[Spongey]

Hi all, sadly I only ever seem to post when I have problems... Any advice or similar experiences would be greatly received! The car is booked into the local dealership next week for a going over but am worried they will simply diagnose a worn clutch plates which are no longer under warranty (24 months or 60000 miles).

Background:
62 Reg I30 Diesel 1.6 CW, 37000 miles, predominantly national speed limit roads and motorway driving. Never ride the clutch (never any need around here) tend to drive with my left leg tucked by the seat. Car not used for towing. Car serviced at the local dealers.

Problem:
I recently noticed the clutch is slipping when the car is in 6th with the rpm above 2000 and the accelerator pedal is pushed fully down. (eg overtaking on the motorway between 60+mph).
This only happens when the car has been driven for 30+ min on national speed limit roads / motorways and I imagine the transmission is fully heated up, the engine temperature does not appear to have an affect, I can not replicate the effect in the first 15min of a journey even with the engine fully heated up no matter how hard i try.
Once the clutch has slipped the engine will rev higher than it should for the relative speed of the car (car will not accelerate). The clutch will regain grip once the accelerator is released (and engine revs drop). I have now noticed this 3 times. It only happens in 6th gear with the rpm at or above 2000 rpm with the throttle fully depressed and after 30+ min of driving .
The car has also developed a gritty rattle at roughly the same time which sounds to be coming from the engine bay when the engine is under load at 1750rpm in all gears.
Have never smelt burning clutch.

So I am drawing a bit of a blank if it is the clutch wearing out, it has hardly had any use relative to other cars i have owned and have never had a clutch burn out, normally keep my cars for 80,000+ miles. I am assuming it is a clutch issue however appreciate forum diagnostics are always going to be tricky but any similar experiences or ideas would be appreciated.

[Surferdude]

Puzzling.
My only thought is that I would expect slipping to occur in lower gears  first.
When the problem occurs have you tried stopping and accelerating through the gears to check their operation?

[Spongey]

Yes tried it this morning, stopped on a local B road after driving for 30+min, then accelerated away quite hard, cycling through each gear no slippage at any gear change (have never noticed any other clutch slippage) but then once at 60 in 6th 2000 rmp throttle past the 90%switch point sure enough started slipping. Released throttle as soon as i felt it slipping as don't want to damage whats left of the clutch.

Have also tried changing in and out of 6th to see if it is a gear box issue but makes no difference. Can not get the same effect in 5th.

One this is for sure will be a fun test drive for the mechanic trying to find the fault, he may have to go on a long drive.

[Phil №❶]

When a clutch ids beginning to fail, it would become noticeable in the highest gear first. For every engine rev, the car is asked, through gearing, to accelerate a greater distance in 6th gear than in lower gears. If the engine has the torque in the high gears, and the Diesel obviously does, then slippage will occur. For safe overtaking whilst you have this problem , I would change to 5th gear to allow the clutch to grip a bit better, rather than slip.

If it is a failing clutch it will continue to get worse and the problem will appear in 5th, then 4th etc.

[Dazzler]

Phil could very well be correct, but I don't think it is a normal clutch wear problem.. (more of a transmission issue maybe) 

Going to be a bu**er to diagnose as you say! 

[crayman]

What's the situation with the pedal?
Do you have correct free play?
As posted, engine will always slip first in the highest gears.
Once it's completely shot she'll slip everywhere.

[Spongey]

@Phil completely agree with the use of 5th i was just using that as an example i actually first noticed it on a very high dual carriageway in the uk called the A66 driving into a headwind and up a hill. As said before i have only noticed this 3 times in the past couple of months as it is not a situation i normally use / find myself in. (First time i noticed i didn't believe that was what it was as the effect is so marginal.)

I also completely agree RE worn clutch and seeing symptoms first in higher gears but why is it temperature sensitive?

As the engine warms up power should increase slightly due to the lower viscosity of the oil and expansion of components which lowers the overall friction of the engine however, it is not engine temperature sensitive.
Higher temperature should also increase the frictional coefficient between the clutch friction surfaces and reduce the viscosity of the gear box oil reducing drag. So this should make it less likely to occur later in the journey after the engine has heated up.

