AWX engine temperature and coolant system pressure question

[bk.bas99]

running a VCDS run on mine show that the temp doesn't get above 87 and I'm guessing that's why I only average around 45 mpg. It has had a new (pukka) sensor fitted, so not that. It could be the thermostat, but I have noticed that the system doesn't pressurise much and over a long period there is some coolant loss, so suspect a slight leak somewhere. Does anyone know if there is any correlation between system pressure and temperature (something to do with boyles law if I remember vaugely from school??) or is it just the thermostat?:confused:

[martin1810]

You're right about boils law but whether this would make much difference at 87 C is debatable. Basically you raise the boiling point by increasing the pressure so the radiator can run hotter without boiling. A new pressure cap is a cheap and easy fix though so it's worth a try. At 87 C you are so close to ideal I doubt you really have a problem with the thermostat.

[bk.bas99]

You're right about boils law but whether this would make much difference at 87 C is debatable. Basically you raise the boiling point by increasing the pressure so the radiator can run hotter without boiling. A new pressure cap is a cheap and easy fix though so it's worth a try. At 87 C you are so close to ideal I doubt you really have a problem with the thermostat.

it generally hovers around the 85 mark, but gets up to 87 after a really long run or on a hot day. I would have thought it should get to temp reasonably quickly then stay there regardless of outside temp or distance which makes me wonder about the pressure thing?

[martin1810]

It should get up to temp and stay there fairly quickly. You can log temp warm up with VCDS. Do a search I think PCDoctor had a similar problem and did some logs.