position of radiator expansion tank

[02GF74]

Does the radiator expansion tank sit at the highest position in the cooling system i.e. higer than the radiator and engine?

Secondary question; has anyone blocked off the radiator filler cap (solding a brass plate say) to use with an expansion tank - any reason why that won't work?

[Les Henson]

Well to be accurtae, the water level in the expansion tank should be the highest point in some vehicles , just so that when the engine cools down the system remains full. Some vehicles (series for example), have the tank at the side of the Rad, and contraction of the water as it cools, sucks it back into the rad.

I don't see a problem with blocking the filler cap as long as

1. There's somewhere else you can fill the system from.

2. You don't create an air trap by doing so.

Les.

[Niall_CSK]

You can mount it lower but you have to be very sure it's going to get sucked back, perished hoses or old connections leak much more easily when cold and under vacumn than when hot under pressure.

We had this with some engines and it was amazing how fast the cavitaion at the pump erroded away the impeller & casing (alloy) with a resulting pressure drop in the FW system.

Edited November 22, 2005 by Niall_CSK

[Lighthouse_jim]

Secondary question; has anyone blocked off the radiator filler cap (solding a brass plate say) to use with an expansion tank - any reason why that won't work?

Don't forget that the radiator cap has a pressure relief valve in it. It maintains a pressure in the system (marked on the cap usually 9-13 psi) to increase the boiling point of the coolant. It seals on both the small lip inside the neck and the large flange at the top. If you seal the top flange only, the system will pressurise the expansion bottle. If this hasn't got a radiator type cap, it will allow the coolant to boil at a lower temperature.

Jim