Hello all, looking for an opinion on whether I'm having a problem with either my master or slave cylinder on my old 87 2x4 pickup. A while back I was having problems with slowly losing the fluid. If I kept it topped off it wasn't a problem, if not I had to crack the bleeder at the slave and bleed the line out to get it working again. I replaced the slave cylinder but the problem seemed to still exist. I couldn't find the fluid ever leaking here so after posting here and getting some good advice I found that the master cylinder had actually been leaking the fluid back through the firewall and it was under the carpet in the cab.

Over the last week I started to notice the clutch having less and less pedal that it engaged. The other day it finally quit working completely, but it is not acting like it did before when the fluid had leaked out. I still have all my fluid (I haven't lost any since replacing the master cylinder) and the clutch pedal still has pressure/tension to it (as opposed to when it lost the fluid and just sat on the floor). I'm guessing I need to replace either the slave or master cylinder again, but how do I know which one? If I crack the bleeder on the slave and pump the clutch will the prescence (or absence of) fluid coming out tell me if the master cylinder is working?

 

It could be that it is time for a new clutch.

If you can get help to push the pedal to the floor while you watch the slave cylinder to see if it moves like it should. the movement of the rod well tell you if the hydraulics are working :jessica:

the fact you have not lost any fluid makes it look like it is time for a clutch

 

I was hoping that was not the case. I've replaced the clutch on 2 vehicles before and on both of them when they went out the vehicle would sit and idle in gear with the clutch not even pushed in. I take it that's not always the case though?

 

Here is the first thing you want to do. Start the truck in nuteral, push the clutch in and see if it will go into a forward gear. If it grinds, or will not go in, then proceed to the next steps.

1: Have someone push the clutch while you watch the slave cylinder. If it does not move, proceed to #2.

2: Try bleeding the clutch, not to bleed it, but to see if there is any pressure in the system. If there is no pressure proceed to #3

3: Take line off the slave, put finger over line and have someone pump the clutch pedal. If there is little pressure in the line proceed to #4

4: Take the line off of the Master, and put you finger over the hole. Have someone pump the pedal. If there is no pressure proceed to #5

5: Replace Master Cylinder

Of course you can skip the steps and go to #4 and check the Master. If the clutch is not slipping, and you are not loosing fluid it is most likely to be the master. Since most of the time when a slave fails it leaks. The Master can fail, and bypass fluid back to the resi. This causes the clutch to not work, without the loss of fluid.

 

Thanks for that great reply, I'll give that a go tomorrow. I'm leaning mostly towards it being the master because it does grind when trying to go into gear but can be shifted into gear fine when the truck is not running. Also (and probably just importantly) is the fact that when I replaced it the only one I could get ahold of that day was a cheapy at Advance auto parts...

 

Ok, here's what I found. Master cylinder is pumping fluid. If I pull the line off at the master and somebody pumps it, it's pumping plenty of fluid out. If I crack the bleeder open on the slave and somebody presses the pedal, plenty of fluid comes out. I do not see anything moving on the slave cylinder itself when the clutch is pumped, should I try replacing it first?

Also, is the correct bleeding method to crack the bleeder, press and hold clutch until bleeder is closed and then release or do I press the pedal, crack the bleeder and then close when fluid is flowing steadily and then release the clutch pedal?

 

pump the pedal 3 times and on the third time hold pedal down. Have someone crack bleeder then tighten. Once bleeder is
tight start pumping again.

 

Great stuff

 

Make sure you have bled the system properly. When I replaced my line, master and slave cylinder it took several cycles to get it bled. In the beginning the rod coming off of the slave was not moving. Once bled it moved fine. Pump clutch pedal several times. Hold pedal to the floor while someone cracks the bleeder valve. Tighten valve. Repeat process.