Sniff test will tell very little (not a conclusive test)
I agree it won't rule a CHG problem out, but it will rule it in if the dye goes yellow.
and the coolant loss is more in line with a weaping seal and not a head gasket (e.g. top up every 1500 miles)
perhaps but how would a weaping seal cause an increase in pressure?
The air comes out, can feel it on fingers
That means there is more air in the system (and possibly less coolant) on day (n+1) than there was on day (n). Assuming the ambient conditions are similar (same temperature and pressure), and the engine was stone cold when you topped it up, and stone cold again when you remove the cap, then how has the extra air got in?
It could be a weaping seal, and when the engie is hot, the water pressure will force water out of the leak. However, it can't let air in whilst the pressure is higher than ambient. As the engine cools again the pressure will drop back to ambient. If the system is sealed, then this will cause a vacuum in the header tank. If the system isn't sealed (weeping seal still open) then air will get sucked in once the temperature drops enough to cause the internal pressure to be less than ambient. But this is unlikely to result in a system whose pressure is above ambiernt the next morning, unless there is a large difference in nighttime and daytime (measurement time) temps.
So next question - is the car garaged, or left out overnight? Next time you use the car, don't open the cap untill mid afternoon on the day AFTER you last drove it. Is it still under pressure then?
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Topic: Coolant bottle pressure (Read 1232 times)