Hello Jag guys,

Ny 1999 XJR with 143K miles recently starting having an overheating issue. I have searched this forum but have not found anything definitive, so I am asking for help!

My XJR has been running well for years, but recently I got an engine failsafe mode warning, and then within a couple miles overheated.

I found a bad hose (that connects the coolant fill tank with the front collant manifold near the thermostat) that I replaced. I also pulled the thermostat based on what I read on this forum and determined it to be faulty as well (it only partially opened at 10 degrees over 183). I replaced it with a new thermostat (though I replaced that one only a couple years before when I installed the metal housing). I DID NOT test the new thermostat.

So everything seemed to be fine, but I took it out last night and it happened all over again. Failsafe mode, engine suddenly raced to overheating. It was near my destination so I continued the one mile to my friends house without problems. The vehicle never boiled over, there was no obvious sighs of overheating and the FAN was not on (this thought just occurred to me). After the dinner I drove it home without issue, though it was cooler and I drove conservatively. The temp did not budge from its normal spot.

I took it out this afternoon and the air conditioning, which has always blown very cold is now lukewarm. I drove it for a couple miles and everything was fine. I got on the accelerator and saw the temp needle jump to 3/4. I back off, and it came right back down and stayed down till I got home driving normally. I pulled into the garage and pushed the RPM up to 2500 and held it and the temp needle jumped to full HOT with red idiot light on, and STILL no fan. Yet when I turn it off, it doesn't boil over or seem hot.

The vehicle threw no codes except P1111, a supposed non-issue. Still, it was reading P1000 before, so if no codes, why change to P1111? I have researched this but still not clear why that happens.

I read these gauges are basically worthless, but it did boil over once with the broken hose.

My main fear is this is the early stages of a failing head gasket. But I have never had one go bad and then get good again, even for a short while. I do see some very fine bubbles in the coolant fill tank, but I just changed the thermostat and refilled it without any "burping" I have been reading about here.

Here is what I am thinking...

1. I have a bad gauge or sensor
2. I put in a bad thermostat. Got it from Autozone, should I get a Jag unit from the dealer?
3. Check the fan to see if it is malfunctioning. Any posts on the procedure?
4. ????

Any advice would be deeply appreciated, I am at my wits end on this one.

Thanks!
Michael Rogers

 

Well, I have read a lot on the issue myself in the last week.
I should first of all not ride the car any more, and be careful with further overheating during testing.

The fact it does not over boil means in my opinion that your thermostat works, allowing for a much larger cooling circuit.

I should start with investigating the fan operation first, they should definitely come on (which I can confirm from recent experience).
I read about chaffed wires but I guess there could be several reasons.

An other advise it to buy a Bluetooth connector, they only cost a couple of dollars nowadays, and it allows you to run Torque on your smartphone by yourself.
Torque (free for the basic version) will give you, among a wealth of info, a digital readout of your temperature.
It will also allow you to read ur fault codes.

Finally, P1111 is related to your emission readiness, and will change from P1000 to P1111 after all check procedures on the emissions are successfully passed (after some different kind of driving for each).
I am not 100% sure, but I don't think P1111 will change back, other then after a hard reset.

 

You are correct in directing me to the fan. The fan fuse was blown, and a new one brought the fans back to life... briefly. I am now deciding if the fan relay can draw excess current to blow the fuse, or the motors must be at fault.

Now that I understand the fan problem as the root cause of my recent series of unfortunate Jag-related mishaps (including a tow), it all makes sense. The first time this happened I saw the engine failsafe mode warning, and it overheated about three to four miles down the road. The failsafe message was because the fans would not turn on (open). When it overheated on that occasion, it broke the hose between the head unit and the cooling manifold up front. But the likely root cause of the fans was the thermostat that would barely open at 195 degrees, causing the fans to run excessively. New thermostat, new hose, properly burped system, AC runs cold again, heater hot, and now on to an electrical problem.

So, anyone know it the relay can cause fuse failure? I am guessing so...

Thanks!

I also just discovered the obd bluetooth devices and will receive one in the morning.

 

P1000 is what you get after clearing codes (which also clears OBD monitors) or battery off. P1111 is what you should have when all the OBD monitors are happy. It then stays as P1111 (unless OBD clear / battery off). Both are status values that do not turn on the MIL.

So, that's all OK.

Except... why did you have P1000?

If you have no other codes or pending codes you probably have OK sensors.

It's worth checking the fan, yes. (With care.) Fuse(s), etc.

 

I jumped the blown fuse and only the passenger side fan came on. Went to check the schematic on the sticky notes but the link to the electrical diagram appears to be broken.

Since the schematic is unavailable I am not sure if the failure could still be in the relay (if it switches them separately).

Can anyone confirm that both fans should come on together? It looks like the driver side fan is drawing too much current and should be replaced...

Thanks!

 

Try switching the relay with one of the others same color.

 

Elec guide probably on JagRepair.com - Jaguar Repair Information Resource

 

I am pretty sure the fans come on in sequence, first one, then the other together with the first one.
I read about the wires chaffed by the serpentine belt if they are not routed correctly, perhaps you got a short on one of them?

 

The fans do come on separately. The passenger side is the main fan, the driver side kicks in with the air conditioning.

