2000 LS V8 Overheating

[rlcop615]

Hello everyone! My name is Trey and I live in Nashville. I've been a reader of this site since I bought my LS a few years ago. I bought it in September 2014 off of an older gentleman that had kept meticulous service records from the dealership. It has 72,XXX miles. I've enjoyed owning the car for the most part, except the persistent overheating problems. Now, before you ask, I have read just about every thread on this subject. I know the six parts everyone says to replace at the same time:
1) OEM Degas Bottle, (p/n 5W4Z-8A080-AA)
2) Jag Aluminum Thermostat housing,
3) OEM Thermostat,
4) OEM Coolant Outlet Pipe,
5) OEM Auxiliary Coolant Flow Pump, (p/n 1W4Z-18D473-AA)
6) OEM Dual Coolant Flow Valve (DCCV).

I've replaced the water pump (non oem)
The thermostat (non oem)
The Degas bottle (Dorman, but with OEM "clicking" cap)
I used the steps from this forum to correctly bleed the system. The car has been running fine since the Degas bottle change out about 3 weeks ago. Today, I drove the car for about 5-10 minutes and got the dreaded secondary fan stage and the temp gauge started to creep up. I parked and popped the hood to check the bleeder valve for a continuous flow, which it did. No sign of air in the system. After letting the engine cool for 30-45 minutes, I noticed the coolant level in the Degas bottle was about an inch below the top full line, slightly lower than the bottom line. Obviously I'm losing coolant somewhere, but if there is no air in the line how can I know which part to replace? The Degas was easy to diagnose, as I could see the coolant bubbling out of it at the middle point where the top and bottom are joined. I'm on a tight budget, so I can't really afford to replace all the rest of the parts at once. Should I start with the t-stat housing assembly? I looked on rockauto under 2001 Jaguar S Type 4.0 V8, and the only one they had was the URO brand. Is that Jags OEM brand? Any help would be appreciated. Thanks for reading.

 

[rlcop615]

Also, after it started overheating today and I turned it off for 30-45 minutes, I drove it back home (same distance and time as it took to start overheating) and it didn't overheat or start the fans secondary stage. I got home and that's when I let it cool and added the coolant. I've since driven it for an hour or so and it didn't overheat or trigger the fans second.

 

[grizzlyls]

Its not jags brand, but it is a major euro supplier. That is the right one for our cars as well. Unfortunately you might need to look at the Dorman as a culprit too. You can look up the Uro degas (jag fitting only for reference, but is same as ours) as a lower cost, the rest of the guys hear swear OEM only, but I got the Uro bottle since my mech gave it two thumbs up and I am glad I did. Very solid bottle thicker sturdy plastic.

My motorcraft tstat didnt last hardly a year, use a Stant Superstat. Far better and my car runs way cooler now. The rest of the issue is about hoses and plastic pipes. Depending on the condition of the engine numbers 5 and 6 can wait if it is a non strained, non weathered engine like mine (So cal).

Btw get an OBD II sensor and monitor the coolant temp on your phone using Torque lite (Forscan too, but Torque has larger readout, easier to setup).