Are head gasket sealant treatments snake oil?

[plasticpig]

So I think I have a failed head gasket on my Range Rover. It's being pressure tested this afternoon. Is it worth trying one of these treatments or are they snake oil?

[eliot]

P38? - may be a slipped liner.

[stevieturbo]

Snake oil, but some may hold back the symptoms for a while.

[ELAN+2]

snake oil

[spend]

I assume folks are referring to 'additives'? some of the 'treatments' like sprays you apply to gaskets during assembly are very effective IMHO.

[plasticpig]

Talking about the stuff you add to the cooling system. I figured they were snake oil but you never know. I will probably try one anyway while I get quotes from various garages. There is no sign of mayonnaise in the oil and the coolant appears to be clear but it's drunk a litre of coolant in a 10 mile drive with no apparent leaks to account for it.

[eliot]

Still dont know what car you have - but on the p38 coolant loss could be leaking heater matrix seals or slipped liner. If air escapes when you release the top cap even on a cold engine - its a sign that its going.

[plasticpig]

It is a P38. I know about the heater matrix seals as mine do leak a bit. The drivers side carpet is only slightly damp though. I would have thought it would be saturated with the amount it's losing?

[agent006]

Sounds just like my old 4.6

Was a cracked/slipped liner. HGs were fine.

[thong]

Headgaskets can only fail on the four outter cylinders,cus theses only water flow there,liners do shift as said above

[Boosted LS1]

^On a rover there are 4 outer cylinders per bank. Can you explain what you mean?

[stevieturbo]

I assume he means the 4 corners where there are waterways

[Boosted LS1]

Ok, that makes sense.

[thong]

yes there's only water flow up the block in the four corners,no water passes the centre cyliners though the gasket

[paintman]

Well known & a frequent subject of posts on Land Rover websites.
With the V8 the slipped liner problem is due to the alloy block holding the steel cylinder liners being poorly machined. Cracks develop in the alloy & the 'grip' on the liner eases allowing the liner to move & water to enter between the two.
Also reduces the clamping effect of the head on the head gasket, esp the fire ring.
Water can enter the cylinder & compression pressures can enter the cooling system. Usual symptoms are unexplained coolant loss, hoses going rock hard & water ejetion through the pressure cap. Very common problem on the early P38 and the late 'Classic' in all engines. Rare on the 3.5.
With the heads off, the cylinders which look unusually clean - due to the steam cleaning effect of the coolant - are the ones affected. Look for differences in height between top of block & liner, these may be only slight.
Garages often diagnose 'head gasket failure' as the symptoms are identical & replace the head gaskets, often with a head skim. The problem rapidly re-appears.
Cure is a replacement block & some are made with 'top-hat' liners which cannot move down as they have a lip at the top (hence the name) and cannot move up as they are clamped by the heads. (have a look at http://turner-engineering.co.uk/html/V8blocks.html )

You MIGHT be lucky with one of the sealants & have little to lose, but generally not.

Edited by paintman on Tuesday 2nd March 17:20