Are there any weak oil seals between the clutch and the gearbox? which could leak oil when warm and the oil has a lower viscosity? The only other thing i can think of which would cause this would be air in the hydraulic clutch system expanding as the transmission heats up.

@Crayman
Not noticed any movement in bite point. It is aprox half way in the pedals travel.

The car has only complete 37000 miles and compared to cars i have owned in the past and taught my wife to drive in this clutch has barley lived much less been abused. Particularly as i now live in the back end of know where and in total the car probably has about 100 city miles on the clock. 

[Phil №❶]

Temperature can have varying effect on friction surfaces. If the surface is coated with friction material, then heat can increase mew or the grip. However, if the surfaces are clean, then temperature will cause fading as happens when brakes overheat. This reduces their efficiency. It is possible that your clutch is slipping more than you realise and that the surfaces are a lot hotter than the engine. This can happen if the clutch is not adjusted correctly.

I would be taking the car to a dealer and have the clutch system bled and reset to proper tolerances. It may simply be a matter of adjustment.

[Spongey]

Thanks Phil Once again you are correct, I am approaching the problem from the theoretical standpoint as friction increasing with temp is a generalisation and for certain materials eg friction materials they do behave differently.

As said the car is booked in for next week, just trying to garner ideas before seeing the garage as have had issues in the past where they have tried to claim no fault when it is visible problem.

Hopefully it is something which can be solved as simply as you say by bleeding the system.

Either way will report back next week once they have seen the car.

[eye30]

If you can see if car will do it before you take it in then get chap to go with you otherwisr when they do it the car will probably be cold and not show symptoms

[crayman]

You'll get an indication by driving under load and lightly applying the clutch to feel where it begins to slip.
If it slips straight up as soon as you apply some light pedal she's stuffed.
Bleeding the system sounds like it's not going to help as you mentioned that the bite point is still where it was and thus you do have a nice amount of free travel.
Once a clutch slips, it's usually all over. The diaphragm will no longer apply full clamping force if it's been cooked. (which doesn't take much)
Was there any evidence of engine or gearbox oil leaking into the flywheel region?

[Lorian]

Was there any evidence of engine or gearbox oil leaking into the flywheel region?

That would be my thought, oil ingress has been know on other cars.

[Spongey]

Have tried to make it slip but otherwise the car is normal in all gears except 6th, eg applying light pressure to the clutch. It will only slip when the clutch is pressed down to the bite point warm or cold which is what I am finding so weird about this issue. The clutch appears healthy unless driven for 30min and it is floored in 6th above 2000rpm. (Which tbh is quite a rare driving condition).
I have driven cars with clutches which have gone or were well on their way out but this one displays none of those types of behaviours.

[Spongey]

Good advice eye, I am coming from work and it's a 30min drive so should give the opportunity to get it warmed up before and check it is slipping.
There is no external signs of oil leakage (eg after being left parked) so will have to rely on the garage to check if they end up pulling the gear box / transmission. Just hope it's not the friction plates and whatever It is under warranty!
As said will keep you all informed!
 

[eye30]

Have you checked the hydraulics and whether there is a leak/problem with the system re release bearing etc

[Spongey]

Only the fluid level, which was at the max level. I dont have a suitable area at home to jack the car (cobbles), is the slave / master easily visible under the car?

[Johnno]

Yes tried it this morning, stopped on a local B road after driving for 30+min, then accelerated away quite hard, cycling through each gear no slippage at any gear change (have never noticed any other clutch slippage) but then once at 60 in 6th 2000 rmp throttle past the 90%switch point sure enough started slipping. Released throttle as soon as i felt it slipping as don't want to damage whats left of the clutch.

Have also tried changing in and out of 6th to see if it is a gear box issue but makes no difference. Can not get the same effect in 5th.

One this is for sure will be a fun test drive for the mechanic trying to find the fault, he may have to go on a long drive.

Did the revs shoot up when it started to slip? as I can't get my head around this, it's either slipping or not, if your accelerating through the gears it would slip in all gears as you stated it starts about 2000rpm which is not far off where the torque peaks
and also leaking hydraulics won't cause it to slip because there will be no pressure on the pressure plate.

