2013 coolant level mystery!
 

Our 2013 XF 3.0 AWD seems to run at the proper temperature (no warning light ever comes on), but lately the coolant level light is going on. When this occurs, the coolant is easily visible in the expansion tank, well above the bottom. It takes maybe a pint to bring the level up to the threads (overfull) and the light goes out. But forty miles later it's back on and the coolant is back where it was, about 2" below the top of the neck. It never puts any on the garage floor. At 75K miles, I suspect a bad sensor, but the dealer says it only comes molded into the bottom of a complete expansion tank for silly money. Has anyone else run into this and do you have any suggestions?? Thanks for your collective wisdom!

If you need to keep adding coolant as you say then you have a major issue of where it is going that needs to be solved Urgently!

Find out where it's leaking from on YOUR time, if you wait for it to show you the leak, its gonna cost you WAY more!

Thanks for the helpful advice, and I DO appreciate how critical identifying an actual coolant leak is with an aluminum engine! I've been monitoring the XF's coolant and the level is right at the top of the tank when cold, even though the sensor says it's low. My conclusion is a bad sensor. Ordered one from Rusnak Jaguar and it'll be here in a couple days. Which brings up two more questions: I removed the 6mm securing bolt & nut and found that the rear corner of the tank is held to the firewall with a black plastic clip. I'm trying to be gentle with the tank, but couldn't figure out how to disengage that clip. What's the secret?! Then, is there any trick to installing the new sensor--after draining the tank, of course? The service guy at the Jag dealer said the sensor is 'molded' into the tank and you have to buy the complete assembly. But there were several vendors selling just the sensor, so I think he was trying to upsell me. As always, thanks for the helpful information.

There are two sensors, one which fits on to the tank externally and one inside the tank.

Stop being such a tightwad and change your header tank. It's a consumable on these cars anyway. Just buy it from an online discount parts seller.

I don't understand. You ordered a sensor because you feel that is the issue, but in your first post you say you have to keep re-filling the tank after a short drive. The sensor could be bad, I know I had to do mine (changed the whole expansion tank BTW, I could not get the sensor out, the circlip at the top of the stalk that the sensor fits onto is impossible to get to with normal tools.... ) but it sounds like you have 2 issues, coolant loss and sensor malfunction. As already mentioned up thread, the coolant loss is a much more serious issue that you need to address pronto. BTW you said you fill it up to the threads, which is not what you are supposed to do. You only fill to the cold level and there is a second higher level that is the max when hot. Of course you shouldn't be filling when hot, ever.... But filling to the threads is going to lead to the excess being vented out. Perhaps that's what's going on?

Thank you for a cogent reply, Tim. You are right on all counts. I was mistaken that the car was actually losing coolant. A few days' driving carefully monitored showed that the level was not going down at all, but I had indeed overfilled it. So, with the tank now full, but a persistent warning light, the conclusion is a bad sensor. It's discouraging that you indicate the sensor, although sold separately, apparently can't be installed into an otherwise serviceable tank. I'll find out soon. I was taught to not throw a new part at a problem if it can be repaired--and can afford Jaguars because of it. Maybe such training will also allow me to buy a new tank!

I could be way off track here, but I seem to recall some discussion about failed coolant level sensors on older XFs where it failed because the "float" stopped working and the sensor sank to the bottom of the expansion tank, and the fix was to bodge up a new/extra float, commonly the foam stopper thingy on the top of a stack of blank CDs or DVDs. IIRC it's a bit fiddly and you need to be careful, but the top of the float can be undone and the new piece added and Bob's your uncle.

Absolutely spot on, I tried to get the CD ring on to the bottom of the sensor (mine had sunk as you say) but no dice. It is like trying to assemble a ship in a bottle. Since the whole tank and sensor was ~$120, I ended up biting the bullet and installing a new one. I drove around for months with the sensor tied in the 'up' position with small diameter copper wire, but eventually chickened out, knowing that if I ever did spring a leak, I would not know until things escalated to a much more serious overheat....

Fantastic news, appreciate the follow-up. I also found the float on it's own (online), but I'll let you judge whether in-tank replacement is possible. If you do manage it, I'd love to see pictures! I concluded it was impossible.... Also if you get some hose clamps you can remove the whole tank for somewhat easier access outside the car....

Despite statements to the contrary, Jaguar sells the XF coolant sensor separately as part #C2Z6566. But, as has been pointed out, you can't install the damn thing! No matter, since the likely cause is a bad float on the in-tank portion of the senor unit anyway. I tried the putting-a-substitute-float-under-the-bad-one procedure outlined in another post, but it was impossible to remove the retaining clip without risking breaking off the post inside the tank. Others said it couldn't be done, but I fancy myself pretty handy, with a garage full of tools and fifty years' experience fixing cars, so I ordered the sensor...and they're right: It can't be done by a mere mortal! If you want your warning light to function, buy a complete tank that comes with a new sending unit (but it may fail after a couple years, too). I put a loop of fine mechanic's wire under the bad float, pulled it up to the top of the pillar and tied it off. Light will never annoy me again and I'll just watch my coolant level the old fashioned way.

That may fix the problem. But given how sensitive these engines are to overheating causing catastrophic failure that's a pretty big risk to take. I'd still strongly recommend replacing the whole tank with sensor unit.