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solarboy 09-28-2012 11:24 AM

Coolant circulating?
Hello -

I changed the coolant in my 04 Focus with SPI.

What is the possibility of an airlock? How do I know coolant is circulating? When I compress upper rad hose, it compresses very easily .... doesn't seem to be any pressure in it?

Seems like a simple question ... but how to make sure?


PS- The dashboard temp gauge - does that measure water temp OR oil temp? How accurate are those? If coolant wasn't circulating correctly, would that gauge properly indicate engine temp? Want to make sure my engine does not overheat.

6SPD_soul 09-28-2012 06:55 PM

A good start would be to check the coolant temp and thermostat operation with the odometer test mode, which is detailed here in numerous places and can be easily searched. You basically just start the car while holding in the trip odometer reset button which activates the test mode and allows you to view numerous data readouts, coolant temp being one of them. It displays in celsius but since you're a wacky canuck it should be easily deciphered.

You want the engine and coolant cold so this is obvious, but start and drive it in odometer test mode while keeping an eye on the coolant temp reading. You should see it gradually rise from ambient temp and peak around 90 C and then gradually drop back down to near 80 and after a bit it should come back up to around 90 or so. The thermostat is always in intermediate positions by design so the coolant temp should just fluctuate fairly slowly, if it does this it's a safe assumption that coolant is circulating correctly.

The instrument panel gauge is the primary coolant temp display, and they're designed to stay in the middle as long as the coolant temp is within a fairly wide range of operating conditions so owners don't freak out about the needle moving too much. Given that, it's a reliable indicator of coolant temp and you can probably trust it as long as it's moving.

If the previously mentioned gauge is staying in the middle, you probably have nothing to worry about and I've spent five minutes too long on the subject, but cheers anyway on this glorious Friday.

solarboy 09-29-2012 06:53 AM

Thank you so much for the answer.....much appreciated!

I will try the diagnostic-mode and see. Even a crazy Canuck like me can probably figure that out [cheers]

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