Air block in coolant?

You worry too much. Once filled, run the car until the rad fans come on then let it cool. Top off coolant if needed and have fun!

The question is where do you top off the coolant? Where do you fill it to begin with? From looking at the overflow tank I would not guess that it is anything but full. But I still get the sound I referred to.

You top it off at the overflow tank. When I have changed coolant in the past, the engine will heat up, the temperature gauge will shoot up, and then suddenly the coolant will suck out of the tank, and it'll take another couple of pints to top it off. On my '85 I used to pull off the top radiator hose and pour coolant down into it to reduce the amount that had to be sucked through the tank. Sounds to me like you're all set, if the tank is full.

Incidentally, I'm getting the same OBD code, and am going to change that coolant sensor, too.

I am still considering it, but first I am going to continue checking it. The light has been out for two days now after removing and replacing the connector a few times. This may be nothing more than the VW electrical problem gremlin. I have another gremlin in a turn signal lamp plug I am working on.

Well... I think the coolant temp sensor is a known QC issue. My CEL is only intermittent for the P0118 code, it seems to reset itself every 24 hours or so, and I have not futzed with the connector at all. I'll replace mine and let you know what happens.

Thanks.

Thanks, but if you replaced the coolant, how would you refill it?

through that bottle.

You mean I could add a whole engine and radiator full of coolant through the overflow bottle? A couple of gallons???

Yes sir.

According to a VW manual, just keep filling it until it gets full (no more bubbles). In order to speed up the process, you can "burp" the radiator hoses (be aware of bubbles coming from the overflow tank). Then close the cap and start the engine. Wait until ir fully warms up (radiator fans begin to turn). Stop the engine and top up the coolant if needed. Oh, by the way - the correct level of coolant between MIX and MAX when engine is _WARMED UP_.

And do not open the coolant tank cap when engine is hot. Or you risk that your coolant suddently starts boiling (due to the lack of pressure) and spilling out.

On my A3 if I waited for the fan to kick on at the first heat cycle, I'd have an over heated engine. I just run it for 5-10 minutes, shut it down, let it cool a little or until it suck most of the coolant out of the ball. Then SLOWLY, CAREFULLY open the bottle's lid, avoiding the steam and coolant. Slowly add in more coolant (cool coolant in a HOT engine isn't a good thing done too quickly). Do another heat cycle. Put extra premixed coolant in trunk, watch the level closely for a couple days, done.

Mark '95 Jetta GLS

Heh, I just re-told it from that funny blue book with VW logo on it :) As from my own experience, I was usually able to fill in the most of coolant (i.e. the complete engine) without starting. Just "burp" the hoses until you can actually feel the coolant in the upper radiator hose, and no new bubbles are comming out. The heat cycle was really needed only to open the thermostat and blast out all the remaining air bubles from the radiator. Of course there could be a different setups, but one could judge on how much of the coolant actually got in.

If you do not wait for the thermostat to open (the full warm up + radiator fans kicking in), then there is no point to run the engine until it gets warm. There should be no such massive "air pockets", which would need a "deairing" through the "thermal expansion". They will be quickly blown out by the coolant pump (so 1 minute of run should be enough) or you are stuck with them ;)

Yes, it's a good advice.

You really mean that you fill a completely dry radiator and engine that way?

Yep, it's completely dry. That's why I have to watch out for the spurting steam and coolant. Try Sylvan ;)

I've also seen to kick the fans on the first heat cycle, but I had one time when it didn't, apparently due to an air bubble I missed somehow. Once it starts bubbling and sucking in coolant, it's time to shut it down and add some more.

Mark '95 Jetta GLS

My dealer replaced my Coolant temp sensor under warranty on my 2003 Golf, I'm not sure if this would be covered under goodwill if your warranty is already up?

Here in the USA that sensor is about $12.

As a side thought, you might want to do this whole exercise with the heater control full on to get any old coolant out of it as well as air?

Ed

There is no heater valve so it doesn't matter if the heat is on or off.