I have done some further investigation.

It appears on my 2007 XK that there is a hole at the bottom of the tank for a sensor...but no sensor is installed.

Searching through the electrical diagrams, it appears they phased the coolant level sensor in starting in 2009 model year. The sensor drives an input into the instrument cluster, which is non-existent on 2006-2008 models.

My guess is that it was either a bad early decision that was reversed, or a rush to market with an known design mistake or parts shortage in order to hit the market window.

It appears the tank is the same throughout the model years. It might not be too difficult to retrofit since the sensor probably already fits the tank. It is definitely something worth looking into.

 

Hmmm - I can't see any coolant level sensors in the electrical diagrams for the 4.2 cars right up to B32752, just a temperature sensor. Maybe you have better diagrams than I do.

The instrument cluster module for the 5.0 has an input called "COOLANT_LEVEL_SW" - but it's been re-purposed for the brake-fluid level sensor.

 

I think the 5.0 electrical diagram has a typo. There is already a brake fluid sensor on the left side of the instrument cluster page. I think the "COOLANT_LEVEL_SW" is really connected to the coolant level sensor.

Also, the 5.0 service manual has a picture of the coolant tank with the sensor and a description of it.

I would have thought it was a 5.0 phase in, except for member Tervuren saying he had a light on his 2009, which in the US would be a 4.2. Perhaps they started phasing it in just before the 5.0 release.

 

Well caught! - yep, looks like a typo.

 

Do you think retrofitting a sensor would really be that simple?? Plug and play? Or would I need to somehow unlock the programming.

 

I can't see where you'd plug in the sensor on a 4.2 - there isn't an input for it on any of the electrical diagrams. The instrument cluster connector pin IP032/14 that is used on the 5.0 cars appears to be unused on the 4.2, but even if you were to get the signal to that pin, there's probably no circuitry inside that connects to it.

 

Plug and play on the tank side...maybe. If the tank does not have a magnetic float, it would need to be upgraded. On the instrument cluster side further investigation is also needed. Just thoughts at the moment....but that is how every upgrade starts.

 

OK, I think I am going to get my car back tomorrow morning. Total for the repair was $1067. Compared to what some others were paying in some other threads I found on the S-Type forum (4.2 SC), I got off pretty easy! My mechanic rocks!!

 

It's interesting that the service manual (VIN B00379 to B32752 for the 4.2L cars) in the Specifications section, for the Expansion tank it says 'Remote - fitted with a bleed screw and a low coolant level sensor'. But says nothing about the sensor in the remove/install section.
Wonder if a 'washer fluid level switch' would fit in there, and then move the electrical connector from the washer reservoir to the coolant expansion tank?
Or maybe it could be monitored separately with an input into the optional I/F unit for the HKS Camp2?

 

After about a month and a half and perhaps 1000 miles of driving, I am smelling coolant from under the hood (it was much stronger after I got the coolant hoses changed, but has gotten less and less over time). Is this cause for concern? I did top off the coolant a couple times (maybe with a few ounces of distilled water) but I'm not sure if this is due to a coolant loss or maybe it just wasn't bled properly? Or maybe wasn't topped off to begin with?

I am going to keep an eye on it for the next several weeks. I used my OBD II bluetooth scanner and after a long drive, the coolant was hovering right at around 91-93ºC. What do you guys think? Normal?

 

[QUOTE=amcdonal86;1406970]After about a month and a half and perhaps 1000 miles of driving, I am smelling coolant from under the hood (it was much stronger after I got the coolant hoses changed, but has gotten less and less over time). Is this cause for concern? [\quote]

Yes! You shouldn't still be smelling any residual spillage this far out.

Small leaks are a pita to uncover, but you'll want too have that looked at.

 

Would the shop be able to do a pressure test to verify no coolant leaks?

It seems like our weather has been cool (engine bay may not warm up) and most of my driving is fairly short in duration (under 20 minutes), so I wonder if this could extend the amount of time it takes for the coolant smell to go away.

 

When you topped off the coolant, if it was inadvertently overfilled, you may be smelling excess coolant that was expelled from the overflow tank after your car got up to operating temperature and that coolant expanded. I'd drive the car for several days and keep an eye on the temperature - I use an ELM327/Torque app/Bluetooth to Android phone. If you don't smell coolant after 2-3days and your car doesn't overheat, I suspect it was overfilled.

If it ain't broke, don't fix it.

 

Maybe I am overfilling it. Today I topped it off to in between the lower and upper plastic bits inside the coolant reservoir when the engine was cool.

 

Go to an auto parts store and see if you can use or rent a cooling pressure test kit. It is simple to do and will either give you piece of mind or what to do next. I borrowed a friend of mine's kit .

 

Changed my coolant tank today. Replacement tank has a sensor, but the XK has no harness to plug it into!

 

Just to follow up here, it turns out the previous shop had crossthreaded the drain plug. It started leaking more substantially (I noticed small puddles under the driver's side).

A new (better) shop has threaded a new plug on there and now it's good to go!