Doug above gave a pretty good explanation to the needle behavoir. Unfortunately, the needle gives you some sense of a gauge at times when you don't really need it (warm up/cool down). It's at the critical moment when the gauge takes on a function of an idiot light.

 

I use a Scangauge II in mine. It helped me notice my thermostat was opening at 70 degrees C instead of 90 degrees C which wasn't doing my car any favours.

 

Hey guys just wanted to let you know that NEW xj6 and xjr6 heads are for sale on ebay for only 399.00, weather I can save my engine or not i just bought one because the price is crazy cheap. I spoke to the vendor and he told me they bought 25 xj6 and 25 xjr6 heads for a crazy discount, now is the time to get that cylinder head if you intend to keep your jag forever like I do.

 

After I put the new coolant rail hose I replaced the ic pump because it was making a lot of noise, thought i burned it out because it ran dry. Its the Johnson pump.the new pump started making the same noise after 10 min. turned on the ignition, motor off, and disconnected the intake coolant ic exchange hose and nothing was coming out. I then disconnected the ic radiator out hose going to the pump and only drops came out, the system has coolant, now im confused. I then opened the cap to the reservoir and the coolant started to flow but slowly from the bottom of the ic radiator. Is my ic radiator plugged or is the cap bad creating to much pressure, or maybe both? Let me know what you think,

 

When I replaced my intercooler pump I had a heck of a time bleeding the air and/or priming the pump. I had to remove the hose from the ic to the ic radiator and trickle coolant into it until the pump started pumping...as viewed thru the hole where the ic bleeder plug goes. Keep going until the ic fills up.

Cheers
DD