Deja vu.

The heater-core, not the rad, is doing such cooling as you have.

'Long ago and far away' ... I had a thermostat that only opened part-way, overheat was blowing head-gaskets, never much fun to replace on DOHC engines, though I got it down to under an hour even at the side of the road.

Removal of the 'stat and placing it into a pot of cool water, then watching it as I brought it UP TO the boil, revealed that the 'bridge' that held the thermal pellet had not been fully-staked where it passes through the rim.

The obturating disk had been lifting off the seat just enough that I was able to see coolant-flow begin whilst observing at the rad fill-cap. The REST of the pellet's movement, however, simply lifted one side of the 'bridge' out of the flat mounting rim. No further opening at the disk occurred. Flow was never more than a trickle.

Having seen the flow begin, I had dismissed the thermostat as contributor, flushed the rad, block, heater core, replaced all the hoses, even changed-out the water-pump.

Needless to say, at the cost and time required, thermostat has always been replaced FIRST the 40+ years since.

BTW - do not simply remove the 'stat, nor even tear-off the bridge and pellet to leave a modest restriction. Too little restriction and the water pump can suck the incoming hose flat, also preventing flow.

DAMHIKT.

 

Thank you all again.
It appears that the T stat was in backwards. I don't seem to be able to get the temp up now which is a good thing.
AVT007 has a great breakdown with one point of confusion. On page 3 it is confusing as to this:
1. Refill the cooling system with a 50% solution of water and Jaguar Antifreeze / Corrosion Inhibitor
ESD-M97B49-A.
1. Remove the threaded plug and Dowty washer from the charge air cooler fill point.
2. Fill the cooling system at the header tank until the level stabilises near the top of the charge air cooler fill point. This will take some time, as air is being purged from the system.
• Ensure that the header tank is full.
NOTE:
To ensure that air is not drawn into the system during the following operations:
• Do not remove the cap from the header tank whilst the charge air cooling system is open to atmosphere

It says to remove the threaded plug at#1 but in the note it says not to open the header tank cap while the threaded plug is open. Yet #2 says to fill the header tank with coolant while the threaded plug is open. Does this just mean to open the tank cap first and then the threaded plug? I'm thinking it means to open the header tank first and then the threaded plug and then fill the tank with the coolant mixture allowing the air to purge out of the threaded plug opening?? Later it says to pour coolant into the threaded plug hole does this mean pure coolant as it infers or should it be the 50/50?
You guys are all amazing so much thanks for your efforts and help!!

2002 Super 8 103k.

 

Open both ports, fill the header tank until it won't take any more and stabilizes. Then fill the supercharger port until it is full. Close off the super charger port and don't open it again after this point. Do the procedure of having the key on the engine off to allow the intercooler pump to purge the air.
After you have done that a couple times should be good to go. Congratulations I hope this is all okay.

 

One question, are the late cars, 02-03,non XJR's, known for plastic cooling tower cracks? I see some pink "cheese" on my hose connection on 2 of the big diameter hoses,on the thermostat housing. Time for aluminum one?

 

I have pale pink watermarks on some hoses - I've cleaned them off, need to recheck them....My brother in law is a professional mechanic and often says he can smell antifreeze...I can't find an actual leak though...I'll keep looking - could be a tower leak.....I am reading this thread as I am thinking about changing the tower, checking the water pump and thermostat and flushing the cooling system.....Allan

 

Vancouver,
Thanks again for all your help with the t-stat. Now I need some help with the water pump. I was headed on a four hour trip this am and at the gas station I raised the hood just to be safe. I smelled something not right and stuck my nose down towards the front and saw liquid draining. It's orange so it's coolant. The water pump is leaking slowly and soon it will go so I turned around and made it safely. I checked the fluid level and it had dropped but only a few cups or so. I can't find any Water pump procedures on this site for a 308 like mine. Can you steer me in the right direction? Can I get to it without pulling the SC belt mount? Looks like I could get to it by pulling the Tstat housing and taking the belt off. Thanks in advance,

Curtis
2002 Super 8 (supercharged Vanden Plas) 105,000 Sarasota, Florida

 

Anyone may feel free to respond to that last Water Pump question, if so motivated


Curtis
2002 Super 8 105k Sarasota

 

Glad I read this !
First, thanks to everyone that contributed......very helpful.

My 2003 XJR overheated yesterday. Earlier in the day, I noticed the cooler fan coming on, or staying on after the car was powered down. I immediately looked it up and got mixed views on it.
Then, the car got hot per the temp guage. The red light came on so I powered down and waited for the cool off.
The coolant is orange and seems that there's enough of it.
I read that a common problem is the tstat.
I cannot imagine how to get that thing out with the s/c right there!
Help please.....
Also, I guess the water pump should be swapped out too?

Just bought the car 2 months ago.......no records.......to this day, very clean engine bay and only 67k miles.

Thanks in advance.