1998 E300 Turbodiesel running hotter than it used to
 

Hi all

I have a 1998 E300 Turbodiesel and it is running a little hotter than it used to. I gunned it recently on the motorway up to 110mph and the temp guage was starting to rise to near 100 deg so i backed off.
Have been keeping a watch on it and if i sit at 60mph it sits just below 80 deg C at 70-80mph it sits at 80 deg C progressively rising as the speed increases, this is with ambient temperature of 15-20 deg outside.

Car has had genuine coolant changes every 2 years and is clean as a whistle inside. New water pump was fitted about 30K ago due to inpeller breaking, new thermostat fitted at same time. New genuine fan clutch fitted in March this year and it works!!! Aircon additional fans are both working etc etc. All parts used are genuine parts.

Anyone any ideas on what it could be?? Doesnt use any coolant.

Had a good look yesterday and the rads all seem clean no dead flies blocking fins etc. One point of note, where does the hot air once it has been through the rad exit the car, there is plenty of room for air to get into the engine bay but not much room for it to escape with the noise encapsulation etc.

Car used to stay rock staedy just below 80 deg C no matter what speed i travelled.

Wary that maybe something is starting to go wrong.

Thanks in advance guys.

McCool300TD

Hot air comes out under the windscreen, and also down the back of the engine around the exhaust.

I'd have a look at the temp sensor first, before anything else.

Make sure the new clutch is working properly. A really easy way to check it is to get the car up to operating temperature, open the hood, and then have someone watch the fan. Turn off the motor and the engine fan should stop dead in under 3 seconds.

When mine was going bad it would coast for about 6 or 7 before lazily coming to a stop.

I agree with the above.
You should also check the radiator, A/C condenser, intercooler and front fans for blockage like leaves or a plastic bag.

That's kind of weird, especially when the temp stays below 80C. The thermostat doesn't even start to open until it reaches that temp. A fully warmed up engine should be at slightly above 80C. Assuming you installed the thermostat correctly, you might want to look at replacing the coolant temp sensor. Also it never hurts to pressure test the cooling system and check for residual pressure in the system after the engine completely cools down. Residual pressure would indicate a head gasket leak which is known to contribute to overheating. Guess how I know. :(

How about getting an infra red thermometer and scan the radiator? See if there are any cold or hot spots. It should be about the same within a few degrees of each other. If not, the radiator is clogged on the inside.

My '98 will stay just below 80 in cooler weather. I think the thermostats must open at around 78C as I have replaced mine and both reacted the same way...they will hover at about 78C unless ambeint temps go above 70F, then it can go as high as around 90C in near 100F ambient but never above that.

Hi Parrot

I have checked and there is no way the air can get out round the windscreen, just seems to go out round the exhaust and CAT.
Rad is clean on the outside and even hosed through the condenser and rad the other day but no debris or leaves or anything like that.

McCool300TD (alias 230K on MBClub;))