Overheating in the Rain/Humidity
 

Hi Everyone-

Hoping someone can offer me some ideas here. I have a 2010 XC70, 6 CYL. Beginning last summer (2018) the car randomly started overheating, this was happening mostly when it was humid or raining outside, especially if it was warm. The car would go into "limp mode", and once the coolant even blew out of the radiator cap. It has been in the shop several times with a quality local shop, all they work on are foreign cars, and a few of them previously worked for Volvo dealerships around NYC.The coolant levels are fine, all fans are working perfectly. There are no codes being shown relating directly to this issue. The are unable to replicate the issue and everyone is really scratching their heads. They thought it might be air in some of the coolant lines, which they bled out, and last month (Dec 2018) they replaced the thermostat. Today while driving in the rain, in Manhattan, the car overheated again. This never happens when the humidity or temperature is low. What is scary is the air conditioning stops working and the windows fog up, this happened today when I was on the FDR, trust me, this is not a place you want to lose visibility! If anyone has any ideas/thoughts please pass them along, thank you!!

Paul From Brooklyn, NY

have you noticed if the radiator fans come on appropriately? Since it sounds like it has overheated when driving in city traffic, you need the fan to force the airflow through the radiator and even in the cold a failed fan can overheat the engine. My only thought is the fan motor or connectors or a temp sensor get wet and fail to kick on the fan when needed. Do you see the temp gauge go up? if that happens, turn the heater on full blast to wick off some heat to avoid a boilover.

The fans seem to be doing their job when the car is idle, but who knows when the car is moving. But this is a good point, maybe there is something the fan sensors don't like with wet conditions. Although, this would not really affect anything when it is just hot and humid outside, the car has also overheated in those conditions. There isn't a temp gauge as far as I can tell, just a warning light that comes on when the car overheats. The whole thing is so frustrating because it can not be replicated unless the car is driven in these exact conditions, so far my shop has not be able to replicate it.

I reread your post and think the clue is where you noted that the AC stops working then the car overheats. there is a tie in between the AC system and the fan - which again suggests maybe the fan isn't working - perhaps due to a fault created by the AC. Did the shop scan the climate control computer for any fault codes? It may be worth going to a dealer with a full VIDA DICE set up.

The AC/climate didn't throw any specific codes, but I do agree, it may be time to bite the bullet and take it to the dealer. They are going to charge more, but I am much more confident they will be able to figure out the isse. Otherwise I am going to continue to pour money into this private shop, which will probably end up costing more. I appreciate your thoughts with this.

Got it Fixed...
 

Just a quick update, I took your advice mt6127 and took it to the dealer. They were able to figure it out, it was the fan module, essentially just a single fan was operating when the car heated up, but it was not pushing any service codes. Anyway, it was fixed (1200 bucks later).. but just happy I don't have to worry about it anymore. Thanks for your help!