Hello again, so my 2007 V50 wagon has been putting me through the wringer lately after a brief overheat on the highway.

first I was told it was the water pump and timing belt. I replaced those, and it still overheated. Next I was told my coolant reservoir was not holding pressure or coolant, so I replaced that. It doesn’t leak coolant anymore, but it still overheats. And now the car idles and runs rough on occasion, like I can feel it trembling. Aggressively.

I’ve also had, since I bought it, a notification that pops up on start that says « gear selector service required. » occasionally (normally when it’s super cold out) the gearshift will make a rapid clicking noise after I start, then settle down eventually.

well, yesterday, I get in it and start it up and it’s rumbling. Not unusual, I figured it’d just die down in a minute. But it didn’t, and I got the red triangle and an urgent notification that said « try slow down or shift up. » the thing is, I haven’t noticed the car having any difficulty actually shifting between gears as I drive. (It’s automatic.) the shift is always smooth.

i had to have it towed and by now I’m really fearing for this car. Is it possible that this is a shifter module issue causing all these problems, including the overheat? Does the car just not know which gear to go into? Is this a common and inexpensive issue?

it’s supposed to get diagnosed later today, but if anyone has experienced this before please let me know what it was and what you did about it. If it’s a $200 repair, then I can get it done already. But a transmission rebuild is not financially feasible for me at this point

 

Did you look at the transmission fluid? Normally I wouldn't think the transmission/shifter issures are related to the overheating but its possible the radiator is allowing coolant and tranny fluid to mix. More typical causes for overheating are 1) an issue with the thermostat 2) cooling system leaks 3) air stuck in the cooling system (particulary if you did a drain/fill or lost coolant due to a leak) 4) water pump (any weeping under the timing belt?) 5) clogged radiator (any serious discoloration in the coolant? 6) fuel mix/ignition system issues causing lean burn or misfires 7) head gasket issue Considering your car is running rough, numbers 6 or 7 move up on the suspect list. Any odd smells in the cabin or wetness in the foot wells to suggest a heater core issue? As to the transmission, I'd check the level/quality of the fluid, look around for any coolant leaks that could have wet some connectors (like the TCM or sensor) etc. It still could be the shifter/ PNP sensor but that would be on the chance its unrelated to the overheating issue.

 

I'm terrified (OK, concerned...) that the car really IS overheating, and that all the rough running is just the signs of thermal abuse, and could by this time be permanent.

I'd suspect the #1 suggestion by mt6127 above - thermostat (more specifically, a stuck thermostat). That would explain all of the overheating issues (though it would also suggest that the original diagnosis wasn't a good one).