Should also have heater on.

Both caps are 200’s. Look identical.


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Coolant Temp Warning - pegged to red. Holy crap.
 

I'm used to seeing maybe 10-20C Delta. 95 in 70/75 out I can't recall.

Something is very confusing here, the topic being discussed has nothing to do with the thread headline. A new thread should be started not related to the software bug that causes an erroneous overheat needle.

It doesn't take long to overheat if there is a flow problem. I recently replaced an electric water pump on an E90 and it would kick on the fan full speed in an attempt to air-cool the water cooled engine within a few minutes of starting.

The electric fan runs based on the output temp I believe so if you don't have the mechanical fan installed it wouldn't be surprising to have an overheat situation if the car isn't moving to get airflow through the radiator however:

If the water pump is moving the coolant and the t-stat is open the in and out of the radiator will become the same temp without airflow through the radiator.

Since a hose sucked in is so often the cap I would be positive they are the same even if I had to purchase a new cap to do so. Perhaps there is a difference in how they seal.

Good point, may do that. Any other possible cause?

Ironically Before I did the head gasket one of the symptoms was the hoses would stay really tight overnight....


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Vacuum suggests high temp difference and/or too much air in the system. I think if you open the system while hot you can expect collapsed hoses when cool. Level must be set cold engine off key on engine off to bleed.


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I can't tell from your posts that the system has been bled properly. What was your process? I would purchase an infrared thermometer. IMO It is one of those must have DIY testing tools. I would like to eliminate one of the new head gaskets as the problem. Have you had to add coolant since you filled it to proper level the first time. If so, smell the exhaust when it is running for a sweet smell or any trace of white smoke or merely for wet soot inside a tailpipe.

Never sure about bleeding. Turnedthe key on position and let the aux pump pull the coolant into the hoses and heater core. Minute and a half or so. Added coolant and purified water until it was near reservoir top. Cracked bleed screw until no air bubbles. Didn’t take long. Not able to get on a slop with wife’s car behind me but I think it’s bled.

Constant stream from the squirt hole. Heat is hot.


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On level ground, engine cold and not running, fill expansion tank until the float is fully extended not to the top of the expansion tank.
Replace the cap.
Let it run for about ten minutes with the heater at highest temp.
Slowly open the bled screw about 1 turn. Close the bled screw so very little fluid escapes and let fluid continue to come out until you haven't seen an air bubble for a minute or two.
Close the screw. Let the engine cool.
Without starting the engine, remove the cap and add fluid as necessary. Put the cap back on. System is bled.

Thanks. Will do that.


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