Hi all, I'm new to the forum and about 8 months ago I bought an XK8 year 2000 (with the AJ27 engine for what it's worth).

It has a coolant leak in two places.

The first place is the OSF sill just behind the wheel arch. I expect this is the atmospheric overflow tank that exists behind there so I'm not worrying about how to fix the source of that leak.

The second place is right below the front cross member that runs below the radiator. I've taken the undertray off and jacked it up and can see it leaking. I've checked all the hoses and have UV dye in the coolant and can't spot anything leaking even whilst the engine is hot. I've therefore come to the conclusion that there must be a hole in the radiator or a plug/rubber bung that's deteriorated.

I've had it pressure tested twice by Swallows Jaguar. Both times it's come back clean.

If anyone has any thoughts please let me know.

Thanks all.

This is the front cross member dripping coolant


This is the OSF sill. (The axle stand wouldnt push back any further and my trolley jack won't go any higher in case youre wondering)

 

Hello,
that's pretty wet.
There are 2 weak points: The expansion tank develops cracks over time. You have to look carefully for traces, even from below. It's best to remove it quickly.
The thermostat housing will also break at some point. There is now a replica made of aluminum.
Good luck and keep us updated.
Best wishes, Willi

 

Hi Willi,

Expansion tank was replaced very recently. The thermostat was replaced too with aluminium upgrade.

 

The leak above the crossmember could be the water pump. Sometimes the seal only allows coolant to pass and drain through the telltale hole in the pump when the shaft is actually spinning so a leak might not be picked up on a static engine.

You should be able to look at the area around the pump with a torch (and a mirror if necessary) and get a good idea of where the leak originates.

Richard

 

Check your plastic Norma connectors. They are notorious for degrading and springing leaks. Most of us cut them out of the system and replace them with brass hose barbs. There are multiple threads describing this job....

 

Yeah the water pump was replaced about 7 months ago and I checked around the pump anyway to see but no leaks there.

 

Thank you for your reply but I wonder would the Norma connectors usually result in a leak off the very front of the engine?

 

Strange that it's been pressure tested and the leak hasn't shown up. How long did they have it pressurised for?

 

Hello,
How much water is lost? Do you have to top up the water after 10km or 1000km? Why I ask: The expansion tank must never be completely full, otherwise it will squeeze it out.
Is it just water or coolant in there?

Greetings, Willi

 

I have no idea how long they had it under pressure but I'm assuming enough time to usually find a leak.

 

I'd have to top it up by about a litre after a 100km drive I'd say. It's major enough for me to not want to drive it on too long a journey that's for sure.

It's coolant in there - red. And the leak is present without having the coolant right up to the top of the expansion tank.

 

The OP has an AJ27 engine which I believe has the same cooling system as the AJ26. This means that the black tank under the bonnet, which many people call the expansion tank, must be filled to the very top.

The tank which should only be 50% full is the atmospheric expansion tank which is hidden behind the righthand-side wheel arch liner and most owners, and indeed most garages, do not even know of its existence.

Richard

 

Start her up and let it idle to come up to temp, then check for leaks on the plastic ends of the radiator

 

Yeah I did try yesterday - I didn't see anything obvious but it might be worth another look at some point. I was hoping there might be a common issue witht the radiators that would explain it but it might be that the leak is indeed on a hose and I just can't see it.
Andy

 

Yeah I did try yesterday - I didn't see anything obvious but it might be worth another look at some point. I was hoping there might be a common issue with the radiators that would explain it but it might be that the leak is indeed on a hose and I just can't see it. I really would think two pressure tests would identify it though since it's leaking at quite a rate.
Andy

 

It's trivial to pressure test it yourself.

This bit of kit is < $100 and it's saved me $1000s over the years: https://www.harborfreight.com/radiat...kit-63862.html.

In my case, my water pump needed renewing: https://www.jaguarforums.com/forum/x...3/#post2312003


X100 2001 XKR pressure testing coolant system

 

Yeah I would do it myself if I thought that Swallows got it wrong twice. How do you actually identify the leak in a pressure test? I had the car running and looked to see where the drips were coming from but couldn't - doesn't that sort of count as a pressure test?

 

Yes, it does. The key here is that you don't need to have the engine running or hot when using this tool.

There are a number of advantages to tracing coolant leaks with the engine off and cool:

• It's safer to examine an engine that's not running, either from above or below,
• With a cool engine, you don't burn yourself using a light & telescoping mirror to reach deep and look in awkward spots,
• Some small leaks evaporate on a hot engine, making them difficult to locate. You obviously have a larger leak,
• With the engine off, you can leave it pressurized for a long time, even overnight, allowing more volume to leak that makes it easier to see and giving you to more time to trace the leak,
• It's quiet. You are not distracted by the roar of the fan & engine and you can listen for faint bubbling/escaping air, sometimes using a mechanics stethoscope with the metal probe removed,
• You can pressurize the system with the electric fans and serpentine belt removed, giving you more room to look for the leak if it's at the water pump or below the intake manifold

Of course, the nature of your leak may be such that the leak only occurs if the engine is hot or the cylinders are pressurized. But pressurizing the coolant system with this tool is always the first thing I do when I need to trace a leak like this.

The other advantage to having your own tester is that after the leak is found and fixed, you can pressurize the system and leave it for an extended to give yourself peace of mind that the problem is completely fixed. If it depressurizes quickly, you have another leak to find.

Apologies if much of the above is already obvious to you. I am not being condescending here. There is a wide range of mechanical expertise on this list and while many members are very advanced, some that may read this thread now or in the future may not be and I don't want to assume anything.

 

^^ What he said. Here in the USA, some of the big box auto parts stores (Advance Auto Parts, Autozone, etc.) lend out these pressure test kits....

 

Thank you muchly for the info. It couldn't hurt to test it myself I suppose. I'm seeing sets on Amazon for quite cheap. Is there any particular fitting needed for the XK8 or Jags in general that I need to make sure is included with the kit?

Andy.