Brake Bleeding Surprise

[Mister P]

On the drive back home after getting the car inspected (1983 911SC) the brakes began to feel spongy. Please note that I am NOT nearly as mechanically inclined as most everyone else on this forum but I figured that I needed to bleed/flush my brake lines to get any air out of the system. The brake lines haven't been bled in a very long time. Purchased a Motive Power Bleeder to do the job and all was going well until I brought the pressure up to 10psi and let it sit as instructed to make sure there weren't any leaks in the system. That's when I noticed fluid running out from under the car and the pressure in the bleeder was dropping. It wasn't leaking around the master cylinder but out of a perfectly round hole in the under pan (see photos) at the front of the car, about two feet from the master cylinder location.
Any suggestions as to what is going on? Is that hole just a factory weep hole?

[blucille]

ah yes. There is an overflow tube on the reservoir. The easy fix is to just clamp the flexible hose that attaches towards the top of the reservoir to prevent the air and fluid to be driven out that overflow.

[Mister P]

Thanks for replying so quickly, blucille.

The attached photo shows what I had done to the overflow. I disconnected the original line and attached a section of flexible tubing clamped off at the end. Is the tubing too long or did I overlook something else?

[tsuter]

You need to find the source of the drip leak first. Is it the braided overfill line that maybe had fluid in it and then when disconnected dumped it out the bottom? Or is it from that nylon line?
Or was it already leaking somewhere else and that's why the brakes got mushy so when you went bleeding the pressure pushed oil out somewhere but not at the overfill and not at the bleeder valve you opened...

[Mister P]

It wasn't a drip leak, fluid was running out of the hole until I released the pressure in the Motive Power Bleeder. I don't think it was leaking prior to the spongy braking and there weren't any fluids on the garage floor. I can't work on it anymore today so I will have to check it out again tomorrow.

Thank you

[blucille]

seems to me, the next thing to check are the flexible lines from the reservoir to the master cylinder.

[Cory M]

Exactly. Those flexible braided lines from the reservoir to the master get brittle over time and can leak when pressure is applied. This happened to me with a motive bleeder as well. Check and see if it's leaking onto your pedals.

[snbush67]

Check the brake light switch at the master cylinder. It’s an easy replacement fix for a contortionist with tiny hands.

[Mister P]

The flexible braided lines were indeed wet as Lucille and Cory M suggested so I ordered new lines ($67, ouch) and installed them. I tried to make sure that they were on as tight as possible and went through the Motive pressurizing routine again, only to find fluid leaking out around the "nipple" of the reservoir. I am thinking that the reservoir might have a small hairline crack in it that only makes itself know under pressure so I just ordered a new replacement reservoir ($95, ouch, ouch) and will see if that fixes the problem.

I have a couple of other questions; first, is the fluid in the Motive still good to use with all the pressurizing then releasing the pressure that I have been doing or should I add all new fluid?
second, the rubber grommets into the master cylinder got worked over pretty good while trying to get the flexible lines off/on. I hope they will be ok because I don't seem to find where they can be purchased separately.

[Mister P]

auto correct messed up. blucille, not Lucille!

[PCA7GGR]

"You picked a fine time to leave me blucille."

[pmax]

Originally Posted by Mister P

The flexible braided lines were indeed wet as Lucille and Cory M suggested so I ordered new lines ($67, ouch) and installed them. I tried to make sure that they were on as tight as possible and went through the Motive pressurizing routine again, only to find fluid leaking out around the "nipple" of the reservoir. I am thinking that the reservoir might have a small hairline crack in it that only makes itself know under pressure so I just ordered a new replacement reservoir ($95, ouch, ouch) and will see if that fixes the problem.

Or just leaking around the nipple to hose seal ? I use speed bleeders instead of the Motive.

I have a couple of other questions; first, is the fluid in the Motive still good to use with all the pressurizing then releasing the pressure that I have been doing or should I add all new fluid?
second, the rubber grommets into the master cylinder got worked over pretty good while trying to get the flexible lines off/on. I hope they will be ok because I don't seem to find where they can be purchased separately.

Exposed to air for a mere week or so, I say it's fine but given this is a Porsche forum, brake fluid is "cheap" so yeah use a new bottle.

[SCadaddle]

I used speed bleeders as well while having a Motive Power Bleeder on hand. Realize brake fluid will ruin your cars finish/ paint job. Given where the master cylinder and reservoir are located there's no way I'm going to pump up a jug of brake fluid into a 40 year old plastic reservoir, or refill the reservoir each time and just put the power bleeder cap back on and pump it back up goofiness...... the speed bleeders are great after installing them after using father time and a gravity bleed, in my opinion.

[Mike80911]

There should not have been air in the system if all was well in the first place, so air is getting in somewhere. Something is cracked or leaking.

[Mister P]

I did finally get a new plastic reservoir and installed it. With the new reservoir and tubing I did the bleeding routine 5 times at each wheel. Seems to be ok now. Did a short test drive around the neighborhood and everything seems ok. Won't be able to give it a real test until I get back home.