Coolant boiling off

[anotherUserName]

Drove my 2020 WRX (stock) yesterday. Outside temp 95-99 degrees. Drove conservatively, highest observed oil temp was 225f. Got home and coolant reservoir was empty. Second time this has happened. At lower oil temps coolant reservoir is full after driving. I feel like 225 degrees shouldn't cause the coolant to boil off. How do people in places like AZ and TX drive their WRX around with out losing their coolant? This can't be normal. Please help.

 

[Ecmbuster]

Normal oil temperature should be close to 210-220 F.
That is all dependent on the scan tool.

1) What scan tool is being used?
2) Was a pressure test performed on the cooling system?
3) Was the rad cap pressure tested?
4) Is the ECT (Engine Coolant Temperature) monitored?
5) What is the quality of the coolant?

 

[anotherUserName]

Normal oil temperature should be close to 210-220 F.
That is all dependent on the scan tool.

1) What scan tool is being used?
Just the readout on the 3 pack in the center of the dash.
2) Was a pressure test performed on the cooling system?
No. Not yet. Hadn't thought of that.
3) Was the rad cap pressure tested?
No.
4) Is the ECT (Engine Coolant Temperature) monitored?
Just the analog gauge in the bottom left of the gauges behind the steering wheel.
5) What is the quality of the coolant?
Brand new from AutoZone. The blue bottle made for Asian cars, Subaru listed on the bottle.

 

[anotherUserName]

As a follow up to help anyone who may have a similar problem; I bought a new radiator cap from the dealer. It was a different size and build structure than the one that came with my car when I bought it (used car). I've driven it two days in hot temps. Oil temp got up to 225 and 230, but no boiling coolant in the reservoir! So far this appears to have solved the problem.

 

[Ecmbuster]

Good solution and the difference with quality replacement parts.

Blog - How Radiator Cap Pressure Affects Cooling

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