Fun71

Finally got around to looking into an issue I noticed a few months ago when it was still too hot to work on the car. I pulled the Cutlass out of the garage and had no brakes. Checked the master cylinder and the reservoir was almost empty.
Hmmm.

Where did that fluid go?
No wet spots on the garage floor to signify a leaky wheel cylinder or brake hose.
Hmmm.

It was too hot to do much else so I just topped off the reservoir to see what would happen.

Got around to looking into it today and the reservoir is still full.
Hmmm.
I pulled the master cylinder loose from the vacuum booster and found dampness.
Dangit.
I just replaced this master cylinder in, uh, well maybe that was 1993.

It seems wierd that the master cylinder would start leaking while the car's been sitting in the garage all summer but then didn't leak after I topped it off. Maybe the difference between the intense summer heat and the cooler winter temps have something to do with it?

Anyway, time to replace the master cylinder. I see NAPA has a reman unit for $33 so I guess I'm off the the auto parts store now. Wait, maybe I should check my records first. This master cylinder may have a lifetime warranty.

oldcutlass

Make sure it didn't leak into the booster as that would eventually cause a booster failure also.

Vintage Chief

I like it when things which can go wrong, go wrong while you're still in the driveway. Lifetime warranty would be a nice find.

Fun71

Well no luck on the lifetime warranty. I found the receipt from Jan 1992 (my guess of 1993 was close) and it was purchased from an auto parts chain that we don't have here in Phoenix, plus no mention of warranty of the receipt. The cost back then was $19.99 with a $1 core charge.

Yeah I know about the vacuum booster failure due to the master cylinder leaking. That's what happened back in 1992. The master cylinder leaked into the brake booster, then later the booster failed. I siphoned a LOT of fluid out of that booster and it still failed, so I suspect this one will do the same.
Dangit. I just replaced that booster with a purty one - 7 or 8 years ago.

Fun71

Picked up the reman master cylinder from NAPA today and installed it. While I was in there with better lighting it was obvious that fluid had dripped down the face of the booster and onto the frame below. I had forgotten how long it takes to get all the air out during bench bleeding. Wow, that was a chore. Took it for a test drive and to fill up and things seemed to be working as expected.

Now onto the list of things that need to be addressed, unless something else pops up and takes priority.

Vintage Chief

Good deal.

olds 307 and 403

Exactly why I have put off swapping mine, Bench bleeding sucks.

1970greensupreme

look into motive power brake bleeders. They attach to the top of the master, hold fluid and you pump pressure into the container and start from the furthest and work you way to the closest. Use a bleeder bottle and it's a one person clean operation. I have used mine myself bleeding a complex system with ABS which are notoriously hard to get all the air out of and made quick work of it
https://www.motiveproducts.com/colle...nd-marine-kits

66luvr

I hate bench bleeding the master cylinder too, so last time I had to do it (which was a few years back) I made a junk tool to ease the pain on my hand.

Fun71

I made my own pressure bleeder for my other vehicles that have plastic screw on master cylinder caps. Bought another cap, drilled a hole, installed a brass hose nipple, and connected a hose from the cover to a trigger blow gun attached to my compressor. Prolly have all of $10 invested in that, lol. Just need to make a cover to use the same setup for the Cutlass master cylinder, but since I don't bleed the Cutlass brakes but once every 10 years or more, it hasn't been at the top of my to-do list.

Fun71

That's a great idea, I like it!