Radiaror / Engine cooling, best fan set up

[Taily]

Keeping the pressure up on the coolant also increases the heat transfer rate between the cylinder walls and the coolant. Otherwise small bubbles would form on the hot metal internal surfaces, then (over time) displace coolant from the system.

Those bubbles are the same concept as boiling a kettle or billy on a fire or gas ring - as the metal kettle/billy etc starts to get warm, small air bubbles form where the heat transfer is taking place. With pressure on the system (ie; a functioning radiator cap) the formation of those air bubbles is (almost) eliminated. I've set my ute up with a 16psi recovery set up for the last 17 years without an issue apart from blowing a welch plug early on when I first set it up. That extra one psi (factory aircon car originally had a 15 psi non-recovery cap) was enough to finish that 25 year old plug off.

[Spike]

Keeping the pressure up on the coolant also increases the heat transfer rate between the cylinder walls and the coolant. Otherwise small bubbles would form on the hot metal internal surfaces, then (over time) displace coolant from the system.

Those bubbles are the same concept as boiling a kettle or billy on a fire or gas ring - as the metal kettle/billy etc starts to get warm, small air bubbles form where the heat transfer is taking place. With pressure on the system (ie; a functioning radiator cap) the formation of those air bubbles is (almost) eliminated. I've set my ute up with a 16psi recovery set up for the last 17 years without an issue apart from blowing a welch plug early on when I first set it up. That extra one psi (factory aircon car originally had a 15 psi non-recovery cap) was enough to finish that 25 year old plug off.

All very interesting and great info. When I purchased my radiator I went to a radiator repair shop and asked the guy what the factory listed for the HX, he dragged out the book and it listed HX with and without recovery bottle and listed the same psi cap for both. I would have thought that the cap would be a little higher pressure rating without the recovery bottle. Taily what bottle do you use, mounted where and is the height of the bottle important?

[Taily]

All very interesting and great info. When I purchased my radiator I went to a radiator repair shop and asked the guy what the factory listed for the HX, he dragged out the book and it listed HX with and without recovery bottle and listed the same psi cap for both. I would have thought that the cap would be a little higher pressure rating without the recovery bottle. Taily what bottle do you use, mounted where and is the height of the bottle important?

I used a fairly simple system. A 2.5lt Valvoline coolant bottle (doesn't matter what it is from, just the shape of the bottle) that I just sat in between the battery and the LH guard. I left the cap on the bottle but drilled a 9-10mm hole in the top, through which I loosly inserted a bit of 8mm (5/16) metal tube (long enough to touch the bottom of the bottle) with a bend where it emerged from the bottle. I attached a bit of clear hose between that and the radiator overflow outlet, with enough slack in the tube that I could slip the top off the bottle easily. As WBute mentioned, the installed height of the bottle isn't important, just that there is enough room in the bottle to accept the (temporarily) expended water from the cooling system and that the tube is deep enough in the bottle to allow the contents of the bottle to be completely drawn into the cooling system if need be.

Mine was only a basic set up but what it worked just as well as the factory set up on the later HX/Z/WB. I used a metal tube in the bottle as a rubber hose can kink and the system wont work. The advantages of doing this to your cooling system are threefold: you wont drop coolant everywhere everytime you stop somewhere; You wont have to physically remove the cap to check your coolant level, and; You wont have any air/oxygen in your cooling system to accellerate corrosion.

If I was going to re-make mine I'd use a clear bottle so I could more easily see the level of the overflow bottle - though you can now buy a repro HX on recovery bottle from Rares (etc). Not sure if it comes with a mount to the LH inner guard though...