Older Vehicles - Part 2

Next up after fixing the exhaust on the Aspen, I noticed the passenger-side frame-rail on my 2010 Dodge Ram had coolant all over it.  This truck has 287K on it.  I had already replaced the original overflow reservoir last year, so I immediately began investigating as the truck just ran too good to have a head gasket issue - although, that means nothing, especially on a diesel.  The overflow tank was full and for some reason, coolant was being pushed out - initial thoughts by many is that this is probably a sign of a head gasket as it would happen on a heavy load.

Test 1 (Coolant Pressure Test)- I used a coolant pressure tester with the engine cold and pressurized it to 15 PSI per the manual.  The manual states that if it holds for 2 minutes, there is no significant leaks.  I watched it for a little over 4 minutes and the needle never budged.  Great!

Test 2 (Coolant Pressure Test - engine running)- I released the pressure from the tester, then started the truck.  I had my son help after the engine coolant temp got to about 186 degrees F.  While I watched the gauge on the tester, I had my son rev the engine rapidly a few times.  I ended up having to place something (a welding jacket in this case) over the front of the radiator to partially block it to get the temps high enough to cause the thermostat to to open.  Once the temps hit 192, the thermostat should have began opening.  A couple things happened:  1) The pressure didn't even reach to 5 PSI and 2) the upper radiator hose was super soft and felt like hardly any fluid was flowing, despite by now, we were able to get the temps up to 203 degrees, well above the opening temps of the thermostat.  The manual states if there is no increase in pressure, to pressurize it to 16 PSI.  I increased the pressure and just like when cold, it held steady.  We let it idle down for a few minutes then shut the engine off.  I took a picture of the gauge, but I think this was after the engine was shut down to show the drop in pressure with the drop in temperature from 16 PSI after around 4-5 minutes:

Test 3 (Radiator Cap) - I'm pretty confident by now that the thermostat is a partial culprit, but it still didn't answer the question why fluid was being pushed into the tank unless the radiator was getting so hot that the pressure was building too quickly and no were else to go except through the radiator cap - logical point.  So, I tested the radiator cap - and it failed at around 10-12 PSI when it began releasing pressure.  This is a 17 PSI radiator cap, so it should have held to 17 PSI.  The original cap was replaced 6 years and 107K miles ago because it wasn't sealing and letting coolant out, misting the engine bay.  New cap on order - Mopar showed the new cap as 18 PSI, so I don't recall how I came about getting this 17 PSI Mopar cap. 

Test 4 (Boiling Water) - To test that the failed thermostat, I pulled it out and put it in boiling water.  Low-and-behold, the cap opened around 195-203 degrees.  Although, it was hard to tell how far opened is fully opened.  I did this test a few times and got the same results, so back in the truck it went.

Test 5 (Pressure Test - Engine Running) - Now that I know the thermostat should be opening, I put it back on the engine and ran another pressure test, just as I did in Test 2.  As we got the coolant temps up to around 190 degrees, the pressure began building on the coolant pressure tester.  As the temps reached 192 degrees, the thermostat began opening and the hose got firm and warm.  The pressure reached about 17-18 PSI and held never fluctuating up.  When we revved the engine, the pressure dropped to about 15 PSI and raised back to about 17 PSI after idling. 

This still doesn't answer whether we actually have a head gasket issue, so after the new radiator cap arrives and I can pick up an actual Cummins thermostat rather than a low-quality MotoRad/Gates thermostat that I put in last year, I'll take the truck for a test drive to see what happens.  If coolant doesn't push out, I'm confident the culprit was the failing radiator cap and a hiccup with the thermostat.  One thing that was never noticeable was bubbles in the coolant, so I'm about 95% confident the head gasket isn't an issue.

Another plus, I sent off another oil analysis and it came back good to go with expected wear.  I'm a couple months over due on a filter change, so I expect some higher levels, but all-in-all, it is good for continued use and the potassium levels were on par with what they are normally at. For those results, go to this link here: https://www.syntheticautolube.com/oil-analysis

When I get all the new parts in, I'll update with another post on the results.  Fingers crossed that it just needed some new parts to keep her going to 300K miles and beyond.