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While driving my XK today, I began getting a red warning light and a "Low Coolant Supply" warning light on my dash. As I have recently converted to the JagWrangler Realgauge system, I began monitoring my temp gauge. It was reading solidly in the normal range. I drove for another 20 or so miles as the warning light only stayed on for a few seconds and went out (stray electrons??). Later in the day without the light coming on again, I began noticing the temp gauge creeping up a bit until it was beginning to reach the warning range. I was heading to my house, so I made it home before it got into the red and allowed the car to cool to the point that I could open the coolant refill cap to add coolant, thinking I had somehow gotten a leak. The reservoir was full! Thinking that the thermostat might have closed with the hose full, I started the car, and allowed it to run up to starting temp. with the cap off. Still full, temp good, no lights. Any suggestion, or anyone with similar experiences????
I suspect that the sensor in the small plastic fill/expansion tank is sticking. The sensor is built into the tank, so if it has gone wrong the whole tank is replaced. These are readily available and surprisingly inexpensive, at about 35 to 45 pounds sterling. Presumably there is a sensible way to test it? However, one not so subtle way could be to bang the tank when the light is on, and see if the light goes out.
Could even be a permanent cure! If so, I claim the title for the technique as the ‘Advanced Diddion Technique’, so that I may be remembered for all time.
Incidentally, I too have the excellent RealGauge unit.on normal motoring it reads as if overheating: about 2/3 to 3/4 up the scale. This is normal. On two occasions with a real overheat the gauge has shrieked at me (I wasn’t looking at it, of course) and I stopped immediately with no damage, so that’s two engines Steve Klonsky has saved.
I suspect that the sensor in the small plastic fill/expansion tank is sticking. The sensor is built into the tank, so if it has gone wrong the whole tank is replaced. These are readily available and surprisingly inexpensive, at about 35 to 45 pounds sterling. Presumably there is a sensible way to test it? However, one not so subtle way could be to bang the tank when the light is on, and see if the light goes out.
Could even be a permanent cure! If so, I claim the title for the technique as the ‘Advanced Diddion Technique’, so that I may be remembered for all time.
Incidentally, I too have the excellent RealGauge unit.on normal motoring it reads as if overheating: about 2/3 to 3/4 up the scale. This is normal. On two occasions with a real overheat the gauge has shrieked at me (I wasn’t looking at it, of course) and I stopped immediately with no damage, so that’s two engines Steve Klonsky has saved.
Unfortunately, 'we' already call that 'percussive maintenance'. But from now on, this particular version can be 'percussive maintenance a la Diddion'.
As I'm a fan of zero dollar fixes, first try putting a pencil magnet down the tank around the back and "hook" the float. Sometimes the float get gummed up and stuck. Then try cleaning the wiring connectors too. If that isn't the solution, then you're in the realm of getting a new tank & sensor. FWIW your comment on the warning coming/going (quote "stray electrons") could be due to a low battery charge at first start up in the morning as that normally gives me all sorts of weird messages.
As an aside, I had one of these blow up - it went like a bomb. The sequence of events was the aircon compressor stopped working. Local mechanics could do nothing, and assured me that I could drive the car safely and sort it on my return to the UK, and I was on holiday, so continued driving. Then it suddenly seized up completely, the belt broke, and everything stopped other than the engine. I am pretty sure that the belt was moving slowly before this, so the system was already experiencing overheat (no RealGauge!). Of course, the ignition light came on, so I decided to stop somewhere safe as soon as possible.
Not soon enough. Within about 15 seconds there was an almighty explosion as the expansion tank let go (and nearly my bowels, if I can be honest). This explosion happened because of the enormous pressure that built up in the system. I won’ t go into details, but insurance paid for the necessary 2 week extension to our holiday (yippee!), even offering to fly us back, and trailered the car 100km to a Jaguar garage in Lisbon, where I had no opportunity to source any used components, and they replaced a load of unnecessary stuff, such as water pump, a perfectly functional radiator, and more, at an enormous and inflated cost of 3000 euros.
Although I had tried to sort the compressor beforehand, so am not totally responsible since I did understand that it was not a problem.
I think this is a real cautionary tale, showing how problems can develop into chains, and how unsafe it can be to disregard some apparently trivial or isolated issue. Learn from this, boys and girls!
Thx to All. That's what I like about this forum, always excellent, highly technical advice(re. Diddion's first suggestion, proper apologizes to Graham.).
