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

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1988 190E Sold
1996 C230K Sport Sold
His: 98 E300TD Estate, 7 seater, Avantgarde, Silver, Black cloth, parameter steering, dipping rvm, folding mirrors, rain sensing wipers, pentagon tints, 17" Elegance wheels. 298K
Hers: 93 300TD, 7 seater, Grey MB Tex pearl blue metallic, 15" 8 hole alloys, OTG, Cruise, not much else 220K

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.

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2005 Pathfinder LE
2001 E55
1998 M3
1982 320i

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.

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2004 VW Jetta TDI (manual)

Past MB's: '96 E300D, '83 240D, '82 300D, '87 300D, '87 420SEL

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.

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01 Ford Excursion Powerstroke
99 E300 Turbodiesel
91 Vette with 383 motor
05 Polaris Sportsman 800 EFI
06 Polaris Sportsman 500 EFI
03 SeaDoo GTX SC Red
03 SeaDoo GTX SC Yellow
04 Tailgator 21 ft Toy Hauler
11 Harley Davidson 883 SuperLow

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.

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Marty D.

2013 C300 4Matic
1984 BMW 733i
2013 Lincoln MKz

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)

__________________
1988 190E Sold
1996 C230K Sport Sold
His: 98 E300TD Estate, 7 seater, Avantgarde, Silver, Black cloth, parameter steering, dipping rvm, folding mirrors, rain sensing wipers, pentagon tints, 17" Elegance wheels. 298K
Hers: 93 300TD, 7 seater, Grey MB Tex pearl blue metallic, 15" 8 hole alloys, OTG, Cruise, not much else 220K