Hi All,
My 04' disco has misfires on cylinder 8. I changed the coils, spark plugs & wires: no real change. This afternoon I remove all the manifolds, etc. to check the lifters, camshaft and the cam lobe on exhaust valve of cylinder 8 is worn out. I'm a bit puzzled: I've read here that the camshafts are a weak point but on lobe much more than the others?? What could be the cause?
Thanks,
Yohann

 

stuck lifter

 

low oil pressure, cracked oil pump rings.

 

OK, thank you. The oil pressure was ok so I guess the lifter got stuck. I know what I need to change now!

 

I replaced all my lifters in my Discovery I at 135K miles.
We sold it at 163K and it was still running very well.
Did not have cam lobe issues.
You may also have metal in your oil pan from cam shaft lobe shavings.

 

In short you are not changing your oil enough--or it wasn't changed enough in its history.

Traditionally engine oil contained measurable quantities of zinc; an additive to protect flat faced tappets or lifters as they are called in the USA. In any case if you neglect to change your oil the film strength breaks down and the first thing to suffer is the cam lobe and tappet face. The other issue is no rotation! If the tappet/lifter is prevented for rotating on the lobe of the cam it causes high point loads leading to heavy localized wear which in turn breaks through the hardness layer of the cam lobe. Look for a tight parent hole or wear on the pushrod or cup restricting rotary movement

Additionally with the advent of modern emission controls the oil blenders reduced the amount of zinc content anyway since the amount of oil passed over during piston reciprocation find its way out into the catalizers and slowly reduces their efficiency.

To combat this problem you can use syn' oils, add zinc additive, or use a diesel engine lube oil like Rotella.
Diesel engines have traditional flat tappet camshafts and the zinc content is much higher due to the valve train loads. Equally their modern cat and particulate filters are not affected by zinc so it has that additive you need for that old engine (after all it was conceived in the 1950's by Buick when zinc was in abundance in crankcase oils).

Also beware of aftermarket camshafts often of Turkish or Indian origin and sold by some US aftermarket suppliers. The hardness factor is /was suspect and one supplier was doing an FOC replacement for failed camshafts which were being reduced to abrasive fine metal particles by premature wear. The particles causing horrendous major component wear.

Sadly I have seen some aftermarket camshafts sold by US dealers which were of Turkish origine, they had the same batch numbers on them buts sold for $300 more in Landrover box!

Naturally the 4.6 cam (orangy-red paint splash identifier) has a more savage and longer duration than the 4.00 camshaft so it is prone to more aggressive wear levels.
These days when overhauling this engine I am inclined to get the new camshaft tested for correct heat treatment and depth of shore hardness by Vickers test before install. By the way the lifter is the same as the Buick 215 so you can save "mucho dinero" by buying this lifter and is the exact same thing thrown in a Landrover box!

By the way if you are replacing the cam bearings use the 215 types from Clevite; being pre-finishied you won' have to pay for line boring of a stepped bushing arrangement which can add alot of costs to the final re-machine exercise the of the block.
Amistades
TV

 

Cause - I'm thinking poor engineering.

Slipped liners, worn cam shafts, failed oil pumps, cracked blocks, overly complicated cooling system. Seriously, do you see a trend. LOL

However, with that said my Discoveries run great and i love them.

 

common problem on LR's always has been I've been told. it just that Discos had so many other problems earlier than people tend to have forgotten.

 

tuercas viejas, Thanks for the insight; I appreciate it. More guys with such insight are needed on this forum.

 

Well in the realm of things the engine isn't that bad and for the most part the engine does very well for the power it is asked to provide and latterly in its development comply to federal emissions standards; clearly not in existence when the 215 Buick engine was shelved as being too expensive to produce.

Essentially it had a severe casting porosity issue which Rover largely eradicated by better casting methods in block production. (about a 95% scrap rate on production)

What couldn't be eradicated however is the basic design of cooling which called for a "through" flow of hot coolant out of the compact block which had to make its way through the two (four) transfer ports at each end of the block architecture and then into the heads where the maximum heat rejection has to take place. Inevitably under high heat dissipation requirements you are going to get steam pocketing taking place around the middle cylinders of both cylinder banks. This heat distress will in many cases cause the block to expand allowing the cylinder liner to creep/slip and become very noisy once the engine has attained operating temperature.

For these reasons LR is pretty emphatic about cooling system maintenance.
If you look into the directives there is specific directives about flushing etc.
Not mentioned is cleaning the outside matrices in in depth.

The D1 is especially prone to plugging the radiator and condenser arr' but can only be viewed by releasing the top radiator supports and the top fan cowl cover to view it by pushing the radiator back by hand against the hoses.
Often found full of leaves and dirt the cooling system on the D1 is usually found running at about 50% heat rejection capacity. Is it any wonder that when an overheat conditions occurs stressing the block the structural integrity suffers.

The D2 and the P38 are less prone to clogging of the radiator with dirt debris but to comply with Federal emissions the engine is running hotter so again cooling system maintenance is very important on these engines.;

The maxim has to be "don't let it glow in the dark"!
T/V