1996 XJS removed Head bolt leaked coolant

Does anyone know if coolant leaking up through the hole when a head bolt is removed from a AJ16 ior AJ6 is normal?

I decided to replace the valve stem seals, and when I pulled out the first head bolt, coolant came out.

I know the service manual said to drain the coolant, but I thought since I didn’t want to pull the head off that I wouldn’t need to. Of course now I have drained it.

FWIW, I think it is a poor design that puts the head bolts through the Cam Shaft Bearing Caps.

It is normal as your cylinder head will twist and spline after bolt tension is released. You may end up with re-skimming / new head gasket…
All depends how big is the leak…

What do you mean by spline?
It is normal to remove the head bolts, one at a time, to adjust the valves, without removing the head.


Not literally! It means that cylinder head will deform over time, that’s why you need skimming after removal. Now explain is that related to AJ6 or AJ16 and what you understand by leak?

Seems to be very risky task. Valve adjustment in your engine is extremely reliable, bullet-proof* (AJ6 only) and usually needs attention way beyond 100k miles…
I have done stem seals once on 120k+ AJ6 3.6. no sign of coolant leaks at all…

Out of curiosity - have you manage to use impact wrench?

When I took out the head bolt, coolant started flowing up out of the bolt hole… slowly, steadily, so I ended up draining the coolant

No impact gun, I removed with a breaker bar

The factory service manual gives repeated instructions for removing the head bolts one at a time and replacing the bolts using a special tool spacer in place of the camshaft cap. I’m not saying it’s a good idea, I’m not sure it is, but when did that ever stop them?

Any chance your coolant system was pressurised? Habe you taken the cap from expansion tank off - prior to unbolting?
Whaaaat engine… ?

No pressure, except head pressure…no radiator cap.


Scott - please indicate which bolt you have taken out / leaking. Reference photo below

I guess it’s the big back bolt?
Clearly the head gasket has deteriorated between the coolant passage around the cylinder and the ajustent bolt.

The bolt is actually between cylinders 1 & 2. I was following the instructions on the service manual.
Yes, I suspect the head gasket had failed, and removing the bolt revealed the failure.

Not entirely failed - as long as it won’t leak to the oil/combustion zones - you’re safe.

I know it will sound like carving in poop, however there is a way to save yourself from taking off the head. Put the heat shrink on the thread as protection and mount the bolt in the drill chuck or lathe. Polishe the flange/check if it has no excessive runout. Degrease the bolt and area around the hole, use good thermal resistant silicone (around and squeeze between hole/bolt equally) mount it and put some (hi temp rtv) silicone on the flange of the bolt. Degrease where necessary. This fix is rubbish but will last another 50k. Addition of small viton o-ring between bolt and hole prior to pooping with silicone will reinforce it.
This is called “shed wiring”.

You seen convinced that the only breach in the gasket is between a coolant channel and the bolt… Why is that?

Could you please explain what you meant by"spline"? Do you mean warp?


Yessss, warpage.

Why I’m convinced? I am not, however you will notice straight away if the leak goes to oil/combustion areas.

By the look of head gasket and removed bolt location you can say that this area is purely isolated from combustion/oil. You’re not risking anyhting with putting it back again.