Resolved Problems with new clutch master cylinder

[A Sharp]

I'm trying to get a fresh 2g build up and running. It's has an upgraded clutch and Fidanza flywheel. During the course of this build, I replaced the clutch master cylinder because the old one was leaking.

The clutch has now been bled multiple times and there are no leaks. The pedal was then adjusted according to Jacks' instructions. With the the adjustment rod in the proper position, the clutch needs to be pumped to get good pedal pressure. Within a few seconds after pumping, the clutch gets mushy again. However, if I turn the adjustment rod in too far, the clutch feels great.

I'm thinking there could be an issue with the new master cylinder. I noticed this when relief valve is able to open (proper pedal adjustment): when pumping the pedal, the reservoir level drops. When I stop pumping the pedal, the reservoir level goes back up. So, too much fluid is leaving the lines.

Or maybe I just bled it incorrectly? I don't see how air in the lines could cause this behavior, though.

 

[joejoe]

Adjust the master cylinder/threaded rod sounds like you need to extend it some more little bit at a time.. Once the clutch pedal feel returns to normal and hold pressure out the car in 1st and rev it up to 6500 or so rpm if the car doesn't move great... if it does move a bit clutch is dragging... Adjust the rod out a bit more.
On my current 1g i extended the rod almost all the way, due to drag... this is with pivot ball shim and all new clutch/hydraulic system. Haha.... so far 20k on a 6 puck, no issues Fpred at 32psi

Also I hope you are using oem slave and master. And did bleed it well.

 

[boostdawd]

+1 on the slave and master being OEM. Auto parts store remanufactured parts have only given me headaches and frustration. Not sure if u mentioned this but did u shim the pivot ball? Also what brand/model clutch did u install?

 

[A Sharp]

joejoe, I believe that the 1g's have a slightly different clutch system. You can probably get away with extending the rod as much as you want, but us 2g guys can't. 2g's can get clutch "pump up" if the rod gets extended too far. The explanation is in here: http://roadraceengineering.com/clutchandflywheeltech.htm I have the rod extended as far as it will go before this happens.

I only replaced the master, not the slave. The MC is whatever reman'd brand O'reilly had on hand. SOOO... probably two mistakes there .

I did not shim the pivot ball. The fork sits on the right side of the hole, so I assumed it was okay.

Lastly, the clutch is a brand new XTD "stage 4" with an unsprung disk. I'm aware that these can be hit or miss, but I thought I'd give it a try since I got it super cheap on the classifieds. I'm not going to make crazy power, so hopefully it holds up.

Ehh, maybe I'll try returning the MC and just replace the entire system with OEM cylinders and a SS line. What kind of trouble have people had with cheapo MCs?

 

[richardlapalme]

They tends to leaks in no time with after market heavy clutch.

My car has act 2600 clutch with fidanza flywheel
SS line
OEM MC AND SC
Speed bleeder valve
And ... lastly, i have to put extended slave cylinder push rod.
https://www.rtmracing.com/xcart/product.php?productid=18900&cat=1410&page=1

All without clutch drag and shift without any grind (jacks stage 2 tranny)
I have this set up since 8 year now, lots of drag, lapping day and street use. Still perfect.

 

[A Sharp]

Thanks for the replies. I ended up replacing the whole system with brand new cylinders and a ss line. Problem solved. I think the problem was caused by the slave cylinder. The old one didn't automatically extend to remove slop like the new one does.