merc A class 160 semi auto clutch problem - Mercedes-Benz Forum

 
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post #1 of 9 (permalink) Old 05-13-2011, 11:52 AM Thread Starter
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merc A class 160 semi auto clutch problem

hi new to this , could any body help we have a V reg a160 semi automatic 78,000 miles , problem is when car gets warm or in hot weather its worse gear changes become very rough, the car goes into gears fine and we have no dreaded F on dash but when gear is selected the clutch seems to engaged aggresively and with a jolt. is this terminal or could a fluid change help...thanks
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post #2 of 9 (permalink) Old 05-13-2011, 12:26 PM
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What does your service manual tell you about changing the gearbox ATF? I would expect it to be every 60k to 80k miles.
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post #3 of 9 (permalink) Old 05-14-2011, 12:03 AM Thread Starter
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Is atf automatic transmision fluid ? if so i do not know if this would help,it feels to me its the auto clutch that is not engaging smoothely but with a jolt.This is a manual gear box and i can select gears without any problems.Thanks for your reply.
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post #4 of 9 (permalink) Old 05-14-2011, 11:11 AM
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Aah... my error. Yes, you have no ATF with the semi-automatic clutch & manual gearbox.

I took a look in my WIS at the operation of the Auto clutch control module (N15/4). It has many inputs from sensors, any of which might degrade the performance of the clutch.

1. Input signals from the engine: a) engine torque. b) accelerator pedal position, c) throttle valve position, d) idle speed switch position.

2. Input signals from ABS/ASR: a) front & rear left wheel speed sensors. b) front & rear right wheel speed sensors. c) service brake. d) parking brake.

You can guess which of these sensors/switches might be the culprit, but I would first do a (very cheap) clean up of the throttle valve actuator as described here. It is known to affect engine running, and this could happen when changing gear.

http://www.benzworld.org/forums/w168...0-bas-esp.html
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post #5 of 9 (permalink) Old 05-14-2011, 11:30 AM
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Further information

From the WIS

Quote:
Self-Protection

If a system overload (eg, excess temperature) is detected, the automatic clutch control module (N15/4) is able to vary the hydraulic actuation of the clutch. As soon as the risk of an overload no longer exists, the control module returns to thenormal operating mode.
So you might be experiencing this known MB design problem, that you have to live with...
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post #6 of 9 (permalink) Old 05-15-2011, 12:57 AM Thread Starter
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thanks for both replys very helpfull ,i wonder is it possible to change the auto clutch hydrolic fluid (if so how) as i doubt it as ever been changed .Thanks again.
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post #7 of 9 (permalink) Old 05-15-2011, 05:08 AM
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Without a lot of numbers from your decoded VIN, it's hard to know exactly what vehicle/gearbox you have. There are 5 versions of manual gearbox listed in the WIS... Also the term 'semi-automatic clutch' is not used. I can only see 'automatic clutch'. Further (I don't know this car apart from the manual) I can find no reference to topping up clutch fluid in the operation. From the drawings it looks like an entirely mechanical device, and maybe the hydraulics is only in use from the pedal, via the N15/4 to the mechanical clutch. There is reference to 'self-adjusting' features on this clutch, (a spring-loaded adjusting ring) to account for wear at the plates.

Regarding gearbox oil change, refer to your service manual. From the WIS it looks like it should be changed ONCE during the first A or B service, and then left alone.

Here's a picture of the clutch to explain the final operation:
Attached Files
File Type: pdf W168 clutch.pdf (321.0 KB, 449 views)
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post #8 of 9 (permalink) Old 06-03-2011, 01:07 AM
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I would be interested to hear the outcome of this, I suffer the same issues, ie aggressive clutch engagement, but not all the time. MB ran their diagnostics & mentioned the vacuum hoses needed replacing, apparently the clutch operation is linked with many sensors as mentioned above & the leaking vac line can effect throttle position etc, I am not entirely convinced.
have a read through Lofty's pages on the ACS
Bert Rowe's-Mercedes-Benz 'A'-class info. Mercedes- Benz 'A' Class (ACS) Auto clutch-less transmission
I wonder if replacing the bushes in the ACS actuator would help?

BTW,
the clutch hydraulic fluid is easy to replace, from memory MB don't recommend the presure bleed method.

(1999 A160 180000km)

Last edited by gtjunior; 06-03-2011 at 01:10 AM. Reason: typo
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post #9 of 9 (permalink) Old 06-06-2011, 05:06 PM
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mods, can you move this thread to the w168 page, might get more response
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