Hi, I was wondering what is the normal operating temp on a NA OM606. Also when should the 2 fans on front of the rad kick in?

In our 95 diesel, the temp hovers just about the 80*C mark, however once the temp rose when the car was idiling with the AC on. The temp needle was just above the next mark after the 80*C. The fans never kicked in so I am wondering at what temp should they kick in.

I have the same car, and live in Montreal where the weather is somewhat similar to yours in Toronto. At least in the summer.

My temp gauge always hoovers around the 90C mark, with or without AC with the occasional climb to 100C when idling or climbing hills.

The fans should activate on their low speed setting when the AC is working properly and the ambient temperature is roughly 22C or above. Additionally, they should also come on on Maximum speed when the engine temperature reaches 105-110C (again approximately)

If your normal operating temperature in the summer is 80C, this is rather on the low side. It may indicate a defective thermostat, or an inaccurate temperature sender or gauge.


Phil

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'95 E300 Diesel, 264,000 Miles. [Sold it]

Around 90C - Phoenix area often in the 100'sF (110 etc) and remains in that area.

I live in South Florida and my 99 E300 hardly ever goes above 85C, even when towing a small trailer in 95F weather. If it went to 100C, I would definitely pull over and investigate. The AC fans do little when driving down the highway but are essential when idling. Make sure both of them are working. A little belt turns one and I can't remember which one it is at the moment. Good luck.

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99 E300 133K
98 ML320 99K
87 Saab 900 Turbo Conv 123K

100C is 212F and perfectly acceptable.

My '95 E300D normally shows 80 - 85 at cruise on hot summer days with a/c on - up to 90F. Come to a stop after a run and it climbs up to 100+. I have yet to have the aux fans come on - I suspect something is amiss. Other posts have indicated that they come on at around 105 or when the a/c head pressure reaches a certain point.

In my so far not too serious attempts to determine if the fans work I have shorted the temperature switch with no luck, and, for the life of me I can not find the power leads to the fan motors to hot wire them to check if they work!

Anyone got a picture or can point me to where the power leads for the aux fans are?

Rgds,
Chris W.

That sounds really high. The average consensus I've seen is between 80-85. 90 and going to 110 means something is terribly wrong.

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'97 E300
'99 E300

E300D, Chris W.,

You aux fans should come on high speed when you pull the connector off the blue 2 prong temp sensor or at a coolant temp of 107c+ (key in second position or car running). Have you checked the fuses in the aux fan relays? There are two aux fan relays a blue 15A low speed (safe to upgrade to a 20-25A fuse if blown) and a green 30A high speed. The relays are located under the cover behind the fuses. To access them remove the six screws on the fuse/relay box (The two front screws are hiding under the front fuse cover (Remove that cover first). Also check fuse #8 (8A).

If the fuses are good check the low speed aux fan resistor (looks like this:http://img.eautopartscatalog.com/live/G504051927BER.JPG) located on left (drivers side) front of the engine compartment behind the headlight, to see whether or not it's blown or the wiring to it has corroded. You can test low speed operation by jumping the connections of the leads going to the fan switch (The fan switch is on the side of the A/C drier and is red).

I had the low speed fan setting for the A/C go out on me due to corroded wiring at the resistor. When running the A/C temps would be fine on the highway but when stopped or at low speed would clime to 100C+ and engage the aux fans on high speed. I rewired from the relay to the resistor with heavier gauge wire and replaced the resistor and it has worked fine since then. It's not good to be running the A/C with non-operational aux fans. It is bad for the compressor and should be fixed ASAP.

The proper operation of the aux fans on your car ('95 E300D) is, low speed on & off with the A/C and high speed on at 107+c and off at 100c.

Hope this helps

Chris

In addition to the excellent information from Chris above:

Any temp between 80C and 100C is perfectly normal. The newer cars (and even some of the older ones) DO NOT necessarily park at 85C all the time like your dad's 1980 300D may have done. Also, the temp sender tends to read low with age, so those of you who think your old car runs at 85C all the time might be in for a shock if you bought a new $10 sending unit. More typical is 85-95C under most conditions. Up to 100-105C is fine if the engine is under heavy load, and/or ambient temps are high. However if it's going past 100C on a regular basis, that's not good, and if you see 110C+, that's definitely not good... time to figure out what's wrong (dirty radiator fins? bad fan clutch? coolant flush needed? bad t-stat? etc, etc...)

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Ok, the car still runs a litlle hot. I need to know one thing. On the temp gauge, it says 80* C, then there is a dash with no vaule and then it is 120*C at the very top. I am wondering where the 107*C - 110*C mark is. What is the temp. vaule of the dash bet. 80*C and the 120*C?