I have replaced just about everything for the cooling system except the fan. Today I received the OEM thermostat housing assembly. I installed it and it’s still overheating. One thing I did notice is that when I put the heater on high it starts to cool down drastically (down from 220 to 203). When I turned the A/C back on it started over heating again climbing from 210 all the way up to 230+. It over heats even with A/C and heating completely off, it’s only cools down while driving or when the heating is on.

This thread I posted earlier this week has the full back story to my situationhttps://www.jaguarforums.com/forum/s...3&goto=newpost

 

You might have a blocked radiator
when you put the heater on, it just diverts hot water to another smaller radiator (heater matrix) and there is a fan which blows through the radiator (heater matrix) and heats up your feet
it works in the same way as the radiator at the front of your car. This is why the temps you are seeing are going down with the cab heater on
Is the fan coming on at the engine radiator?

 

i just got the whole radiator replaced with a new OEM one last Friday and it did not make a difference.

Also I have not physically checked the fan, but the only time I do hear it running is when the engine starts to get hot. In the beginning when I didn’t know of the over heating issue, I would let the engine get extra hot unknowingly and once turned off, the fan would run on high. But in general while cruising and idling I have never heard the fan run unless the engine gets hot/overheats, which at that point the fan runs on high

Im starting to think it might be the radiator fan. I will check the fan if it runs or not while idling tomorrow

 

I think simply having the AC on should be enough for it to run the fan at the very least at a low speed.

Not sure if the '09/4.2 XF fan is the same as the '10> 5.0 fan, but if it is, they're a nightmare and (at least in my experience) a known failure point.

They are controlled by a PWM signal from the ECU which tells the fan what speed to run at, and then the fan itself has a 4 pin connector: two large pins/cables for the power supply for the fan motor, and two small pins/cables for the PWM feed. The motor speed controller is built into the fan unit, and it appears to be this item that fails.

Unfortunately, I can't find anyone making these fan controllers in the aftermarket. so you either have to pay frankly eye-watering dealer prices (~$1000) for a new fan from Jaguar, buy an aftermarket fan unit for even crazier prices ($1400 from Autozone), or pick one up used which will last who knows how long.

The search continues....

EDIT: According to the EPC the 4.2 fan is different to the 5.0, runs a bit cheaper in the dealers too, but still pretty expensive for what is just a fan with a speed controller.

 

yeah I’ve heard about this fan issue on the 5.0 a lot but not that much on the 4.2. At this point I will be glad if the fan is the issue. It’s been a year now with this car overheating, it’s been to two dealers and my mechanic multiple times, and I’ve spent over $4k on what the dealers and my mechanic said would fix it. I will be very happy if this it.

i will check the fan tomorrow and see. Thanks!

 

Ah...
The newly fitted radiator blows my theory out the water...
it’s starting to sound very much like the fan now!
crazy prices for a new one, so I think I would go down the road of getting a used one - breakers? Ebay?

 

I'd be amazed if the two dealers and the mechanic you took it to didn't pick up the fan issue, but I guess it's possible. If that turns out to be the issue I suggest you find a good indy.

You can certainly get a used fan from a breakers or eBay but the usual caveat would apply and there's no real guarantee on how long it will last or if it even comes with issues. Personally, given that breakers/eBay sellers appear to know the new cost of these fans and adjust the costs of their used parts accordingly, I'm not sure it's a gamble I'd be happy with long-term.

 

UPDATE: so the fan is working how it should. Throughout its running and as the car gets hotter is spins faster. Here is one thing I noticed tonight. So while the car was idling and overheating 220+, I touched the top of the radiator and it was ice cold. So I went in, gave it some gas around 1500-2000rpms for about 30-45 seconds. The temp dropped to 217 and was continuing dropping and the fan was slowing down like it should, BUT I touch the radiator on top, same spot and now it is really hot. After letting it idle again for about literally 30-45 seconds the temp starts rising and I touch the rad again and it’s now ice cold like it was first?!?! I touched the upper radiator hose and it’s nice and firm as well as hot. There is also a steel line going to the radiator (idk what it’s for) but that was hot too, yet the radiator is cold while running. So I turn the car off, let it sit for around 30 mins or so go back and touch the rad with the car off and it’s now hot to touch but not super hot. It felt almost like it hot from the engine heat/heat soak.

Isn’t the radiator supposed to be hot WHILE running if not at least warm?

I would hands down guess it’s the rad, but I just got it replaced last week.

I know it’s two possibilities, either flow blockage or air. I’m leaning towards there being air in the system, but I’m not sure. I would guess he would have bled the system when he replaced the radiator right?

