Hello All,
2003 Jaguar S-Type 3.0 w/ 81,000 miles is running around 215 - 220 F while monitoring temp live data with scanner attached. Engine fans also run after I shut the car off an have taken out the key and I fear that the battery may die as I am not sure how long they will run for and I found that if I turn the key on and off again, the fans go off. I also fill the coolant up to the bottom step on the overflow tank and a few days later it is down a bit and won't stay at that level and the low coolant light comes on. I don't see any leaking underneath the vehicle, and I put a block tester on it and the liquid stays blue after bubbling air from the coolant tank through it, so no signs of a leaking head gasket. I also pressure tested the system through the tank and separately on the cap and both hold pressure at 20psi.

Anyone else had this issue and know what else to test on this vehicle?
Thank you,

Doug Slater

 

Have you replaced the DCCV? Does the heat and AC on both sides work OK?
With the age of your car ALL rubber hoses are now needing replacement. It's up to you but otherwise they will fail one by one and you will do the repairs over and over. Best to get it all fixed at once.

Good you checked for head gaskets but that's pretty rare on the V-6 unless it's been badly over heated in the past.
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The temperature sensor on the 3.0 litre engine does not monitor coolant temperature but cylinder head temperature.

If the coolant level is normal, and the cooling module fan continues to run after the engine is shut off, most likely the thermostat is sticking.

 

I believe this only applies to the early V6. On 2003+, you've got a regular sensor for coolant temperature instead.

 

Hiya Doug,

I wonder if maybe you've got two issues happening at one time.

Let's look at the potential coolant loss first. The pressure test and block test are both excellent ideas, and fortunately didn't turn up anything bad. By chance have you done any recent work with the cooling system open? New thermostat, replaced hoses, etc.? The reason I ask is the bleeding process for the cooling system is kinda finicky. Even if following the factory procedure to the letter, it seems like you need to keep topping off the system for a week or so. The system is self-bleeding, but the process isn't instant. So in other words, it may be perfectly normal to have to keep topping off the system after any recent work.

Next is the temperature indication. From what you've told us so far, we don't even know if the engine is actually running warm or if this is just an indication problem. Beg, borrow, or steal in infrared thermometer to be sure. No whining, you can get an el cheapo version under $30 that will work great. With the engine warmed up, point the thermometer at the thermostat housing or the inlet at the radiator (upper hose). For best results, get a reading on metal, not the rubber hose. Make sure the observed temperature is close to the rating of the thermostat. I'm not sure of the exact value, but think the stock thermostat is rated at 192F.

If the observed temperature is close to 192F, you've probably got a bad temperature sensor, feeding a false high signal to the temperature gauge and your scanner. (Please be aware the factory gauge is deliberately misleading, with the needle centered from approximately 180-230F.)

If the observed temperature is closer to the 220F your scanner is showing, a bad thermostat is the most likely culprit. Pick up a new one, but be sure to test it before installation. Use an old pot full of water heated on the stove. Here's a good guide showing how to test:

https://knowhow.napaonline.com/tempe...ps-and-tricks/

Note the thermostat only starts to open at its rated temperature. It's not fully open until about 20F higher. I have found new thermostats highly likely to be inaccurate, so be sure to test before installation. OEM, name brand aftermarket, white box, it didn't matter. Test to be sure and save yourself some grief. Save the old one to test for comparison, too. It's always nice to confirm an old part was bad.

 

Ok, so I have an infrared thermometer and I put the laser on the metal thermostat housing while the vehicle was running and well warmed up and I was getting about 175 degrees reading on the outside of the housing. I also did replace the thermostat just for safe measures a month ago. I did notice that I am getting a p0128 code too.

also, is it normal for the fans to keep running after I take the key out and will it kill the battery, or would it shut off on its own after a minute or two?

 

I just got an S-Type a week ago, so I'm not very familiar.

But isn't 220F a normal temperature?

 

Hope you don't mind me peppering you with questions. I'm trying to piece together all the little clues. With a 192 thermostat, your reading is probably a little on the low side. Was it taken after a cold start, running at idle in your driveway? Or was it taken after a normal drive? If the former, I'd suggest taking the measurement after a good test drive, working the engine hard. Idling from a cold start, the engine doesn't generate much heat. You want to recreate the scenario of max heat generation.


Ah, another little clue. How much have you driven the car since then? Is this a daily driver with multiple drive cycles on the new thermostat? Or a Sunday driver with only occasional use? Back to the potential coolant loss, I'm wondering if air is still getting worked out the system.


I'm a bit perplexed by this one. The official Jaguar definition isn't especially clear. Open the link here:

JagRepair.com - Jaguar Repair Information Resource

Per Jaguar, it means "Coolant thermostat range/performance". It's not specifically saying high or low, just that the sensor seems to be out of range. Reading between the lines, you'd get P0125 for low temperature. I get that code occasionally on my car on cool mornings if I take the back road (lower speed, engine not working hard) versus just hopping on the freeway.

