Hey all - something strange going on with the engine cooling system in my 2009 XF 4.2L Luxury... I've done a fair bit of searching across the forum, but now I've got another data point (as of about 2 weeks ago) that I haven't seen in other posts.

Up front: I'm thinking this is a coolant pump issue, but am looking for confirmation or other input before I take her to the shop. Here's the symptoms...

• Very slowly loosing coolant - get a 'coolant low' warning about every 3 months (has happened twice now);
• Coolant is pooling on the edges of the coolant reservoir in the engine compartment, almost as if it had seeped out of the top, which I can't understand;
• Slight smell of burning/vaporizing coolant in engine (no surprise there);
• Radiator fan comes on and remains on for 1-2 minutes after turning car off.

It's the last bullet that's the new data point. Just started happening now that the weather temp has consistently reached mid-90s (F) in my area. I assume this means the engine isn't cooling as efficiently as possible now for some reason.

So, what is is? I assumed a pump issue because of the slow loss of coolant, but can't understand why I see coolant on the edges of the reservoir... is it possible that it's hitting the engine, vaporizing, then condensing back above the reservoir..?

Lastly, the car is throwing P050B every few days. I don't know if it's related or not - seems there may be several different causes for this based on my searches...

 

Do a pressure test when the engine is cold.

I bet you need to change the top tank. It's cracked from age and temperature. Very common and I would not even pressure test if this has NOT been swapped out before.
Why would the pump cause a loss of coolant if you see stains on the top tank?

Next is your code. It's a rare one but has been reported. Check out this TSB it's sounds like a trip to the dealer is needed but it's just a reprogramming issue and nothing is really wrong.
.
.
.

 

Thanks for the response!

Would this account for the fan now running? When I monitor the temp whole driving, it stays around 200°.

I've read elsewhere here that when a pump fails it'll leak coolant, thus leading to the loss of fluid over time..