Expansion tank

[colin mee]

Hello all.I never have any water in my expansion tank.is this normal. And if so what is the purpose of it

[LLantrisant]

than there is something wrong.

[mrzigazaga]

Hi Colin.

You should be able to maintain 1.5 litres or around two inches from the top opening of coolant in the expansion tank..any more will get ejected to the catch tank under it...Is it warming up quick?...are you getting any water under the car?...is there any scale on the side of the water pump housing?..



Ziga

[colin mee]

Sorry I meant the catchment tank

[KKson]

My expansion tank is always to the correct level. The idea is that if the coolant expands and lifts the cap then the surplus water should enter the overflow tank (TR7 washer bottle). You need to ensure that this small overflow pipe is air tight and there's water in the overflow bottle covering the bottom of the overflow pipe. When the engine cools down if there are any air pockets these will reduce, forming a partial vacuum. This in turn will pull the water from the overflow bottle back into the expansion tank. If either the bottom of the overflow pipe is not submerged or the overflow pipe is not air tight, then instead of pulling the water back into the expansion tank, air will be drawn in.

[colin mee]

Thanks Keith. So if I have no water covering the end of the pipe it is not air tight

[KKson]

Correct. Also check that the overflow pipe to expansion tank is tight. If not then fit a small jubilee clip to it. When it cools it needs to be able to suck the water back in from the overflow bottle.

[colin mee]

Thanks for the info.I did half fill it from cold.but after a run it was empty

[adam quantrill]

Since fixing my remaining head gasket to an Elring one, all my water burping problems have gone away.

Also I have given up keeping the expansion tank topped up to the top, three's now a 2 inch gap under the pressure cap.

The result is that I haven't had to top up the water in over a year, and the overflow tank has remained permanently dry.

So - for a properly working wedge, it will find its own level and be happy. It's only taken me 25 years of wedge driving to stop fighting it and let it do its own thing.....

[colin mee]

I don't get any water coming from the header tank to the over flow tank.may be a drip but that's it.I am running 2 fans now so maybe it's not getting that hot

[adam quantrill]

Sounds normal then!

[colin mee]

Thanks Adam. Nice to know. You going the wedge fest

[adam quantrill]

Arooga! Just booked me room.