Hissing noise - Jeep Wrangler JK.

[Banshee]

So, just to confirm, in neutral & stationary, you can hear the noise. Then once you put pressure on the clutch, but not enough to release it completely, the noise goes away?

Or does the noise continue until the clutch is fully disconnecting the engine from the gearbox?

[humdingerslammer]

Mmmm... have an 07 JK 3.8. First (OE) clutch went at ~85000 km. Second (centerforce dual friction) at 195000km. Third (Centerforce dual friction again) in place and about 207000 km on clock. Changed throwout bearings at same time. Machined flywheel with the first clutch change and changed the flywheel with current (3rd) clutch.

Have not ever had hissing etc noises.

No warning tho when the clutch is about to go... they seem to die and that's it. 2nd clutch did slip on load and when changed was shot to shit (as was the case for the first (OE) one). I do a bit of towing.

When u change the clutch get a better quality & stronger one. The Centerforce dual friction does well for me. They do rattle because of the centrifugal weights that r part of the design and that give the added pressure force and strength to the clutch. You should also always change the throwout bearing (once again get a better brand than the OE) and it is also a good idea to change the clutch slave cylinder at the same time (OE for this is OK).Changing to a better/different brand might help the OE problem go away.

When I travel out bush I always carry a spare clutch, throwout bearing and a slave cylinder because u never know when it will die. I know this seems 2B overkill but they don't take much room & I know that I will always have paid a lot less than from a dealer and also the "out bush" rip off price and there is no wait time for the parts to arrive.

Obtuse answer to your problem but there must be something useful in what I have said.

Somewhere.

[Banshee]

My OE clutch gave me a couple of months of (domestic driving) warning, so I was able to baby it along until I got all the parts. The first symptom was it not releasing completely, even when the pedal was on the floor.

By 'babying it along', I mean that I mostly drove along changing gear by matching the revs to the speed & gear without using the clutch. Yes, it wears the synchos a bit, but if you are doing it right, not significantly more than normal changes.

[JKBall]

Originally Posted by Banshee

So, just to confirm, in neutral & stationary, you can hear the noise. Then once you put pressure on the clutch, but not enough to release it completely, the noise goes away?

Or does the noise continue until the clutch is fully disconnecting the engine from the gearbox?

Sorry for the delayed response.

Yes. In neutral and stationary, the noise is present. Yes, again. Enough pressure applied to the clutch stops the noise but not enough pressure to release the clutch completely.

[JKBall]

Originally Posted by humdingerslammer

Mmmm... have an 07 JK 3.8. First (OE) clutch went at ~85000 km. Second (centerforce dual friction) at 195000km. Third (Centerforce dual friction again) in place and about 207000 km on clock. Changed throwout bearings at same time. Machined flywheel with the first clutch change and changed the flywheel with current (3rd) clutch.

Have not ever had hissing etc noises.

No warning tho when the clutch is about to go... they seem to die and that's it. 2nd clutch did slip on load and when changed was shot to shit (as was the case for the first (OE) one). I do a bit of towing.

When u change the clutch get a better quality & stronger one. The Centerforce dual friction does well for me. They do rattle because of the centrifugal weights that r part of the design and that give the added pressure force and strength to the clutch. You should also always change the throwout bearing (once again get a better brand than the OE) and it is also a good idea to change the clutch slave cylinder at the same time (OE for this is OK).Changing to a better/different brand might help the OE problem go away.

When I travel out bush I always carry a spare clutch, throwout bearing and a slave cylinder because u never know when it will die. I know this seems 2B overkill but they don't take much room & I know that I will always have paid a lot less than from a dealer and also the "out bush" rip off price and there is no wait time for the parts to arrive.

Obtuse answer to your problem but there must be something useful in what I have said.

Somewhere.

Hi humdingerslammer,

According to the mechanic who worked on my JK last month, he machined the flywheel, replaced the throw out bearing and replaced the spigot bearing while replacing the clutch.

[Banshee]

Originally Posted by JKBall

Sorry for the delayed response.

Yes. In neutral and stationary, the noise is present. Yes, again. Enough pressure applied to the clutch stops the noise but not enough pressure to release the clutch completely.

OK. From a troubleshooting perspective.

You have pinned it down to fewer moving parts. Those attached to the gearbox side of the clutch. (Because it occurs when you are not moving.)

Now the moving bits are the throw out bearing, (no pressure on it), and the input shaft to the gearbox, (shaft, bearings, seals. The pilot bearing only moves when the clutch is fully disengaged and there is rotation between the flywheel & clutch plate.)

Given that the clutch does not need to be fully depressed to stop the noise, that would seem to indicate the ToB, as the noise goes away once pressure is on it, but not enough to disengage from the gearbox input side, (so it is still moving, but now no noise).

My ToB failed last year. In my case, it was quiet, until I put pressure on the pedal, then it screamed like the gates of Hell had opened under the car. LOUD! (You should have seen the face on the cop pulling into the shopping center carpark who had stopped there and was next to me as I was coming out & had to stop before entering the street! ) Mind you, that was, as far as I know, the original ToB, at ~80,000km - 150,000km old. I got the JK 2nd hand & the PO might have had it done in the 70,000km they had it.

Your sound is the opposite instance. Where my ToB seized and was scraping the pressure plate fingers & wearing them down. By the time I got all the parts in, it had worn through most of them. And the ToB itself was also worn through.

Pressure Plate


Throw Out Bearing
That loose bit is what is supposed to apply the pressure to the fingers...

My guess, and that is all it is, would be that the ToB may be tightening up and rubbing a little on the fingers, but as soon as you put pressure on the pedal, the friction between the fingers & ToB surface overcome the tight bearing & it turns normally. The slave cylinder piston is spring loaded, so that a slight pressure is always applied to the ToB so it always remains in contact with the pressure plate fingers.

Or, given that we have not heard your JK, in particular, to compare, it might just be the normal noise of spinning bearings as the mechanic said.

[JKBall]

You have pinned it down to fewer moving parts. Those attached to the gearbox side of the clutch. (Because it occurs when you are not moving.)

No, the noise/issue also occurs when driving/moving, most prominently in second gear. I mentioned this in my original posts, last week. The noise/issue only began to occur while in neutral and stationary in the past 2 to 3 weeks.