Delayed Acceleration and High Revs

[omar_little]

Hi Forum

I have a problem with my 2005 4200. When taking off from a standing start, there is a noticeable delay in the car accelerating. The car revs very high, but takes ages to get going. I thought it might be the clutch, so had that checked at last service. It's at 38% wear.

Another symptom is at high speed on a motorway, when I accelerate I get loads of revs (red lines occasionally) and delayed acceleration.

The garage claimed the clutch bite point was too low and adjusted it, but the problem still remains. Any suggestions please?

 

[allandwf]

Got to be the clutch if it's reving but not moving much.

 

[omar_little]

I was afraid that might be the case. The clutch was changed two years ago and has only done 10K.


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[conaero]

That's collapsed spring tangs on the clutch for sure. Does it have problems getting into gear from standing still?

 

[omar_little]

Nope gear changes are normal. No issue engaging.


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[conaero]

Maybe your clutch is contaminated with Cc fluid, any leaks under the car, there is pipe that runs over the bell housing that is prone to splitting.

Rear main oil seal is rare but worth checking.

Is you pump priming for 5 seconds when you open the door?

Next step if I were you would be to get an endescope into the bell housing checking for contamination and any slight bending of the spring fingers.

 

[omar_little]

Pump primes when doors unlocked and there are no sign of a leak. Car is parked in a dry garage so easy to check.


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[omar_little]

I assume the endoscope investigation would have to be done by a garage?


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[conaero]

I assume the endoscope investigation would have to be done by a garage?


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Yes, it's a camera on a flexible wire and can look inside tight places.

Your clutch bearing might not be returning fully and might just need the PIS point resetting.

 

[omar_little]

Many thanks

Is the investigation and the PIS point resetting a big job?


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[CraigWaterman11]

It sounds also like a sticking thrust bearing/slave cylinder though if the PP tangs are functioning properly I would find this a bit hard to envision. It takes quite a bit of pressure to engage the friction discs. If you have a scope you could check it yourself, either with a lift or jack, you would need enough room so you can slide underneath. However our Mas. has a double disc clutch design with a floater in the middle. You can check the PP but it's going to be hard to get the scope in both sides of the friction discs. I agree Conaero if the discs have fluid on them or alternatively if they are glazed over. It could of began as a PIS issue (you did say the mechanic adjusted this already in your first post?) that glazed the discs, in which case this could happened no matter how much clutch wear was registered on the car. But I definitely believe it to be a clutch issue.

 

[omar_little]

Silly question, but I assume the PIS reset is the same as adjusting the bite point?


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[conaero]

Silly question, but I assume the PIS reset is the same as adjusting the bite point?


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Yes

PIS - Point of initial slip

The car should start to move at 900rpm.

 

[voicey]

If the release bearing is sticking the TCU will log a "clutch over PIS" error and the box will drop into neutral (which you don't mention).

Your comment about the delayed acceleration on the motorway - is that when changing gear or when flooring it whilst it is in gear?

 

[omar_little]

The delay only occurs when you floor it. No issue with car dropping into neutral.


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[voicey]

The PIS isn't going to change anything. I doubt it is the release bearing sticking. I would guess friction material failure (wear or contamination) or pressure plate failure. Given the latter is well documented I would guess this is your problem but you'll need to take a look in there to be sure.

 

[Emtee]

Any squealing Omar?

 

[omar_little]

No squealing.

 

[CraigWaterman11]

The PIS isn't going to change anything. I doubt it is the release bearing sticking. I would guess friction material failure (wear or contamination) or pressure plate failure. Given the latter is well documented I would guess this is your problem but you'll need to take a look in there to be sure.

I could see friction material contamination, or wear but again I don't see it being the pressure plate. I suggested a sticky release bearing only because it's one of two likely possibilities though I could see it should log a fault code as you stated, then again, I've seen these cars not log fault codes when they should as well. A collapsed pressure plate would keep the car from going into gear or some gears because it won't allow the release of the full clamp load on the friction discs. The friction discs are caught constantly engaged between the flywheel and PP with little relief when the Thrust bearing is engaged because the fingers are collapsed. So if the car is switching gears, but the clutch is slipping in acceleration it's something preventing the engagement of the full clamp load, or alternatively, there is a full engagement of the clamp load but there is a friction disc failure. That failure doesn't necessarily mean there's no friction material. Again like has been suggested contamination or I also suggested the friction disc could be glazed. If the PIS was initially set wrong it could of allowed your clutch to consistently slip at first though it was re-adjusted later. This as well could have caused the excessive heat that brings the glaze or binding agent of the friction discs to the surface. When this happens it cools on the surface of the friction material making it become like glass. This will inhibit clutch engagement, and allow clutch slippage. I'm not saying that's your issue but it also could be. In either of these situations you obviously need to either check it out yourself or get someone else to do so to have a definitive answer. Just my two pence............

 

[safrane]

If the clutch is slipping when the car is moving would it not slip even more if you were starting from still esp if on a incline.