Hi Guy's,

I'm running a SAAB 9000 Turbo radiator and am going to convert it to run a radiator overflow bottle rather than the expansion tank. The reason being, is my radiator is a bit taller than the 1600 front and the highest point I can fit the expansion tank in the car doesn't sit high enough to allow for the radiator to fill up to its capacity with fluid. So there is about a 1-2" gap of air at the top of my radiator.

I'm going to make an overflow tank for it.
My question, because I had a look at the Datsport radiator kits is.

1. Can I just weld a bung and cap onto the radiator to fill it, and have the pressure relief valve on the overflow tank. Essentially it would do the same thing, except it would expel and suck in Air into the overflow tank rather than coolant in and out of the radiator.
As long as there is coolant into the tank, I can't see it being a problem, can anyone?

_________________
Ongoing Project: 1972 Datsun 510 S13 SR20Det. http://ozdat.com/forum/viewtopic.php?f=33&t=17898
New Daily: D22 Navara (The new workhorse)
Retired 12/2016: MY98 Subaru Impreza RX
Previous Car: Restored Green 1972 Datsun 510, Hot L18

Essentially, that is exactly what the later model Datsun Fairlady uses.
The system is sealed by a cap on the radiator proper and the pressure relief is done at the external tank via the tube at the filler neck.
The coolant is siphoned back into the radiator from the external tank.
The radiator cap will need to allow this to happen, i.e. no pressure spring or seal.
You will need to have an air bleed at the highest point in the system.
That can be the radiator cap but you will need to burp the radiator to tank line of air if it is mounted down low.

_________________
Regards, Graeme
Just trying to help...
http://nissanman.shutterfly.com/
graemes@internode.on.net

Hi Graeme,
My thinking is that the overflow tank will still be used as an "Expansion tank" like I am currently using, but the radiator will be filled at the radiator proper, rather than through a hose connected to the bottom of the volvo expansion tank that it currently works.

I understand removing the air, but why would the spring cap on the overflow tank be no good for allowing coolant to syphon back in?

It would still hold pressure to 15/16psi when getting hot, then expel the excess air out of the overflow tank when pressure is built up in the whole system, then once it cools down it would syphon the coolant from the overflow tank back into the radiator, which would create negative pressure in said tank/system, then draw the air in again through the pressure cap to equalise it.

Will that not work? Or are we talking the same thing just in different language?

_________________
Ongoing Project: 1972 Datsun 510 S13 SR20Det. http://ozdat.com/forum/viewtopic.php?f=33&t=17898
New Daily: D22 Navara (The new workhorse)
Retired 12/2016: MY98 Subaru Impreza RX
Previous Car: Restored Green 1972 Datsun 510, Hot L18

I was referring to the cap on the radiator.
That must be such that it will allow coolant to exit and enter without any pressure factor involved since that function will be done at the expansion tank cap.

_________________
Regards, Graeme
Just trying to help...
http://nissanman.shutterfly.com/
graemes@internode.on.net

Yep, I was thinking the same thing then.
Currenly there is a barb fitting off the radiator where the normal air would go to enter the expansion tank, it is currently unrestricted. I'll just use that.

_________________
Ongoing Project: 1972 Datsun 510 S13 SR20Det. http://ozdat.com/forum/viewtopic.php?f=33&t=17898
New Daily: D22 Navara (The new workhorse)
Retired 12/2016: MY98 Subaru Impreza RX
Previous Car: Restored Green 1972 Datsun 510, Hot L18