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75evo
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Clutch slipping when car gets warm

Post by 75evo »

My clutch is behaving strangely. When the car, actually I suspect when the fluid gets hot the clutch starts to slip. I suspect an internally leaking slave cylinder. I can't see how this failure mode can be a clutch finger springs.

The disc was recently replaced and flywheel resurfaced. The clutch world fine when cold.

The problem is most of the time my experience with a leaking slave cylinder is the pedal being stuck on the floor.

I wonder if exhaust heat is a problem since my exhaust is custom so I need to make sure that it doesn't run too close to the slave hose .

Any ideas?
kevin
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Re: Clutch slipping when car gets warm

Post by kevin »

Yes , I had this exact same problem on my race car that had new clutch etc and after a few laps it started slipping . It happens when their is still air trapped in the slave and when it gets hot it puts enough pressure to engage slightly . Pump clutch a few times and then just release nipple on slave . Make sure its set the top . You don't have to hold clutch down as you're not bleeding it as such . Also when you release nipple just watch and see if few bubble are release first .
MD says its similar to when you go jogging in the morning :D
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MD
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Re: Clutch slipping when car gets warm

Post by MD »

...I release a lot of things first thing in the morning :mrgreen:
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75evo
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Re: Clutch slipping when car gets warm

Post by 75evo »

Thanks for the tip Kev. I will try it out for sure.

BTW MD, like most things, seals get a little leaky as they age. Do you hang this outside the bathroom or when you go jogging? :wall: :mrgreen:
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MD
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Re: Clutch slipping when car gets warm

Post by MD »

Think I got it worked out Zeefa. You're definitely suffering from a cripple nipple syndrome. Commonly caused by a loose screw here and there.
I also think there is a plausible argument in excessive radiant heat from your exhaust causing a fluid and/or residual air expansion which partially dis-egages the pressure plate which then turns into the other clinical problem referred to as a slipped disc.
Give the clutch hydraulics a good bleed routine and install an insulation barrier between the slave cylinder and the exhaust system. Be sure to have your nipples tight like Kevin does and you wont go wrong. Kev knows what he is doing, trust me, he's got it all in hand.
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75evo
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Re: Clutch slipping when car gets warm

Post by 75evo »

I hope the Greekster will chime in too. Especially when it comes to the topic of leaks, releasing "excess air" and nipples, he has been around the block a few times and should be of some help. :D

My exhaust is custom and I run a bigger pipe closer the the slave hose, unlike the stock exhaust which runs slightly further away. I will bleed the system again and make sure the nipple faces upwards, possibly change the slave, and insulate it.

Thanks.
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Re: Clutch slipping when car gets warm

Post by Jim K »

Hahahah! Your 'exhaust is custom'! Did you have plastic surgery to install a blow-off valve -show off? :lol: And ...leaks?? Use heavier grade oil and lay off the beans! :oops:
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Re: Clutch slipping when car gets warm

Post by Mats »

One time I forgot to reinstall the heat shield for the brake master cyl on my 75 T, after a while when the brake master had heated up enough the brakes were dragging, badly. Stopped and poured water on it and reinstalled the heat shield and it never happened again.

So check your clutch master for heat.
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75evo
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Re: Clutch slipping when car gets warm

Post by 75evo »

I finally removed the booth from my slave cylinder and it was completely wet. So I'm guessing the leak is part of the problem. Probably sucking air in as it got warmer and pedal action increased.

So I ordered a replacement and will put in a wilwood adjustable bias valve to replace the proportioning valve.
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