Cm2250 Air compressor or head gasket ?

[Rawze]

(06-27-2019 )SIDE_SHOW Wrote:  ...
when I stick it in a bottle of water but nothing like it was its minewt now compared to before
...

Even a perfectly healthy truck will make bubbles when tested like this. This is because the system will build pressure and boil off water at a very slow rate (a few small air bubbles bleed-off every so often) simply because of the wet liners making steam as the engine runs. What rate that is can be anyone's guess, as every truck is slightly different.


It is not a bad idea to put a pressure test kit on the coolant system and pressurize it to 20 psi, let it sit for a few hours with engine not running. This will allow you to find all external leaks and fix them. Unlike what others have said (above), it IS NORMAL for the pressure to fall off a few psi as the engine cools down and contracts in the system (engine cooling off). - In fact, unless it is massive, an actual leak will not show up as pressure loss, because the system is 15 gallons+ big and that equates roughly to about only 1 psi of pressure drop for every whole gallon lost if there is an actual leak.


Once all the external leaks are fixed ...

- If you use an actual pressure gauge, it will tell you a lot more than the method your trying to use. The system is designed to hold roughly 15 psi pressure, so with a pressure gauge on it, truck idling, all pressure relieved check to see how rapidly it will build pressure again...

Once pressure starts to move slightly above the zero mark again, If it takes only a minute or two (or less) to build up from slightly above zero (measuring from about 1 psi to 10+ psi), then you likely have an issue worth investigating immediately, but if it takes a something like 5 minutes or more, engine simply idling, then the only thing you can do is test drive it and see if it is pushing coolant out of the pressure relief cap over time, or ...

If it builds very quickly (less than a minute or so) only when getting on the accelerator, engine under a load, or when engine brake kicks in on high. This can be checked by extending the hose for the pressure test gauge set and putting it in the cab of the truck during a test drive.

-- Like others have said, any time a person has coolant issues of any sort, pressure testing the system and repairing all external leaks is the first step. Right along with this is to check the EGR cooler for seepage, as well as the doser injector, and checking any lines that go to the aftertreatment system components, your APU if you have one, and checking for seepage into your transmission if it is water cooled. Past that, if it is still making enough pressure to blow coolant out of the pressure relief cap, then the next thing would be to drop the oil pan and pressure test if over night,.. see if the coolant is seeping into the engine from somewhere, like past a liner, or past the piston rings, or other component.