I'm optimistically hoping for good news...

I have a 2016 XJ V6D Autobiography and I love it. Recently I had it serviced, and not long after that, the coolant light came on. So I checked it. It was low, so I filled it up, figured it was a servicing issue and carried on with my life. I then had it MOT'd and red flags began to emerge.

1) The garage owner (Jag specialist) told me there was a tiny amount of moisture in the exhaust which he thought could be from needing a regen. ( not massively worrying in it's own right)
2) I began to notice little, tiny whisps of white smoke when it is cold/rainy from the exhaust.. not enough that I'd even notice usually but coupled with the coolant refill and the mechanics comments I'm getting wary.
3) The coolant has dropped slightly. I filled it to the max line on the 23 October and now, a month and about 700 miles later, it's dropped to about 2/3 below the max when cold.

Key points.
* The car has done 145,000 miles.
* The oil is fine, no emulsification
* It drives, starts and runs perfectly. No overheating, no weird smells or noises.
* It sailed through the MOT - surely if coolant was getting into the combustion chamber... it would fail emissions?
* The smoke is barely visible, I know you get a bit of white steam on cold mornings anyway, which I get but there's a very, very faint trace that still wafts out that you can see if you pay attention even when the engine has warmed up ( I haven't checked this on a long run yet though).

I've ordered a new expansion tank cap in the optimistic hope that this will magically be the issue behind the disappearing coolant, but I don't think it will be.

What are people's thoughts? Anyone had a head gasket or cylinder head go very slowly, with symptoms like this?

 

I just realised, I don't mean cylinder head, I mean a crack in the block.

 

jackrobo1994, keep in mind that when diesel is burnt, it should turn into water vapor and CO2 in an ideal world. On cold, humid mornings, seeing white mist coming out of the tailpipe is normal, even after the car is warmed up. So, i would not worry about that. The loss of coolant is one of those things that about the only way that you are going to find that is to get your hands on a pressure tester, connect it to the overflow bottle, and then press the system up to 15 psig. From there, you should see a small stream of liquid coming out. That will be your source of the leak. If you loose a visual amount from the overflow bottle but do not see any water reaching the ground, then that would be grounds for caution as this would indicate that it is leaking into a cylinder.

 

Diesel engine have very high compession. If you have water leak from coolant to the combustion (headgasket, heads), for sure you have much more gasses on coolant side than coolant on exhaust.
There are possible that EGR coolers leak coolant to the intake. You should see this as "cream coffee" colour inside of throtle body where EGR pipes meet intake. No fix, only change.
Check plastic coolant connection adapter under throtle body. (front middle of V) If you see wet on that area: the seam of that adapter might leak. Plastic OEM last forever but chinese don´t. Many have changed OEM for new chinese as preventine measure, only find out that they created an disaster themself. Now available as metal : AJD-V6 Coolant connector (it states as thermostat housing, but its not)
Water pumps are known to last on Diesels for age of the car, but worth to check. Easy to change. (runned by serpentine/auxilary belt)
Like written above an pressure tester with simple USB endoscope is gold to search coolant leaks. (example: USB endoscope

 

did someone here mention head gaskets my ears are buzzing ?!?? I swear to god if I never heard that word again. Good luck brother. Just put my post on my ordeal

 

You need to do a coolant system compression test. You can get a kit from an auto parts store (in the US, you can rent a set for free that otherwise costs $250). You fit a proper cap in your coolant tank from the kit and pump it to a pressure of about 20 psi. Then look for any leaks in the system. I had a very slow drop in the coolant level over time and I could also smell the sweet scent of hot coolant, but could never locate any wet spots anywhere. After doing the test over the last weekend, I discovered a crack in the thermostat housing on the side facing the engine. It was dripping profusely while under test-pressure. I ordered a new thermostat already and will be replacing it shortly. In your case, if you are unable to do the said test, check the area behind your engine, just by the firewall. There is a cross-over pipe there that's prone to leaks and breakage. Ask me how I know...