Hi Guys,
This is from Dubai, Can anyone advise regarding a engine cooling problem with a 2004 XKR, It seems that the engine goes into an overheat condition when stuck in a traffic jam or stuck at lights, after a long 1 hour drive at motorway speeds, with the AC running then coolant ( Green in colour ) is dumped through the overflow hose on the expansion tank.
To date I've had a bottom hose replaced and a new coolant pump replaced.
The repair shop has now advised me that the problem is with the engine cooling module and have advised a replacement at an eye watering cost.
My own observations are that only the RH fan is running when the engine is started and the engines reaches working temperature at idle, the RH fan can run at low speed and high speed, the LH fan does not appear to run at all although it is free to turn.
I've read that the fan's low speed is with the motors in series, and high speed is with the motors in parallel.
Looking at the electrical schematics it appears that there is a cooling fans fuse box shown on page 17 " Main Power Distribution " and a cooling fan module shown on Fig 04.2.
Can any one let me know if the fan motors are fused separately an if so where is the fuse box?
Is the cooling fan module incorporated in with the cooling fans?

Any advice would be appreciated

Any advice would be appreciated

 

has the thermostat been changed?

 

I dont know how much help this is, but I can tell you that without a dout on my 2004 XK8, when I start the car with a cold engine, both fans do not run, and when the A/C compressor kicks on both fans run at a slow speed, and once the engine is up to operating temperature, both fans will run at high speed at the same time, and then they cycle between high, low, and off, all with the A/C on. I know this because I was just watching my fans to see if a noise I am having is coming from a fan (it is not).

 

I live in a "Cooler" climate but:

The ONLY time that the Fans came on at High Speed was when the Thermostat had failed!

 

Both cooling fans are driven separately from the cooling module which has a single supply.
The LH fan wires are orange/yellow and orange/green.
I'd suggest checking the resistance of the fan motor disconnected from the module.
If that's OK then check voltage coming out of the module to the LH fan with the engine hot.
The fan control module is located on the twin fan and motor shroud.

 

The Engine Control Module (ECM) monitors inputs from the A/C 4-level Pressure Switch (A/CPS) and from the Engine Coolant Temperature (ECT) sensor and outside ambient air temperature to control operation of the two radiator fans. Output from the ECM signals the Cooling Fan Module (CFM) to operate the fans in OFF-SLOW-FAST mode. In the SLOW mode the fans are connected in series while in the FAST mode the fans are connected in parallel.

Since you describe one fan motor as not working at all, you may have a bad electrical connection or bad motor. Track down and fix that problem. If the suspect fan motor works when energized, and therefore not seized or defective, then one of the electrical connectors or a control component is faulty.

The ECM performs self-test routines and stores faults in the ECM as Diagnostic Trouble Codes (DTC). I have attached a procedure 412-04 AC Fault Code Extraction.pdf for checking the presence of A/C panel fault codes. I know it works for early XK8's but I do not know whether it works for your MY 2004. Give it a try.

Sometimes it is easier and cheaper to replace suspect parts than to shuttle the vehicle to-from the mechanic and pay hourly rates. This may be one of those occasions. Start with the cheapest parts first. Try the following:

1) The ECT is mounted on the thermostat housing. The removal and replacement is very easy to perform. See attached 303-14 ECT R&R.pdf (non-supercharged) for replacement if considered faulty. Price for ECT sensor should be under $20.

2) The A/CPS is screwed into the A/C refrigerant discharge pipe that runs along the bottom of the radiator. It provides a hard-wired signal to the ECM to switch the radiator fan speeds between OFF-LOW-HIGH within certain refrigerant pressure parameters. If it fails, the signal can be "stuck" in the wrong mode. The switch can be swapped quickly without loosing too much refrigerant. If you do lose too much refrigerant, then add back a can to the system. See attached 412-03 AC Pressure Switch R&R.pdf.

NOTE: My '97 XK8 cooling fans were on high speed at all times whenever the A/C was "on". And would cycle OFF-ON at inappropriate times such as when the engine was still cool. Replacing the A/CPS fixed my problem.
For model years 1997-2002 the part number is LJA7658AB and cost was $61.30 from Jagbits.com in Aug-2010, not terribly expensive compared to other electronic units on the car. You will have to look up the correct part # for your car.

3) The CFM is located on the fan side of the radiator. See attached 303-03 CFM R&R.pdf Replace the RFCM if suspect.

Good luck!

