Awag

Hi, I have a 1987 951 that I use as a daily driver and is my first car -I love it. But recently I have been having some issues with a "ghost" brake fluid leak and now some AC problems (which is great now that it's starting to get hot an humid in KC). Somehow I feel like the two are linked so here is the breakdown:

I already had to fix the heater control valve arm for the AC in the summer because it got stuck. It worked great up until this morning, but now it's only blowing hot air like it did in the summer.

I replaced my brake fluid in October, then it started running low in March. I replaced it again in March, figuring that I hadn't put enough brake fluid in October, until the brake fluid light came back on again last week. I looked for any obvious leaks but did not see any.

My Verdict:
From what I have read I think that the brake fluid is pooling up somewhere and being sucked up into the vacuum system. The fluid in the vacuum system is then causing the heater/AC arm to get stuck. I am not a master mechanic by any means, but this is what I came up with. If this sounds even remotely close to what might be wrong, or if you have any ideas or advice please let me know. Sorry about the long message, and thank you for your time.

-Alex

PorscheDoc

The brake master cylinder is likely leaking into the brake booster.

Heater issue is either the heater control valve or one of the clips.

They are not related

Should be fairly easy fixes.

lart951

leaky, brake master, leaky clutch master or slave, or a caliper piston seal could also be leaking, in regards to the a/c, what the DOC said.

Awag

Thanks, I'll check them out.

Now that you mention the caliper piston seal leaking, both of my rear brakes need new brake pads. I replaced the front brakes a few months ago and instead of rebuilding the calipers like my mechanic recommended, I pushed the pistons back in using a huge set of pliers and replaced the pads (I read online that others had done it). It seemed to work well. Would doing the same thing to the rear caliper pistons when I replace the rear pads possibly fix the problem (if that's the case)?

User 52121

The fluid level will go down as the pads wear, since the pistons are extending further out of the caliper.

But going so low to trip the light suggests to me that you have a leak somewhere. If it's not obvious (puddles under a caliper or something) my guess is that the brake master is bad.

Had the master go bad in my Lemons car (86 N/A) and the booster was full of fluid.

(Edited out the bad info...)

PorscheDoc

Fluid in the booster isn't because the booster went bad, but because the master cylinder was leaking internally into the brake booster. That is the only way brake fluid can get into the booster.

User 52121

I know better than to post in tech threads before my morning coffee has kicked in. :/

Awag

Alright, it's probably a leak in the master cylinder, but I'll check the calipers anyways when I replace the brake pads soon. Thanks for all your input and I'll let you all know what it is when I figure it out.

Also just realized that prom is this weekend, so I'm going to need to figure it out before then... or else I can't take it haha.