Residual Valve - discs all around

[nuclearlemon]

A friend that is a Toyota tech told me that the master cylinder Marlin sells is a for 94 and newer 80s that had discs in front and drum rears and needed residual pressure. the 95 and newer master cylinders do not have the rear residual pressure. I will be given Marlin a call...

newer 80s have discs all the way around...only the parking brake is drum. do you mean 94 and earlier?

fwiw, i'm running a 74 master with both residual valves removed on an 83 fj60 booster with no issues.

 

[Mendocino]

I meant 94 and older Ige.

I called Marlin and they told me to buy a proportioning valve from Summit to solve the problem. AFAIK a proportioning valve will only slow that rate that the residual pressure builds in the rear circuit. Am I wrong?

 

[Friendly Persuasion]

You are abosultely correct. A smaller numbered residual valve is what you need. If memory serves correct the diameter of the free flowing hole in the middle of the valve is bigger in the the smaller numbered valve which allows fluid to return to the master cylinder faster when the brakes are released. This allows the rotor to push the pads and in turn the piston back in away from the rotor stopping them from rubbing.
Gavin

 

[Mendocino]

Marlin just called me from Marlin Crawler and he thinks my rod is too long and preloading the MC. I will see about adjusting that and report back.

 

[brooklyn]

Marlin Master and Rear Brake Lock

Did the shortening the rod solve the pre-loading problem? Did the folks at Marlin tell you if the have 2PSI or 10 PSI valves. I know and earlier post said it was 2PSI in both, but I never got that confirmed from Marlin. I have called a few times, but keep missing the tech guys.

I am still trying to get my brakes shorted and have found that the rear brakes "lock" after they have been applied a few times and then they slowly release.

I have checked the rod length and it looks okay, i have checked all the break lines and they are good. The rear systems seems to be holding pressure and then releasing.

This led me to think maybe the adjustable proportioning valve was not working correctly and holding pressure to the rear. I bought a new one and will try that this weekend.

 

[Mendocino]

I backed off the MC bolts and took a short drive and the problem appears to have gone away. I shortened the rod as much as possible and it is still a bit long (~1/16 to 1/8"). I will have to cut it.

So, Marlin was right.

 

[handcannon]

I backed off the MC bolts and took a short drive and the problem appears to have gone away. I shortened the rod as much as possible and it is still a bit long (~1/16 to 1/8"). I will have to cut it.

So, Marlin was right.

Get some sheetmetal and make some spacers to go between your MC and booster. Add/subtract number of spacers until you get the desired results with no rear pressure buildup.