4.6 head gasket replacement.

[trendkill]

Anyone know if there is a thread on this somewhere?

Thinking of buying a p38 & this may need doing.

Any help would be, Erm, helpful!

[FridgeFreezer]

Sure it's around somewhere - apart from a few more pipes & wires it's no different than any other V8, they just have fewer head bolts. It'll be in the RAVE manuals.

Just make sure you use the composite head gaskets.

[zim]

It might be more than "just" a headgasket. Have a look around on the forum for slipped liners.

I've done my HG's on my 4.6 and it's pretty much the same as every other engine (just twice lol).

G

[FridgeFreezer]

It may also be less - stuck thermostat, knackered radiator, hose, etc. I find it's best to exhaust the cheap & simple options before listening to the harbingers of doom.

[Bowie69]

And a £30 block testing kit is well recommended to (dis)prove combustion gasses in the coolant.

http://www.uktools.com/block-tester-p-12508.html

[Range Rover Blues]

IIRC the bolts are stretchy on the P38 so a new set of bolts might be in order along with composite gaskets.

If the lner has slipped you'll be able to tell but I've seen them checked with dye penetrant too, it's pretty good TBH. Obvioulsy a steam cleaned piston top is a dead giveaway.

[scotia]

In my experience they liners only slip if the engine has been roasted.

If it's just a head gasket failure whip the head off and check where it's gone before you make any decisions.

[landybehr]

In my experience they liners only slip if the engine has been roasted.

I might think you were lucky then. 3.5V8 are known to have had slipped liners and they run lower coolant temps, by much, than the P38. Overheating isn´t nice, no doubt about that. But the liner problem also applies to later RRC as well, which hasn´t had the coolant hose / Thermostat problems of the P38.

[Range Rover Blues]

I've read somewhere that an engine that's overheated 3 times is likley to be cracked behind the liner. There are a number of typical failures including the top deck separating from the bore (horizontal crack) but the problem is made worse because the liners were never pushed home onto the lower register when they were made.

True indeed that later RRC suffered, the 4.2 had something of a reputation and later 3.9. The 3.5 is often thought to be a stronger block because it has smaller bores (more metal round the liner) although later service blocks were made from 3.9 castings which varied somewhat in quality, the core which makes the water jacket often moved so the cylinder wall thickness varies. later engines were built using ultrasonic testing and the best ones kept for the 4.6 engines.

However this is all talk about engines that are 15 years old now, or therabouts. |Chances are all the badly built ones have now failed, so if it's been looked after it's quite possibly a good one, which makes it all the more of a shame when one gets cooked through poor maintenence.

The hot-wire EFi engines should all run at over 80 degrees BTW which is more than the V8 was designed for originally, it's all about emissions though and if a hot-wire is running cold it will run rich.