Drag GT-R Cooling system Q's

[MattSR]

Hello everyone,

If you look at the following pic, theres a little coolant tank thingy on the far left hand side. Various water outlets from the head go into the side of this tank, but where does the hose coming out of the bottom of this little tanky thing go to...

I would've thought that it went into the radiator inlet, but it seems to go nowhere....

Can anyone explain this to me?

Cheers,

Matt

[DoughBoy]

It's just a steam tank, can either connect up to the regular overflow tank or vent to atmo.

[MattSR]

I don't think that's right... the header tank that i'm talking about is at full cooling system pressure.... if the hose at the bottom dumpted to atmosphere, the cooling system would empty itself in seconds.

The hose at the top of the tank vents to atmo, but i'm wondering where the hose at the bottom - as the picture shows - goes to.

[DoughBoy]

Having a look at the pic, and noticing your arrow, it's obvious that it goes to the front diff to cool it down. It's running a very special diff, with very special water cooling.

Seriously, that cooling system is pretty trick. Not sure if it helps cooling much... is that on an R32? That lower red hose could go to anywhere under the manifold, really can't tell. Maybe to the fitting on the block near the lower radiator hose?

[MattSR]

Doughboy - stop infecting my threads with your bullshit.

[Sydneykid]

Hi guys, the idea of the separate (from the radiator) header tank (HT) is to make sure there is no air trapped anywhere in the cooling system. So the hoses come to the HT from all over the engine and, since it is mounted higher than everything else, the air moves to the highest point. So when you fill the cooling system up, via the HT, you know there is no air trapped somewhere in the system.

The lower hose on the RB26 in the picture can go to a number of places, the oil cooling coil at the oil filter mount is one I have seen. The cabin heater and the bypass fitting on the thermostat cover are also common. You can run hoses to anywhere you like really. The only thing you have to be careful of is not changing the direction of flow of the coolant. The hot coolant needs to go into the top of the radiator and the cool coolant needs to come out of the bottom.

Why have a HT? All it does is get a little bit of air out of the system, why does that matter? Well, as you increase the pressure of water, its boiling point goes up, this pressure is controlled by the radiator cap (and/or the HT cap). But if there is some air in the system this decreases the pressure as the trapped air is compressed (water doesn't compress). Thus lowering the boiling point of the whole system. The second, and some would argue more important reason for having a HT, is you don't want any places in your engine cooling system where there is no coolant. Air does not cool very well and, if it is trapped, it does not travel though the radiator to get cooled. Result is hotter spots in your engine, this can cause cracking of things like cylinder heads for example.

Why don't standard Skylines have a HT? They simply don't need one, Nissan (clever little engineers they are) fitted them with air bleeds mounted high on the inlet manifold. You crack open the air bleed when you fill up the radiator and wait until all the air is forced out (coolant flows). Then close the air bleed, the result is there is no air in the coolant system. When you replace the inlet manifold you loose the air bleed. So that's why you see highly modified RB's (with aftermarket inlet systems) with HT's.

So if you have the standard inlet manifold, use the standard Nissan air bleed to let the air out. You don't need a header tank, but they are nice and shiny aren't they?

Hope that helps.

[MattSR]

Sweet - thanks for that sydneykid

[Guest RedLineGTR]

thanks