Replacing rusty g-box/tranny oil cooler pipe - problems?

[C280estateguy]

Hi all. Advice needed for my 1998 C280 Estate/stationwagen/break (owned for 16 happy years and counting).

I need to replace the corroded solid thin gearbox/transmission oil pipe which runs down from the top of the oil cooler beside the radiator (on the R/H side of the car viewed from inside the car), then turns at right angle to run across the front of the car behind the bumper/fender under the rad (this is where it's corroded) before connecting to a flexy rubber pipe (with metal spiral protector) which then joins back to solid pipe to run alongside the engine to the gearbox/transmission (on the L/H side of the engine when viewed from inside the car). I've ordered both the solid and the flexible pipes in case I damage the latter getting the former off (had to be ordered from Germany!).

It looks like a straightforward job (apart from rusty retaining clip), but are there potential problems I might face? Is access to the retaining clip straightforward (remove radiator cowl? easy? anything else to remove?). Is the oil under pressure? Will a lot leak out? If so, can the gearbox/transmission oil be topped up (is it "sealed for life")? Is there a risk of air getting into the system and causing an airlock? Should the gears be in "Neutral" rather than Park? Any problems I might discover too late to be able to drive the car to the garage/shop?

Any advice and suggestions gratefully received!

Many thanks!
Cheers,
John (London, UK)

[W202FTW]

Hi all. Advice needed for my 1998 C280 Estate/stationwagen/break (owned for 16 happy years and counting).

I need to replace the corroded solid thin gearbox/transmission oil pipe which runs down from the top of the oil cooler beside the radiator (on the R/H side of the car viewed from inside the car), then turns at right angle to run across the front of the car behind the bumper/fender under the rad (this is where it's corroded) before connecting to a flexy rubber pipe (with metal spiral protector) which then joins back to solid pipe to run alongside the engine to the gearbox/transmission (on the L/H side of the engine when viewed from inside the car). I've ordered both the solid and the flexible pipes in case I damage the latter getting the former off (had to be ordered from Germany!).

It looks like a straightforward job (apart from rusty retaining clip), but are there potential problems I might face? Is access to the retaining clip straightforward (remove radiator cowl? easy? anything else to remove?). Is the oil under pressure? Will a lot leak out? If so, can the gearbox/transmission oil be topped up (is it "sealed for life")? Is there a risk of air getting into the system and causing an airlock? Should the gears be in "Neutral" rather than Park? Any problems I might discover too late to be able to drive the car to the garage/shop?

Any advice and suggestions gratefully received!

Many thanks!
Cheers,
John (London, UK)

No need to do anything fancy, just gently loosen/break the lock nuts and remove (heat up the threads with a pocket torch if they're rusted out) - ATF will leak out but nothing terrible; but do keep a bucket close by!

REPLACE THE COPPER CRUSH WASHERS! DO NOT SCREW THE HOSE ENDS ON WITHOUT THEM!

Don't worry about air getting lines during the repair, this will not affect the operation of the transmission. Do leave the transmission in park though.

The transmission is not actually sealed for life but you will need to break-off the end cap to the transmission dipstick tube (pry up/break the red cap then remove the black cover) to adjust/add ATF fluid. These cars do not come with a dipstick - you will have to purchase one from the dealership or by whatever means available. Do keep note on how much fluid actually leaks out during your repair.

When finished, top off all ATF fluid lost and start up the car. Check the connecting points of the lines for leaks (adjust as needed of course) and then road test for about 20-30mins (we cannot check the temperature of the ATF without Xentry or the Mercedes factory scanner so we'll do it the traditional way) and then check the ATF level.

[W202FTW]

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[C280estateguy]

Thank you W202FTW - your advice is much appreciated! Checking the ATF level may be beyond me though - maybe I'll get a quote from the garage to fit the bits I've bought and refill the ATF. Also, I need crush washers. Thanks anyway.
Cheers
John