QuestionQUESTION: Howard,
I seem to have both blowers now working, but I am concerned that I will never really have much heat if the cooling system is working "too well". This afternoon, I noticed once after a short stop, that when I turned the car on, the temp gauge moved right to 90 degrees, but when I started the engine, it fell rapidly. I noticed the same this evening after dinner as I started the car, I had very warm air flowing from the vents, but after driving about a mile, the temp gauge had fallen back towards 50 degrees, and the air coming from the vents was comparable to ambient temperature. Any suggestions for this seemingly over-active cooling system?
Thanks,
Michael
ANSWER: Hi Michael,
The Jaguar cooling system does is NOT capable of over cooling unless you are in subfreezing weather. Usually when the gauge drops in temp and the heater quits heating, it means you are low on coolant.
Howard
---------- FOLLOW-UP ----------
QUESTION: I check the tank after every drive, and it is full of a nice, bright green mixture. Right up to the filler neck. I have no leakage, and this car leaves NO spots on the drip pan I keep under it in the garage. No oil, nothing. Do you have any other suggestions, or ideas?
Thanks!
ANSWER: First start the engine cold and feel the upper radiator hose and let it run a while and keep feeling the upper hose to confirm when the thermostat opens and keep checking the gauge to see that each confirms the other.
I have been working on Jaguars since 1960 and have never seen any Jaguar start up and go to 90 C. and cool down to 50 C. running. Either the gauge reading is wrong or there is no coolant in the coolant rail.
It is common for the temp to climb to 90 C. quickly as the thermostat system with the large bypass and the blank disk on the end of the thermostat which controls the temp very well. However, even when the thermostat is fully open and the disk has completely closed off the bypass and all coolant is going through the radiator it can NOT cool down to 50 C. unless you are in Northern Alaska.
You can't gauge anything by the heater because the AC is operating all the time even when the heater is on because heat from the vents is controlled by vacuum door blending of heat and AC.
You need to first confirm that the engine is ok and then that the gauge is reading correctly and after all that is done, only then can you look at the heater system.
Something troubled me that you said. You said "when I turn the car on the temp gauge went to 90" Did you mean when you turned the key on or started the engine?
Howard
---------- FOLLOW-UP ----------
QUESTION: Howard,
I haven't had a chance to perform any resting yet, but on a ten mile round trip errand today, the engine seemed to hold at around 70 degrees on the gauge.
As to what troubled you before, the answer is in the very statement I made - that I turned the car "on" and it the gauge went to 90 degrees, but when I started the engine, it fell rapidly. I stated this quite clearly. I know very well the difference between "on" and "start".
Thanks,
Michael
AnswerThis would have been normal if you had run the engine recently. When you turn the key "On" the gauge reads what the coolant temp is in the coolant rail and that is always hotter than running temp because coolant standing still will absorb more heat from the engine than when circulating.
If, however the engine was cold when you turned it "On", and it went to 90 then you need to check the engine to frame ground as that is not normal.
Howard
