I have a 2005 XJ8 4.2L. I am experiencing coolant loss, and have been unable to find the cause, even my local garage cannot find it! But I am definitely losing coolant. New Water pump fitted, but still loss. Before I commit to anything major, anyone any advice?

Cheers

 

It has to be going somewhere, if it’s not being lost externally (an obvious leak) it has to be internally (combusted), if it’s leaking but you can’t see where I’d suspect the valley pipe, it’s apparently notorious for it. If there’s no signs of leaking you’ll want a pressure test done, could be a head gasket. Is the expansion tank heavily pressured? That is a usually an easy sign to notice

 

I will check it out, thanks

 

If the amount of coolant loss is small the head tank cap can leak and not leave much evidence

of dried coolant.

 

Dried coolant is what your looking for, then look above it for your leak.

Small pin holes in smaller hoses can be hard to find, leaks can be covered by other hoses.

That then seep, and run down the back side, of your hoses, leading you away from the leak.

 

Thank you will take look

 

I lose quite a bit, but will check for more evidence. Thanks.

 

Hi Grahber,

Have you checked the thermostat housing. Mine was losing coolant from that. You should see coolant staining down the front of the engine in this case if the leak is bad. Here is where mine was leaking on my NA car. You can see where the leak was due to the slight orange staining in the ridge in the housing. Mine got a lot worse than this in the end but this is how it started to leak.


Coolant leak from thermostat housing.

As others have said, there is also the valley hose to check which is on both the NA and supercharged versions. When I changed my housing the valley hose was ok and looks to have been recently replaced so I left it alone. Although you do have to disconnect it to get the throttle body off.

Thanks,

Chris

 

I could use some help, my 04 xj8 4.2 NA has a coolant leak at the very rear of the engine.Looks like a copper tube below the intake manifold that attaches to the right exhaust pipe near the O2 sensor. Almost impossible to see attachment hardware. Looks to be a flange attachment at the exhaust pipe area with 2 bolts.