Ok I have a 99 s10 blazer 5 speed 4x4 I am having some clutch issues. But first a little history I bought the blazer 2 years ago with 205k ran great just had the master cylinder slave cylinder and clutch and pressure plate and flywheel replaced with less than 1000 miles on them well the previous owner drove it for about 6 months prior to the clutch being replaced and the motor had a really bad intake gasket leak mixed the coolant and oil well long story short washed the bottom end bearings so I replaced the motor in the process also replaced the slave cylinder because the line went bad and the slave seen better days so I figured why not just insure no issues and replace it well got that all done replaced put back together and bled the clutch it always had a heavy clutch since I had it well it got so heavy that the clutch master cylinder actually blew through the firewall I replaced it three times before modifying it to a bolt in master cylinder rather than a cheap bushing drove it for about 9 months or so now with no issues put about 8k on it and now when I drive it it's fine till the motor warms up and then I lose clutch pressure I am thinking the pressure plate may be bad and once the engine heats up its losing pressure there are no leaks what so ever fluid level is perfect I am just wondering if anyone has some input or has experienced this before

 

By "losing pressure" do you mean the pressure plate loses spring tension and the clutch starts to slip, or the master cylinder no longer provides enough fluid to release the clutch when you depress the pedal??

 

Well for about the first 20 minutes to a half hour on driving it for the first time after a cold start it's perfectly fine great pressure but after the motor gets up to temperature it grabs fine but it's like the clutch doesn't fully disengage 2nd and reverse grind and it's hard to get in and out of any other gear but when you push in the clutch it does release enough that it doesn't stall or pull but it could be slipping at that point

 

From your description after a while the clutch no longer fully disengages when the pedal is pushed. It pulls fine when the pedal is released, right? Probably not a pressure plate issue.

Could be several possibilities. The pilot bearing could be too tight on the nose of the input shaft, keeping the shaft turning instead of stopping when the clutch is disengaged. The hydraulic system could be not providing enough movement to fully disengage the clutch. Or you could have debris (usually a broken spring coil from the center) between the clutch disc and flywheel or plate.

Does the pedal feel different when it works OK and when it doesn't? At what point in the pedal travel does the clutch start to move the truck when it is being engaged? Different when OK and problem?

Unfortunately you have introduced unknown variables by replacing the MC with a different unit. Are bore, stroke, and fluid volume supplied by the MC identical to the OEM one? Is the line routed close to the exhaust?

 

The master cylinder is an oem replacement right bore stroke etc all I did was modify it by replacing the spacer washer with a bolt in plate from another master cylinder same thickness and every only change is now there is two bolts that get installed after the bushing is locked in

the line is ran in the exact location as stock it's got at least 4 inches away from the exhaust

The clutch does feel different after motor heats up you can tell there's a big difference in the pressure

I was thinking about pulling the clutch and pressure plate and replacing it with a stage 3 clutch if nothing else it should help the heaviness out of the clutch

 

Well, that's a weird one all right. I can't see heat affecting the pressure plate much, springs either lose their temper or not, they don't normally change back and forth.