What causes pressure build up in cooling system?

When the fluid in the cooling system heats up, it expands, causing the pressure to build up. When the radiator cools back down, a vacuum is created in the cooling system that pulls open another spring loaded valve, sucking water back in from the bottom of the overflow tank to replace the water that was expelled.

How do I know if my Duramax head gasket is blown?

If your temperature gauge suddenly starts running colder than it always has, you may have a head gasket problem. The quickest and easiest way to check for combustion pressure in the coolant system is to squeeze the upper radiator hose while the truck is running.

Why is there pressure in my coolant reservoir when the engine is cold?

Yes, by “hg” he means headgasket, and probably that it isn’t sealing the coolant passages in the motor off properly from the cylinders, thus the pressure inside the cylinders is leaking into some of those passages and pressurizing the system.

What controls the pressure in the cooling system?

As coolant temperature increases, so does the pressure in the cooling system. This pressure is regulated by the radiator cap. Correct system pressure is required for proper water pump seal lubrication. Increasing the cooling system pressure raises the boiling point of the coolant.

How can I tell if my coolant is circulating?

Also, touch the lower radiator hose, after the engine has reached operating temperature. If the lower hose is hot to the touch, coolant is circulating. If the lower hose is not hot, it’s possible the radiator is restricted.

What year Duramax has head gasket problems?

In the GM world, the 2004.5-2005 LLY engine seems to be the worst for having gasket failures. These years seem to have temperature issues and I believe it’s because of this, that we see these trucks more than any other Duramax for head gasket issues.

Is pressure in coolant normal?

At normal temp the in-system pressure will be around 10psi, but there can be transients when high engine load causes momentary increases in coolant temp, and thereby pressure.

How long should a cooling system hold pressure?

The system should hold pressure for at least two minutes. If not, check for leaks in the system. To test the radiator cap with the hand pump, attach the cap to the pump using the proper adaptor and operate the pump until the cap starts to release pressure.

What can be done to prevent air from getting trapped in the cooling system when the coolant is replaced?

What can be done to prevent air from getting trapped in the cooling system when the coolant is replaced? Use the coolant exchange machine that draws a vacuum on the system or open the air bleeder valves while adding coolant.