My sons 87 244 is overheating intermittently. Left it at a shop and they couldn’t recreate it . I’m thinking the first step is the thermostat and flush. Any better ideas? Thx

 

Is the fan shroud installed? the car will overheat at idle if the shroud is missing.

At temperature (temp gauge in the middle) Is the upper radiator hose (hose coming from the thermostat) cold or hot to the touch?

Is the return hose (bottom one at firewall) cold or hot to the touch?

If the hose at the thermostat is cold when the vehicle is at temperature, you likely need a thermostat.

If the bottom hose is cold to the touch at the firewall when the heat is turned on full blast, you likely have a clogged heater core.

Keep in mind that you may just have a bad water pump. Poor circulation due to a bad pump will cause overheating.

 

Is the engine actually overheating or are you basing the "overheat" on what the gauge is indicating?

1986 - 1993 240s have a "temperature compensation board' in the instrument cluster that malfunctions and makes the temp gauge inaccurate.
Check this website for temp board info

https://cleanflametrap.com/tempFaker.html

Or a partially clogged radiator will cause the engine temp to increase/creep up when out side air temp is above 80 or so is another cause of actual overheating. A broken/stuck closed thermostat can cause that also. When it's overheating does it continue to overheat if the heater is turned on full blast/maximum heat maximum fan?

 

That’s a good question. I’m 2000 miles away and he is pretty inexperienced in things automotive. How do I check the temp manually to see if it’s actually hot or it’s the gauge?

 

An infrared thermometer can give you a pretty accurate reading on the block near the thermostat. Most techs should own something like below -

 

Where is the best place to read the temp? Water pump? Thermostat I suppose?

 

"can give you a pretty accurate reading on the block near the thermostat."(On the block below the thermostat)

 

And ideal reading is….?

 

Between190°F-210°F roughly when the car is at operating temperature.