I bought my 2004 XJR in March. Shortly after I noticed a slight coolant smell when I would walk past the car after returning home (when the car was hot). I looked as best I could and did not see anything leaking. The coolant level has always stayed consistent.
When I had it in for some other service I had them check it, and they couldn't find anything wrong.
I read some posts on here from others saying they had smelled the same thing but never had an issue.
Today I drove about an hour from home to meet my dad and noticed right before turning the car off that the temp gauge was above half (have never seen it do that before). No warning lights. I was leaving the car for the morning and riding with my dad, so I popped the hood, saw nothing obvious wrong (nor did it smell particularly hot), so I let it sit. I said a little prayer when I got back to drive home. Unfortunately I only made it about 15 miles and it rose above half on the temp gauge again. I pulled over, waited about 20 minutes, and tried to make it home. Within a couple of miles it was getting hot fast, so I quit. AAA brought me home on a flat bed.
I never got any steam, never had any overflow or leaking. The coolant level is fine.
I would figure I have a thermostat issue, but the fact that I have had a coolant smell for so long has me doubting myself.
Thoughts?

 

And to provide a bit more info, the car did NOT seem to overheat when idling. After I pulled over the first time, I sat with it idling for 5-10 minutes to see if it would climb. It stayed right at the half point like normal. It when up as soon as I got it to speed.
The fans were running, and stayed on for about 5 minutes after I shut the car off.
No warning lights ever came on.

Thanks...

 

Hi Drb007,
I am as quizzical over your issue as you are, could it be more to do with your oil?
I am at first pointing toward your thermostat, but really not sure.
Is there anything else you might have noticed like the fan running longer or a different noise from the engine or a lack of pace/acceloration, I am curious but I am sure another more informed member will be along soon?Good luck, Stu

 

On my xj8, the thermostat housing is plastic, stupid engineering, and it cracked internally. It is a double wall kind of design. No leaks at all. But it overheated at idle, was ok at 40mph our higher.

 

I don't think it's an oil issue. And I have the opposite issue...not overheating at idle, but gets hot as soon as I drive away...
As always, hoping for a simple easy fix

 

I bet its a stuck thermostat

Replace the thermostat

Cheers
34by151

 

Mine did this, wasn't overheating at all, just the temperature sender unit, I also suffered with coolant smell, best way to check is to pressurise the system cold and leave for a good hour, go back and investigate for very small leaks, mine turned out to be the thermostat housing leaking slightly, this is fairly easy to change and costs about £40, complete with sensor and thermostat, it also comes with an 90deg elbow that goes to the block, I reused the old as it is more involved if you change this (inlet manifold has to come off, or it looks like it does).

 

My vote also goes for a sticking thermostat.

As to the coolant smell, this is an issue on several other models where a pinhole or minute crack in the Expansion Tank occasionally allows a drop of coolant to fall onto the hot exhaust manifold and vapourise with the pungent smell of OAT. It could be a similar situation with your X350.

Graham

 

Third on the thermostat sticking closed.

 

..... and the perfect opportunity to fit a shiny new Air Intake whilst he's in there, John?

Graham

 

Ok, some more info.
I got a few minutes this morning to take a better look.
First, I apologize for misinformation. The IS coolant loss. This is the first car I have ever had that had the coolant level marks INSIDE the tank. When I looked at it yesterday when it was overheating, the tank, from the outside, looked full. Today, I took the cap off and it is far below minimum, though not empty. Moving a few items for a better look, I have residue from coolant at the front center of the engine, top side. Nothing wet, just a slight colored scaling. The expansion tank looked ok, but I think I am going to have to start pulling stuff apart to see what my culprit is.
I will add in coolant and see if it overheats. If it still does, I could still have a stuck thermostat on top of a chronic slow leak.

 

Well there may be a loose fitting or hose now you have found the leak and at least you have the correct symptoms to go by.

So that should be easier to sort. I'll see if I can find any useful posts to help.

I've had coolant woes on my X Type but I believe that there is a major difference.

Good Luck, Stu

 

Hi Drb007,
You may want to use water to top up to save on coolant as it may help you to discover exactly where the leak is. Just a thought....

 

Buy or rent a cooling system pressure tester....this usually makes it easy to spot the leak.

Also do not overlook the possibility of a bad pressure cap on the tank.

 

I'll be what...number 5.....I'm thinking this is a Thermostat housing....those little buggers can get coolant pretty much anywhere in the engine bay they want when they go, just depends on the cracks location. But yeah, since this is a little puzzling, it really doesn't make sense to not change the housing, thermo and temp sender in one go

 

I just fixed a coolant leak over the weekend.

Ended up being the o-ring seal in the aux coolant pump
I never would I have located the coolant loss without an inspection camera as it was on the back side of the pump.

A leak (and I dont mean an open pipe) wont produce an overheat condition unless you have one of two things as well

1. Low coolant to the level that allows air to circulate
2. Loss of pressure stopping the system pressurizing

The pressure increases the boiling point and forces the coolant out the leak
Where the leak is not a gusher it will leave a telltale red stain where the leak is
You may need to look hard to spot it but it will be there

Dont be tempted to run the system with the cap off, its a closed system (no overflow) and you can easily harm your engine.

You should be able to fin the stain with an inspection camera. the only other option is to test each hose manually by taking them off and pressure testing to 15psi.
If all the hoses are ok you need to look wider. IE waterpump heads ect but this is rare unless you have cooked the engine

Cheers
34by151

 

Well, I spent the $70/gallon for the coolant from Jaguar and topped off the tank. It wasn't terribly low, but I added about one liter. I ran it with the cap off for only 20 seconds, then put the cap back on it. I drove it down the road a back a few times and it seemed fine. But I noticed that the fans were running, and I don't usually hear that going constantly. I tried to drive it to work and only made it a few houses down when it started to overheat again. Back to the garage, I popped the hood, and now I have an obvious leak from something at the top of the engine, behind the thermostat housing. It was really spraying out, so I couldn't tell exactly. I will try to move the plastic covers out of the way and see if there is anything obvious.

 

Found the leak. The line that goes from the reservoir tank to the top of the engine was ruptured at the engine. I cut it off and reattached it with no leaking (I will get a new one ordered). No more leaking, but still overheats. I will change the thermostat tomorrow.

I am confused by something. Everyone talks about the thermostat housing being plastic and that I should replace it. Mine is cast aluminum. ?

 

I seem to remember that there is a company out of Ohio that made aluminum thermo housings. Mind attaching a pic? Preferably with the engine shroud off and air intake elbow removed?

 

I believe the XJR is aluminum, but the XJ8 is plastic, so that is probably not an issue for you.

Also you did not mention it, so I will...the Jaguar coolant should be diluted 50/50 with distilled water.