What are y’alls thoughts on this?

 

I’m no expert and have not measured my radiators temperature while driving, but temperature of the radiator should be dependent on functional water pump, thermostat, and fan/wind. If it goes from ice cold to hot and then back cold all while reading high temps, then it sounds like the thermostat is opening/closing at the wrong temperature. To me it suggests that either the coolant temperature sensor is wrong or the thermostat is broken. Hopefully someone more knowledgeable will chime in.

 

Do you know where this sensor is located? I keep hearing about this sensor for the past year, but googling it and nothing really comes up. Also is there are part number for it?

 

On my XJ, which I believe uses the same parts as a 2010-2015 XF, the sensor is part of the water pipe (part# AJ814007). It appears the sensor also has a stand-alone part number (JDE1634) that can be purchased on its own. Of course please verify these parts are correct for your model vehicle/ VIN.

The coolant temperature sensor won't change the opening and closing of the thermostat (that function is built into the thermostat), but it does control your fan and can also trigger false negatives/ positives in terms of whether your car is actually overheating.

Best of luck!

EDIT: Just realized you have the 4.2L 2009 XF. Unfortunately my knowledge is largely limited to the 5L models. Sorry.

 

The engine coolant temperature sensor is on the back right side( ie passenger side) of the thermostat /water rail housing. The part no from my EPC is AJ 88655 but there may be a supercession.

 

AJ88655 (e.g. https://www.britishparts.co.uk/jagua...perature-p3283) is what you are looking for

 

Thank you for that. But I highly doubt it’s the sensor. My car is still sluggish and it just seems like is pushing itself. When it’s over heating or not, it feels like the car is really just pushing itself past 2.5k rpms, specifically 3k rpms+. I don’t hear the supercharger whining at all either, it feels like the car is running like naturally aspirated. I’m guessing it has something to do with the Supercharger coolant pump. But then again no codes, and I just got it changed again at the beginning of this year... idk at this point

 

Agree it seems unlikely, but you asked for the part number and location. Having said that, a failed ECT is listed as a possible cause of overheating in the workshop manual so you never know.

There's a load of radiators in this thing, (I think 7), the SC and the engine have different rads, if the SC pump was dying I'd expect to see either the SC overheat message and the SC rad not feeling that hot. When its running it would be interesting to see if you can feel a big difference between the two rads.

Both the SC and the main water pump are belt driven so they will run no matter what, if the SC overheats the ECU shoves you in to restricted performance mode and limps you home, as you have experienced before.

It does feel like the thermostat isn't working correctly or there is something else restricting the flow around the coolant system. The manual says:To check the stat you can remove it and heat in water and check it opens at the correct temperature.

I recall from your other post that your radiator had failed, have you had the whole coolant system flushed out to make sure there aren't any bits stuck somewhere in the system? If there were some blockage somewhere that might explain why it only seems to get warm when the engine is revved, i.e. there is more pressure coming from the water pump forcing its way through. Also a failing water pump might give these symptoms (I'm assuming the belts and tensioners are all ok at this point so all the "accessories" are running fine).

 

Thank you for that info! I actually just replaced the whole thermostat assembly as well as the thermostat for the 3rd time this year about 2 weeks ago. It made no difference, it clicks on and off at the right temps. So I don’t think it’s that. I also just got the water pump replaced again for the 2nd time in a month, and once again it didn’t do anything.

I’m really thinking it has something to do with supercharger/supercharger cooling system since I don’t hear it whine anymore and the power after 3k rpms is really weak. But then again I just replaced the SC coolant pump at the beginning of this year, and plus there are no codes or anything. I honestly don’t know at this point what to do. 2 Jaguar dealers and a specialist can’t figure out what’s been causing this overheating and loss of power. Even now I’ve changed a ton of things and some even 2+ times to no luck

 

What do you mean - the thermostat clicks on and off at the right temps?

 

Meaning it clicks shut when the car is warming up and clicks to stay open when the car is at operating temp and/or overheating

 

Your 4.2L should have an AUX coolant pump in addition to the SC inter-cooler pump.
Do you know if it's working? Generally if it's not you will notice a lack of heat from your heater but maybe something to check?
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I don’t know if the actual pump is working or not, but when I changed the thermostat a few weeks ago, I did notice it wasn’t blowing hot air like it used to. It was blowing between hot and warm. But that’s just me and plus it was a little warmer outside so it could be just me.

I’m waiting for it to get a little more colder in the next week or two to test and see if it’s actually blowing hot or not