Could it be the head gaskets?

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My 98 3.9 disco with 104k has never run quite right since i've had it. I'm now wondering if the problem could be to do with the famous rover head gaskets.

It's using about 1/2 a pint of coolant every 5k and only seems to use oil when a give it a dose of right foot on the motorway. But the more difficult problems have been missfiring under light load (steady 30mph or less) from cold on petrol, but now the missing has got even worse on petrol and has started to show when running on gas. Oh and these symptoms are exagerated after a ragging, but return to normal when cooled off.

I've been through the ignition system already but i'm sure it can't be that as ignition faults always show up first when running on gas as it's more difficult to burn.

thoughts anyone?

[Range Rover Blues]

Could be the head gaskets or the infamous porous block syndrome, the water only gets used when you stop a hot engine, hence the misfire when cold untill the water is boiled away again.  Tell tale to one or the other is a very clean piston.

Try some K-Seal in it.

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Thanks RRB

I have been reading up on that K-seal stuff and overall it seems to do the trick, but doesn't work every time. From what I can make out it won't do a thing if the HG has blown between 2 cylinders, not suprising really.

The other course of action is to do the gaskets myself but while i'm in there I'll do the camshaft, rockers and timing gear, It seems to be that by 100k it's all very worn, but that's according to the RPI website. Are they just touting for business or is it true?

[Range Rover Blues]

Yes at 100,000miles it will be showing the signs of any neglect.  These engines can go on for far more miles but if they havn't been serviced properly.........

My mate sells K-Seal but he does a bundle along with another product that you use first, but you need to drop the anti freeze.  The K-Seal then stays in the system as a back-up and to catch any further leaks.  It's an effective treatment when applicable.

If you are sure it's a head gasket then get both heads off, skimmed and rebuilt.  Take about half a mm off and fit composite gaskets, unless they have been skimmed already.  The stock tin gasket is 0.5mm fitted, the composite is 1.2mm and far more reliable.  There is a tell-tale mark which can help determine if the heads have been skimmed but as they often go concave the front and rear will have had more taken off.

You can also try measuing the volume of the combustion chamber int he head with alcohol in a pippett, the later (composite) heads were about 28/29ml IIRC.

Whilst apart you can also try using die penetrant on the top of the block to see if there is any cracking.

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It looks like i'm going to have to consider my options carefully, though I thinks it's going to be heads off and compo gaskets.

 I rekon it can be done with the camshaft and other bits for about 500 beer tokens if I do it myself 8)  but I need to be 100% sure it's the heads before diving in.

Thanks for the info,