2008 XKR (FLorida, warm weather climate) -> So I have had intermittent check engine light for a couple weeks, and I borrowed a friends scanner, and the error code was P0128 "coolant temp below thermostat regulating temp". After running for a bit the temp itself was climbing from low 100s up to ~130 after 5-10 minutes idle, and then I drove on the highway for about 10 minutes, and it went up to ~197.

Anyone know anything about this (i.e., serious or can be ignored?).

Based on my limited research, it sounds like I may need to replace the thermostat, but it may not be urgent?

 

Defintely sounds like a sticky thermostat.

Not a massive emergency, but it should be tended to. Slow warmup can cause sludge buildup in the engine, and excessive pollution.

Also there is no telling whether the thermostat might start sticking hot, and then you could have a far more serious overheating problem.

It is an inexpensive repair....just do it.

 

Youre a 08 and i would not do just the thermostat as the housing is plastic and will does crack. Buy the whole assembly because if the inside cracks loose it will overheat and leave you stranded. A p0128 is becasue the seal around the t stat inside is split and bypasses coolant. I think the housing is about $70 on partsgeek.com which is oem and includes a new t stat inside.

 

How hard is replacement in an XKR? Any tips for refilling/burping the coolant system after replacement?

 

As for tips on refilling..............I did this on just a regular XK and followed the manual. T The manual for a plain XK says to fill the reservior tank til pure coolant comes out around the bleed screw (which you will have loosened prior to filling the tank). Once I did that procedure I also reached over and grabbed the upper right radiator hose and squeezed it several times and observed that the coolant in the reservior went down, so I poured more coolant in the reservior and squeezed the hose repeatedly till the coolant stayed up on the line in the tank./

Then you warm up the engine with the heater turned full warm so coolant will fill the heater hoses (which by the way are tied to the hose on the reservior). You do this to get all the air out. Never remove/unscrew the reservior cap when the coolant is 'hot'.

I don't have a XKR but I'd do what the manual says about removing it's bleed screw and getting all the air out of that system.

Refill is not really anything special imho. Different than some other cars but not scary different.