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Bruiser
07-01-2010, 09:20 PM
I think I have what is a pretty quick question for you guys. I noticed the rear cylinder on my master cylinder was empty the other day. Since I cannot find a leak on any of the lines or connections I assume it leaking into the brake booster and then getting burned. So, my questions are:

- Is there a test I can run to confirm my suspicion
- What is the best replacement option? Rebuild, Used (years and Models?), aftermarket?

Anything I am missing? By the way, I have a 78 FJ40.

Thanks for the help.

Justin

wesintl
07-01-2010, 10:11 PM
ubolt the 4 nuts to the booster and look.. you'll see if it's leaking in there.

Bruiser
07-02-2010, 07:30 AM
I opened it up expecting to find a soupy mess and while it wasn't clean, it wasn't a disaster. There was definitely some crap in there but most of it looked older and dried out. So, I am not sure what that means. I would expect to find some stuff in there since the car is 30 years old but I am not sure how much is too much. I can post pics if that helps.

Justin

Art Volmer
07-02-2010, 04:39 PM
Have you pulled the drums off the rear to see if the shoes are wet? Good luck with locating the leak.

Bruiser
07-02-2010, 05:24 PM
Have you pulled the drums off the rear to see if the shoes are wet? Good luck with locating the leak.

I have not tried that. Thanks

Rzeppa
07-02-2010, 06:10 PM
Have you pulled the drums off the rear to see if the shoes are wet? Good luck with locating the leak.

I *think* he was referring to the rear reservoir of the master, not the slave wheel cylinders.

Justin, I assume you are referring to the rear reservoir for the brake master cylinder and not the actual cylinder, right? I suggest simply refilling it in conjunction with a good bleed session on all 4 rear slave wheel cylinders, then monitor for leaks after driving some miles. In particular, look for streaks on the inside of the rear tires from leaking fluid.

It would be helpful in diagnosing the root cause to know whether you have had this rig for a while and are familiar with it, whether the brakes seem otherwise normal, how stock it is, whether this occurred suddenly or over a period of time, etc.

Bruiser
07-02-2010, 07:18 PM
Yes, rear reservoir of the master. It has gone almost empty twice in the last couple of months. I filled it before the Argentine Pass run a couple of weeks ago and it has be fine since but I don't think the problem just magically cured itself. I have had this rig two years but this is the first time I have had this happen.

Old40Dog
07-02-2010, 07:58 PM
Yes, rear reservoir of the master. It has gone almost empty twice in the last couple of months. I filled it before the Argentine Pass run a couple of weeks ago and it has be fine since but I don't think the problem just magically cured itself. I have had this rig two years but this is the first time I have had this happen.


Most likely one of the rear wheel cylinders are leaking. Jeff's method of identifying which one on the tire is the easy way. Pretty easy rebuild on the wheel cylinders Justin. Just a bit time consuming with the tear down, rebuild, bleeding...should fix the problem though.