Hi All,
First of all, happy newyear.
After rebuilding the engine i'm stuck with a cooling issue and I can't seem to solve it. Any help is much appreciated.

The following is the case. The fans are not kicking in even with the temp (real gauge) moving well past the 3/4 mark.
I've replaced the temp sensor, thermostat, coolant, and the fanrelay. Also checked the fuses. When I turn on the ac then both fans do rotate. If its off, fans are not running.

I've also get the idea the thermostat doesnt open at all, as the driver side hose doenst get warm. That would indicate it won't open, or not?
Maybe i'm being to carefull not to have the engine get to hot. I just don't want to ruin my freshly rebuild engine....

On a side note I also get the limited power message on the dash. ALso there i really have no clue what is causing that. All in all some strange things going on, and me being a beginner in the jaguar world I can really appreciate some help from the community to get this solved.

Thanks so much!
Jeffry

 

The fan sensor is in the radiator. If the drivers side hose does not get hot, the radiator will not get hot, hence the fans will not work. The solution is to fix the circulation problem.

 

Ah ok thanks Mark. So where is that sensor located then in the radiator? I havent conciously seen it nor plugged it in. I'm only aware of the top coolant sensor on the thermosatat housing.
Will the circulation not function fully when not driving the car? I haven't been able to drive it on the road because its suspended....

 

If the temperature gauge is reading high, and the radiator is not getting hot, there is a serious problem with coolant circulation.

Reasons I can think of :

The radiator is blocked.
The thermostat is jammed, or in backwards.
The water pump is not working. (belt not installed properly, impeller broken?)
The system has an airlock.

 

+1 Mark.
Air lock in the cooling system is one check to make. Did you turn the heat up to full after refilling the cooling system? Did you remove the plug at the top of the intercooler? Try pumping the upper radiator hose to burp the system with reservoir cap off.
I don't recall if the XJR has two bleed lines out of the tank. If so, they should be crossed.

 

I bet on a faulty or backward thermostat. I have never had a problem burping the coolant system in an XJR or XJ8 for that matter. Just keep it topped up at idle and "massage" the top hose.

 

Yes, 2 bleed lines should be crossed like this.
Vector

 

I will give it a check today to give it another try. thanks for all the pointers.
Cheers

 

i am guessing the thermostat...i had a similar issue after doing an engine swap...i'd order a jag one from SNG or britishparts

 

Jeffer: where are you and what car? Sounds like a bum TST. Maybe one of the pros will weigh in, but I am guessing you are getting the reduced power message because it is overheating.

 

Was the thermostat installed as part of the rebuild? Or to try and fix this problem?

For the second time, I would like to ask if it is installed with the correct orientation.

 

Pull the thermostat and check for correct operation in a pot of water. I put a new thermostat in mine during a rebuild; said 84c on stat, didn't start to open till 92c. What sort of coolant did you use? Might be worth pulling off bottom hose to see what comes out, as regular and long-life coolant aren't compatible; can form sludge.

 

LH radiator fan fuse(30A) blows after about 500 miles. The oly part I haven't replaced is the fan itself. any clues?

 

Check the fan(s) for obstructions. Turn the fans by hand and feel for any dragging while pushing blade towards the front.

 

Jeffer, did you ever figure out what was causing overheating?

 

I had trouble with random periodic overheating on my 98 XJR after replacing the overflow resevoir. After reading one of the above threads I burped the system Voila! probel cured.

 

When burping the XJR, remember to check the supercharger coolant top off, the plug on top.

 

I got the random overheat cured and am now getting random low coolant messages. The coolant level is good. I even made sure there was no air in the system. Turned out the problem with the raditor fan was a bad connector on the fan. Not fully seated, high resistance excess current poof goes the fuse. Now have 2200 miles with out loosing a fuse. I have checked the electrical guide, and other than a bad sensor, can not see any reason for the random fault. OBTW the sensor is only 6 months old.

 

Check that the float in the reservoir is not hanging up. I realize you replaced the reservoir, but the float may be defective.

 

If the expansion tank is only 6 months old, you could have it warrantied out for another one.