in brake fluid
replace plastic bolt, remove the other plastic bolt
repeat step 5
Note, do not, as I did, stand so closely (for observation purposes) that you end up with brake fluid in your face.

you might even be able to cover the outlets with your finger, that worked for me when I lost one of the bolts....its like priming a pump, you are just getting the fluid into the outlets.

Its a 2 minute job - good luck and keep us posted!

[scott]

i rebuilt my master a few weeks ago. i reinstalled it, hooked up the reservoir, left the out line disconnected, filled reservoir, had bro pump brake slowly until i could see fluid rising up in the port for the line. took about 2 pumps. pump'n slowly is critical or you get fluid squirt'n out and all over the place. connected the line then did the line bleed thing.

[amcordo]

OK! So I went and replaced the brake MC; super easy job as promised. Also, I must have stumbled onto a way of replacing it that doesn't require bleeding the brakes. Run the car a while, use it and use the brakes good so they're nice and warm. Shut off the car, and fast-like swap out the brake MC. Swapping it took me maybe five mintues and the whole time the fluid was still expanding from the warmth of the brake pads so it was slowly oozing out of the brake pipes. Bam. No air go it. Still have one press brakes.

Merry Christmas!