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Old 12-17-2010, 07:46 PM
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Join Date: Dec 2008
Posts: 73
help were is the temp sensor that causes cold start issues

hi guys my girlfriends 300e with only 47k miles on it has a really rough time starting i have pretty much done most the basics like change the ovp clean the icv and seafoamed the gas tank. the issue has been helped out a little but still takes forever to start. i noticed that the coolant light stays on until car is warm,the car has no missing coolant completely full. i read some were that the coolant temp sensor could be the cause of bad cold start were is it located. the car runs excellent when warm and the temp light goes away most of the time thanx for the help guys its getting very frustrating trying to hunt down the cold start issue. winters in nebraska are very unpredictable lol

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Old 12-17-2010, 09:33 PM
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Join Date: Nov 2008
Location: Canada
Posts: 600
What year is the 300E? The coolant temp sensor is located on the end of the cylinder head on the driver's side near the firewall. There is also a seperate sensor for the coolant level. It sounds like yours is defective causing the low coolant light to remain on. You may want to check your fuel pressures to see that they are up to par. I have found low fuel pressure to be a common cause of driveabilty issues on the CIS equipped M103.
1989 300CE
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Old 12-18-2010, 05:32 AM
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Location: Melbourne Australia
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Location of sensor on later M103

Old type two pronged sensor - is in same position as newer one - i.e. at the rear of the head.

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Old 12-18-2010, 06:00 AM
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Thanx guys that helps alot will try that hope it works the dead bug parts the best lol and the 300e is 1990
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Old 12-18-2010, 06:02 AM
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Join Date: Aug 2002
Location: Southeastern PA
Posts: 3,035
nebraska190E, inspect the distributor cap, distributor rotor, ignition wires and spark plugs. Despite the low mileage these items may all need to be replaced.

The coolant temperature shows on the dashboard guage. There is no coolant temperature warning light. As mentioned, it's likely the coolant level sensor (in the expansion tank) is bad and needs to be replaced; or there could be air trapped in the cooling system. Do you hear gurgling sounds when the engine is running and the HVAC system is calling for heat?
Fred Hoelzle
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Old 12-18-2010, 01:59 PM
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Join Date: Dec 2008
Posts: 73
Ferdman I do not hear any gurglin and everything appears to be good on the engine no part is even missing.I will voltage check things today wen I replace that sensor. The cold start issue has been cut down from 5 min to start the car to 2 mins to start but still takes forever. Thanx for the advice

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