Thread: Plumbing in a V8

Second question, how critical is it that I connect a small pipe from radiator to the inlet manifold? Does water actually travel through this pipe or just hot air / steam?

It's important as if you get an airlock in the highest point of the engine , it will overheat. It's very common for the little stub on the manifold to get blocked by crap, and it can be cleaned out with a drill.
I guess you could fill the motor completely then block off the pipe but any pockets of air will migrate up the manifold.
I think you can just block off the heater stubs.

Third and final question, can I just have an overflow tank or do I need to go with the expansion tank set up (i.e. allowing coolant to return to the radiator as things cool down)? I ask because I have a new custom made radiator and I am reluctant to add two additional outlets for the expansion tank and inlet manifold.

Huh?
You will either need a pressure cap with bypass on the radiator if you go for just an overflow, so would need a radiator cap fitting. If you have say a RRC expansion tank you only need a stub.

Regards Philip A

You can blank off the heater pipes so long as you have the hose from the front of the inlet manifold to the back of the water pump. This keeps the engine temps reasonably even before the thermostat opens.

The small pipe from the inlet manifold bleeds off any air in the engine and normally flows a small amount of coolant. On Australian cambered roads it's connected to the high side of the rad, reducing the chance of an air lock. A 3mm hole drilled in the thermostat skirt will do a similar job but not as well.

A low pressure overflow tank will work but it's pretty hard to get caps nowadays that seal the cap mount well enough to return coolant to the rad. If you have an expansion tank plumbed to drain into the lower hose you can run the manifold small hose directly to the top of the expansion tank, so it becomes a useful part of the system. My '89 Rangie had a brass expansion tank that had both the 5/8" bottom outlet and the 5/16" top inlet.

So it looks like there is a coolant leak from the underside of the inlet manifold - when the engine gets up to temperature there's lots of coolant forming on top of the valley gasket. By any chance, is there a Welch / Core Plug here? If there is, I suspect this is the cause of my coolant woes... thanks

Originally Posted by jdobson

So it looks like there is a coolant leak from the underside of the inlet manifold - when the engine gets up to temperature there's lots of coolant forming on top of the valley gasket. By any chance, is there a Welch / Core Plug here? If there is, I suspect this is the cause of my coolant woes... thanks

No plugs that I'm aware of but it's common for newer style inlet manifold gaskets to fall apart and leak at the ends. Check the inlet manifold bolts for tightness before doing anything else.

Okay cool - will try that. I am now thinking it could be the steel heater pipe that runs underneath the inlet manifold - the leak was pretty big. Do you know the torque setting for the bolts?