Please help!! I have a 2013 Mini Cooper Base model, hatchback with the 1.6L N16B16A engine.
I recently had the engine replaced as the timing chains went out, and everything is working great that way.
HOWEVER! Every time it rains or snows or is in general wet out, the temperature gauge light comes on as if it is overheating.
The shop has replaced the water pump, albeit it was an aftermarket water pump I believe, but an actual MINI water pump pulley. They replaced the thermostat and adapter with an actual MINI one.
Sometimes the light is yellow, sometimes the light is red. I did have to add a little coolant because I couldn't get it into the shop. Sometimes the check engine light also comes on when that happens, but a lot of the time it does not. If I pull over, shut the car off and sit for 5 minutes and then turn it back on the light is off when I start it back up, which has made it hard for the shop to diagnose it as well as the fact that it hasn't been raining when I am able to bring it in and therefore works fine.
It normally only happens once I am into my drive a little (like 15-20 minutes into my drive).
Thank you!

 

Have you verified that the engine is actually overheating?

Or is the rain water somehow reaching and affecting wires or connectors in the coolant sensor circuit, leading to a false temperature sensor reading?

 

The mechanic said it isn't actually overheating. And it literally only happens when it is wet conditions outside. They said they took it for like a 70 mile test drive (which the milage did reflect so i know they arent lying) and monitored the temperature on their scanners and said it operated as it should, but it also wasn't wet out at the time.
If its dry out, like we didnt have snow or rain for a few weeks and it ran fine and nothing happened. It literally only happens in wet weather.

 

Sounds like you need to locate a water leak. Why not hose car with water to see if you can reproduce the false overheat. If so, go hunting for water incursion at logical locations -- coolant temperature sensor connector, wires, junctions connectors, DME, etc.

 

Update::: it was doing it again so I pulled over and checked the coolant and it was bubbling.

 

Mechanic missed the overheating problem. Pressure test the cooling system to pinpoint the location of the coolant leak(s). At this point you should stop driving the car because severe overheating can destroy the engine.

See any white smoke in exhaust?

 

I brought it back to them, and they pressure tested it and it passed their pressure test. They really aren't sure what is going on because it literally only happens when it's wet out. I sprayed the car with a hose and it didn't do anything, and they also did it and it didn't do anything. They are leaning towards either a slipping serpentine belt that is only slipping when really wet and the engine is warmed up, or a plugged radiator. I don't know. I've also noticed, and maybe because I'm paranoid about my car so now I'm paying super close attention, but I noticed that it kind of idles funny when I first start it. The RPMS kind of bounce around (not a lot). Could that be related? Can that be caused by a serpentine belt?

 

I like the serpentine belt idea because it's logical and an inexpensive fix.

Air trapped in the cooling system may cause idling issues. Did the mechanic bleed the cooling system of air and also check for exhaust gases in cooling system?

 

Let the car idle parked and see if the fans are actually coming on......do the car have any leaks anywhere?