Clutch fluid overheating?

[CrUZida]

I'm having issues with my clutch, and I think its temperature related.

When the engine is cold, the friction point is right at the floor.
On a normal day when it heats up, the friction point moves to about the middle.
However today, with the temp around mid 30s, the friction point decided to move right up the to, to the point where its just beginning to slip.

I'm assuming this is being caused by the fluid overheating and expanding.
Is there anything I can do?
Shielding the line is obviously an easy step, but I'm not convinced it will solve it.

[Rens]

Have you tried flushing the fluid.? Moisture in the system could be affecting it.

[lexsmaz]

If the friction point is changing as you said & especially it slipping when hot i would be looking at the clutch master cylinder not having enough free pedal clearance, just get under the dash & adjust the pushrod so you have a couple of mm clearance / slack & it should fix it ..

Moisture in the system would have the oposite affect to the pedal ...

[mattysshop]

if it is indeed getting hot - what have you done in the way of ceramic coating/heat sheilding etc of the extractors or the clutch line itself?

a very typical approch for example with 4AGE into aussie Sprinters (not having the JDM bellhousing which puts the clutch on the other side) is to simply use some of that heat reflective wrap over the clutch line - whilst you can make it look very very dodgey easilly, spend a little more time with a few clamps and or zip ties, and it can look neat..

or - possibly just spend $60-$70 on a new braided teflon coated line that is longer, and puts it furthur away from the heat source..

[CrUZida]

Extractors are ceramic coated, and where the clutch line runs closest to them there is a heat shield.
The soft line is already a braided teflon coated line, but not sure if there is any reflective wrap on it. I know there used to be, but can't remember if it got reinstalled.

Can't afford to adjust the pedal, as its a Tilton HRB, and they are pretty specific on how much throw the pedal can have, so that it doesn't over extend the HRB.


It may not be heat causing it, but I'm not sure what else could be?

[CLG]

Rebuild clutch master and slave to suit silicon fluid, install silicon fluid, job done.

[mattysshop]

on that note, have you tried a higher boiling point Super Dot 4? whilst it may not be as good as silicon based, there is a fair bit of difference between brands etc. cheapest highest dry BP i have found under $15 a bottle is Castrol Super dot 4. ofcourse there are plenty of other more exotics that may offer better performance.

[lexsmaz]

If the pedal is taking up higher as you mention & especially if it also makes the clutch slip when the car is hot it shows that the clutch fliud when hot is not being allowed to return to the resorvoir with your foot off the pedal ( due to there being slight preload on the clutch pedal to master cylinder push rod & so the compensating port in the master cylinder is actually then covered ) back off the push rod as i mentioned & it should fix the problem by uncovering the compensating port ( i have seen the same issue years ago & backing off the m/cyl fixed it .. )

Backing off the m/cyl will not make the clutch over throw / over extend as you are actually giving it more clearance, which in a small way makes it actually throw less, but as i said only give it a couple of mm clearance & throw wont be affected ..

If you dont want to fix the problem dont do anything & just keep posting up here asking lots of questions ..

If the fluid is boiling etc the opposite affect will happen & you will find you cant even disengage the clutch with your foot hard on the floor & will get worse when it gets hot ( basically its like having air in the system & what happenss then ? you cant disengege the clutch no matter what you do .. )

[CrUZida]

That makes sense, and thinking about it, it will work.

It does however raise another issue, which will throw a spanner in the works (I only just remember it)
I had an issue at a track day a few months ago, where the clutch wouldn't disengage at all even with the pedal flat to the floor. So I tightened up the clutch (opposite of backing it off, not sure on the terminology..) about 2 threads. Obviously in the long run its caused this issue, but why?

Is there a happy middle ground I need to find? Something special with these HRB's?
When you first start the car the friction point is about 3mm from the floor...

Every clutch I've done in the past has just worked once bled properly.

[lexsmaz]

I'm guessing when you were at the track you might have had issues then with possibly the clutch fluid overheating & hence possibly boiling on the day, so if you flush out the clutch fluid using some fresh unopened brake fluid & adjust the M/cyl pedal rod back to where it was & all should be good ..

[CrUZida]

Its possible it was heating up then but unlikely, as it was around June, and only motorkhana, so 2 mins on the track at a time.

But I will back off the clutch and rebleed. Hopefully the stars will align and all will be good in the world again.

[CrUZida]

Just a small update.
I adjusted the rod as you suggested lexsmaz, 4 turns in total, and rebled the clutch.

Everything was ok after a quick drive, will take it for a decent spin soon and report as to whether its fixed.

Cheers

[SillyCarS]

do what clint said.. my screamer pipe is actually just touching the line in mine.. hasnt been a prob

[CrUZida]

I'm still not sure if its a heat issue (although it is definitely possible...), as it never happened before this thread.

Finally got to take the car for a 20min drive on Saturday, problem came back exactly as before.
Adjusted the clutch rod a further 3 turns the next day but didn't have time to rebleed. After another 20min drive the problem wasn't as bad, but was still there.

Should I adjust the rod a bit more, or am I barking up the wrong tree?
The friction point still starts at the bottom of the pedal in the beginning, and slowly moves its way up (~3" of pedal throw).

Its a Tilton HRB, so I'm not too keen to remove to replace with silicon friendly parts.

[stealth]

Do you have any oil leaks? specifically rear main?

I had very similar problem with my 1JZ. Clutch would get all soft and doughy when it got hot due to oil in the bell housing. The oil seeps out of the friction material when it gets hot, until its all burnt off.

Just an idea...