As Lynall says it's knackered. It should get stiffer as the temperature rises...if you know what I mean..
By 100c it should really whoosh when revved.
There is much on the go in this forum re MB's overheating and/or being overcooled. Dieselman is trying his car without the fan, and even with the radiator blanked off, and not having any problems.
I have also been having trouble of the overheating kind on 3 cars this year, and underheating on the Merc (which is now overheating!). It is said elsewhere that the E300td is overcooled. So it probably is -in the UK! But these cars have to be able to drive comfortably in the Arctic circle and in Central Spain in the Summer. In the USA even more marked temperature differences have to be coped with. Even here where I am at present in South Africa, you can have 40 degree (C) and a few hours drive away be in snow. (Not snow as we Europeans understand it: just a smattering.)
The cars have to cope with this and worse. Then factor in normal things like radiators getting sludged up with the passage of time. On two occasions I have had cars driving normally in the UK, without any overheating problems, only to find that near Tours, halfway down France, in July, the car overheated. A new radiator was the cure in each case, amply tested in Central and Southern Spain and through the Pyrenees, with wife and 7 children aboard. A similar load on the M6 over the Pennines had given no such problems.
The underheating was caused by a jammed thermostat, and was a pain until fixed because it was winter in the UK. The heater never got warm even on the motorway, and the temp gauge was stubbornly low. So yes, the car without thermostat in January is overcooled!
The Land Rover Discovery tdi here in SA in the local summer was under cooled with a vengeance! I was advised to look at the head gasket by the local dealer: it is a problem area with Discos, perhaps because when off road they can be called on to perform in arduous conditions. It started with overheating due to a hose problem, during which the header tank developed a leak under high pressure. BUT it did not happen under idling, only under load when the system was fully pressurised. When this happened the coolant disappeared quietly, until it was too low and then overheated vigorously (it was in the 30's here). The pressure cap blew off some of the presssure and dirty coolant went all over the header tank, nicely concealing that there was a small crack in the bottom of the header tank, well out of sight.
I was not wont to do the cylinder head as there was no combustion gas contamination in the coolant, no steam in the exhaust gases, and no oil emlsification. On this occasion I was correct. On others I might not have been.
In my SA based 500SE I had similar problems a few years ago. It was the top hose that had a pinhole leak, which under extreme heating of the coolant sent a small jet of coolant straight onto the floor, so visible signs of a leak were absent when mobile. As the car lost coolant it was no longer present in the top hose, so when you saw the temp rise and stopped there was no jet of coolant from the top hose to be seen!
You can see how small problems lead to coolant leaks after owners have replaced all sorts of things without success in the various LR fori.
The trick is to avoid paying £110 or more per hour to a dealer while you sort this out, which is my current predicament. The MB dealer was unaware of the testing kits for coolant contamination (one is marketed by the repected Sealey, and ebay has others), and it would appear that this is not part of the MB diagnostic regime. Incredible? Yup. Yet he insists that the cylinder head gasket or the head itself or the engine need s replacement. There is no coolant contamination visible, no emulsified oil, and no steam coming from the tailpipe.
I strongly suggest that the use of fori such as this is your cheapest bet, by a long shot. The viscous fan has been replaced, but I never did think that would be the problem anyway.
However I don't think it fair to criticise Mercedes designers for the cooling capacity. The cars need an ample reserve of cooling capacity to cope with harsher conditions than found in the UK. It may lead to higher fuel consumption, as Dieselman suspects. He is being sensible and testing his theories, and would no doubt undo his modifications if faced with a trip to Greece in the summer.
Some difficulties with modern cars arise with current design practices. In days long gone cars did not have header tanks for coolant, and you could see by taking off the radiator cap when the thermostat opened and the coolant circulated. So if the top hose were hot, and there were no coolant motion, the water pump would be suspect. It is not too easy to check with header tanks.
On the Eclass estate certain rear lamps cannot easily be accessed: the handbook says that you should go to the dealer. Fine, but expensive, and try telling that to a French traffic policeman trying to up his municipality's income over Easter weekend. If the light is necessary it should be accessible: if it is not necessary it should not be there!
Some French cars are designed such that you have to take the front bumper off to change the headlight bulbs. Unforgiveable in my view.
My Xantia TD has the thermostat in the top house, and needs a screwdriver and 10 minutes to replace, as it is in the top hose. No gasket needed for the traditional thermostat housing, and much better than the E300td location and access. And they say Citroens are poorly designed from the servicing viewpoint. (Some are!!!)
Good luck with your problem!!!
