The W123 chassis covers 240D's, 300D's, 300TD's, 280E's, and several other models of Mercedes coupes, sedans and wagons from model years 1977 to 1985.

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1981 Mercedes 280e: Wants to stall out at about 90 deg

My 280e ..well has no working heat, but ...... more problematic ..it wants to stall out if it reaches about 90 degrees, it will start back up and will run fine again for a bit after a little cool down time, but man........ pain.. lol

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Your lack of heat, and the issue of the car stalling, are likely unrelated.

Your new monovalve could have been defective from the factory. New ones are not made like they used to be.

Another potential issue is that the electromagnet in the monovalve is going bad.

In either case that would lead to a failure for the monovalve to close properly allowing hot coolant to bypass the heater core.

The stalling issue is likely something else entirely and likely related to your electronic fuel injection. I unfortunately do not know about those systems. Hopefully you'll find an answer for that somewhere else!

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I'm assuming that you are saying 90 deg C? correct?

If so that is 195 deg F, since you say the heater doesn't work my guess is that the thermostat some time in the past taken out or has failed completely. With no thermostat the water never has time to slow down to make the heater work, as well spend enough time in the radiator to cool off. There by causing a sensor to tell the computer that it's getting hot and to shut it down. I'd get a new thermostat for the recommended temp and see if that helps.

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It has a new thermostat and water pump, (as part of an attempt to resolve the ((stil)) no heat problem) though spring is springing lol. Also the monovalve near the firewall was replaced. I'm Just falling deeper into a clueless hole. A sensor you say? :)

And thank you :)

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Quick comment - a 1981 Mercedes 280E has no computers. This was well before the era of central computer controls in cars. The only temperature sensors on these cars are for the gauge in the dash, a simply resistance device, and a sensor that keeps the fan from turning on if the system is set to heat but the coolant is cold so you dont have cold air blowing on you.

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sthrnbel33 will be eternally grateful.
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