Can anybody out there tell if there is any real reason to fit an expansion tank on the cooling of my v8?I see that everybody has but why?
Phil

Depends on the cooling system employed - if the rad is flooded i.e not the highest part of the system -which it generally is with these installations due to hieght restrictions - to ensure that the heads etc. are free from airlocks there must be a water level higher than the heads and this is usually the header tank as it can be positioned on the bulkhead and up into the bonnet bulge.

Water expansion has to go somewhere. - the header in the rad is the usual place when its the highest point. Water expands about 4% volume from 0-100C so your expansion tank/system miust be able to accomodate this - remember water is generall incompressable so when it starts to expand pressure can build alarmingly.

I did write a few pages on this recently - glad to forward it on if you think it will help.

Cheers

Andrew

Hi Andy
What you have written makes perfect sense and i should have thought of that myself,but i,m having a lights on but nobodies home moment when it comes to the b+.My thought was to use a 3ltr capri rad and an overflow bottle attached to the overflow pipe on the rad idea bieng that as the water expanded it blew into the bottle and then as the system cooled the water was then sucked back into the radiater.I used this set up quite sucsessfully on my sprint cars but never on a road going motor, which is how the question of expansion tanks came about as these tanks appear in the main to be under pressure from the coolant system and since your reply i,ve realised the expanded water still circulates round the system where my way the expanded water is sat in a bottle on the side of the radiator.Measuring up the rad will just sit leval with the top of the rocker covers but i will have a water pipe which is higher between the SU,s.Do you think my way will work on a road going car?
Phil

B)

What you have to make sure is that air is always removed to a safe zone in the cooling system - in short never the engine. - The normal installation had the hose with the T-stat as the high point of the engine feeding into the rad header - so no problems - our installations generally have that bit of hose still at the highest point. but with the rad below it meaning air is trapped in the hose or the top of the heads/manifold - the solution is a joiner with an air beed to a header/expansion tank at this high point so the system continually auto bleeds. it is possible to get all the air out and seal it kind of as you describe but i would not rely on it.

Andrew

The more i think about it the less sure i am that my way would work on a road going car this small with a lump that size in it so i guess its time to get out the tape measure and go radiator shopping

Phil