M7040 bubbles from radiator

[pbooch]

Hello, hoping I could get some help here. I have a Kubot M7040 we bought new in 2008 that now has 5000 or so hours. When I opened the radiator to check coolant it violently expelled air and some coolant into the overflow. I have tried changing the radiator cap twice and no luck. Did a combustion gas detector with Lisle unit using diesel fluid and could not get a color change but did notice a steady stream of bubbles even without vacuum. This gets to be a gush of bubbles if I upped the throttle to 2k rpm, but still no color change, even with extended time running bubbles through the detector. No milky oil, no weird exhaust, no oil in coolant, no coolant leaks, no loss of coolant (other than into the overflow when opened). Any ideas on what to do next? I considered checking radiator pressure but seems like it's holding pressure just fine. A cylinder leak down test would be next, is there a step by step on how to do this on a Kubota diesel avaiable? Thanks for any help, Paul

 

[North Idaho Wolfman]

Is it overheating?

 

[jaxs]

First off I'll say that overheating in a diesel can be catastrophic so proceed with caution and understand what you see and do.
It isn't unusual for steam and water to erupt from radiator if cap is removed while at operating temperature. I suggest making sure radiator AND AC CONDENSER fins are clean then getting some actual engine temperatures before doing anything else.

 

[whitetiger]

When I opened the radiator to check coolant it violently expelled air and some coolant into the overflow.

That is a normal occurrence from a cooling system. Not all units do it, but a large share do.

 

[pbooch]

Is it overheating?

Hello, no, not overheating.

 

[pbooch]

That is a normal occurrence from a cooling system. Not all units do it, but a large share do.

Thanks for the reply Bubbles coming out of a radiator at a steady stream out of a radiator is not normal. Have owned this tractor. for 20 years and it never forced air out when the radiator cap was opened cold, and neither do our 2 7060s. At this point its the rapid bubbling at high idle that has me most concerned.

 

[Runs With Scissors]

Could it be the something(i.e water pump, hose,…) is sucking air somehow?

I can’t explain “How” that would happen, but it would explain your situation.

Maybe a "pressure test" of the cooling system could help?

Just spit-ball’n…...

 

[Tx Jim]

Hello, no, not overheating.

If engine isn't overheating & radiator overflow isn't puking coolant I run engine as is.