Wrong PSI radiator cap or defective radiator cap installed.
NEW ANSWER: The above answer is true ( COULD BE ) But I would bet you have a BLOWN / LEAKING head gasket that is building pressure in the water / cooling system.
14 to 18 psi in all of the cooling system
System pressure will run abnormally high, the AC system will vibrate, and you won't get proper cooling.
The usual cause of cooling system pressure surges is a bad head gasket. The compression from the cylinders gets into the cooling system and raises the pressure. Have a mechanic run a compression test to see if there are any big pressure changes between the cylinders.
The Detroit 60 Series engine is known for having issues with excessive pressure in the cooling system due to a variety of reasons. One common cause is a malfunctioning pressure relief valve in the cooling system, which can lead to a build-up of pressure. Another possible reason is a faulty head gasket, which can allow combustion gases to enter the cooling system and increase pressure. Additionally, a clogged or restricted radiator can also contribute to increased pressure in the cooling system. Regular maintenance and inspections can help identify and address these issues to prevent damage to the engine.
Pressure in the radiator is created by the cooling system when the engine heats up. The thermostat regulates the flow of coolant to maintain the optimal temperature. If there is pressure in the radiator while the thermostat is working properly, it is usually due to the natural expansion of coolant as it heats up, which is necessary for efficient cooling.
Need to know what type of pressure check, engine compression, cooling system, ac system, air pressure in tires, etc. Then we need to know the year, make, model and engine info.
For starters, you'll get insufficient cooling from your system. Refrigerant changes states from liquid to vapor and back again in order to achieve cooling, and the system pressure is balanced to facilitate this - excessive refrigerant makes it much more difficult to do this. Additionally, your system will generate excessively high pressure, which will ultimately damage or destroy system components.
Replace the thermostat and radiator cap.
Blown head gasket or air lock in cooling system.
You can overcharge the a/c system. This causes too much head pressure in the compressor hendering it from cooling. Usually when you overcharge, it damages o-rings and seals in the system causing it to lose freon and a/c oil.
No - actually, it'll have a more opposite effect. The superheat will be low, system pressure will be high, and the result will be insufficient cooling.
Thermostat be not be opening creating excessive pressure Radiator cap may be defective You can get excessive pressure by running straight water in the system. Antifreeze also provides boil-over protection. Run a 50:50 mix. Don't mix red (GM) with green...it causes sediment to clog the radiator.