Don't get fooled by coolant levels

[simpo two]

I set off in the Griff today, having previously checked that the coolant level in the expansion tank was OK. It was.

And yet after 3 miles the temp gauge was 90+, the fans were on and the engine was sounding a bit unhappy. Promptly pulled over and called the AA.

The answer? No coolant - he checked the swirlpot (which IIRC in a 500 you're not supposed to use) and it was empty.

3/4 full expansion tank, empty swirlpot. Not good. In future I can't really trust what I see in the exp tank - so I guess I'll have to look in the swirlpot each time?

Oh yes, and 3 rads in 3 years is not imporessive. Are they made by Cadburys?

[ATG]

You must check the level in the swirl pot. It is part of the main circulation path of the coolant between engine and radiator. The expansion tank is on a spur off this path, so the level in the expansion tank is not a good indicator of what is going on elsewhere.

[angusfaldo]

Go very easy with the big brass screw though.

A previous owner of mine had managed to twist the aluminium roof of the swirlpot when removing it. And then used areldite to fill in the holes

Had to have a new swirl pot put in a couple of weeks ago.

Apparently the trick is to use a long lever and turn it sharply, so as not to give the ally time to bend. Slow application of force with mole grips or something else could lead to problems.

Question is - what was wrong with your system to let that much air in? Could be a minor rad leak that draws in air at higher temps?

[simpo two]

After a long run last weekend it seemed fine. Then, with the engine still warm (not hot) I opened the exp tank to check levels and there was quite a release of pressure. After that, it started dripping. I've heard that sudden pressure release might have fractured some solder joints - is this true?

What we need is a way to check coolant levels without opening anything!