I am the original owner of a 1998 E300 Turbo Diesel that has 93K miles on it.

My car overheated a few weeks ago so I took it in for repair. First I was told that the thermostat was stuck so it was replaced. Then I was told that the engine was still running hot due to some blockage in the radiator. So I ended up with a new radiator and a new thermostat. The bill came to $1700. Since it was repaired, I expect the engine running in the lower end of the operting tempere but noticed that the engine temperature is still high, above 90 degrees Celsius (To be honest, I became obsessed with the engine temperature since it overheated. But I don't remember what the normal temperature was before the overheating.). I called the service rep at the dealership and was told that the 90+ is within the normal operating range of between 80 - 100 C). Does anyone have any idea what the normal operting temperature should be per a published spec.?

Coincidentally, I have been watching the temperature gauges in my younger son's 2004 BMW 325 and my older son's 2001 Nissan Maxima while riding with them. I noticed that the temperature indicator sits dead in the center for both cars. I deduce from my observations that the middle point at 80 degrees Celsius should be the normal operating temperature for MBZ cars.

In my case, the engine is always running at the 90+ temperature no matter whether I am on the freeway going 70 miles per hour or driving in the neighborhood at 25 miles per hour. Once the engine is warmed up, it stays at 90+. This is also winter/Spring time. I am wondering how hot the engine will be running in the Summer time. I am not convinced that the engine overheating problem is totally solved with the installation of a brand new radiator and a brand new thermostat.

Please advice.

Thanks.

TJ Lee

 

I agree my diesel runs at about 80-85 and my 560sel runs pretty much always at 85. They may have put the wrong thermosat in ur car. But the temp does stay the same at 25 or at 70 mph.

 

I have a 94 SL500, and it runs just below 80 degrees C and just above it. 80C is equivelent to 176 F. So the dealer was right in telling you of the range between 80-100 C

I also have an 87 BMW which runs just under the dead center, which in fact is supposed to be 182 degrees F. The mark before is 144 F. The thermostat in the BMW is an 80ยบ psi.

Therefore, I think operating temp should be around 176 F

 

The temp gauge should sit still under normal driving conditions since the temperature is regulated first by the thermostat (to get the system up to operating temperature quickly) and then the capability of the cooling system. The cooling system should be capable of cooling the engine under something like 75% power and elevated 40deg c ambient temperatures CONTINUOUSLY. Exact power and temp conditions depend upon the manufacturers test regimes.
The temp sensor is fitted in the engine (usually in the cylinder head) and NOT the radiator.
Once theradiator / cooling system to struggle (due to fault or poor design) the temp gauge to rise the position of the gauge will be dependent upon how much work the engine is doing. Going up hill requires more power and therefore generates more heat, therefore the needle will rise.
If the gauge does not sit exactly in the middle of the range on your gauge don't worry, this is most likely just a calibration problem due to extremes of tolerance in the electrics, sensor, gauge etc..
The key thing is that its steady.
Stuart

 

I have a 98' 300 Turbodiesel and in Portugal with temperatures of 40ยบ C the engine temperature stays at 85 and sometimes 90-93 in the city traffic. But this is the station wagon.

The limousine version for the same car same engine same year, (my father's car) stays at 80 and sometimes above (75).

To see the engine temp, and if you have the digital climate control, press the key REST for 3-5 seconds and will appear on the left a number (1) and on the right another number (temp of the car interior).

If you press the left key "auto" until you get the number 6 on the left that is the temp of the engine. Press again the left "auto" button and appears the number 7 on the left is the pressure of water pump and number 8 is the radiator temp.

Check if the radiator fan turns on.

I ask the same thing when I bought the car in 2004 and some people says it's normal to reach 90ยบ C and even in shops of mercedes for auto repairs they always confirm that 90ยบ C in the low speed traffic is normal.

 

Hi,

90 deg C is absolutely within normal range.

Pressurised antifreeze doesn't boil till about 130 deg C. Thats why the top rad hose should be made of "rubber" compound that can handle temps up to at least this temp C.

Stuart

 

My 99 C280 runs between 80 degrees C and 90 degrees C. My 79 450SLC runs between 175 degeed F and 200 degees F. Both cars are in there normal temperture range.

The 450SLC owner manual goes as far as saying the temp gauge may go into the red under certain circumstances, It advised heavy traffic, long standing periods in stopped traffic or justing letting the engine run while your talking to someone, (a no no). The paragraph recommends to put the car in neutral TURN OFF the AC if on. Now a day's it is the other way around. and the emgine should cool down. Of course if is doesn't it says to take the car to the dealer. Almost forget, it says under normal operating conditions and on a hot day the cars temp gauge could run up close to the red but shouldn't go into the red if you are driving at posted speed, under these condition, it might get as high as 200 DegreesF but usually sits between 175 degrees f and 200 degreesF. The 450SLC is a 4.5 liter V8. It has a lot of torque around 220 ft pounds and around 195HP.

One think that I find might be a problem is, it take forever to warm up, even in warmer weather. I bought a new thermostat from a local Mercedes dealer. He gave me a 75 degree stat. The shop manual says 80 degee stat. I pointed this out to him. I was told, due to slow warm up complaints from owners going back to the early 80's the thermostat requirement was lowered to 75 degree. Which to me makes no sense at all. As I would think it should be a higher temp stat. That way the engine would warm up faster?

But I also discovered while email the former owner of the car. He changed the water pump and stat in the summer of 05. The car started running hot. He bought a aftermarket water pump and came to find out the impeller was smaller then the OEM. Now I am thinking if the pulley can be replaced and should I try and find a larger pulley, which in theory would run the water pump faster and thus circulate the coolant more efficiently? But would the pump handle this?? Or should I bit the bullet for a new pump? or intall the new stat and see what happens?? Decision, decisions, decisions

My C280 once I start it and go, within a couple of minutes it is up to 80 degrees C. Don't know if it has a thermstat or is electonically controlled water pump?

 

The Mercedes resouces say that it's normal for the temp guage to rise above the middle point sometimes, especially after long drives such as sitting in traffica a while or alot of city driving. But it shouldn't rise too high because at that point the coolant system is suppose to really kick in and the temp should drop way before it overheats.


(Just as when my water pump sprung a leak after sitting in storage after a while, it slowly rose, after driving a while, then it kept creeping upward and never went back down. Come to fid out, it was leaking so rapidly and reducing the amount of coolant that it started to make the coolant hot to the point that it started to eveporate inside the system while some laked out the bad gasket and reducing the cooling capacity causingthe car to slowly over heat. I never let it just straight go into the red though. I hate storing vehicles for a long time. I think if they move me they should pay for the repairs that is associated with having a car sitting.)