I noticed the hose going from the manifold to the expansion bottle was looking a bit tired at the manifold connection. I replaced it and the bottle as well as the nipple to that hose was cracked. I had no cooling issues just a little preventative maintenance. Nor did I have codes. I also didn't notice any slowness in the initial warm up on the dash temp gauge.

Bottle is on the full line when cold. Since the replacement I've noted the temp gauge a bit slow to get to full temp from a cold start. Well, today I got the P0128. I have a scan tool that allows me to watch the sensors in real time. The engine runs at 185-192 degrees F once fully warmed. No issues with cooling or overheating.

Could I have air in the system? Is there a prescribed method for "burping" this engine? I had a 5.0 Mustang that had to be run with the nose high and the cap off in order to remove all the air.

Thanks.

 

silkcat: Thermo's guide to "burping your kitty" is post #10 in this thread:

https://www.jaguarforums.com/forum/x...-x-type-28628/

 

It's not air in the system. We had a cool 57 degree morning. The faster I drove, the cooler the engine temp was (monitoring real time while driving with scan tool). Order new thermostat.

 

silk: Glad that you diagnosed the thermostat as the problem. When you replace it, go easy on the rigid black plastic coolant pipes above the thermostat & beneath the air filter box. Some folks have accidently cracked this plastic pipe while working on or near the thermostat, causing coolant to leak.


Good luck.

 

I was pleasantly surprised that I had the old t-stat out in less than 30 minutes including grabbing tools and removing the belly pan from beneath the radiator. It had the dreaded floating seal preventing the stat from fully closing. New stat arrives tomorrow.

I also renewed the serpentine belt. That was interesting!