Head / Block Leak (Possibly)

[John P]

This car is driving me mad.  Every time I think everything is sorted and go for a short run something new occurs.

This time there is a hissing sound from the engine which seems to be coming from the head / block joint area at the side of the engine just below the top water branch (High Compression Head).  When first started there are a few small bubbles along this joint line but I can't be certain if it's actually from the head / block joint or something related to the exhaust manifold joint.    The car doesn't seem to be loosing any cooling water.

After a few minutes it seems to stop visibly bubbling but still makes the hissing sound.

Curiously the noise isn't continuous, as I would have expected from a water leak, but related to the firing of the engine, rather like the hissing of a steam engine when it's running.

Having only managed to drive the car around 30 miles this year I'm very reluctant to strip it without any clear idea what's likely to be the issue.

The only thing I've done since it was last OK is remove and re-fit the spark plugs.  Previously I've only tightened them fairly lightly but having seen a recommendation of 30 ft lbs I did tighten them much more than in the past.

Any suggestions?

John.

[Chris KC]

Sounds like you have a leaking gasket, either the head gasket or exhaust. 
If it's running OK and not consuming water it can't be all that bad, but better attended to in case it gets worse.

There's no need to torque up spark plugs, finger tight + a quarter turn should be sufficient.

[Alan]

Get some soapy water and a paintbrush. Brush the water along the head/block spilt line and the spark plug holes. It will be obvious where the leak is.

[Austin in the Shed]

Get some soapy water and a paintbrush. Brush the water along the head/block spilt line and the spark plug holes. It will be obvious where the leak is.

Was going to say the same thing !

[Nick Lettington]

This car is driving me mad.  Every time I think everything is sorted and go for a short run something new occurs.

This time there is a hissing sound from the engine which seems to be coming from the head / block joint area at the side of the engine just below the top water branch (High Compression Head).  When first started there are a few small bubbles along this joint line but I can't be certain if it's actually from the head / block joint or something related to the exhaust manifold joint.    The car doesn't seem to be loosing any cooling water.

After a few minutes it seems to stop visibly bubbling but still makes the hissing sound.

Curiously the noise isn't continuous, as I would have expected from a water leak, but related to the firing of the engine, rather like the hissing of a steam engine when it's running.

Having only managed to drive the car around 30 miles this year I'm very reluctant to strip it without any clear idea what's likely to be the issue.

The only thing I've done since it was last OK is remove and re-fit the spark plugs.  Previously I've only tightened them fairly lightly but having seen a recommendation of 30 ft lbs I did tighten them much more than in the past.

Any suggestions?

John.

When I bought my ORT it had four ancient spark plugs, one of which developed a leak between the ceramic insulator and the metal body. It hissed like a train...

[AustinWood]

I wouldn't expect the Austin cooling system to make a hissing sound. It isn't pressurised unless it's actually boiling.

[John P]

Thanks for the various comments.

Whilst I didn't really think it was leaking past the spark plugs I have now ordered two different types of sealing washer from what was Green Spark Plugs but now seem to be Green Classic and Vintage.   One type are what they call "Budget" steel washers whilst the others are rather like copper "O Rings" and is their recommendation.

I'm going to change these when they arrive and see if it has any effect as this would be by far the easiest fix.

If I've still got an issue I'm thinking the exhaust manifold gasket would be the next most likely culprit.   It's an Ulsteroid and has a replica Ulster design exhaust manifold so there's a manifold plate which bolts to the block and the top edge of this plate lies along the head / block joint which is why I can't really tell where the apparent leak is coming from.

I'm actually rather reluctant to disturb this as the inner fixings, which also retain the aluminum manifold, are sock head cap screws rather than studs and, knowing my luck, these will shear or damage the block if I try to remove them.

Anyway, I'm awaiting delivery of the spark plug washers and will see what effect that has.

John.

[Chris KC]

I understand your reluctance John. 
Maybe take this opportunity to replace the manifold screws with studs?
I have the same manifold arrangement and you might find you need to get creative with it - I have long tubular brass nuts on mine which makes getting at them and seating them a lot easier.