Somewhat worryingly since I collected my S/C last week from having new lights fitted, I'm now getting a low coolant alarm when the S/C is being driven quickly / at high rpm / Sport Mode.

Coolant levels are consistently fine. Yesterday, on a long drive to Devon, the coolant warning was followed some time later by a Reduced Engine Performance warning. Switched off, checked and normal service resumed.

This never happened before the lights were replaced.

I'm seriously considering paying for a specialist to sort this rather than waste my time with another dealer visit.

Before I do, though, any suggestions as to what's causing this? Si. <This is my name.

I eat rat poison.

A man ain't truly been insulted until he stands buck naked in front of a woman and she didn't even notice. Or care.

May be a red herring but check the fan is rotating the right direction?

possibly something was 'knocked' when the lights were fitted...i'd have a good look and see if its anything obvious around the headlight areas.. ... - .- -.




Y. O. L. O.
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Reduced engine performance warning normally means overheating of engine or gearbox....

The reduced engine performance could be un-related - i.e. it could be the normal issue of the supercharger coolant pump being wired up in reverse and bringing on the reduced engine performance warning when the charge cooler temp gets too high such as on a long hi-speed journey.

The low coolant warning could be as simple as a defective level sensor in the expansion tank - again, these are known to fail / give spurious readings.

The wiring on my coolant pump was back to front plus I changed the coolant level sensor as a precaution.....new expansion tank complete with sensor was only about £18.00 if I remember correctly ! Stolen / Gone: 2006MY Supercharged LPG Autobiography - Zambezi Silver with Sand/Jet/Jet Oxford Leather.....

If not a passing glitch methinks 'a rocket' might be heading somewhere soon!

Just behind your driver side headlight is the coolant tank. In the bottom of the tank is a sensor that senses density/level. Now assuming that they removed the tank for the work, they may have re-filled it with water iso coolant (bad mistake) and that screws up the sensor so it thinks the level is too low.

They could also have damaged the connector.

As for the reduced engine performance, I have never had that so it is not linked to the coolant sensor so I think you may be looking at the coolant pump wiring here as that seems to be the classic issue !! MY 2010 5.0 SC Galway green and sand interior!!
Have the Faultmate MSV2 Extreme to be tinkering with the settings etc. !!

Thanks all!

As said above, everything was fine before the lights were replaced so I hope it's a simple fix.

Rocket?... More than one methinks... Si. <This is my name.

I eat rat poison.

A man ain't truly been insulted until he stands buck naked in front of a woman and she didn't even notice. Or care.

There's a VIN range for the badly wired ones, so thats an easy check. The coolant level can happen if you sling round too many corners for a while, goes away when th coolant returns. 
07 Supercharged - Still breaking her in!

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Just driven home from deepest Devon via Bath (150 miles) and I had the low coolant warning ONLY when the engine was thoroughly warmed up and ONLY on reasonably hard acceleration and never on bends.

Coming out of Bath towards the M4, overtaking up the hill on the short dual carriageway and both Low Coolant and Reduced Engine Performance warnings appear. Pull over, switch off, key out, lock, unlock and start up. Same warnings. Drive further. Stop and check coolant. Perfect. Fiddled with black sensor on bottom of expansion tank. No obvious connection issue. Restarted and same error messages. Drove home with no noticeable loss of power. Use hard acceleration deliberately on M4 and no errors.

Switch off at home and get the Low Coolant message yet again!

I've informed the dealer but want an independent repair done for peace of mind. Si. <This is my name.

I eat rat poison.

A man ain't truly been insulted until he stands buck naked in front of a woman and she didn't even notice. Or care.

My guess is on water to top up the coolant in the tank. Suggest to drain the tank and fill it with coolant to see if that helps. Otherwise replace the sensor, easy job with the tank out (and that is also easy). Sensor is quite cheap I remember. Don't forget to take the little rubber cap on top of the probe of though, it protects the little metal sensor tip. MY 2010 5.0 SC Galway green and sand interior!!
Have the Faultmate MSV2 Extreme to be tinkering with the settings etc. !!

PM returned

I've sent two emails to the dealer on this but have decided I cannot afford the time or the hassle of a 250 mile round-trip each time, so will book the work into a local Jaguar specialist and will invoice the dealer for the repair.

Thanks to Craig for his insight and to all of you above for your advice and detail.  Si. <This is my name.

I eat rat poison.

A man ain't truly been insulted until he stands buck naked in front of a woman and she didn't even notice. Or care.