How to test a clutch?
Discussion
Going to view a 997 and wanted some advice on the best way to test a clutch. There seems to be various different ways to do it such as running in 30 mph and then putting the gear into 5th/6th and looking for linear revs as the car accelerates. If the revs go up but the car doesn't accelerate to match the revs, clutch is on the way out. Another suggestion I have seen is starting the car, putting it in 3rd gear and try to pull away. If the car stalls = sign of good clutch. If it moves = clutch slipping. The final suggestion I have seen, is that if the clutch feels firm to press in, sign that the clutch is on the way out. Also seen another suggestion around high biting point. With so much info, is there a definitive way to test for a wear on a clutch without obviously dismantling it.
Yep, top two methods.
Issue is though, you'll get the same results from 0% wear to around 80% wear, it's only when it falls off the operating cliff edge that it actually slips in the manner noted.
If it passes the top 2 tests, don't worry about it but you'll never know how hard a life the clutch has had so just budget in if you're keeping it for more than 6 months(ish).
Issue is though, you'll get the same results from 0% wear to around 80% wear, it's only when it falls off the operating cliff edge that it actually slips in the manner noted.
If it passes the top 2 tests, don't worry about it but you'll never know how hard a life the clutch has had so just budget in if you're keeping it for more than 6 months(ish).
The first notice I had of a slip was with 3 adults inside + some lugagge in the front. So heavy car, then as I accelerated hard in 5th gear on an uphill section of the motorway the revs rose for a second but no acceleration as if it had wheelspin. It didn't do it again for a few months, but then again I was mainly on my own, At this point I got the clutch changed.
Take somebody else with you and put them in the back for the test drive.
Take somebody else with you and put them in the back for the test drive.
There are two issues here - clutch pressure plate, which causes a heavy pedal, and clutch friction plate, which is the bit that's lined with brake pad type material and designed to wear away.
Unless you've experienced a few examples of the same model it's hard to judge whether one is heavier than it should be or not.
As for the friction plate, the tests described will be OK but nearly all clutches will pass. A more thorough test is a little more abusive, but gives a greater chance of determining how healthy it is. Drive along an empty straight road in 5th at 30mph or below, depress the clutch pedal, increase the engine speed significantly (not quite "revving the t!ts off it" but not far off) and then release the clutch pedal quickly and put your foot flat to the mat on the accelerator.
A healthy clutch will force the engine to slow right down to the transmission speed, a badly worn one will slip a lot and a partly worn one may still slip a little - either way don't let it slip for long (it's causing more wear when you're slipping it), lift off the gas and let everything settle down.
Unless you've experienced a few examples of the same model it's hard to judge whether one is heavier than it should be or not.
As for the friction plate, the tests described will be OK but nearly all clutches will pass. A more thorough test is a little more abusive, but gives a greater chance of determining how healthy it is. Drive along an empty straight road in 5th at 30mph or below, depress the clutch pedal, increase the engine speed significantly (not quite "revving the t!ts off it" but not far off) and then release the clutch pedal quickly and put your foot flat to the mat on the accelerator.
A healthy clutch will force the engine to slow right down to the transmission speed, a badly worn one will slip a lot and a partly worn one may still slip a little - either way don't let it slip for long (it's causing more wear when you're slipping it), lift off the gas and let everything settle down.
And feel for judder when warm - reverse car on lock just by releasing the clutch slowly (no throttle). Uptake should be silky smooth - judder = tired clutch plate / flywheel issue.
Ignore all the above if the car has a LSD! Judder in that situation is both common and normal (as GT3 owners know all too well)
Ignore all the above if the car has a LSD! Judder in that situation is both common and normal (as GT3 owners know all too well)
type-r said:
Going to view a 997 and wanted some advice on the best way to test a clutch. There seems to be various different ways to do it such as running in 30 mph and then putting the gear into 5th/6th and looking for linear revs as the car accelerates. If the revs go up but the car doesn't accelerate to match the revs, clutch is on the way out. Another suggestion I have seen is starting the car, putting it in 3rd gear and try to pull away. If the car stalls = sign of good clutch. If it moves = clutch slipping. The final suggestion I have seen, is that if the clutch feels firm to press in, sign that the clutch is on the way out. Also seen another suggestion around high biting point. With so much info, is there a definitive way to test for a wear on a clutch without obviously dismantling it.
Good grief. If the clutch is ok and you do some of these tests it could not be ok after.First question: Is the clutch slipping?
Next can you with everything warmed up and the engine idling and the car on level ground depress the clutch and move the gear shift from any gear to any other gear without any real difficulty?
If so the clutch is fine. If not the clutch is probably ok but the clutch fluid needs to be flushed and bleed. Every 2 years, just like the brake fluid.
The only clutch test I can recommend if the clutch is suspected of slipping - this is not a test to be done over and over again -- is on a flat stretch of road with the tranny in 4th gear at say 2500 to 3K rpms floor the throttle. Do not be tentative and feel your way to the carpet. Floor it.
'course you want to be sure everything is up to temperature.
Use of 4th which is near enough to a 1:1: gear. No torque multiplication like what happens in a lower gear than can trigger wheel spin and no diminishing of the torque in one of the overdrive gears (5th or 6th, or even of course in the newer cars 7th).
Anyhow, if the rpms rise and the car's speed doesn't increase concurrently the clutch is slipping. No need to test it again. Time to get the clutch done. Anymore slipping risks ruining the flywheel. These can be resurfaced if the need to be and reused as long as they are in otherwise good health and the dual mass feature works ok. The techs have a test for this once the flywheel is exposed during a clutch job.
BTW these clutches can last a long time. 106K miles on my 03 Turbo's original clutch. 266K miles on my 02 Boxster's original clutch. Focus on proper use of the clutch and forget how to test the darn thing.
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