Mercedes Benz C320CDi - Mis-behaving 7 speed auto gearbox

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Tue 28 Jun 2011 11:10
Mercedes Benz C320CDi - Mis-behaving 7 speed auto gearbox - LLI0 0DS

My Nov 2006 (56) W203 C320CDi estate is just lovely to drive but has recently started to occasionally refused to accelerate or change down when asked (even past kick-down point). Driving in 'sport' mode (holds gears longer) seemed a bit better but still occasional hesitation or refusal with gearchange needing to be forced manually.

Today my wife has called me to say its doing it again and refused to go down more than one gear even manually - but was then fine again and changing happily whenever urged on. I did drive through VERY heavy rain and spray about a week ago on M40. Any thoughts / suggestions welcome.

Thanks.

WOODS

Edited by LL10 0DS on 28/06/2011 at 11:10

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Wed 29 Jun 2011 12:43
Mercedes Benz C320CDi - Mis-behaving 7 speed auto gearbox - injection doc
Is it the auto box or the engine power output causing the autobox to hesitate or even miscalculate ! I have had these with blocked exhausts , and secondary dpf,s casuings loss of power and kickdown etc
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Wed 29 Jun 2011 13:24
Mercedes Benz C320CDi - Mis-behaving 7 speed auto gearbox - injection doc
I also meant to add that these engines also suffer with the inlet manifld butterfly valves becoming disconnected from their linkages causing lack of power and preventing the autobox from sensing commands
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Sun 3 Jul 2011 10:43
Mercedes Benz C320CDi - Mis-behaving 7 speed auto gearbox - LLI0 0DS

Thanks Injection Doc

i think you're spot on - it's looking like an engine power problem rather than a gearbox problem. Prime suspect at the moment looks like a manifold motor malfunctioning.

Will keep you posted. Thanks again

LL1O ODS

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Sun 3 Jul 2011 13:41
Mercedes Benz C320CDi - Mis-behaving 7 speed auto gearbox - piston power

Might also be worth a oil change on the gearbox merc said there sealed for life but over on the merc forums plenty drop the oil and filter & you need to buy a dipstick.

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Sun 3 Jul 2011 14:20
Mercedes Benz C320CDi - Mis-behaving 7 speed auto gearbox - LLI0 0DS

Thanks Piston Power.

Ii will do that.

I had an E320CDi previously where i changed the gearbox oil and it benefitted from it.

LL1OODS

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Thu 7 Jul 2011 14:06
Mercedes Benz C320CDi - Mis-behaving 7 speed auto gearbox - LLI0 0DS

Thanks guys for the help and suggestions.

Full power and gearbox functions restored.

The problem was not gearbox related but was diagnosed to be loss of power (thanks Piston Doc) due to malfunctioning inlet manifold servo motor, located under and accessable only by removing the turbo. This confused the gearbox. New motor fitted, wallet $390 lighter but car running beautufully again. Thanks again,

LL1OODS

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