Expansion Tank

[Chewy]

Does anyone know the expansion ratio of water when heated?
Every time I fill the water expansion tank it empties completely during a good run.
I would expect it to empty to about the half way level. Once it is empty the engine does not loose any more water and the most I can ever fit in the swirl pot is about half a cup. This has never caused any problems but it does not seem right.
I am confident that I do not have any airlocks as the engine has been out of the car a couple of times, the car has done about 12,000 miles and the problem has been constant.
The expansion tank does look a bit small so I am thinking of changing it.
Anyone else had similar problem.

[canam-phil]

0.000210

Edited to say this is the volume coef at 20C Its not linear.

>> Edited by canam-phil on Monday 31st January 12:38

[B1 ECC]

Hi Glynn, I had this problem originally, were it would throw out more water than it needed to refill the system as it cooled. Solved the problem with an ally expansion tank that was nearly double the capacity of the plastic tank.

[Chewy]

Thanks - 0.000210 doesn't seem that much compared to the amount of water it throws out. I assume that is per each degree rise?

Hello Ian
The tank I have is an alloy tank as supplied by the factory but it doesn't seem that big. I'll try and measure the capacity tonight.
Are you meeting up on Thursday? If so you can compare, as I'll be in my GTR.

[ultimacz]

Don´t want to scare you and most probably you don´t have the same problem. Just what happened to me when I was wondering where the water was going and was also thinking about a bigger expansion tank:

I tried to catch the water from the expansion tank into a bottle and measured how much was actually pushed out. Found out then that coolant must be lost also another way. Could not see any marks, though, also no coolant in the oil... We also made pressure tests and no water leaking anywhere, not one drop... After several weeks we found a very small crack in the block, where water was lost probably only under certain conditions, i.e. block being hot... It is an AS engine, ran approx. 8.000 miles. Problem is that the blocks used by AS are >30 yrs. old so there is no real guarantee that they will last. Replaced it now with a new Dart block which looks great (machined and prepared by AS - great work).

Hope that helps, or better said, hope it will not be the same in your case.

Peter

[ultimacz]

Forgot one thing. We had a similar problem also when we once took the motor out and when putting it back confused the caps of the 2 tanks, i.e. put the cap without pressure valve on the expansion tank, if I remember right. After each run all the expansion tank was empty then, because it pushed all water out on the street.

[canam-phil]

Chewy said:

Thanks - 0.000210 doesn't seem that much compared to the amount of water it throws out. I assume that is per each degree rise?

Correct it is per degree. Just so used to coefficients of expansion being per unit temperature rise