Man, I just can't win with this thing. I just drove the Jag only for the 3rd time since I replaced the bad coils and 2 months without being able to use it.
So I take a trip to the bank and no problem. On the way back I start hearing a sound like an air raid siren starting up. Its a steady rpm noise and not tied to engine rpm. I get home and leave it idling and the noise seems to be coming from one of the 2 radiator fans but I can't be sure which one. So I shut it off and the fans spin for a short time after the engine stops and the noise is present until the fans stop. I try turning them by hand and examine them for obvious damage. They spin fine and no obvious drag or play. So I start the car again and this time no fan noise! I take it for a short drive and come back and no noise. So now I have a fan crapping out and if I keep driving it will likely fail catastrophically in the middle of nowhere. If I can figure out which one is doing it I will replace it proactively. Though I guess if one dies it likely won't overheat very quickly as its cooler out now. Not really a super bad repair but this damn car is being brutal with just one thing after another. It couldn't even go 40 miles before the next thing broke.


Dave

 

Look at post#2 by Don B. If the XJ8 fan works on the XJ6, it might work on the XK8 also.

https://www.jaguarforums.com/forum/x...ldable-151566/

 

Also looks like you can replace just the motor if the blades are still in good shape. Looks like just 2 nuts and a connector to get the whole tray out that has the fans on it. Hopefully its that easy. First I have to figure out which one is doing it.


Dave

 

Dave,

Here's an idea that may help. Check out JagWrangler's installation instructions for the RealGuage. Go to the part about using the potentiometer to calibrate the display - you can easily connect a variable potentiometer to the temp sensor's connector on the engine. Turn the pot until its resistance value makes the engine/computer think the temp is over 200 degrees or something which will activate the fans [ignition on engine off].

Once you figure how to turn them on like this, you can disconnect one fan and listen to the other to ID the bad fan.

 

It stopped making the noise so I have to wait until it does it again. Also I think the fans are wired in series and no easy way to get to the individual fan wiring with them mounted. I made a stethoscope out of fuel line and a funnel to find the coil arcing sound and I will try that next to find the offending fan when it does it again. I didn't have it handy when it did it.



Dave

 

I'm beginning to think that something like a leaf or a piece of plastic got stuck in the fan and then fell out when the fans stopped. I just drove it for about an hour around town and no unusual noises from the fans this time. Either that or one of the fan motors has self healing bearings


Dave

 

Even hypochondriacs can get sick, Dave. It's going to take a while, but eventually your car should calm down and stop seeking attention.

 

Ok turns out one of the fans only makes noise when the fans switch to high speed which isn't often. Still can't tell which one is making the noise as it seems like its coming from both. I will probably have to remove the fan tray and power them up off the car with 12v to see which one is the culprit.


Dave

 

What I have discovered - The fans are only loud when on high speed. Both fans seem to be making about the same amount of noise. They both turn easily by hand and the blades seem perfectly intact. No obvious play. Some attempt was even made to balance them as they have metal clips on one blade on each.
I am beginning to think the sound is "normal" and for some reason I just never noticed it before. Its loud enough you can most definitely hear them sitting at a stop light or driving slowly.
My question: How loud should these be when on high speed? It takes a fair bit of driving even on a warm day before they switch to high. They still shut off about 15 seconds after turning the engine off whether they are on high or low speed.
So should the sound of these be pretty noticeable on high? Or are both fans noisy?
And yes I am very paranoid about every sound this car makes after all the problems I've had.


Dave

 

Your fans are run in Series (Low Speed- 6v on both) or Parallel (High Speed - 12v on both).

In Low Speed they are quiet. In High Speed they are VERY LOUD. 4 times the power during High Speed.

In moderate climates High Speed is seldom required.

The only time my fans came on at High Speed was when the Thermostat had Failed. This was also the only time that they ran for a while after Engine Off.

 

Yes I know that they switch to parallel when on high and thats how they change the speed. They only seem to switch to high after lots of slow speed in traffic driving. I've not lost any coolant or gotten any overheat indications. I've found other threads that state that the '97's for some reason always keep the fans running for about 15 seconds after shutoff regardless of engine temp. Its done this ever since I've owned the car. But I have never noticed the sound of them in high speed until after the recent problem with the bad coils.

