Hello folks! I have a 2003 Dodge Caravan with a 3.3 Liter. The engine has around 100k miles on it and is a used replacement for the original 245k that dropped a valve on cyl 1.

After running it for a few hundred miles, I noticed the coolant level is down 1/3 in the radiator and I can smell coolant coming from somewhere. I pressure tested the system for over an hour and it did not drop. I also tested the cap.

After sitting for an hour or so after last shut down, it will run rough for about 30 seconds. After that, its fine and has all kinds of power. The temp gauge reads just under 1/2.

To observe, I let it run with the radiator cap off and I am seeing bubbles coming out. There is a pending OBD code of P0300 for random misfire. It previously had a cyl 1 and cyl 3 misfire code P0301 and P0303 as well. I did change out cyl 1 plug and wire for gas fouling, due to a bad plug wire.

The classic head gasket symptoms do not apply to this engine, such as milky oil and white exhaust smoke, but bubbles in the radiator do. It is using coolant somewhere.

My theory is that because the head gaskets are a triple laminate steel design, coolant is leaching into #1 and #3 at one of the two siamese coolant jackets (between adjoining cyl 1 and 3 cylinder walls through the laminates) on initial hot soak until cool. I cannot get it to leak with only 16-18psi from the coolant tester, but I think that if I run a cylinder leak down test at 125psi cylinder pressure, I may be able to identify if my theory is correct.

Is there any issue with a "newer vs older design" head gaskets on 3.3 or 3.8 liter MoPars??? These things are one of the best engines I have ever seen, but this puzzles me. Its out of character for this mill.

Suggestions welcome.

 

Any signs of overheating? Might consider testing for exhaust gasses in the coolant. Are you smelling it sitting inside the cabin? Heater core leaking?

 

No overheat unless coolant starts to get low. I suppose I could check each cylinder head with an infrared thermometer to determine if any one cylinder is hotter than another. No smell inside and no window steaming.

 

Check for exhaust gasses in the coolant. If the bubbles are from a head gasket leak then this test would confirm it.

As for the coolant smell coming from somewhere, there are lots of potential coolant leaks on these vans, can you be more specific?

 

not really, unfortunately. If I pressure test the cooling system at the radiator cap, it holds 16-18 psi for over an hour. One thing I need to check is the overflow. But it loses coolant (Down 1/3-1/2 in the radiator with perhaps a few hundred miles of driving) and it does have a coolant odor under the hood, not out the tail pipe. The bubbles and eventual geyser HAVE to be exhaust gases as there is no other place they could come from. I will remove the rear valve cover and loosen the rockers to allow valves to close. Then, I will perform a cylinder leak down test and see if the radiator starts bubbling. If it does, off with its head