Hello Everyone:
I have a very slow coolant leak. I had my xk jag parked for maybe a month in my garage. I went out and drove it around and the low coolant light came on. I drove it home, coolant overflow was almost dry and added half a gallon of antifreeze to fill up the coolant overflow. I have been watching the level on a daily basis. The coolant overflow goes down maybe 1/8 - 1/4 inch daily without driving the car. Has anyone ever had this happen to you? How would I check for coolant leaks? Do I add pressure to the radiator or coolant system and look for leaks? Any help? Thanks .

 

You can't access the radiator directly but you can use a pressure tester on the expansion tank to apply pressure. With that amount of coolant loss, especially when the engine is cold, I'm surprised that you don't find a puddle on the garage floor which would enable you to find out where the leak is. Remove the undertrays to see if there is any coolant collecting on top of them.
Is there any sign of emulsion when you remove the oil filler cap? I don't think you have a dipstick so it's more difficult to check directly whether there is any water in the oil.

Richard

 

You can rent out a coolant pressure tester at the autoparts store. Pump up the system when the car is cold and you will find your leak. This is how I found out my thermostat housing was leaking on my 2013 xkr and replaced it myself for $120

 

There are no puddles under the car. Maybe on the undertray. I will try to check. So where is the coolant going, if I can't see any fluid puddle?

 

+1 to a pressure test.

Losing coolant from a cold engine is unusual. Hot and under pressure is more normal.

There's a lot of pipework and connections to check.





I'd remove the engine cover and undertray to first look for any obvious source.

Graham

 

That's a good question. Coolant loss from a hot engine can be tricky to diagnose if the coolant loss is only slight as the leakage evaporates on the hot engine before you can see it. Coolant loss from a cold engine, especially in the case of significant loss. is usually obvious once the undertrays are removed as there is very little evaporation.

If the coolant loss is definitely not found under the car or in the V between the cylinder banks, and even here it will eventually build up and find its way onto the floor, then it can only be leaking into the cabin area from the heater matrix or into the cylinders from the head gasket. If the footwell carpets are dry (and you will usually smell coolant in the cabin) and there is no white emulsion under the oil filler cap and the oil level is not rising in the sump and there is no excessive steam in the exhaust, then the leaking coolant from a cold engine must eventually appear on the floor. Pressurising the system with a test kit should expedite matters.

 

Slow leak today…. disastrous tomorrow.

 

+1

Any coolant loss on a Jaguar V8 is high risk. It's a low volume / high flow rate system which can very easily and quickly overheat the engine if the level drops significantly.

Graham

 

OP, I would grab a flash light and look behind the engine to the top of the trans bell housing for coolant residue. If you see residue, its the rear crossover pipe, fairly easy/cheap job. Thats where my wifes XK and my 2016 Range Rover was leaking from.


If no bueno, add some coolant UV dye and a pressure tester.

 

Do you smell "burning" coolant after it's warmed up and you park it? Usually, that's the tell. Small leaks in the engine valley you might not be able to see. However, "1/8 - 1/4 inch daily" loss in the expansion tank is a lot.....

 

Consider changing the crappy factory plastic pipes out for the lifetime Aluminum versions.
They don't have the rear water manifold out in Aluminum yet so your limited to replacing it with another factory plastic part.
But the main 2 front ones are also very failure prone.
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How does your oil look? Leaking gasket somewhere?