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Unread 12-20-2014, 12:24 PM   #1
kirbot
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1981 CJ7 
 
Join Date: Jun 2010
Location: Nj
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Clutch pedal goes soft at higher rpms...

I've been puzzling over this one for a while...


Any time I take the engine over around 3200-3300 RPM, the clutch just gives out. It doesn't slip, but the pedal goes soft and I have to pump it up a few times to get it back. Happens in any gear.


The clutch and flywheel are fairly new, the master and slave cylinders are fairly new....

The only thing I have to go on is... I know one of the engine mounts are shot.
MAYBE the engine twisting and moving around is compressing the slave cylinder? Hopefully I'll have a chance to fix that this week sometime.

But if that doesn't solve it, I'm clueless.


I've been driving it like this for quite a while, but keeping the revs down that low puts my 0-60 in the 27-30 second range....
That's starting to get old....

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Unread 12-20-2014, 12:57 PM   #2
Partsmke
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1987 YJ Wrangler 
 
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Quote:
Originally Posted by kirbot View Post
I've been puzzling over this one for a while...


Any time I take the engine over around 3200-3300 RPM, the clutch just gives out. It doesn't slip, but the pedal goes soft and I have to pump it up a few times to get it back. Happens in any gear.


The clutch and flywheel are fairly new, the master and slave cylinders are fairly new....

The only thing I have to go on is... I know one of the engine mounts are shot.
MAYBE the engine twisting and moving around is compressing the slave cylinder? Hopefully I'll have a chance to fix that this week sometime.

But if that doesn't solve it, I'm clueless.


I've been driving it like this for quite a while, but keeping the revs down that low puts my 0-60 in the 27-30 second range....
That's starting to get old....
The only thought that I have is when your engine is running at higher rpm it is heating up the exhaust system and transfer heat to the slave cylinder or clutch hose causing the fluid to percolate. Most slave cylinders had heat shields, check yours you may want to try shielding it.
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Unread 12-20-2014, 01:30 PM   #3
Mike Romain
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1986 CJ7 
 
Join Date: Nov 2007
Location: Off the Grid in Chester Grant, Nova Scotia, Canada
Posts: 15,129
I would first be sure the transmission isn't falling out. Don't laugh, one of my Jeeps has had the tranny fall out 4 or 5 times since I have known the Jeep. (1999). First symptom is the clutch acts like you describe.

Otherwise, like mentioned, maybe boiling fluid from hitting the exhaust.

Edit: I mentioned fluid because you said you could pump it up. If it is mechanical, 99% it is your bad engine mount just moving the linkage.
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Unread 12-20-2014, 02:13 PM   #4
hutch1200
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Location: Clarks Summit, Pa
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For Sale: Ford T-18 adapted to Jeep CJ. Located on the Garden State Parkway, somewhere between exit........
Just kidding, please don't be offended. I'd just HATE to see you lose that unit. I know how hard (and expensive) it was locating/adapting/fabbing etc... to get mine to work. If I lost mine, I'd puke. Then cry!
Good luck, & please let us know what turned out to be wrong, so somebody else doesn't chew up parts.
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Unread 12-20-2014, 02:38 PM   #5
kirbot
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Join Date: Jun 2010
Location: Nj
Posts: 351
Ok... losing a transmission sounds scary enough.
I spent way too much time and money (and sweat) on this swap to see that happen....

I'll go over the mounts and make sure to keep it secured.



I forgot to mention, but yes, it's a hydraulic. I'll rig up a little heat shield and see if that helps.
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Unread 12-21-2014, 01:19 AM   #6
hutch1200
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"I spent way too much time and money (and sweat) on this swap to see that happen...."
Getting that trans, which weighed 2x as much as my T-150, will make you do anything to keep it in there. Heyna or no?
And if a Hyundai hit that trans in the road, that car would stop instantly and not even dent the T-18!
Best wishes.
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