Only a few days into my 98 xk8.

Temps here in NY about 90 degrees with high humidity.

Tonight, i was sitting in a parking lot with the car running for about 15 minutes. A/C was on.
At one point, I hear a loud "roar" from the engine, and then the battery gauge dropped slightly to 12V.
Battery is 6 months old.

My truck never shows any voltage fluctuations, but was wondering if this is normal?

 

My guess would be that the fans switched from low speed, 6 V in series, to high speed, 12 V in parallel, operation. Do you have any of the 'RealGauge' products installed, or know if they were installed prior to your ownership? The factory gauges do not read back realtime data, you may have noticed that your coolant gauge goes to center and stays there. This creates a huge problem if you get into an overheat situation, as you will get very little warning that the car is overheating from the factory gauges, until it is almost too late. If you are interested in upgrading your factory gauges to display the actual temperature and oil pressure; search for 'RealGauge' on this site. A forum member manufactures and sells minimally invasive installation upgrade kits, that enable your factory gauges to display realtime data.

 

The car is stock.
when I did open the car door to exit, I felt a tremendous amount of heat hit me i the face from under the driver's side door.
Not been too familiar with the car, I attributed to the duel exhaust possibly running under the driver's side .
The engine does "feel" hotter than any other vehicle I've driven.

When I shut car in garage, fans stay on a couple minutes, then all seems ok
Water temp gauge warms gradually to center and stays there.

 

Check the STICKY links at the top of the post page, first 5-7 posts, there you can download an owners manual, if you did not receive one with your car, I did not, and other model year specific information about your vehicle. There are also tonnes of other links for DIY maintenance, instructions, etc.

From what I have read on the site, the fans are not supposed to run after the vehicle shuts down, and could be an indication that you need to have your fluids flushed, make sure the radiator is not plugged with dirt in the coils, etc., however, these cars do run hot by design, just ensure it is not running too hot. All the correct fluids are listed in the manual, and make sure you know what coolant was in there first i.e. do not mix green coolant ethylene glycol based, with OAT, or Organic Acid Technology coolants which are orange as they will gel.

 

The car came with the dealer service records.
Car had a multipoint service at 45,770 and passed all inspections including cooling system check
Current mileage sits at 46,200

Service records also show that water pump, thermostat, hoses, (inlet and outlet were changed) at 31K.

I would guess that coolant is 15K and dealer installed when the work was done.

 

That is the fans running at high speed. My 2003 does the same thing after hard driving, and I have variable speed fans in mine, but that blast of heat from the door area is the heat being pushed from the engine bay, and in my case the Supercharger as well. However, they have never run after the car has been completely shut down; although at times I thought they should be running after the car was off due to the temperature outside, not to mention my driving habits. So I shut off the car, turned the key back to position II, but did not re-start the car, and the fans began to ramp up to full speed, lingered on high speed for a moment, and then tapered back off to barely running in less than 1.5 minutes.

 

The fans are set to run after shutoff until a certain lower temp is reached OR run for five minutes if it still hasn't cooled down enough.

Mine does that sometimes in the Texas heat and coming home from rush hour traffic.

BTW, RealGauge is a great product but does not install to the amp meter.

 

Two completely different replies to this:

NO!


YES


You are wise to be concerned and asking questions about cooling (or lack of it) on the XK8. As has been stated, the standard Temperature Gauge is useless and doesn't move from the centre position until the vehicle is seriously overheating.

The cooling system is 'low volume / high flow rate' and very efficient when properly maintained. However, there are many plastic components and rubber hoses which deteriorate over time. Failure of any of them with rapid coolant loss can very quickly do serious damage to the V8.

From the information you've given, your vehicle does appear to have been well maintained and the cooling system sounds to be operating normally.

Graham

 

If the stock gauges do not indicate "real time" data, what do they provide? How often is the data updated?

 

Little more than a warm, fuzzy feeling that all is OK...

Seriously, what GGG said, although the voltmeter is a little better.

M

 

It's best to think of them as needle-driven idiot lights. They only respond when there is a problem.

Luckily, the gas gauge works as expected.

 

An observation from today....

NYC today temps were high 90's very humid.
I took my 12 year old for a ride and she insisted on having the top down (oh the things we do for our kids ) No A/C of course.
Rode around for about 2 hours.
Got home and put car in garage. Shut car off.... NO FANS!
....Hour later, went to get lunch. Roof up, A/C on Ride no more than 10 minutes in total.
Came back home, garage.. and fan was on for exactly 1 minute after shut down.

Cooling fans are somehow directly related to A/C use.