FJ40 brake fluid reservoir empty

Joined
Jun 11, 2015
Messages
51
Hello all a real overly new FJ40 owner here.

I have a 1980 cruiser, she sat garages all winter with regular start ups and a drive around the block about a month ago. I was under it today noticed a puddle under the driver side near the pitman arm. I followed it up to the brake booster area. The reservoir of brake fluid is basically empty… how can I tell if it is the brake booster or the master cylinder? I am a newbie but I have a good service manual, and might need a few diagnostic tips.

DCDDD6C3-C897-4E23-9248-3455F03A9997.jpeg


B9F8A9CB-747D-4C15-B53F-8AAB92954CAE.jpeg
 
Joined
Jun 11, 2015
Messages
51
Here are better pictures…

5612B290-0064-4A2C-BA0B-59968178B35B.jpeg


B42D263D-90CE-4BA4-97FE-3B01978DB2D7.jpeg


25EDC097-CE0F-4B58-B524-6C31BD89D1CF.jpeg


D4407B33-D396-4686-82AB-C60D34091186.jpeg


35E0F015-97C0-4A19-B578-7016C92DA357.jpeg
 
Joined
Jun 11, 2015
Messages
51
It looks to me by the bubbles in the booster paint that was leaking down where the push rod goes in? Or maybe at the grommet and check valve.
 

Skreddy

SILVER Star
Joined
Feb 3, 2020
Messages
1,568
Location
Stanwood, WA
It looks like the rear seal on the master cylinder is leaking and the fluid is running down the front of the booster. There is a little spot (indent or groove) where fluid can run out right there if a leak develops. Probably like a waterpump weep hole so you find out there’s an issue before there’s a big problem.
In short: you need a new master cylinder, booster is likely fine.
 
Joined
Jun 11, 2015
Messages
51
You guys are awesome. Any recommendations on upgrades or just order replacement?
 

Pighead

Stop calling it an FJ
Joined
Aug 31, 2004
Messages
9,188
Location
Camino
Yes, a very easy rebuild.
An upgrade might be the 80 series non-ABS brake master cylinder.
 

3_puppies

SILVER Star
Joined
Dec 2, 2002
Messages
16,634
Location
Helena MT
if brake fluid was getting into the booster, you may want to be proactive and replace that also. the booster doesn't like brake fluid in it.
 
Joined
Jun 11, 2015
Messages
51
if brake fluid was getting into the booster, you may want to be proactive and replace that also. the booster doesn't like brake fluid in it.

This what I should have done. Replaced just the cylinder now the booster is going. It must have sucked up some of the DOT 3.

Any recommendations on booster? City Racer vs Cruiser corps vs eBay cheap-os?
 

Users who are viewing this thread

Top Bottom