Coolant Pressure Drop

What is your coolent? Is there air in the system?

Has it got anything to do with the reduction of viscosity of the coolant with increasing temperature?

Good point there. Most negligent of me not thinking of this. Thanks for covering my back.

Incorrect coolant type? Coolant leak? Air in the system?

Mark

You should ask this to Cummins factory people, not the dealer. Ask the local Cummins dealer to give you the name of their factory contact for technical questions, or go to their web site and find 'contact us'. If you still need help, click on my name and send me a private message and I will contact them for you as I am a diesel engine power consultant and they want to keep me happy. Some ideas: Higher load adds heat but also peak pressure inside the cylinders and heads. So we need to find out if this is load sensitive or coolant temperature sensitive. Check pressure after 450 kW and then immediately drop load to zero while coolant is still hot and see if pressure inversely follows load or temperature of the coolant. Then next time it is cool, start and run no load until you arrive at the highest temperature possible NO LOAD but full speed. This should be about 80*C or so coolant temperature. See if pressure still goes down with temp rise, no load. then apply load after you have reached maximum temp no load and see results of adding load in 100 kW steps. Tell me the results.

These thermostats are full blocking type where they recycle 100% of water back to the engine in a loop until the engine is warm. When warm they start to open a bit, and a small amount will go off to the radiator, or heat exchanger system if no radiator, and the rest will continue to recycle. Then as it gets hotter, the t-stats open more and channel more to the radiator and less to re-cycle. So depending on where the pressure sensor is, one can see that the coolant 'pressure' from the water pump flow (hitting resistance of a radiator core) and expanding coolant temp can change as more coolant is being routed to the cooling system (cooler water contracts and system pressure is reduced). This is why you must wait to take off your automobile radiator cap until it is cool as the coolant has expanded while hot making trapped pressure in your automobile's system even though not running while hot (the pump doesn't make the pressure, the expanding coolant does). We also change pressure rating of radiator caps and 'vent' the extra expanding coolant to raise the boiling point (1 psig = 3 * F boiling point raised). So a 10 psig pressure cap can have 242 *F water without boiling inside. We want to run diesels very hot so 20 psig or more systems are common. Low pressure in the system will cause the coolant to boil inside. You can try to block the radiator air flow and make the coolant hotter (careful with getting too hot) and see if you can control pressure by changing the efficiency of the radiator. So tell me results of your tests and I'll think about this further.

George

hi. check the expansion pot for vapor leakage.

regards,

AA.

How are you taking the pressure readings. If from the machines monitor recommend taking it with a gauge. The problem could be with voltage regulator as load increases voltage could be dropping. If it drops off enough would cause errors with monitor.

Please post your solution when discovered so we can all learn something! Thanks.