I've tried to check the actual coolant temp using Torque Pro but 3 different code readers come up with "No Data" for the temp. I've seen others have this same problem using Torque here and don't know if there is a fix for that.
If the thermostat is bad it must be working enough to keep it from obviously overheating but high enough to trip the temp sensor to switch the fans to high. So its possible that I never noticed the high speed noise before because the thermostat only recently failed, if that is indeed the problem.

So I am going to replace the T-stat as I don't know how long its been in there and will replace the plastic parts with the updated metal stuff and see if that changes anything.


Dave

 

My fans run for about 15 sec. after shutdown if the engine is up to temp., but they have never run at high speed.

The 97 ECU does not communicate well, so you may have trouble getting temp. readings, but my Ultragauge does read the temp.

Last spring I found the engine would heat up to 205 quickly and even higher in traffic, so I replaced the thermostat that came with the Welsh Ent. housing with a Gates 33948 and it runs at 191-195 now, but takes a long time to get there on a cool day. I'll switch to the other one soon and see if that's a better choice for the winter.

The Welsh unit ran at a lower temp. for a couple of years then started running hotter. They appear to be opening the same in a hot water test. Considering the low cost, it's certainly worthwhile replacing yours.

 

Yes mine still has the black housing with a metal color bleed cap so it may still have the original t-stat in it.
Its funny that the fan problem started along with the bad coils. It may be the T-stat failed first and the extra head helped the coils fail.
The coolant is an odd color also like someone mixed green and yellow so that will get flushed and replaced also. No telling how long its been in there either.
Just ordered all the parts needed (hopefully) including a new bypass hose.


Dave

 

A little late to this party as it sounds like you have a plan, but thought I would add some more data.

My '01 can reach 215F in the summer with traffic. If switched off hot, in a hot area like the garage, the fans will run on high past the 15 seconds noted above. The manual says they are programmed to run until the engine temp drops or 5 minutes have elapsed, whichever comes first.

New thermostat certainly won't hurt and if you are flushing anyway, will be a simple fix.

 

Hopefully it will just be the t-stat, Or maybe gelled yellow coolant, or both...

No signs of it gelling in what you can see passing through the reservoir though.

Dave

 

I have noticed on occasion at Idle while I open my garage the secondary fan or the fans hi speed kicks in and it does sound like a jet taking off.
I recently found my upper radiator hose collapsed, even though it looked fine. Once replaced, the engine temperature stabilized.
I have a Scan Gauge very simply plugged into the OBD connector. I can watch the engine temperature change a degree at a time. I highly recommend it for a low level tech install. Rich

 

I've tried 3 different code readers and they all show "No Data" for the temp. It seems to be an issue with the ECU on the '97's. My upper radiator hose used to collapse occasionally and for me replacing the radiator cap fixed that as I have never caught it happening again. I think it just has an original or very old t-stat and its failed to where it letting the engine run above 200 but not hot enough to actually to put it into overheating. The coolant level is staying constant also, in fact I've never once had to top it off in the year and a half I've owned it. The coolant looks suspicious also like its several types mixed together so Its getting flushed and replaced also.

Dave

 

The Ultragauge works on the 97, and it's not expensive.

UltraGauge OBDII Scan tool & Information Center

 

I also ordered radiator hoses and a new water pump as this is a good time to replace all that while the fluid is drained. Then I'll know most of the cooling system stuff is new. Everything is supposed to be here by Monday and the T-stat already arrived.


Dave

 

This can finally get marked solved.

I just replaced the water pump, radiator hoses, bypass hose, T-Stat and housing, ECU temp sensor and coolant. And so far no more hyper-speed fans. The water pump, hoses and t-stat were likely original. The orange coolant likely was also and appeared to have been topped off with multiple other types as it was no longer exactly orange. A thorough flushing didn't turn up any gelling.
I drove it long enough for it to fail and then some but no hyper fans and after shutting it off the fans ran at slow speed for about 15 seconds just like it used to. So hopefully it fixed!



Dave