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So my master cylinder looks like it might have a slow leak. The metal on the body seems a little moist. I cleaned up body of the M.C, then added fluid to the reservoir for the front brakes (front resv was real low, but rear resv was full). Next I bled the brakes (3 different sessions). The pedal still seemed soft, and had to push hard to get brakes to work. I didn't see any obvious leaks after that. The break calipers look ok, and no leaks on calipers or the brake lines.

I went ahead and ordered a new master cylinder. My question is: How do you know if your break booster needs to be replaced? I saw another post where a Luv's master cylinder was leaking into the break booster. Once I pull the old mater cylinder I'll check to see if there's fluid in the booster.

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1980 Luv 4x4 with a 5 speed tranny.



"When all else fails, follow the directions".

Make sure to set the correct length of the adjustable rod between the booster & MC that regulates the piston travel.
Also make sure to bench bleed the MC prior to install, a piece of steel line 18" long cut in two will allow the open ends to be bent around into the reservoir.

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'78 Chevy LUV,1.9,4sp,headers,31's,SAS Dana 30,Dana 20,SOA rear w/Aussie Locker, rough body, bought new 12/4/78.
'87 Trooper,2.3,5sp,headers,31's,ball joint flip & spacer,Aussie Locker rear,Superwinch hubs,brush guard w/5.5K winch,more to come.

So I toke a 18" line, cut in half to get two 9" lines. Then put the rods into the reservoir (of the booster> This will provide a way to measure the adjustable rod? Once I get new M.C, and I pull of the old MC, I can take a picture if need be.

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1980 Luv 4x4 with a 5 speed tranny.



"When all else fails, follow the directions".

The open ends of the cut brake line put into the filled MC reservoir will allow you to bench bleed the air from the MC by pumping the piston with a screwdriver. This will reduce the amount of bleeding required after the new MC is installed. BTW bleed the brake lines with the engine running, the booster doesn't work properly without engine vacuum.
You'll have to fabricate a measuring device for checking the rod length as detailed in the second image. I used a piece of aluminum flat stock, a piece of thick plastic such as the hang tag from a socket or wrench would work also. I think you could also carefully use a combination square & not have to fab anything.

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'78 Chevy LUV,1.9,4sp,headers,31's,SAS Dana 30,Dana 20,SOA rear w/Aussie Locker, rough body, bought new 12/4/78.
'87 Trooper,2.3,5sp,headers,31's,ball joint flip & spacer,Aussie Locker rear,Superwinch hubs,brush guard w/5.5K winch,more to come.

So finally I bench bled my master cylinder, and hooked up my brake lines. As I start to pump the brake pedal to get the fluid going thew the lines, I saw I have a leak where the flexable hose connects to the brake caliper. The Bolt was a little loose, so I tightened it with a ratchet/socket. I wiped down the area, and started pumping the brake again, yet it still leaks in the same spot. The leaks is pretty steady especially when the brake pedal is pressed. I'm not sure what to do next. Maybe replace the copper washer that goes between the connector and caliper. In the picture you can see it's still leaking.

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1980 Luv 4x4 with a 5 speed tranny.



"When all else fails, follow the directions".

Is there a washer on both sides of the brake hose hole?

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Certified pilots, looking down on people since 1903.

I believe there is just 1 (at least that's my current setup). It's between the bolt head and the connector.

Should be 2...

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If you think no one cares, try missing a couple of payments...



FIAA!

SFPP!

Great info . My 78 has always had a brake drag . This has me investigating why .

It will leak if there is not one on each side of the hole on the hose.

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Certified pilots, looking down on people since 1903.

Thanks mytmouz and Luvr8. I must have misplaced the extra washer when I had everything apart.

At least you found the problem.

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Certified pilots, looking down on people since 1903.

I believe the thinking is that if your master cylinder was leaking into the brake booster, you should replace the brake booster as well because the brake fluid deteriorates the booster. I did mine a few years ago. The brake booster is cheap and replacement is easy while the cylinder is off.

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1979 4wd Mikado. G200, Gemini 250 Turbo, Clive Cam, Offenhouser Intake, JE Pistons, maXspeeding Forged Rods, Blow Thru Weber, Trooper 5spd, Intercooled