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| The best Jag I've ever owned, hands down. No I don't miss British Racing Green |
I drove the car for another 1,000 miles without thinking much about it as the light was intermittent, but then it became more frequent.
After a pressure test, I discovered my coolant reservoir was the problem ; a clear plastic tank that sits right up top on the radiator support .
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| Jaguar XJ8 Coolant Reservoir / Overflow Tank / Expansion Tank |
** ALWAYS LET THE ENGINE COOL BEFORE DOING ANYTHING ; BE SAFE AND CLEAN UP EXCESS RADIATOR FLUID, IT IS POISONOUS **
The first thing you want to do, is make sure you have not been using water to re-fill this tank, or anything other than the recommended Dexcool coolant. The sensor is very sensitive to other coolant types ; so make sure you are using the proper coolant ; and not water . The sensor hates the stuff.
Ok, so the problem with this coolant expansion tank ; is that it loves to develop small cracks in the plastic upper hose connection ; thus dropping pressure in the tank and throwing the low coolant light. It's really a poorly engineered design, because the hose isn't supported by anything and is constantly putting pressure on that fitting.
Sometimes you cannot see anything wrong / I could not see any residual fluid, or signs of a leak. But I could faintly smell coolant when the car had been running for a while.
Order a replacement tank, and make sure it comes with the "bleed screw" as mine did not and I had to request one. You can find an aftermarket tank on ebay for about $30-40, not $200 from a parts supply store such as Autozone. Your new tank should also come with a new cap. I saved my old cap as a spare ; but honestly hope it's a part I'll never need in the future :)
Tank removal is pretty straight forward, I used a lighted mechanics mirror to disconnect the lower sensor connector on the left underside of the tank. You'll have the top hose, and an electrical connector at the bottom of the tank, then you have a clip to pull for the hose connection which easily comes off once you pull that clip out.
All and all, a pretty easy job for most non-mechanically inclined. I did not re-order a new sensor, I used my old one which is released from the bottom of the old unit. Remember to make sure your bleed screw is tight, and has it's rubber "o" ring attached.
My annoying coolant level low light has stayed off now for months, and I can now recommend this as your best bet for a fix. Remember to use Jaguar approved radiator fluid , and double check all of your connections to assure they will not come off under pressure.
Also remember to inspect for leaks behind the block, and under the intake manifold (there is hose under the intake manifold that loves to leak in the valley of the engine) if this does not immediately fix your problem, and of course if you can still smell coolant. However, this problem seems much rarer than the aforementioned fix for "ghost leaks" on the XJ8.