So with that said, I'm not sure exactly what to tell you for P0128.

Let us know about how you recorded that 175F reading. I suspect that was low due to the conditions, and would be more like 190 or so after a good test drive. Even more important, what is your scanner showing at the same time? If there is a major difference, I'd suspect the sensor is bad. If your infrared thermometer and scanner are showing fairly close readings (maybe within 15F, just a guess) with both on the high side, I'd suspect your new thermostat.

If the clues do lead to a bad thermostat, remember to test a new one before installation. Don't discard the old one, either. Ideally, you can test them together for comparison.


Define "normal". The best way to describe the situation is the fan will be commanded to run for a few minutes after shutdown if the engine is sensed to be warmer than normal. In other words, you're getting a "normal" response to an abnormal situation. On my my '02 V6, this will occasionally happen on very hot days when the engine is shutdown quickly after a freeway run. It never happens after putzing around town, when things are not quite so warm under the hood.

 

In terms to how much the car has been driven, the answer is not much. I was afraid it could be overheating, so I told my son to only take it to and from school and use my wife’s car for anything else while I try to figure this out.

you may be onto something in terms of it taking a while to get the air out. After replacing the thermostat and filling the coolant, I tried to purge the air by loosening the small cap on the overflow tank with a screwdriver while it was running and got some bubbles at first, but closed it back up after a minute or so when it looked like it was entirely spurts of coolant coming out as I did not want to lose too much.

there was a gurgling sound by the dash when it was driven for the first week, which I assumed was air in the radiator. That’s when I added the most coolant - 3 or 4 12 oz cups over the next week. This week, I put in one 12 is cup and it has only gotten slightly lower than the min mark in the tank so I have not put any more in yet.

Regarding the 175 degree temp, I got that by pointing the laser on the outside of the thermostat hosing from about 10 inches above it. It was read with the car running after my son got home from school - about a 5 mile drive and we are in Tampa Florida with outside temp of about 70 degrees.

I can do it again when he drives up home from school today and I will also connect the scanner and read the live data to see what the disparity is.

is there a better place to read the temp with the infrared thermometer aside from the thermostat housing? Also, any way to test out the temp sensor?

The replacement thermostat is an advance auto duralast 4139. It says it is a 192 open. I still have the old one. I can heat it up in a pot on the stove and see if that one opens at the correct temp to see if it was bad to begin with. I don’t recall how much coolant you lose when you pull the thermostat out, but should so do that and check the new one? I don’t know how long I would have to wait for the car to cool down enough to do that?

lastly, I should also mention that I replaced the radiator at the same time that I did the thermostat. Anything worth noting on that?

 

It certainly sounds like you introduced a good bit of air into your cooling system with those repairs! The air may not have found its way out and be causing some of your issues.

Did you turn the climate control system to "max heat" to clear air from the heater core? You mentioned gurgling sounds from behind the dash...

Also, a five mile run on a 70 degree (F) day may not be enough (depending on the nature of the trip) to get the car fully up to operating temperature, bearing in mind that the indicator gauge on the dash can be very mispleading.

Over to you, Karl...

 

Not a fan of after market thermostats but if tested before installation at least you tried.

I have had many, many problems with air bubbles and while this might not help you right now. I finally got a vacuum coolant filler and that WILL solve your air problems!
It just works so good I don't know why I did not have one before! Many out there and the price has fallen as well. I have used it on my 2014 XJR and my wife's 2013 MKS.

Both were vacuum filled and I have not had to add a drop afterwards and no over heating either.
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Nah, I was thinking the same thing. I think a few cycles of spirited driving may be in order, heater set to max HI, to help finish purging air.

For best results, monitor the coolant temperature with your scanner. If you see it getting too close to 230F, throttle back and be prepared to pull over. Most likely this will not be necessary, so don't be too worried about it.

 

Maybe at the inlet to the radiator? This would be the upper hose. Poke around with your thermometer, looking for the hottest spot in the cooling system.


Probably somewhere somebody has a chart of expected resistance values at specific temperatures. Heck if I know where to find it. In practice, comparing the observed temperature (with your IR thermometer) to the scanner value is usually adequate.

Hope you don't mind me continually peppering you with more questions. Why was the radiator replaced? Was it leaking? Or was it part of an attempt to correct an overheating problem?

You can run a quick test to make sure your new radiator is properly dispersing heat. With your spiffy IR gun and the engine fully warmed up and running, compare the radiator inlet and outlet temperatures. You should see at least a 30F drop across the radiator. If not, there may be a problem with inadequate airflow. With an old radiator, internal scale can also restrict heat transfer, but that shouldn't be an issue if new.