clutch wont hold pressure

[draco2188]

so recently i have been working on my 88 comanche pioneer and still can't seem to figure out why my clutch will not hold preassure. this all started last spring when i had to park it for that exact reason. during the down time i did a full BA10 to AX15 conversion. my set up is as follows; 88MJ body and engine, 98 XJ front and rear axles, 98 ZJ rear disc brakes, aftermarket crossmember and trans mount, AX15 trans and T-case from 92 wrangler. and now for the clutch set-up, replaced master cylinder last spring, new clutch, re-surfaced flywheel, new internal slave, new clutch line, and new brass clutch line fittings. my problem is as i stated before the clutch will not hold pressure for very long a few days at very best, has been bled many times. nothing leaks that i can tell. could this be a bad master cylinder (i know this can happen) or am I missing something critical? please help, i love my truck and don't want it to just sit there.......

[H8PVMT]

Probably not your issue but I know you have to put a New diameter pilot bearing when changing from 2wd to 4wd, might be worth googling that route for a ba/ax15 swap

[JENSSEN]

Possibly have some air trapped in your line by chance?

[draco2188]

it was 4x4 to begin with thats not a problem. and its not that theres air trapped in the line air somehow keeps getting in to the line. its been bled many times.....

[H8PVMT]

I got my mc off Amazon for20 bucks, only takes 5 mins to swap it, I've read a lot about slave cylinders being crap right out the door also

[draco2188]

i havent replaced the MC since last spring so i still think it might be that. but it doesnt surprise me that the slave could have the same story. my concern is i don't think its the slave because this is the 3rd slave i have had in the there and its the second new on. i just don't understand why it won't work........... :headpop:

[Comanche County]

I'm thinking one of three things. The MC needs to be bled or is bad (I think the latter). The slave is bad, yes again. Or, there is a leak in the hydraulic line somewhere.

 

Look on the line where it runs close to the exhaust on the fire wall and check for cracks. It could be leaking slowly and burning up before it drips down the line. Best to remove the line and inspect it carefully in good light.

 

Bench bleed the MC, attach the line and run the other end back into the top of the MC reservoir and pump the clutch and look for air bubbles. Also check closely for leaks around the MC.

 

Then bleed the Slave again.

 

There's only those three components, so don't give up. You'll figure it out eventually. Good thing is you've got an external slave so no need to remove the transmission.

 

Only other thing non hydraulically related that I can think of is a weak pressure plate. Sometimes when they go out they just get weaker and weaker as if your clutch pedal eventually just doesn't do anything.

[JENSSEN]

I will be digging into a simular issue here shortly on the 90 Eliminator. If you pump it a few times clutch engages, there was an air sound by the master when I first pumped it so I will start there. I hope its not the slave ,.. :no:

[Comanche County]

I've chased downed clutch issues a time or two. Each time I solved the issue by the directions above....but most standard issue transmission shops will have more experience than I since they troubleshoot this stuff everyday. But there is nothing except for a complete clutch kit that will cost more than 100 bones.

[draco2188]

well first off a few things may not have been mentioned or have been misread in my initial post. The entire clutch system is all brand new including the clutch and presure plate and i had the flywheel resurfaced. also the slave isnt external its an internal. plus the clutch line is also new and i know its not burning off the fluid cuz we don't even get as far as running it to test it out in most cases. i did not bench bleed the MC so that will be my first task, and I too am leaning toward a bad MC, but it started this little b*@$£ of a problem before the MC was replaced last spring. but that doesnt mean the old one wasnt going out and i replaced it with a bad one..............I never do see any fluid leaking out of anywhere either. idk if its relivent but about a week ago my cousin was looking at it and pinched off the line to see if the MC would make presure and he said the pedal was rock hard. i greatly appreciate any input at this point

[H8PVMT]

How did he pinch off a hard line

[draco2188]

its a hard line for about 2 feet from the MC and about a foot up from the slave line. but in between those 2 points its a braided line encased in a rubber sleeve.

[JENSSEN]

Swapped a new master onto my 90 Eliminator even though the fluid levels were ok and I now have pressure,..

[Abyx]

Go bleed it until it holds good solid pressure; then tighten ALL of the fittings, every single one. One of them is loose.

 

A fitting can be fluid tight but not air tight.

[Comanche County]

its a hard line for about 2 feet from the MC and about a foot up from the slave line. but in between those 2 points its a braided line encased in a rubber sleeve.

 

Yep, if that's the original line, then its rubber section is fairly close to the #6 cylinder header tube and prone to heat damage. Check closely there against the firewall.

[draco2188]

I have been busy as hell lately but next week i will between my old job and my new job for a couple weeks so i plan on getting to the bottom of this mess. As for heat damage, that clutch line is brand new and it was doing this before and after the new line installed. I believe i will bench bleed the MC to see what happens first. if that doesnt work i think I'm just gonna pick up a good new MC and install that. if none of this works i think I'm gonna just bring the damn this to a trans shop and let them monkey around with it.......

[my86mj]

master cylinders areabout 30 at autozone swap it out real quick. had to do the same when the cylinder itself seized shut leaving me at a gas station smoking the clutch and gears