Hello Everyone, So thankful for this Forum. I have a 98 XK8 with 100k miles. has been running great, but recently started overheating.
I've changed out the housing, the thermostat, the water pump, Still overheats. It overheats in an unusual way, It will drive for about 30 minutes
just fine, Then the gauge starts to creep up. You can turn the ac off and manage it, But still it will fluctuate, eventually going over 3/4's, letting the
engine slow down and idle and the temp will go back to normal. I've added a little coolant a few times, will the air work out naturally?
I do have fan concerns, though when I'm stopped they seem to be working fine, Both will run in both stages,
I notice that the Ac cuts off when its overheating too.
Please help, Brian In North Carolina

 

Brian,

Wondering what if a defective temp sensor exaggerates the temp reading. Open question to others: how does one test the sensor for accuracy?


I was hoping you had the original pump, sounds like you replaced it so the defective pump is eliminated. Darn, would have been an easy fix.

FWIW the car is working as designed when it gets an overheating temp reading ac is shut off.

if sensor is accurate we have to figure out why the fans and radiator can't cool the coolant.

John

 

Welcome to the forum Brian,

You can NOT rely on the temperature gauge. It is designed to barely move before the engine is already seriously overheating. An app like TorquePro will allow you to monitor actual temperature or the excellent Realguage (XK8 / XKR / XJ RealGauge - TheJagWrangler) by member WhiteXKR will make the gauge itself accurate.

As you have replaced all the usual suspects, the sender (as Johnken suggests in post #2) could be defective. Also, a faulty thermostat is not unknown.

When you get a minute, please follow this link New Member Area - Intro a MUST - Jaguar Forums - Jaguar Enthusiasts Forum to the New Member Area - Intro a MUST forum and post some information about yourself and your vehicle for all members to see. In return you'll get a proper welcome and some useful advice about posting to the forum.

Graham

 

Try another thermostat. I have found a large variation in fully open flow.

 

Folks have reported it is possible to put in the thermostat the wrong way and it causes overheating. Double check that to be sure. Something about the jiggle pin up or down, I am not sure.

Also, what coolant did you use to refill? Coolant types cannot be mixed and can result in gelling.

Do your fans come on when the A/C is on?

Does it overheat in traffic or at high speed?

 

Thanks guys, Can someone tell me where the temp sensor is? I'll change it.
And whats the best way to read the accurate temp info.
I like the idea of the actual gauges working properly.
my 98 xk8 is the non navigation model with 3 clusters mid dash.
How involved is that kit?
I have installed 2 thermostats with the jiggle up.
It overheats in traffic or at high speeds. Thanks!

 

The sensor is in the water outlet pipe that is just below the thermostat. Being plastic, it is also subject to failure with age and hoses have blown off due to erosion of the lip, so replace. The new one will have a temp. sensor included.

The kit from Steve is easy to install for the owner with average mechanical skill. I went for the full kit including oil gauge on my 97.

 

Thanks, I will get or order a new sensor. My OBD connector is not connecting to the vehicle.
Does is have a corresponding fuse? Any idea why this is happening? Thanks.

 

Would you please tell us more about the bad OBDII connection. Is it that she won't activate Once plugged in? On my 1998 it often takes multiple attempts to set up the link between car and OBDII.

go to the jagwranglers website. Look at his excellent instructions for calibrating his realguage. Shows how a potentiometer can be used to test fan turn on [potentiometer is a variable resistor, higher ohms tells car temp is higher. IOW your car reads temp by monitoring the resistance of the sensor.]

his instructions show exact location of sensor, though RJs description is perfect.

 

There is a dedicated fuse for the diagnostics connector. If you have the option, make sure your OBD tool uses the old serial ISO-9141 protocol. The car features CAN and SCP, but OBD is not available over these protocols.

 

 

I just went through the process of getting my '97 temperatures back to normal. Same procedures should apply to a '98. (Don't know about an old school temperature gauge, but manual gauge or OBD, you will want to track your actual temps reliably because the dash gauge typically doesn't move past half, until it's too late.)

1) Thermostat can go in both ways...the wrong and the right way.. The repair manual has detailed drawings, which are really confusing. The big spring goes in on the engine side and the side with the pins goes toward the radiator (I think !).
2) There is another way you can mess up your thermostat installation. (I did !) The rubber gasket goes around the edge of the thermostat but can be placed in the t-stat receptacle before installing the t-stat. Some of the drawings seem to show it this way. Don't do this. After having problems with my temps, I placed the gasket over the ridge of the t-stat, then put the whole thing in place. This worked. It seems obvious now, but the proper way to do it is not clear in the drawings.
3) The catch tanks between '97 and '98 are not the same, but can be interchanged and sometimes are. The later tanks have only one open outlet, but the routing is different. See TSB 303-15.
4) The temperature sensor is only about three bucks, so it can't hurt to replace.
5) Your radiator may be clogged. It's messy to flush, but not that hard to do. If the simple fixes don't work, flush the radiator. Might not be a bad idea in an old car at any rate.

In my case, I had installed the t-stat incorrectly and had a radiator that was obstructed, but still usable with a flush. Your experience may vary.

 

Agree with RJ to replace the crossover pipe complete. It is around 3x the cost of the sensor alone, but this plastic item will fail sooner or later.



Part # AJ85885 complete with the gaskets.

 

Thanks for the replies. I have replaced the plastic crossover pipe, And i remember the temp sensor coming with it.
Still trying to read accurate temp, My obd lights us my device, So i Know its got power to some degree, But it wont connect....
No one has replied about a place to screw in an old school manual type, or they even have digital nice ones on ebay,
To me, that would be the safest way top know.....
I'm thinking it could be a clogged radiator......?
How Could I confirm this? If its any indication..... The water pump I changed was in like new condition.....
Would a radiator be stopped up and the water pump look that good?
Thanks for the help, please keep it coming.
I have a great picture of this car and the hot chick that drives it...over in the show off your xk8 post.
Help me be a hero! lol Brian

 

Re: Clogged radiator.
When I first opened the drain "button" at the bottom right of the radiator, the water flowed rather sporadically.
After I flushed it, the water flows smoothly.

 

ok, So I pulled both of the lines off of the radiator, I blew with my mouth through the top pipe, I was easily able to blow all of the water out of the radiator....
Sure doesn't sound like a stopped up radiator.
I checked the ohms on the existing temp sensor compared to the new one, They were the same,
So I don't think the temp sensor is the culprit.
Brian

 

 

Brian, do the read the same in boiling water?