Topping up coolant?

[paddy1000111]

I think I might get a new cap for the expansion tank. It's not come back after a clean but when I got the car there was some dried coolant around the lid. Fingers crossed a new lid and the "three click" method it may not come back.

I've filled the tank up to the point where it just covers the "max" marker inside the tank. I'll monitor it this week and post back with an update.

[Moss]

Mine actually also loses a bit of coolant over time and I have no idea where and how. No obvious leak traces, smell or stains on the garage floor. I know these issues fairly well because I had the same engine in an XF in the past and had several parts of the system + the water pump replaced over time.
……..

Like you, my previous superdupercharged 5.0 XKR lost a little coolant over time. Perhaps every thousand miles I would need to add a half cupful.
Other than that, the car ran perfectly well for 50,000 till I moved it along to a new owner.

I had Jaguar pressure test the system, and nothing untoward reported, nor was there any visible sign of leaks anywhere. Of course, there’s always the worry of the aluminium engine but I doubt I’d have reached 50K miles if there’d been any weaknesses.

[MajorTom]

Mine actually also loses a bit of coolant over time and I have no idea where and how. No obvious leak traces, smell or stains on the garage floor. I know these issues fairly well because I had the same engine in an XF in the past and had several parts of the system + the water pump replaced over time.
……..

Like you, my previous superdupercharged 5.0 XKR lost a little coolant over time. Perhaps every thousand miles I would need to add a half cupful.
Other than that, the car ran perfectly well for 50,000 till I moved it along to a new owner.

I had Jaguar pressure test the system, and nothing untoward reported, nor was there any visible sign of leaks anywhere. Of course, there’s always the worry of the aluminium engine but I doubt I’d have reached 50K miles if there’d been any weaknesses.

Interesting. Another case where there's a minor coolant use without any obvious leaks then. Still only anecdotal but perhaps it is normal that some of these engines somehow use a bit of coolant over time.

[paddy1000111]

I took it for a spirited drive and haven't lost anything between that and commuting so far this week. I borescoped the "V" and the pump straight after the drive and can't see anything damp. I'm starting to think it is cap related. I've ordered a new one from Jag (£13.65) and I'll put that on in case the "clicks" aren't strong enough or the seal is old as it's 7 years now. I have a longer trip this weekend in it so i'll see if I lose anything else.

[scm]

I wonder if the water pump is weeping just a little coolant that's being evaporated away before it leaves any trace?

[paddy1000111]

I wonder if the water pump is weeping just a little coolant that's being evaporated away before it leaves any trace?

Quite possibly. Only way to know for sure would be to add a UV dye to the coolant and then look with a torch. I've borescoped it hot and looked at the front, back and checked the plastic connecting piece all of it is bone dry. If it was a weep that was evaporating instantly on the pump it would be so tiny that 300ml in 4 months sounds a lot. I would also expect a red/orange buildup around the leak point as the water evaporates and a considerable amount of the agent is left behind.

Just worries me that it's burning it off inside leaving no trace

[ninetails]

The plastic coolant pipes under the super charger are sealed with an o ring, and as the pipes are just a push fit together (held down by one bolt) they rely on an interference fit between the o ring, the outside of the plastic coolant pipe and the aluminium hole in the engine. I suspect at certain cold air temperatures (when car is not being used) the sealing fit at these joints is not as tight as intended due to the different expansion/contraction rates of aluminium and plastic and also the o ring will not be so pliable when cold. So when left over night a few drops of coolant seeps out onto the engine under super charger. When car is next started and engine gets up to operating temperature the o ring and the pipe joints get hot and expand, they fit together tighter and seal. The small amount of coolant under super charger evaporates (which you can smell but not see). As every component is made to a tolerance some "push fit" pipe joints will be tighter than others. unlike an oil filter joint (for example) where the o ring is constantly held under compression. I had a motorcycle (YAMAHA V-MAX) which had a "push fit" plastic coolant pipe on the side of the engine, which was easy to see, and every winter it leaked a few drops of coolant onto the garage floor but as soon as it was started up and got to operating temperature, it sealed.

[paddy1000111]

The plastic coolant pipes under the super charger are sealed with an o ring, and as the pipes are just a push fit together (held down by one bolt) they rely on an interference fit between the o ring, the outside of the plastic coolant pipe and the aluminium hole in the engine. I suspect at certain cold air temperatures (when car is not being used) the sealing fit at these joints is not as tight as intended due to the different expansion/contraction rates of aluminium and plastic and also the o ring will not be so pliable when cold. So when left over night a few drops of coolant seeps out onto the engine under super charger. When car is next started and engine gets up to operating temperature the o ring and the pipe joints get hot and expand, they fit together tighter and seal. The small amount of coolant under super charger evaporates (which you can smell but not see). As every component is made to a tolerance some "push fit" pipe joints will be tighter than others. unlike an oil filter joint (for example) where the o ring is constantly held under compression. I had a motorcycle (YAMAHA V-MAX) which had a "push fit" plastic coolant pipe on the side of the engine, which was easy to see, and every winter it leaked a few drops of coolant onto the garage floor but as soon as it was started up and got to operating temperature, it sealed.

Is this the bit you're talking about?

[ninetails]

The plastic coolant pipes under the super charger are sealed with an o ring, and as the pipes are just a push fit together (held down by one bolt) they rely on an interference fit between the o ring, the outside of the plastic coolant pipe and the aluminium hole in the engine. I suspect at certain cold air temperatures (when car is not being used) the sealing fit at these joints is not as tight as intended due to the different expansion/contraction rates of aluminium and plastic and also the o ring will not be so pliable when cold. So when left over night a few drops of coolant seeps out onto the engine under super charger. When car is next started and engine gets up to operating temperature the o ring and the pipe joints get hot and expand, they fit together tighter and seal. The small amount of coolant under super charger evaporates (which you can smell but not see). As every component is made to a tolerance some "push fit" pipe joints will be tighter than others. unlike an oil filter joint (for example) where the o ring is constantly held under compression. I had a motorcycle (YAMAHA V-MAX) which had a "push fit" plastic coolant pipe on the side of the engine, which was easy to see, and every winter it leaked a few drops of coolant onto the garage floor but as soon as it was started up and got to operating temperature, it sealed.

Is this the bit you're talking about?

20231015155842005.jpg

It does not look like it. I have not changed the pipe assembly myself, and would not like to attempt it, after watching the video, I was just giving my opinion on this type of joint in general. If you want to watch the video, google "jaguar f-type coolant y-pipe replacement on YouTube video".

[cj10jeeper]

Whilst replacing the expansion cap take a good look a the tank itself. A common reason for loss of small amounts of coolant with no visible evidence is due to hairline cracks in the expansion tank above the water level. No idea if this is common to any JLR cars, but you'll see it on many forums.
Difficulty is you never see anything as it vents as tiny amounts of steam and go looking for ever more complex issues