Elusive coolant leak

[Rebelstag]

I have coolant dripping from the rear of the engine block below the Temp sensor at the rear of the cylinder head but I can't see where it is coming from. Doesn't seem to be coming from the vee and only leaks when the engine is running. Can you get the cover off the end of the head in situ to check the seal or could it be coming from the sensor?
Roy

[DJT]

You can remove/replace the rear transfer housing cover in situ, but be prepared for a struggle. I had to do it a few years ago when I cross threaded the new sensor when replacing it. 7/16 ratchet spanner and a 1/4-inch drive socket if I recall correctly. Plus a few choice swear words, so try it when the neighbours are out.

[dasadrew]

and there are FIVE bolts of which the centre one is invisible and can lead you into thinking it just needs levering off after removing four bolts!

[DJT]

and there are FIVE bolts of which the centre one is invisible and can lead you into thinking it just needs levering off after removing four bolts!

That sounds like the voice of experience........

[dasadrew]

That sounds like the voice of experience........

... nearly.....! Fortunately brain kicked in quicker than the screwdriver!

[brian buttimore]

My suggestion is take your time and try to locate the leak before removing the rear transfer housing.
Can help to use talcum powder or similar around the area to track the approx source.
Then use the camera on your phone to record where the water droplets forming.
Often as not not where you first thought.

Good luck.

[Rebelstag]

I came to the same conclusion as I don't want to make work if I can help it. Trouble is it doesn't leak until under pressure and then it is so hot it makes it difficult to get in close to look. The Talc is a good idea as it is bone dry at the moment.

Thanks Roy

[Rebelstag]

Looks like it's leaking from the head gasket. I am wondering whether it is worth torquing the head nuts and bolts.
Roy

[mole42]

How many miles since the heads were torqued? My experience is that they may need tightening several times after replacing the gaskets so it’s probably worth doing.

[richardthestag]

I have seen a batch of head gaskets where there is barely any gasket material between the rearmost coolant hole and the fire ring for #7 and #8 depending on side.

see here for location of the fault

head gasket issue.jpeg

[Rebelstag]

The gaskets were replaced about 5 years ago and it has done about 6000 miles in that time. The heads were torqued after a month or so but not since so I guess it is worth a try.

[mole42]

Many have experience that the heads need torquing several times before they are settled, mine needed doing four times in the first 5,000 miles. I’ll be doing them again tomorrow because, after 30,000 miles, I have symptoms of a head gasket leak.

[Rebelstag]

Have retorqed both heads and there was was only a small of movement on a few of the nuts and bolts. Seems less of a leak after a test run but the back of the head is now looking oily as well. I think the head is going to have to come off.
Shame as the Stag is running really well!
Roy