When I am driving along my car starts over-revving up to 4000 RPM randomly. I've carried out a slippage test and there is no clutch slippage. Any ideas guys?

  • How often does this happen @mikepont, and how long does it last? If you keep the car in neutral does the same thing occur? – GdD Feb 6 '19 at 14:29
  • It varies,some times just once or twice on a drive of say 20 miles. Other times three or four times within 10 miles. – mike pont Feb 6 '19 at 14:37
  • It never happens in neutral, and its back to normal after I release the accelerator for a second. – mike pont Feb 6 '19 at 14:41
  • Does the car accelerate when it revs, or stay at a constant speed? – GdD Feb 6 '19 at 14:46
  • It stays at a constant speed, the rev counter just races up to 4 or 5 thousand revs.Normally when I'm going over 60. – mike pont Feb 6 '19 at 14:52

Frustrating! If it's happening intermittently then there's a few things it could be:

Oil leaking into the clutch casing

This could be coming from various places - but if you get any oil on the friction plate you'll get temporary slip from the clutch until it burns off.

Bad flywheel

Possible.. but I think you'd be seeing more consistent symptoms then you are.

Misaligned/sticking clutch bearing

If you're seeing the symptoms happen after you've changed gear then the clutch bearing could be at fault - if it's not doing it's job properly the friction plate might not be settling back in contact properly. Have a listen to see if you can hear any growling or rattling sounds coming from the transmission when the symptoms occur.

Clutch linkage

Again this would only be happening when you change gears, and you'd usually feel some vibration or sticking when moving the pedal.

Broken friction plate springs

This is incredibly rare - but it does cause symptoms remarkably like what you describe:

Broken clutch plate springs

Basically when the bits of spring come away they get trapped against the friction material and cause it to intermittently drag.

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  • Thanks very much for the detailed response, I'll have to do a bit more investigating before taking on the clutch change. cheers. – mike pont Feb 6 '19 at 15:31

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