So I bought a 2001 disco 2 from a friend who just had the head gasket replaced. Put about 8k miles on it and then one day on my way home I noticed the temperature gauge spiked up. I shut it down and had it towed home. Engine visor has just under 100k miles on it sho decided to replace the washer pump, thermostat, radiator, and fan clutch. Added coolant and burped it. Start it up and connect my obd2 to monitor temp. Temp holds steady around 183-188. Drive or around for about an hour and tempo stays good. Then all of a sudden tempo starts increasing. Made or home newbie it got over 220 degrees and shut it off. Let it cool down overnight and tried it again ther next morning. This time the temperature seems to just want to keep climbing. Decided to pull the heads and check the head gasket and sleeves although no coolant mix in the oil pan and the exhaust test through the overflow passed. The head gasket looked fine and none of the cylinders were steam cleaned. Spark plugs looked brown like it was running fine. Decided to change the spark plugs, plug wires, and coil pack due to an low intermittent misfire on the even cylinders since I had the heads and intake off. Also replaced the head bolts with arp head studs ans the coolant overfill cap. The sleeves haven't moved at all. Put everything back together and add coolant and burp the system. Start it and lat it idle. Temp I'd showing consistent around 197-203. Let it idle for 30 minutes and temps hold. Drive it around and temp drops to a steady 194. After about 30 minutes driving, temp stays to increase. It gets to 210 and I start heading back home. Temp goes up to 223 and then back to 217. As soon as I pull in the driveway, temp suddenly spikes fron 210 to 143. I shut it off and it's been parked since. Any ideas on what might be going on? Could I still have air in the system somehow? Thanks in advance. Vehicle is a 2001 land rover discovery 2 SD with 4.0.