Brake bleed fail. Please help
 

Hi Team. After finally getting my new rotors, rebuilt hubs and calipers installed in my 87 Carrera, I'm now trying to bleed the brakes. This is my first attempt. A friend lent me a pressure bleeder. I connected everything and began pumping with a target of 20psi. At first, there was no increase in pressure, although I was forcing fluid from the bleeder container into the master cylinder reservoir. But then, as the pressure began to build, but well shy of 20 psi, the car began to pee a steady stream of fluid out of a tiny hose at the left front corner of the bumper. I released the pressure from the system, but the peeing continued for a good while. What a mess!

What am I going wrong??? Thanks very much for your patient help.

Steve Yeatts
Chapel Hill, NC

Did you clamp the vent line on the reservoir? Sounds like maybe not.

The overflow from the brake fluid reservoir is carried by a small diameter hose to the vent hole behind the front bumper onto the ground. This vent prevents damage to the paint in the trunk from brake fluid overflow. You need to clamp this hose to channel fluid through the brake system. Also it is best to pre-fill the master cylinder with brake fluid before beginning this process (I say this for a conventional pedal push bleed, this may not be necessary with a power bleeder) to eliminate little air bubbles in the master cylinder which have a nasty way of giving a soft brake pedal until the last bubble is found.

Do you have a photo of the tube you are referring. It could be the reservoir overflow. If you did not clamp off that tube that is probably your problem. 20 PSI seems bigger than needed. Also, try the use a friend to pump the brakes. Even with a pressure bleeder, I prefer the friend pumping the brakes the best for finishing the job. Also, I like the speed bleeders. They make things easier.

No I didn't clamp the overflow off. Duh! But which hose is the overflow? I have two hoses coming from the reservoir. One is a small black one at the very top of the tank and a larger one about midway up the side of it. How do I get these hoses completely clamped off. They seem pretty stiff and not amenable the squeezing.

I don't know what year car you have. If you post a picture it would help. Typically the overflow is a small hose off the rear near the top of the reservoir.

The smaller line at the top is your vent. The larger one below (probably blue) goes to your G50 transmission. You need some hose clamp pliers. Orange plastic and you can get them at local auto parts store.

15psi.~ 20 psi. for G-50.........
 

For typical pressure brake bleeding, 10 psi. is more than sufficient for your need but with a G-50 transmission clutch saver, slightly more pressure is needed. 15psi.~20 psi.
For my SC's with 915............... 10 psi.
For my 3.2 with G-50............... 15 psi.+ (not to exceed 20 psi.).

I have used pressure bleeding since the late 90's for all my cars including the '78 track car. Once you learned how to use pressure brake bleeding successfully, you won't need a second person to pump the pedal.

Warning: Make sure the vent hose/tube is properly secured at the brake reservoir. If for some reason the hose popped off while under pressure, the over flow (brake fluid) would be all over the brake booster area. Nasty mess.

Tony

Clamping overflow hose
 

If you think the old hose is too brittle to clamp, you can remove it at the tank and put on a short piece of flexible hose and clamp that. Replace the old, brittle hose when you can.

Make sure your bleeders are facing up on the calipers. If you swapped the calipers around you may have inadvertently ended up with the bleeders facing down and you'll never get the brakes to bleed.

gomezoneill, you may be on to something. I thought the calipers only go on one way, with the bleeders at the bottom. I will reverse them and give it another try. You are a genius!!

I remember the first time I bled the brakes on my 911, what a mess.

Clamp top right

http://up.picr.de/29408215zq.jpg

I've definitely learned a lot. It's sort of like what they say about sausage -- it's better to eat it than to watch it being made.

Clamped it or plugged the end of the vent hose......
 

It tends to leave mark on the hose using a clamp or worse damage an old and brittle vent hose. Instead try to plug the end of the vent hose near the front left side tire. And use an appropriate size drill bit to keep the compressed air from escaping. Just remember to remove it after you are done.

Tony

Full brake bleed and flush procedure in this video if you are interested. It is an older 84 with 915 tranny so cable clutch but the basic procedure remains the same. Video gives a heads up on the vent line to plug then uses the Motive bleeder available from our host to do the flush/bleed. Might help a few.

https://youtu.be/c_mooEGdzBU

plug the vent hose at its end?
thats gonna fill you the hose and will drip all over the place.
not such a good idea.
in this case on should rather change the venthose to a new one if you feel its gonna brittle when beeing clamped.