The possibilities are

worn clutch plate
weak pressure plate [ but if some of the fingers on the plate are weak you would also get clutch pedal judder]
oil contamination on flywheel / clutch plate and pressure plate  [ spigot/input shaft oil seal or rear crank oil seal]
I don't know if the i30 clutch can be adjusted

[Spongey]

Completely agree Johnno, it is bizarre the only thing i can think of is that in 6th at 2000rpm is when the clutch is under the greatest torque hence starting to slip but i can not get it to slip in lower gears even when accelerating away aggressively. Equally it shows no signs of any slip in any gear when cold???

When it does slip in 6th it is not as though the engine is reving without load, the revs increase slower, i have always backed off fairly quick when it has started to slip to try not cause any further damage but it has been up to a 1000rpm higher than it should of been, releasing the accelerator causes the rev to drop back to the cars drive speed.

I have not noticed any form of judder but not really sure what i would be looking for.

[Spongey]

Well the rattle mystery is solved just been as far under the car as I can get without jacking it up and the engine skid plate is hanging off only one bolt left holding it on and that is half out managed to get a socket on the last bolt and tighten it up anyone know how many bolts there should be?? There appear to be 4 holes I can see.
(It was serviced by a main dealer 4 months ago)

[eye30]

Do they need to take this off for service?
Oil filter access?
If so, after service not checked so what else has been scimped on!

[Spongey]

I think the oil filter is on the front of the diesel but I would imagine the oil sump and hence drainage plug is under there, it isn't dented or damaged and to my knowledge the car has never been grounded out.  Managed to tighten the only remaining bolt up so it looks like its not been tightened up properly and vibrated itself off.
For it to nearly be falling off 4 months after it's last service, becoming less impressed with their service (as have had other issues in the past such as been told there rusty roof rack wasn't rust but was surface oxidation), still one more thing to mention before they try to work out what's wrong with the clutch. Hope they tighten everything up when there in there!

[eye30]

it looks like its not been tightened up properly and vibrated itself off.

May be you don't have a clutch as it has worked loose and fallen off

[Spongey]

Hopefully they haven't serviced that part yet

[Johnno]

Get them to sort out the skid plate and don't let them charge you

[crayman]

I'm not familiar with the engine control on these cars but the ecu in some vehicles will not allow full Hp until the car is in top gear, warmed up etc.
Quite easy to control Hp in a turbo engine by limiting boost.
Perhaps it's not slipping in 5th for this reason?

[Spongey]

True crayman not sure if the i30 has a variable boost turbo although that would help explain it. It's the hot cold I still don't fully understand, surly it's engine temp which should primarily effect hp and torque output of the engine but engine temp doesn't seem to be a factor with the clutch slipping long after the engine has reached temp??

[Phil №❶]

It is not necessary to tough the skid plate to attend to oil filter or oil change on the Diesel. I've performed both on the FD without that requirement. Not sure if it is necessary to touch the skid plate to CHECK gearbox oil level, though. Even so, you need to speak to the Service Manager to make them aware of their tardy performance at the last service. Let them know you expect much better performance in future.

[Spongey]

Thanks Phil I am intending on making the service manager aware of my disappointment as have spoken to him before about customer service in the past (I sound like the customer from hell but but really am not, I just expect things to be done right). The skid pan on the i30 is a rather substantial piece of steel had it come off and hit another car it would of caused a significant accident.
For the premium paid for the dealership service I am very disappointed and with local garages quoting 40k services with genuine parts for £190 vs their £250 + effort you begin to wonder what you are paying for!
Thanks Johnno, there is no way I will let them charge me for the skid pan! They are fixing that!

[Johnno]

I'm not familiar with the engine control on these cars but the ecu in some vehicles will not allow full Hp until the car is in top gear, warmed up etc.
Quite easy to control Hp in a turbo engine by limiting boost.
Perhaps it's not slipping in 5th for this reason?

Never heard that for a standard production car, because most dyno run's are done in 4th gear but this can also vary depending on the dyno. they use a set formula,which is Horsepower equals torque X 5252/RPM.   

Thats my reason in thinking thats it's not limited .  But I stand corrected if it is so.

The boost is controlled by adjusting the  actuator and mapping

[Dazzler]

Just to throw a cat among the pigeons... Being that it has been 4K driven since the last service it would be hard to prove the loose plate was their fault. It probably was and I agree about everything else that has been said including coast of dealer service etc... 

I would be tactful about pointing the finger..