Machine

Two weeks ago: Rebuilt McLeod master cylinder, reinstalled and bled the whole system with the front elevated. After excercising it a bunch it firmed up for a 10 minute test drive and was firm the next morning. Then...constant problems with low engagement and varying engagement.

Today, bleed #1: Bled it again with the car perfectly level. Went GREAT! Super-firm pedal, no softness at all. Went for a test drive and it stayed ROCK SOLID until about 10-15 minutes of city driving. Then it got soft with an engagement near the floor.

Today, bleed #2: Tried bleed again with driver's side inclined (considering position of bleed screw). Got it rock solid again, but then 5 minutes into the test drive it GOT SOFT AGAIN!

I have run out of ideas. I can still "pump it up" during driving which normally indicates air in the system. I don't think there is air initially in the system after bleeding because the pedal is PERFECT until I drive it around awhile. There is no fluid in the master cylinder boot and no seal fragments in the reservoir.

I need some serious help before I totally lose it. I need to race the car on Oct 7 and then going to MFBA Road America the next week.

rudyzturbota

iTrader: (13)

i would say your slave is slowly going out, you get any kind of leakage from the bottom of your bellhousing

Machine

I am not getting leakage and no drop in level in the reservoir.

Thanks for looking.

CW00BlackTA

iTrader: (31)

Since air is getting in, you have a bad seal somewhere. It can only be the slave or master--as you know. I believe with the master, it's possible for the fluid to blow back and forth past the seals without actually leaking out of the system.

EXTANKER

long shot bit what fluid and are ya too close [lines] to heat

Machine

Thinking the same thing, I just insulated the lines and it didn't resolve it. I think it must be the MC seal. I occassionally am having firm pedal, but rarely. It seems to come out of nowhere, which makes me think it isn't air.

Machine

Insulating the line didn't help....but I do have some new information!

If I push the pedal to the floor and reeaaally slowly let it back up, it will sometimes have a firm pedal for the next depression.

This is my theory: The cylinder cup is getting tilted/jammed on the return. Keeping pressure on the cup from the top side keeps it oriented properly and helps give it a better chance to return.

What to do?:
Should I try to get a finer cylinder hone to reduce the friction on the return?
Should I try to stretch the spring or go back to the original?
Should I wait it out and hope that the cylinder cup wears itself in?

Comments?

Machine

Well, I think I figured out what has been going on with my McLeod master cylinder.

The piston is galling.

http://www.americanconscience.com/im...eod piston.jpg

I re-honed the cylinder, put the old piston back in, and took it for a test drive. It is better but not perfect. It still "sticks" occassionally, even after I spent a lot of care with a cylinder hone and follow-up with a fine-grit sandpaper wrapped around a dowel (to hopefully plateau the surface to remove any high spots from the hone).

I'll give it a couple days to see how it goes. After that, I think I will give it up and go with a different brand.

Does the piston really need to be this tight at the front edge? I wouldn't think that it is necessary, since the cylinder cup is doing the work. Thoughts?

DriveATransAm

i think you should just get an automatic.