Pressure (closed) radiator system

[Hilux01]

I have noticed with some of the other KZ-TE guys on this forum that some times the heat gauge does tend to go a bit higher than usual.

Can anyone explain this closed or pressure radiator system to me and will it provide any cooler running of the engin? :problem:

[Mud Dog]

Hi Henk, all automotive cooling systems are designed to work at pressure, the peak of which is set by the radiator cap. It's much like a pressure cooker which is able to cook faster because it cooks hotter. As the coolant heats up it expands, providing the pressure. The boiling point of a liquid is raised under pressure and water (without additives) in a typical automotive cooling system only starts boiling above 108° instead of at the normal 100° The radiator needs to be able to keep the coolant below that temp., even on very hot days and while the motor is working hard (like when towing). Anti-freeze additives assist and raise the boiling point even higher. Should the water start to boil, the expansion of gas cannot be contained (it would burst the radiator or a hose) and is released at the radiator cap, resulting in the coolant being forced out and the motor overheating. Some motor manufacturers like their motors to run hotter than others, and their cooling systems are designed accordingly and are then obviously able to contain a higher working pressure.

I hope that helps to explain your question.

[louis fourie]

Andy

Thanks for the explanation. Of you look at the technical section you will see that I am complaining about the overheating of my KZ. Maybe you can tell me: After driving, I open my radiator cap the next morning. When I do this there is pressure in the system and the water in the overflow tank was not "sucked" backed. Would this indicate a blown head gasket and/or cracked head?

Hear from you soon.

[Mud Dog]

It's most unlikely that what you hear is pressure release when you open the radiator cap the next morning after the motor has cooled. It's far more likely to be a vacuum release which would sound very similar, and would also explain why the system is not drawing water back from the reservoir bottle. I would replace the radiator cap as a first inexpensive step and take it from there. if you are still loosing coolant after that, a good idea would be to take the vehicle for a radiator check and Dye test to see if the radiator is firstly still good and then if there is any sign of head gasket leakage.

Hope it's just the radiator cap.

[louis fourie]

Andy

I have already done the following:

1) New radiator & Cap (radiator was leaking )
2) New thermostat
3) New waterpump

It is definitely a "blow" not a "vacuum" sound.

[Mud Dog]

That's really strange Louis .... It's got me stumped .... as the coolant cools off it contracts creating a negative pressure in the system which should be relieved by the valve in the cap allowing coolant to be sucked back from the reservoir bottle. Maybe the new cap is faulty as well .... not likely but also not impossible.

Perhaps you should take it past your local Silverton dealer and let them have a look at it anyway. They probably won't even charge you.

[Hilux01]

Dankie oom Andy

Ek vertsaan nou beter.

I have also experienced some increase in temp's when loaded and driving through the Karoo in Dec - even for slight up hills. Will start at step 1 and work my way through..

Louis please keep us updated