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Overheating Honda Odyssey

2007 Honda Odyssey. 105,000. Driving from Chicago to Michigan. Temperature about 0. 6 hour drive. About 15 minutes from destination, no heat, car starts blowing cold air. Temperature gauge still registers in normal range. Arrive at destination. Later that night, drove about 15 minutes to local ER, and drove back from ER about 2 hours later. No heat, but car otherwise fine. Next day (happened to be Christmas Day), begin drive home. Drive a little more than 15 minutes (about a minute passed the hospital), stopped at a stop light. Car stalls and dies. Restarts, but immediately temperature gauge shoots way paste “H” in a bad way. Over the next day, local mechanic (in Petoskey MI) checks car, says it is low two gallons of coolant. He says radiator leaks, but he has no radiators there. Everything else works fine, and he says it is safe to drive back to Chicago, as long as I stop to check coolant. Drive home to Chicago, no leakage. Everything works fine. Get home, take car to local Honda dealer. They do “pressure test.” Find no leak. Head Gaskets are fine. They see evidence of massive coolant leak (dried coolant all over catalytic converter closest to radiator, and over lower portion of radiator) but find no leak, and coolant level is fine. No sign of any leaks at top of radiator. So, what gives? Car is since running fine, no leaks. Everything works. Still driving in extreme weather in Chicago. Coolant level normal. Anybody know what happened here?

I’m guessing the radiator cap stuck open and allowed the coolant to boil out through the overflow tank. Try a new radiator cap.

+1 for jesmed here. There could also be one other explanation…your engine thermostat could have stuck in the closed position.

I appreciate your two comments. But the radiator cap appears fine. At all times, upon inspection, it was closed and there appears to be no trouble with its seal. Regarding the thermostat, would it make sense that it somehow became stuck, but then became “unstuck” for no reason, and now appears to be functioning completely normally? And would the stuck thermostat cause the fluid to leak?

I’d replace the radiator cap anyway. They’re pretty cheap.

A radiator cap can’t “appear” fine upon any kind of inspection other than using a device that tests radiator caps. And anything can work intermittently or get temporarily hung up for some reason or whatever. A radiator cap is less than $10 and installs in about 10 seconds, so there’s no reason not to put one on.

Has the cooling system ever been serviced? I would do it, including new cap and thermostat, and a careful inspection of all hoses - or just straight out replacement. The cooling system components are the kind where you want to replace things long before they malfunction because the consequences of malfunction are often really bad.

Then just keep driving with an extra eye on the coolant levels and temp gauge. If there is any kind of larger issue it will rear its ugly head eventually.

Thanks for everyone’s help. I replaced the radiator, hoses and radiator cap. Stupidly I did not give the mechanic a thermostat to do at the same time. I guess I should just have him do that too, even though it would have been so much cheaper to have him do it while the radiator was replaced.

Yes, corroded thermostats can stick, then get unstuck. I had an old Ford Galaxy years that would start to overheat, then I’d actually hear the thermostat “click”, quite noticeable sound, then a sort of rumbling sound would ensue (presumably the hot coolant flowing into the radiator) and the overheating would immediately cease.