Bill Unger
1969 E-type, 1997 XK8, 2007 XKR

 

Bill,
Thanks for your detailed help.
The OP says the LH fan doesn't run at all so I think it has to be either the fan motor or the control module LH drive burnt out.
If the fan motor is OK, bearing in mind he's in Dubai where spares will be stupid prices, he may get away with a simple lash-up to run the fan independent of the control module.

 

I think he should throw loads of money at it then change the thermostat

 

+ 1 to the Thermostat votes for first item to check.

Reading through the threads, your fuse question doesn't appear to have been covered.

Engine Compartment Fuse Box - LH Side
Fuse No#12 : 30 amp - Cooling Fans series/parallel
Fuse No#14 : 30 amp - Cooling Fans parallel

Graham

 

Hi Guys,
Thanks for the information, I'll see if there is a voltage to the LH fan motor when the system is up to temperature at idle speed. The guys at the repair shop tested the thermostat in boiling water and said that it opened and closed OK. I'll report whatever conclusions I can arrive at.
Regards, Finetune45.

 

This is probably not the best thread for this question: "
I have spent many hours trying to find an answer to the question On a 1997 XK8, can I replace the air conditioner pressure switch without losing my freon charge?". Does anyone have the definitive answer?
Thanks in advance for any help! I think this is the most useful forum I have ever found!!!
Steve - "Harleyman" turned "Jagman"

 

The binary switch in most cars is hard-plumbed into the air con system, so you will need to discharge the gas before removing it. If you need to remove the switch officially the gas needs to be recovered as it's "illegal" to discharge it to atmosphere. However, if it was to escape slowly who would ever know ? If the gas pressure's are OK but your switch is showing otherwise, then you may need to change it.

 

As for the cooling fan fuse locations, some are mentioned above. The main fuse is an 80A strap-type fuse mounted to the inside of the left suspension tower under a plastic cover. It has battery power AT ALL TIMES! So be careful! Disconnect the supply wire at the left side engine fuse box if you need to. If you need the fuse part number, I can get it for you. Just bought one! Since your one fan runs, I suspect this fuse is just fine. Use a test lamp across it and check. You can't see the actual filament on this one. Have you tried removing the left fan connector plug, and simply jumping power and ground to the motor terminals to see if the fan even functions?

 

Steve, as I posted above:

2) The A/CPS is screwed into the A/C refrigerant discharge pipe that runs along the bottom of the radiator. It provides a hard-wired signal to the ECM to switch the radiator fan speeds between OFF-LOW-HIGH within certain refrigerant pressure parameters. If it fails, the signal can be "stuck" in the wrong mode. The switch can be swapped quickly without losing too much refrigerant. If you do lose too much refrigerant, then add back a can to the system. See attached 412-03 AC Pressure Switch R&R.pdf.

Have the new switch ready, wear gloves, work in a well ventilated area such as outdoors (maybe set up a fan), and keep your face away from the junction. You can change the switch very quickly without losing too much refrigerant.

 

I thought I would resurrect this thread since I am going through the same issue right now. I was in slow traffic on a hot day and I notice that the AC is going warm, then all of a sudden the temp gauge starts climbing and the red light comes on. I pull over and turn it off, looking in the owners manual for the fuse location. There is no fuse for the fans in the manual. After getting over being aggravated for about 10 minutes by this, I restart the car and the fans start and the temp immediately goes to normal! I suspect a failed fan module, so I go home, pull the fan unit and test everything. Motors have about .5 ohms each and the connectors are clean. I put it back together and let it idle with the AC on until hot. Everything is fine. I do notice that the left fan is larger and runs faster than the right one most of the time. My guess is that this is the primary fan. The smaller right one will go onto high speed rarely, but the left one cycles constantly between low and high. I wish I could figure out the failure mode but so far, it acts like it is functioning brilliantly! Irritating, I hate a potential disaster in the cooling system that I can't isolate.

 

I meant to mention a key item, when I pulled the fans, I took off the cover panel at the top of the radiator. When I looked in there, the front of the radiator was literally covered in debris! I took a hose and cleared it, but this reminded me of something a tech told me...he replaced a water pump in an 07 with 25,000 miles due to overheating. It didn't fix the problem. He then found the radiator completely plugged by debris! Its easy to pull this panel and look, a good idea.

 

I am not so sure it is a fan problem. I would say replace your thermostat, which may be intermittently sticking and a far more common problem.

 

This did occur to me, but the ac going warm at the start of the problem led me to believe the fans had stopped. When I pulled over. I shut it down so I didn't really know if the fans were running. I will change the thermostat since the car just turned 60K. This is always a good time to replace it.