Ok I did multiple searches etc but didnt find any info.

I replaced the radiator on my 400E along with the fan clutch (after the fan clutch destroyed the old rad).

On removing the old radiator I poped the right bottom plastic fitting off since it was interfering with the fan clutch - couldnt get the rad out, the black plastic piece colided with the front of the fan clutch. I assumed it was because the front of the fan clutch was all torn up.

When installing the new one. Bolted up the fan clutch then went to install the radiator. Same problem in reverse. Ther is about 1/4 inch interference of the lower plastic mount with the fan clutch housing!

I was able to install it by removing the drain plug (this buys a couple mm) and unbolting the AC condenser. This allowed the radiator to come in at an angle with only some rubbing of the ac fins.

So is there a secret to RR a 400E/E420 500E/E500 radiator? It looks to me like if you make a special 8mm hex tool on a steel arm you may be able to install the fan clutch after installing the radiator? There is not enough room for a standard ratchet between the fan clutch and rad (even with the mercedes 3/8 drimve 8mm hex which I bought). If not, if I ever need to remove it again I'll pop off the plastic fitting again and then bend the aluminum back after install to hold it snug.

On the plus side its reassembled and running, now to get at at least one of the block drain fittings and put the correct coolant in - I refilled with only water to check things out.

Thanks
Paul