Air block in coolant?

Joseph Meehan · 2005-09-07T23:55:08+00:00

I have a 2002 NB TDI. I suspect I may have a air in the system. Maybe maybe not. I am having an intermittent problem with the CEL activating indicating a problem with the coolant temp sensor. The sensor appears to check out OK with the right resistance at several temperatures and I have cleaned the contacts as well. Squeezing the upper radiator hose I get a sound that to me sounds like there is air in the system based on my experience on other cars. (the rush of fluid sound) The coolant was replaced by VW about 6 months ago and there has been no indication of any problems since then (or before it was just prescribed maintenance.) The expansion tank is slightly above the full line and I have never observed it changing noticeably hot or cold. Looking at my Bentley manual I don't see where the coolant is added when it is being changed. The manual shows both the drains but seems mute when it comes to filling it. So any suggestions about pinning this down and maybe ruling out air in the system that might cause unexpected temperature sensed changes? Any other things to check? Any why to check for air in the system?See next question about sensors, if you are not already tired of me.