Hi all,

I’m trying to help a friend solve an overheating issue on his car so trying to find out a bit more information. He believes the radiator fan isn’t kicking in which is then causing the car to overheat.

Does the fan have more than one speed?
Is the fan controlled from multiple control modules?

i know the fan kicks in when the ac is on but he says that he hasn’t heard the fan overrun when he turns the car off for a while. I’m wondering if it’s not kicking in when at temp. I seen the thermostat was 86 degrees c.

I checked the relay and fuse in the luggage compartment and both of those were ok. Think it was r7 I checked.

Any info on when you would expect it to kick in would would be great thanks.

Thanks in advance.

 

hi
what year and what engine is it, I assume its a S-type
cheers

 

+1 on providing vehicle information and background.

Has the thermostat been replaced, or other work performed that required draining and refilling the cooling system?

 

 

Be VERY careful as overheating = heads warped, all too often.

 

 

2003 S-Type R 4.2 litres supercharged.

Use OBD port to confirm temperature of coolant. Thermostat should open by 85 C. Fan running at high speed when ignition is in the off position is indicative of a sticking or stuck thermostat. Check all electrical connections and loom for any wiring issues.

Follow bleed procedures outlined in Workshop Manual to eliminate all potential air pockets.

 

+1 on that.

Be aware the dashboard temperature gauge is deliberately misleading, as detailed at the following link, so don't rely on it. Read the coolant temp with a scanner to be sure. This is from the XK forum, but the general principle is the same on the S-Type:

https://www.jaguarforums.com/forum/x...e-gauge-62813/

Also, you mentioned the thermostat was recently replaced. Was this an attempt to cure the overheat issue, or was it changed for some other reason?

If convinced the present thermostat is good because it is new, excuse me while I quietly chuckle. Here's my tale of woe with new parts bad from stock on my '02 V6. I had a combination of a bad thermostat AND an inaccurate temperature sensor, followed by bad replacements:

https://www.jaguarforums.com/forum/s...rature-186873/

The early V6 models use a different style temperature sensor than your car, so not all particulars will apply, but the thread still shows what can happen.

Also, some more details of the symptoms will help. When exactly does the overheating occur? Freeway speeds? Low speed around town? Is steam venting from the cap, or is it just the dash gauge climbing? Have you used an infrared thermometer to confirm an actual overheat? Or could it be just an indication problem? As previously mentioned, be very careful of actually overheating the engine, but you should be able to get some quick temperature readings at the thermostat and radiator inlet.

 

On the 4.0, there is an auxiliary heater pump. Went through the same, replaced thermostat, replaced water pump (prior), but still overheating until I discovered the auxiliary pump. No issues since replaced.

 

 

The fans should certainly be on with a/c and on high if the car is overheating (such as, believed to be by the PCM as it monitors the ECT).

Don't rely on the dash gauge! By the time it says the car is overheating it can mean terminal engine damage! The STR cannot cope with actual overheating so monitor via OBD to see the ECT value. You can also use ETM (Engineering Test Mode) - search to read how.

As well as the water pump there is an aux coolant pump and an IC pump. Details via Search or download the free workshop manual from here / go to JagRepair.com - Jaguar Repair Information Resource

Also has info on fans & the module that drives them etc.

 

From my limited experience, if the overheat occurs at higher speeds, the fan is not the problem. I've had the fan completely fail on my '02 V6 and on an Audi A4. In both cases, as long as I kept above approximately 35 MPH, the coolant temperature was okay. Ram airflow through the radiator was sufficient without the fan. Below that speed, the temperature would quickly rise as airflow dropped off. The symptoms you've described seem to be the opposite, so it's probably safe to say the fan is operating properly.

Have you confirmed the actual temperature yet, using an infrared thermometer? From what I've heard so far, you still don't know if you have an actual overheat or an indication problem. Just trying to save you some grief...