Recently my low coolant light went off. I topped it off, but when I changed my oil a few days later, I noted some coolant in the splash shield. It's not a lot, but it is leaking somewhere. I know these cars have a reputation for leaking around the coolant reservoir, but I didn't find anything obvious. I've seen many coolant leak articles here regarding the 3.0, but I have the 4.2. I'm sure there are differences. Can anyone shed some light on where I should concentrate my efforts?

 

The entire plastic thermostat housing assembly often develops small cracks. At the age of your car, the entire assembly should be replaced. It includes a new thermostat and all seals and runs just under $100.

You should rent or buy a coolant pressure tester to help find the problem if it is not obvious.

 

Mine had a leak at the bottom hose connection of the coolant header tank.The O ring in the tank side of the connection had deteriorated.

 

Both good suggestions. At this time I would replace the upper tank and the thermostat housing. The plastic degrades with time and heat and your car is now 10+ years old and maintenance must be done.

If you have not done so consider a transmission service which is more than just a fluid change too.
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2004 S-type 4.2L, no supercharger, 113,000 miles.

Have a coolant leak that's pretty bad, around a quart every couple days. I always use Dexcool orange, never mix colors, so I know it's not gunk.

Doesn't happen much when the engine is running, but after I shut the engine down and it sits for a few minutes, there's a puddle. The puddle is at the back of the engine, towards the driver side of the centerline. It's about in line with the back edge of the front wheels.

Does anyone know where this leak might be coming from? My mechanic is clueless and keeps hearing those 'cha-ching' bells go off.

I sure would appreciate the help.

Thanks. John

 

What is a ball park number on having the radiator replaced ?

 

After a cold soak, have the system pressure tested to determine the source of the leak.

Given the age of the vehicle, the water outlet should be replaced, which includes a new thermostat and seal and coolant temperature sensor. The plastic water outlet can only withstand a finite number of cold and hot cycles before failing. The water outlet should be replaced each time the coolant is changed. The JLR part number is AJ811793.

Find a competent Jaguar specialist, or obtain the Workshop Manual or JTIS and work on the vehicle yourself.

 

Depending on where the work is done and by whom, it can run from 500$US and up.

 

Thanks, I took it to the place that changed out my DCV and they were the ones that located the leak. On the down side they said that after looking at the book time on changing out the radiator that I should probably take it to a different place so I'm trying to find a place that will actually take the job. I think by the book its something like 5 hours, plus I would have to source the new part .

 

Thank you for your advice, but this doesn't seem to be the source of the problem. The water outlet is in a different location from the puddle. I would like to give some guidance to my mechanic so he can focus, instead of testing everything, everywhere and racking up the bill, if you know what I mean.

Thanks. John

 

Pressurising the cooling system and looking for leaks can help him find the leak in the area you mention. Bear in mind that there may be more than one area leaking. Have him look at the hoses and connections paying particular attention to the heater pipes and hoses near the throttle body and to the radiator end tanks.

At some point in time, the water outlet pipe will fail, which can result in catastrophic engine damage.