New Master Cylinder squirts fluid up [Archive] - Classic Cougar Forums

: New Master Cylinder squirts fluid up

October 10th, 2013, 12:28 AM
Guys im having an issue with my new Dorman Master Cylinder# M71248. Ive been bench bleeding it for the past 6 hours and have gotten rid off all the air bubbles but on the small front chamber for the rear drum brakes the fluid squirts a solid stream of fluid up every time I depress the piston with the screw driver

so is this normal?

I even use this Cardone 10-5000MCB bleeder tool as a last resort to get rid off that squirting stream to no avail :angryfi:

October 10th, 2013, 05:07 AM
When you say up do you mean out the top of the reseviour? No, I have not had that happen before. When I bench blead a master I do it as follows.

Screw in some old cut off brake lines (about 4 inches) into the two fittings. Run a piece of clear hose into a bottle with some brake fluid in it. About 2 inches worth. Fill the reseviours of the master and pump it with a sxrew driver. This is done with the lid on. The fluid sqirts into the bottle and draws back fluid if needed. All the air is exspelled in 5 or 6 pumps.

Takes 20min tops.

Are you soing it with the lid off?

October 10th, 2013, 07:15 AM
I think your "bleeder tool" can be had for free anywhere in the alleyway around 16th street here anyways...! LOL

Here's a vid Chris has -

October 10th, 2013, 12:31 PM
As long as the stream is not inches in the air (should be around or less than 1/2"), it is normal. This is why you generally need to have the cap on when bleeding in the car for instance.

October 10th, 2013, 03:00 PM
They do that .... it is the piston returning from being fully depressed into the 2nd stage ....... cap it and install it ......

October 10th, 2013, 06:42 PM
I tried all methods, plugged both ports, used that kit Chris uses on the video and as a resort bought that Cardone syringe bleeder tool.

Yes, Its squirts up like a fountain back into the reservoir. The harder you depress the piston the higher fluid shoots up about 4-5 inches. Im just going to return it for a replacement.

My 45year old MC does this as well but the stream is so strong that it even leaks out through the tightly locked cap after some moderate braking and without the top it squirts about 1 feet into the air making a mess. Im pretty sure the new MC will do this if i decide to keep it. I just finish rebuilding my proportioning valve, brake distribution block, new brake lines and now this MC has to hold me back for another week :uhoh:

October 10th, 2013, 10:53 PM
I know the feeling. I start with carb problems and get hung up on a water neck issue.

The brake system is a standard hydraulic preasure and return system. With the cap on the MC the only place fluid should go is out the two brske line fittings. If you have fluid leaking out the cap there is a problem
I have rebuilt 40+ brake systems and worked on hydraulic lifts, jacks and forks. There can be no leaking for the system to work right. Also the bleeding of air is always done with a closed system meaning the lid on and latched tight.

If the seal around the lid is bad or the lid is bent replace it. Do not reuse a chrome or decretive lid on a new MC. Always use the lid they come with. I have had a few MC's leak after braking and the problem was the rubber gasket under the lid, bent lid, bent or broken lid retainer, debris in the line causing a clog before or at the proportioning valve, bad proportioning valve or a combination of the fore mentioned.

Go ahead and return the MC for another if you don't feel right. Always trust your gut. Brakes are not a place to hope it all works right. However, I think if you drain the MC, flush it and start over you will clear the obstruction in the MC. Most likely air in the piston. And always bleed or preasureize with the cap ON. Never off. It will draw air into the system and air does not compress. Correctly and moves around causing some very odd outcomes.

Keep us updated. Wish I was close so I could come see this cool fountian you have created. Always look for the " dang, that is cool" factor or you eill go nuts!!