All suggestions are good, Except for the further problem with the actual overheating later in the day when the temp reached almost to the 'redline' on my RealGauge temp gauge. It began slowly moving up after about 20 miles from the initial red warning light which lasted only about 45 sec. When temp was climbing, there was no red warning light. Initial, I had to let the car sit for about 5 minutes as I went into a local store. On returning the temp had continued to rise(as would be expected if o'heated situation, and no fluid was flowing). On start up, temp dropped slightly, but then again continued to slowly rise. I made it to my house before temp reached actual full red zone.
I allowed the car to cool for approx. 1 hr. Temp was well low. That was when I removed the cooling reservoir cap to discover it almost full.
In all, the red warning light came on about 4 times during a 30 mile drive, each time staying on for approx. 45 sec. It was never on during the time the temp began climbing. The first time it came on was after about 3 miles of driving.
Did the Realgauge shriek at you? I would have expected it to if there was a real overheat going on....but you are right not to make assumptions or take risks.
..... that does assume you still have a tank to fit it to!
Absolutely!
I had 1 sensor fail but 2 tanks fail on my XK8's. One of the tanks had a split seam and the other developed "pinholing" in the base leading to mysterious coolant smell from a hot engine with little apparent loss. Pleased to find the later XK's rarely have tank issues.
I didn't realize that the RealGauge would 'Shreak'. It did not. At what point does the noise go off? In my case, the temp needle only reached the beginnings of the redlines. I did not catch the actual temp, as I was too busy trying to get through traffic and get home before it went out off limits.
I am going out again today, and will watch to see if it happens again, and get better readings if it does.
It certainly does emit a loud sound when it detects overheat! I think is is possible to disable that warning noise, though I can’t imagine why anyone would want to. May be an idea to Steve Klonsky and check things with him?
-The alarm should go off above about 230 F, which corresponds roughly to the red area. There are system tolerances in both the vehicle and RealGauge so the exact value can vary slightly.
-'96-'99 vehicles can vary more than is acceptable, that is why we included a 'one time' calibration kit with RealGauge shipped for those early models.
-The alarm can be TEMPORARILY suppressed during a drive by pressing the 'TRIP' button at the end of the blinker stalk for 1.5 seconds.
-The alarm can be permanently disabled by cutting the red jumper wire on the RealGauge module...not recommended though!
-The alarm and gauges can be tested by pressing the TRIP button at the end of the blinker stalk for 4 seconds with ignition on and engine off. This runs a test cycle.
-And last but not least (very important) the temperature sensor used by the 4.0 and 4.2 V8 to detect temperature sits near the top of the radiator in a coolant pipe. If you loose a significant amount of coolant the sensor could be sitting in air and not in coolant fluid. This can cause an erroneous coolant temperature reading and possibly completely missing an overheating event, which as we know can quickly render these engines boat anchors. Therefore, it is extremely important on these vehicles to pull over immediately check out a low coolant warning. If the tank is empty DO NOT DRIVE. If the low coolant float or switch in the tank is erratic then replace it...it can save your engine!!
Last edited by WhiteXKR; Oct 31, 2019 at 10:15 AM.
I just got back from a roughly 12 mile drive. During that time, the red warning lite did not come on. The temp gauge needle rose slowly to the middle mark, then moved slightly up to 1/2 way between the middle mark and the next smaller mark. It remained there except during stops for traffic lights, when it would creep up slightly toward the smaller mark, then move back as I moved forward.
This was all city driving, roughly 35-45 mph. I had not noticed before now the exact location of the needle, except that it had remained roughly in the middle range. Since my gauge has no numbers I can only go by the marks.
I can only say, that I am certainly glad I have the RealGauges!!! I have never liked 'Idiot Lights'. This is a perfect example. WhiteXKR, use my experience as a good seller if you want.
I hope this was a passing problem, but I will continue to monitor to see if this continues. Also hope someone else has seen a similar situation??
Would pushing the cabin heater to full heat help? The face vent seem to push a lot of air.
Would running the A/C help? This always turn the fans on (check!) and should help removing heat from the radiator.
Check the radiator hoses for temperature. If they feel somehow too cool, maybe your thermostat is stuck closed. Confusingly, running with no thermostat also leads to overheating as it messes with the water flow.
Is there a chance the cooling system is now a mix of incompatible fluids? Your '06 needs Dexcool, the orange stuff. Mixing with the old green stuff may lead to gelling, clogs and overheating.
Last, check if the big radiator hoses collapse when cold, or if they feel soft to the touch. Soft hoses can significantly restrict flow if they collapse when driving, and it can be hard to tell.
Low Coolant Warning light??
