Hi guys. Ambient temp of 108 fahrenheit today. Jag(02 sport) and I in heavy traffic. AC on, and saw the temp go to 221 fahrenheit. Got on the highway right after, and it came down quick. Then I got off the highway. Turned the AC off, still in super heavy stop and go traffic. Car wouldn't go above 210 fahrenheit with the AC off. I notice the car runs cooler with the AC off. Anyone have any ideas as to what I should check?

I looked between the radiator and condenser, and it's clean. No road debris in between.

 

Is the fan working?

A lot of cooling upgrade options you can choose from deoends one the budget.

High flow cooling pump (least expensive)
larger intercooler(most $)
I know some one custom made a larger coolant reservoir as well.



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Yes, both fans work. By high flow cooling pump, is that an upgraded water pump? No intercooler for me, I have a Sport, so NA.

 

https://rover.ebay.com/rover/0/0/0?m...2F272611632281

I installed this one on mine. Very simple and easy task and dollar to dollar. It is the best upgrade.

I could feel the difference it makes

 

My temps always seem to be 197-205 deg F. I don't use the AC much, but if I'm going uphill, the temps climb to +208 deg F. I think the efficiency of the cooling system is limited to that range (197-205) in any type of environment--hot or cold--for my car at least. Mine is an XJR, so it's naturally going to run hotter.

I would suggest flushing your coolant, and filling with the correct type. Then another option is to add a chiller, which spays water on the radiator fins making it conduct heat out of the system more efficiently. You can also upgrade the radiator to a larger one. A thermostat that opens at 180 deg F might help too. And lastly, I would check the water pump, and make sure the impellers are in good shape.

 

Your system is working as it should: the fans come on at 203 (slow) and will go back off if the temp drops to 194 .....should the temps continue to rise above the 203 they will not switch to high until 221 .. they will stay on high until brought down to 212.

The AC pressure will also effect the operation depending on what's going on with the pressures in the system.

The car will naturally run cooler w/o the AC running -- the refrigerant is giving off heat ahead of the radiator when AC running.

don't mess with something operating correctly

 

There is something about coolant lines being crossed

 

Yes -- you have the sport ..so you don't have the second electric pump. While the two systems (R's intercooler) are separated by fluid principles -- they use the same coolant capacity. The question that would have to be asked is what is the extra capacity of the larger pump in the intercooler circuit doing? When pull water through a cooler ..pulling it faster can often increase the temp as you are overloading the cooler ..... the overall temp of the system will drop but the exit temp can increase. The only way to be sure what's happening would be to have sensors at various points along the system.

 

Heavy traffic, slow speeds, AC on, and 108°F ambient temps sound like a perfect stress test to determine if a cooling system is working properly or not. The 221°F coolant temp you observed is the upper limit of what the car considers "normally hot" for coolant (when it turns the radiator fans on full speed). Your description of temps dropping once normal highway speeds were resumed also points to a normally-functioning radiator. Your cooling system appears to be OK, and I think you're worrying yourself sick for no good reason.

 

I see different (lower) fan switch points in the Jaguar Service Training, at XJ / XK Climate Control System:

 

That appears to be from this file: http://www.jagrepair.com/images/Trai...des/703_SG.pdf , which is in the "2004 and newer" section at jagrepair.com.
The info I posted is from this file: http://www.jagrepair.com/images/Elec...jm18151280.pdf , page 37.

EDIT: That first file appears to be posted under BOTH the "1998-2003" and "2004 and newer" sections at jagrepair. Page 1.1.2 definitely shows the 2004-2009 climate control panel though, so I'm almost sure it's erroneously posted in the 1998-2003 section.

2nd Edit: This file: http://www.jagrepair.com/images/Trai...s/701_1998.pdf in the 1998-2003 section at jagrepair DOES show the values you posted. But it also shows the AJ16 and V12 engines, neither of which were used past 1997. Now I'm thoroughly confused.

 

My numbers come from the x308 training book ... the earlier S6 x300 engine had different values.

If the coolant temp drops when the fans go to high ... you have nothing to worry about.

 

The radiator fans on my 1999 Daimler Super V8 (AJ26) go on and off exactly as per the table I posted above, temperatures read on a "real" digital thermometer that I have installed. Is it possible that the lower switching temperatures are for SC engines and the higher ones for NA?

 

Can't explain ..... you are in a different location. There is not much point of a pressurized system to manage the boiling point of water when you are not allowing the system to go above 212. Mercedes Benz has different specifications for the same cars in different parts of the world .. I can only assume this is the reason for the Jaguar.

 

Good stuff guys. Thanks a lot, as always. Currently doing HID fogs from the retro fit source, and some LED stuff. Will post pics in a different thread.

 

Mine (1998 N/A 4L) works exact as the table posted by Samilcar, so I presume the N/A are indeed allowed to run a tat higher as you already presumed.

 

I found out that there is a difference between NA and SC with regard to the thermostat opening temperatures (higher on NA), as shown in the attached extract from the Service Training - Engine (Publication Code - 168). However, these thermostat temperatures are for AJ33/34. Otherwise, the different thermostat opening temperatures shown correspond (more or less) to the higher and lower fan switching temperatures included in the earlier posts here.

 

Thermostats are one those little items that one has to be very careful about when going aftermarket -- outwardly they can appear to be the same but the values different.

They are also very reliable -- I would never switch out the OE for an aftermarket as a simple maintenance item.


The early cars did have a change -- so they ned to be switched.

 

Hi Vincent, I am curious as to what this modification/upgrade was? The eBay link no longer works