The main fan was drawing too much current. Ordered used fan motor and relay (it was inexpensive) and soon the cat will be back on the road! Thanks for all the replies!

Checked the wiring, it all looks good.

Main take home, if the motor goes into failsafe mode, it could be the fan is not working...

Michael Rogers
1999 XJR
Always garaged, and looks fantastic in its original gold!

 

I always find a way to make a simple job difficult! Fixing my overheating problem has turned up another issue that has been there for some time...

My new used fan assembly came in, and when installed I noted it was pressed up against the crankshaft pully (bottom fan, driver side). I checked the mounting of the fans and all seems correct.

I then reexamined the old unit that came out and sure enough, the bottom motor housing has a massive groove cut into it by the crank pulley! Apparently there is simply no way to get this right with the vehicle as is.

My next step is to remove the radiator to see if it may be mis-installed, pushing the rest of the assembly back into the crank.

Has anyone else experienced this problem on the XJ or XJR? What is the cause and fix? I am a bit discouraged at the moment, so will give the Jag a couple days sitting while I adjust to the new reality, and wait to see if any of you guys can direct me.

Thanks for the help!

Mike
1999 XKR
143K miles

 

I have no experience with SC units, but, something is wrong that causes the crank pulley to run against the fan housing. Maybe bad motor mounts or loose pulley?

With the hood up and engine running, does the engine rock forward when braking (go slow, try it in your driveway with somebody walking alongside the car).

 

I was checking all my hoses after a test ride (new thermostat tower, etc).

I have about 6 inch of space between the front of the crank shaft pulley, and the fan housing, really a lot.

As I presume there is no difference here between the SC and the N/A in this aspect, there must be something wrong on your side.

Just to let you know.

 

Eric, there is a difference as the SC pulley has to accommodate the SC drive belt.

 

Off course, how did I not think about that ... too early a flight this morning I guess

 

Here is a pic of the current situation with the crank pulley sitting up against the fan motor. I also uploaded a pic of the old fan, which shows it was being ground for a while.

I do have one wheel jacked up to get better access, and I am going to drop it to see if it makes a difference.

The other idea is to put spacers on the fan bolts to push them forward 1/4" or so. That would give me more clearance, though bring the fan closer to the radiator. I think there is room.

Thanks RJ237 for clarifying the spacing issue. I was scratching my head on where that 5 inches went...

Thanks for all your help.

Mike

 

Let me repeat #11: you have something loose. You don't need spacers, you need to tighten down the fan, or the hub, or the water pump, or the engine.

 

Thanks, Jim. The fan was tight, but the other items will be checked.

In the category of when it rains it pours, trying to jack the fan assembly around with a screwdriver to give it a bit more space did not work out well for me. The screwdriver slipped and I now have a new hole in the bottom of my radiator. So, the radiator is coming out now too.

I am so glad the Jag is a third car and I can take my time figuring this out and making it right.

If anyone with an 308 XJR could take a look and tell me how much clearance i SHOULD have, it would be much appreciated.

Thanks,
Mike

 

Mystery solved. Removing the radiator revealed that it was not in the correct position.

The radiator does not appear to be bolted in directly, but held in place by a hard rubber shield at the top. The bottom of the radiator sits in two curved sections that hold it in place along with the top piece.

My radiator somehow came out of the bottom mounts/holders though the top piece was still in place. Now that the radiator is in the proper mounting position, I have over an inch clearance (and a much easier time getting the fan assembly in and out).

I have no idea when that occurred, but by the look of the motor housing, it was some time back. The radiator has never been out to my knowledge. Should have recognized this earlier and saved myself a lot of heartburn, but at least the end of the road is in sight. Now to get that radiator out and repaired.

Going to sticky notes to look for a procedure...

This community is a tremendous resource and service to Jag owners. Thanks to the people who maintain this place and those who frequent it too!

 

To ALMOST tidy up this thread...

Got my radiator repaired and installed it properly and the spacing issue is resolved and the Jag is up and running cool. However, I am not done with it yet...

On the fairly lengthy test drive, the Engine Failsafe Mode came on again. No performance issues and the fans are working. However, they do not seem to turn as fast as the unit it replaces. I pulled codes from the OBD but got P1000.

I have a suspicion this has to do with the new fans. The coolant filling procedure calls for the vehicle to be held at 1500-2000 rpm till the fans come on. These come on immediately, and they do not seem to run as fast as the original.

Another oddity, when I first pulled it out it gave me traction control and antilock brake warning lights, which went away and have not returned.

+++

I have done another test drive and no failsafe mode, despite running it at high revs at low speed, and getting the coolant temp up to 212. The fan speed never kicked up, but it did not overheat. When I shifted pack into Drive for normal operation the temp dropped to 200 and stayed there, and it is fairly hot here in the 90s.

SO... is there any way to determine what causes Engine Failsafe Mode if no OBD codes are generated? I am off to do more searching about how these fans operate, but any guidance is welcome.

Thanks

 

The battery may have been a little low, so charge it and drive some more. The fans do not run at high speed until you get to a temp of 215 or so.

P1000 means the ECU has not completed emission checks, at which time it will be P1111.