So I posted up just less than a year ago about doing a clutch in my brother in law's truck. When he first started having issues we replaced the master and slave cylinders with LUK aftermarket parts from Pep Boys. That did not solve the problem but we replaced the clutch and all was well. Fast forward to yesterday.

He calls me and says his clutch is gone again. I figure there is no way so I have him describe his issues and I immediately realize that his clutch reservoir must be empty. I tell him to go check and sure enough it is.

He is 3 hours from me and lives by himself so I don't know how to tell him if it is the slave cylinder or the master cylinder. Is there one that more commonly goes than the other? They only have 10-15,000 miles on them. Should we replace with OEM or another aftermarket? Thanks in advance.

 

I would find a source for Aisin (factory) parts.

The master tends to go out more often in my experience, but it is a good idea to replace them both in my opinion.

 

Okay thanks. If the master fails where does it usually leak? Inside the cab or against the firewall?

 

They usually leak inside the cab.

 

Hmm. No brake fluid in the floorboard. Since our slave is on the outside of the bell housing I would guess a leaking slave would end up with brake fluid leaking onto the ground. Correct?

 

Okay so we just checked it all out. I refilled the master and bled it. Pumped the pedal about 50 times with no loss of fluid or resistance. We went on a drive about 10 miles with lots of stop lights and came back and the level is exactly the same. My brother in law said that the resistance lessened over the course of 2-3 weeks of driving 50 miles per day. I see no fluid leaking in the floorboard or around the slave. I pulled the push rod out and there was no fluid in the rubber boot. I also checked both ends of the line for fluid and didn't find any. I'm at a loss.

Does anyone have any ideas? Something has to be leaking but I can't find it anywhere and it is obviously a very slow leak.

 

Long shot, but I've had hard-to-find leaks where cracked reservoirs turned out to be the culprit. It's something we don't look for and sometimes easy to miss. Maybe try cleaning all the crud off and taking a good look at it--especially right at the bottom, plus watching for any leaks once it's clean. Cheapo part makes this maybe more likely.

 

It's less than 5,000 miles old so there is no crud on it but I'll definitely check all around it and see if I can find a spot it might be leaking from. Thanks for the suggestion.