Best aggressive coolant flush for Chev blitz

We done some testing years ago on a overheating problem, found removing the whole thermostat didn't help our cause however cutting the guts out of it and replacing just the flat plate with a hole in it helped regulate flow considerably.
Problem was finely sorted with custom radiator and returning the factory thermostat.

Exactly, as I said previously the restriction of the thermostat helps build the pressure on the hot side of the cooling system, although this isn't readily understood by most. If you look into the pressure differential on either side of a fixed orifice(in this case the thermostat) it will explain it, I understand why most don't understand it and why it probably wasn't taught to most mechanics, it's just too far above a lot of peoples thinking.

Of course the pressure would be different on the engine side of the thermostat..
You have water getting hot along with a water pump ramming it against a blockage till the thermostat opens.
No different to squeezing a garden hose..

But what was the thermostat fitted for initially?

Wheres Onetrack when we need him?
He would have been all over this on the first page!
Including url references, diagrams and complete and accurate explanations...

Where are ya Ronny Onetrack?

Chocs,
you are right on the bit about the pressure until the thermo opens but the opening is designed to hold pressure when it is fully opened.
You can find this pressure in the major engine (Diesel) spec's and it does not include the rad cap rating

Thank You

Assuming the radiator is full there is water on both sides of the thermostat. Water is an incompressable liquid.

Saying the engine heats the water and creates pressure on one side of the thermostat is wrong. It is a continuous circuit so as the water expands, finding it can not go forward it expands back into the bottom of the radiator and compresses the air in the tank and the pressure comes (instantly with no time lag) right around to the front side of the thermostat which feels no pressure difference either way.

The water pump is a paddle and if flow is restricted water can easily bypass the paddles to go back. It is not a pressure pump, if it was it would blow the system apart when the thermostat closed.

The pressure comes from the gas compression (air and steam if it is very hot) above the water in the top of the radiator tank. This acts on the water - in all directions. All this pressure does is raise the boiling point of the water. When the car first starts there is zero pressure and in fact a car will run quite happily with the radiator cap off forever with zero pressure if you accept it is going to boil at exactly 100 degrees instead of having the 5 or 10 degrees fat the pressure gives you.

A hydraulic jack or ram works the same way (instead of air or steam they use a pump or piston to provide the pressure). Air over Hydraulic brakes also make use of the incompressability of a liquid. The difference is a jack or brakes do not have the liquid circulating in a solid body to the back side of the pump or ram. If it is a hydraulic motor continuously pumping it draws and empties into a tank after doing its work so has no continuous circuit like a car water pump.

Water is an incompressable liquid. There is the same pressure on both sides of the thermostat. This is basic high school physics.

All a thermostat does is alter flow.

The water pump is in the middle of this pressure pot and just moves a "solid" mass through the pipes creating flow but any pressure it (or engine heat) creates is transferred instantly through the "solid" water through the system to the back of the pump. It either has maximum flow with a full open thermostat or wheel spins as the thermostat restricts the flow. It is just a paddle that allows "wheel spin" and you can see how poor a pump it is by noting it has no seal and big gaps between impellor and the pump body unlike an oil pump or hydraulic motor which must be sealed to do their job.

Choc's garden hose sample is not applicable because the water pressure comes from an outside "pump" with pressure one side and none on the other. If you put a garden hose full of water in a circle (like a car water system) and hooked it to the "in" and "out" of a pump, squeezing the hose would only alter flow not pressure just like a thermostat because any pressure changes on one side are instantly transferred through the solid liquid to the other. This would continue as you squeezed the hose because no matter how small the gap, the pressure would equalise to the intake side. The moment you completely closed the gap and removed the connection between in and out, the "out" hose would blow because the soft "in" hose would squash to allow the pump to draw enough water to expand the front side. If it was a steel hose the pump would stall. - hydraulic lock.

Lang

Wow. I'm learning more every day on this thread. A great discussion.
cheers
Pierre

Lang, just to clarify a few points.?

Q. Is hot water behind a closed thermostat the same pressure as that in the cold top radiator hose?

Q. With a closed loop of pipe, full of water, the pressure remains the same all the way around the loop even if one section of the loop is rapidly heated?

Q. Does water expand as it is heated? what is the given result if it does?

Thank you

Pump cavitation in an old poorly maintained cooling system can be another source of over heating or high temp problems, in most cases due to a worn backing plate and been well documented on Nissan TD42 and holden v8 on sites.