markVIII radiator and fan in classic

[67rcks]

I have markVIII radiator+fan assembly installed in 67 (still tuning it). It seems to me that this radiator, instead of an expansion tank and cap, has a build-in valve that opens at critical coolant temperature, or PSI, and coolant starts to flow to overflow tank.

Can someone advise whether the coolant will be sucked back in from the overflow tank through this valve once being cooler? Does the tank need to be above the valve, or where it is best to place it? Is there an expansion tank with a pressure cap in cars with this type of radiators? (mark8, sn95)?

 

[Tim65GT]

Almost all cars since the 70's have a coolant overflow/recovery tank and they work pretty much the same.

Some have the tube/line/hose going to the bottom of the tank and some have it in the top/cap assembly. Some systems don't a cap on the radiator, but have a pressure tank with the cap located there.

If you look at the radiator cap, it has two seating/gasket areas. The large surface seats against the top and the smaller surface has a spring that relieves the pressure at its rating. When it does, coolant goes into the radiator filler neck area where the hose carries it to the overflow tank.

When the car is shut off and starts to cool, the system contracts and a siphon is created and pulls the coolant from the overflow back into the radiator and i think there is a one way check valve built into the cap to allow the flow back in.

It shouldn't matter where you put the tank, but it probably should be close to the radiator.

Did the Mark VIII have a pressure tank?

 

[afast93stang]

Got pics?

I have a 67 and am thinking about puttnig in a MK8 fan - I already have one in my 93 and love it. I used a Canton overflow tank on my 93 and had to install it on the opposide side of where it is from the factory.

 

[67rcks]

The radiator is shown below. Where would you connect the hose coming from the red-circled area? There is a valve inside the radiator that opens at high temp, so does additional pressure tank with cap make any good to the cooling system except taking space in engine bay (well that's not good)?

 

[afast93stang]

Correct me if im wrong but from those pictures it looks like the overflow tank is a sealed system. Im not seeing a provision for a traditional cap on the radiator.

 

[brh66cobra]

The mark8 does have a plastic pressure tank with the cap on it. I think it would be easier to use another radiator with a fill neck on it and use the mark8 fan with it. The cars that use that system have a water nipple that comec off of the themostate housing and attaches to the tank and another hose from the tank to the nipple on the radiator. I don't think there is a valve in the nipple you are asking about.

 

[afast93stang]

To use the fan in my 93 I did have to shave off about 1/2in around the MK8 fan shroud. I have an extra MK8 shroud that I eyeballed to see how well it would fit on the stock radiator in my 67. The width is fine its the radiator hose inlet/outlet that get in the way. It looks like you could cut out the space for the fittings and seal it up pretty easily if you want to go that route.