The running temp of the coolant is 105c as read by my diagnostics device.

 

For giggles, I monitored the coolant temp on my '02 V6 during my drive home today. 26 miles, mostly freeway, ambient air 72F. My scanner showed 215-220F. 220F translates to the 105C you are seeing.

 

Another thought, from the Hail Mary Department:

Maybe the bearings are starting to fail in your fan motor. The control circuit to the fan may be perfectly normal, but due to bad bearings, the fan is making more noise than usual.

I'm not sure how you could inexpensively test my TheoryDuJour™. Maybe with all power off, try spinning the fan by hand and listen for any grinding and feel for any roughness.

Also double check the fan is securely fastened to the motor shaft. If that nut has worked loose, the blades could be wobbling and making more noise than usual. I think the nut has left-hand threads, but I'm not 100% positive.

 

Hi again Stretchy. You refer to 105C as if that is a problem, yet from my reading (and experience), that is within spec (and fits with 215-220F reported by kr). Methinks you have no problem whatsoever . . . but one final test should be interesting.

Prior to a cold start, turn your aircon/heat temp setting(s) to the prevailing air temp. Turn your aircon control from auto to OFF. Startup and repeat your spirited road test. Drive home, park, and immediately switch off. Record if, when and for how long your fan switches on. Post results.

Let me guess result . . . assuming moderate ambient air temp, fan now either does not come on at all, or only very briefly at end of run. Explanation in my earlier post . . . but detailed far better by aholbro1 at post #12.

Cheers,

Ken

 

But it seems the fan runs a long time after engine off and should not.

Restricted radiator flow?

Broken impeller blades left in the system some time ago?

Or what?

 

Yep; agreed John. And a 5min fan on after shutdown, as posted initially, seems abnormally excessive . . . apparently now down to 1min. But, if ECM is calling the fan ON at a sensed coolant temp of 105C, then perhaps the trigger is neither a high coolant temp nor a duff coolant temp sensor, but may involve the sensed aircon head pressure. My suspicion is the latter.

Am I right in believing that switching the aircon OFF, will disable its communication to the ECM to trigger the fan on? If so, and fan still runs after shutdown, then pump, thermostat and rad all need to be checked. But if fan no longer runs after shutdown, then attention should shift to a full check of aircon system's sensing and connectivity to ECM.

Gotta say, I have spent most of my years worrying over the big coolant failure events . . . generally nasty and expensive; sometimes terminal.

Cheers,

Ken

 

Interesting premise, Ken. If I read you right, you reckon a misleading high pressure sensing on the a/c pressure is holding the fan on post-shutdown? I don't know if shutting the a/c off at the control would kill the comms between the pressure transducer and PCM or not, nor do I know if the documentation in JTIS and such goes that deeply into operation.

However, I would hazard a guess that if it does, then shutting the key off would do likewise, which should also kill the fan excitation signal, should it not?

 

According to this the OP has not changed or checked the sensors.

https://www.jaguarforums.com/forum/s...7/#post1691825

Since the coolant remains within the normal operating range at all times, the fan should not be coming on at all, other than when overridden by HVAC commands.

 

hmmm

I think we don't know for certain.

However, I would expect an overly high pressure to result in the a/c compressor being shut off and have no effect on the cooling fan (which would be on high at the time). Key off ought then to shut off the fan (and most other things).

It's the PCM that controls the engine cooling fan as I understand it. To keep running it so long sounds to need the PCM seeing something bad - which I would say excludes the a/c.

If it's not the ECT (the one I would suspect), then how about the CHT? Both are critical sensors on the V6.

 

You might wanna re-think that one, Mikey. I don't know what the trigger temps are for low fan and hi fan, but I'm reasonably certain they are below the highest spec operating temp. At least on the X300, BOTH are below the T-stat spec.
In other words, it isn't designed such that the fan stays off until the temp goes too high! But yes, as mentioned before, high-fan is normally invoked by the HVAC long before the Rad temp calls for it, unless it is uncomfortably cool out.

 

Then we're all shooting in the dark.

 

OOps! I've re-thought my own position: Low fan trigger on the X300 is 86C vs. 92C t-stat setting. So I reckon the hi-fan trigger is closer to the hi-end of the allowable temp spec. I still maintain it should be below the max temp spec. However, my operable copy of JTIS is on the 17" Dell laptop that is trying to update itself into a "convertible" or 2-in-1 or whatever the new ones that you can detach the screen are called - typical hinge failure that Dell calls "normal wear and tear.." so that thing is a PITA to use and I'm not looking up the hi and lo fan temp triggers until I have the problem...sorry Stretchy....oh, and sorry Mikey (I still believe you are wrong, just not as wrong as I thought!:-))

 

105C strikes me as very top end and surprises me.

The design is to run hot for mpg and lower emissions but 105 may be beyond where it ought usually to be. In case it's being over-reported (i.e. real temp is lower) then it would fool the PCM into needing extra fans.

If the ECT has not been changed then I'd change it and if it has then I'd read both it and CHT, and compare the values plus see when the fans run hard.

 

Hi guys,
As you know i have been giving you all headaches about the fan operating at low journeys and at intermittent times. ok well i purchased a new thermostat and fitted it today.......but i must tell you all, my theory was correct, the bottom hose was filled with rusty water not pink coolant, so there was obviously no circulation in the bottom half of the cooling system, i also tested the old thermostat in boiling water and plunged in to cold water both for 5 minutes or more,....it never budged. Yes i do agree with a lot of you it could have been a number of other things....but i always go back to basics and work my way through the process elimination...after having 21 cars since i could drive and worked on many this is a tried and trusted method for me and i never let a problem with my cars get the better of me.
So having said all this thank you all for your advice and help...and as i have mobility issues this was a bit of a challenge for me...and i have to say i was a bit hesitant on working on my Jag as i have never owned one before, but at the end of the day...take away all the electrics and sensors they are after all the same as any other car to work on....but i am still a proud owner of a purely thoroughbred piece of motoring history (even thought it is only 17 years old) .

 

Hey Stretchy . . . not so fast. Let me be first to admit that I maybe led myself off on somewhat of a tangent, even though I believe valid, but . . . there's always a butt (LOL) . . . I really do want to know what your OBDII scan now reports as coolant temp after spirited drive similar to what you first reported . . . and whether fan on after shutdown, has changed.

Am I right in assuming you did full reverse flush of both rad and block when you had bottom hose off? Great to see your problem resolved, but please post back results to help build our group knowledge of these issues.

Many thanks,

Ken

 

Another not so fast from me.

Read this thread and you'll see that 205*F is routine operating temp for modern cars.

https://www.jaguarforums.com/forum/x...3/#post1692414

If your thermostat was stuck shut the engine would far exceed this temp.

 

Not So Fast˛

The S-Type thermostat works backwards compared to most. When shut, a radiator bypass passage is blocked off and more coolant is routed through the radiator for maximum cooling.

Now one could talk about a failed thermostat causing overheating, but that would be one that is stuck open.

I'll be hiding in my survival bunker until this one blows over. Somebody shoot me a PM when it's safe to come out.

 

Chicken . . .

 

Right you are. The OP says that his old thermostat never opened.

 

You may be right but JTIS says otherwise:

When the coolant is cold, the coolant thermostat is in the closed position and the coolant flow is restricted to the cylinder block, cylinder head(s) and heater system.As the engine coolant temperature increases, the coolant thermostat opens and allows the coolant to pass into the radiator.