Recently bought a XK8! Awesome looking car, very nice condition! Its got just a bit over 130K miles
Always getting (Restricted Performance message, and (Coolant LOW message) It's full on coolant.
The seller informed me it does overheat at times, so I replaced the Thermostat and also the thermostat housing to metal (brand new) But still continues to overheat just after 10-15 minutes of driving and idle.. I do know it's not a head gasket issue, there's nothing in the oil, I've checked for some air leaks, coolant leaks, nothing.. I do believe the Water pump was replaced but I can't be 100% sure... Also I replaced the MAF sensor and it jerks each time i acclerate 50% on the gas, can I get some insight to what these problems might be?

 

Welcome to the forum JaguarXK8Vegas,

The Coolant Sensor fitted in the bottom of the Expansion Tank is a known fault triggering the LOW message even when the tank is up to level. As for the overheating, you've replaced the first suspect of thermostat, water pump has to be next to check.

To troubleshoot the poor running, have the codes read and post any stored or pending back here.

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

 

My XK8 has a tendency to run warm on hot Northeast Summer days, however the cooling fans usually take care of the temp at idle. I'm sure you've checked that both cooing fans are working. I do agree with GGG, water pump ( which is not hard to replace) could be a problem. Plastic impellers have a tendency to disintegrate. If so, could get caught in system somewhere. I would think Jag has the low coolant light hooked to the computer. Restricted performance light will do just that regardless if its a false reading or not. Good luck Rich

 

I also agree on looking into the water pump next. Simply put in the laws of physics, it most likely is overheating due to 1) no coolant (ruled out) or 2) no coolant movement.

 

I'll be checking into it today, thank you for the reply!
And yes I am brand new on the forum!

 

Maybe it's not overheating and GGG is right -it's the coolant level sensor. With an inexpensive ELM327 scanner and the Torque app you could read actual temperatures and see if you are really overheating. Above 200 deg F can be pretty normal, and reported numbers above 210 deg are not unusual for when sitting in traffic on a hot day.

 

I read the JaguarXK8Vegas's post as a being genuine overheat situation; pbuck has read it as a being a low coolant and possibly temp gauge reading situation. Re-reading the OP, I'm now wondering which of these it is?

The low coolant warning sensor serves no other function than to trigger the warning - it's not part of the engine management sensor group linked to the ECM. The temperature gauge is useless and the only way to get a true reading is with a scantool or RealGauge.

The Restricted Performance is likely to have set error codes so it would be a good plan to have the codes read to see what is stored or pending.

Graham

 

Two things:
1) Make sure your engine temperature sensor is plugged in snugly. If it works loose or pops off, and they do, it will throw the restricted performance and cause the stumbling. It's located next to the thermostat tower and goes into the cross over pipe.

2) Restricted performance will cause the engine to not let you accelerate above 3,000 rpm (your 50%). Try it, go for a drive and watch the rpm level where it stumbles. Keep in mind that the engine is just doing what it's supposed to do by keeping you under 3000. Also, you can indeed drive your car at normal freeway speeds, which is around 1900 to 2200 rpm. You just have to pretend you're not driving a Jaguar, a.k.a like a good boy driving a minivan.

Driving it will not cause any damage providing it's not truly over heating.

Make sure your temp sensor is snug...I bet that's the issue.

 

There was an issue with the water pumps on the early 4.0s, and they are not that difficult to replace. Another possibility is a clogged radiator. Good thing you got the aluminum thermo housing. Don't burn that thing up.

 

Hello, so here's an update to my previous overheating issues that keep happening!

Ive replaced the thermostat, and housing to metal. And I've replaced the water pump. It still gets hot.. very.

And I've noticed the Fans are correctly working.
i'm out of ideas..

 

What happens when you put the heater on? Any heat? Does it allow the car to coll off some?

Have you checked the radiator hoses? Is there a marked difference in temperature between the hot side (passenger) and the cool side (driver)?

Has there been a refill/change/top off of coolant? Mixing incompatible types makes the mix turn into a gel and clogs everything.

You definitely need data. Get a cheap ELM327 off of eBay and a mobile device app to get a read of the coolant temp, as per the sensor.

Best of luck, keep us posted.

 

I have had issues if I do not fully burp the cooling system after changing water pump etc. That would be the only thing left I think to look at, barring a clogged area of the system.

Also, use a code reader to get the actual temp while warming up- this allows you to see in real time how and when it is getting too hot. I have found if it hits 210 something is up, but if it doesn't go over 208 all good. I think the fans should go on at around 203 or 204.

 

You've yet to tell us how you know it's actually overheating vs. an indication issue.

 

You need to have the OBDII codes read then past the codes. You need to know what is causing the restricted performance. Also you need to know what your temperature really is when the car is running so your best bet is to get a code reader like Torque for your smart phone and a Bluetooth device to read the codes.

Do you know if your fans are running? If not sure start the car and turn on the a/c and both fans should come on. If the car is overheating the fans will go from low speed to high speed when they detect a high temperature. However, that is if the module for the fans is working and it has power. Torque can monitor the temperature so you know what is going on.

 

Didn't all the early XK V8 4.0L's have an auxillary coolant pump as well?
Like the S Type 4.0L?
Does it also have the interior dual climate control?

With the dash temp gauge approaching half way, does hot air get into the cabin?
If yes, can you turn it down so you get cold air without having the A/C on?
Or does it stay hot all the time?

 

Yes all xk8/r have an auxiliary pump for heat in the cabin and runs all the time. However, the xk8/r does not have a DCCV. At any time you can switch from a/c to heat and back to regulate the cabin temperature.

 

That answers half the question, the other half is, is the auxillary pump working? It forms part of the overall cooling for the engine.
​​​​​​​As already said above, need real time monitoring of the coolant temps.

 

One would agree that the pump does add value to cooling the engine down. The question is by how much?

 

Quite a lot if my S Type is anything to go by.
Until I got that working I struggled to burp it properly because of an air lock.
My solution was to jump the relay to activate the pump and send water round the system. Worked a treat.
Systems working properly now.

 

Really need live data (OBDII reader). Without that, it's like winking at a pretty girl in the dark.

I've had "LOW COOLANT WARNING" (both amber and red) which were false alarms. Had to stick a screwdriver into the coolant tank and stir it around to free up a sticky float.




Stu