Thread: Lemon????

Maybe not dead, but certainly severely poorly. Presume it's a 3.9, not 3.5?

If you're loosing coolant, and have low compression, then it's possible you have dead head gaskets, or dropped liner(s).

How much coolant does it use? Does your coolant header tank pressurise and overfill?

Does it have a good Service history?

Sorry. 3.9L v8. Its not losing huge amounts of coolant but what it is losing I presumed to be leaking out the radiator hose. Would a cooling system pressure check help determine that? Coolant tank doesnt pressurise, had that with a hilux once.....cracked head. Ahh being all alloy they have a liner for the bore.... are they prone to shifting?? Bit worried bout the low compression on two middle cylinders....head warp??? or blown gasket. Strange how it just happened all of a sudden though

Dropped liners are known issue on the 3.9, not as common as on the 4.6.

If the engine has been overheated at all, it makes it more prone to the liners shifting.

Have the heads been off before? What year and how many kms does it have on it? Any signs of previous over heating?

Cleaned out the breather ( totally clogged with carbon) replaced and started car, no worries. Went for a drive but a couple of hundred meters down the road felt like it was running on 5 or 6 cylinders . Went searching for pcv valve but cant find one?????

Its appears that the trouble started when you "soaked the breather".

There is no PCV valve in a 3.9 Disco.

The breather arrangement consists of an air inlet at the rear of the LH rocker cover, and an oil separator at the front of the RH rocker with a large hose going across to the throttle body. There is a T piece about 3/4 along with a small hose going to the bottom LH of the plenum chamber.

This small hose comes off a T piece which has a very small hole in it to control the air bypass into the plenum. If you have broken the T piece and replaced it with a normal T piece it will not run or idle well. If you have not reattached the hose ditto. The most common place for carbon to lodge is at the hose stub on the throttle body itself. This should all be cleaned out with Throttle body cleaner.

The low at 4 and 6 looks like a blown head gasket on the RH bank between 4 and 6. This will have no effect on the cooling sytem as far as pressurisation is concerned as the only water passages are at the front and rear of each bank..
However the rough running sounds more like an air leak after the MAF . Check your work re the crankcase ventilation , and check the hose from the MAF to the throttle body.
Another thought is, did you remove the injector plugs when changing the rocker gaskets? It is possible to mix up the ECU temp sensor with the injector plug for no 2 cylinder. They are a different colour.
Regards Philip A
Regards Philip A

You guys know these cranky old bastards well. The T piece I need to check as I am unsure if it is the original one. Small amount of carbon to throttle body stub not enough to worry about though I dont think. Yeah it was the oil separator that was cleaned out. Pulled the mesh out and soaked in degreaser cleaned the body out let it all dry reassembled and reattached. Nothing else was disturbed but I have now since doing compression check removed and replaced the maf to throttle body and made sure connections are good. It seems like once warm enough and under load this misfire is happening. Im not sure if the heads have been removed previously and the rocker cover gaskets were done just before I purchased the vehicle so I havent removed anything electrical.......Yet. The old girl is a july 96 model with 242000 on the clock. Thought it might have had quite a few more good kms left in it yet. Everything when I bought it was spotless, was detailed beautifully even an engine bay steam clean so no signs that I could spot of previous leaks and such.
Cheers for all this advice guys. Never owned or worked on one of these before so its reassuring to have you guys helping out like this.

If the thing has been steam cleaned, remove all the connectors around the engine, have a look at the blades , give em a jiggle and give em a shot of WD40.
Give particular attention to the ECU temperature sensor which should be on the RH front of the inlet manifold , pointing vertically with an injector plug on it. Any additional resistance will make the ECU think the engine is still cold and keep the "choke" on.

If you have a multimeter check that the resistance across the terminals is about 300 Ohms when at operating temperature.
Regards Philip A

Will give that a go in the morning Phil, that and a recheck of hoses. Wouldnt be the distributor module???? Although thats more of a wont go at type of thing. Anyone know of the correct way to check it?

Pop the dissy cap off with the engine warm. If there is condensation inside the cap you will have to let it all evaporate! Water in the dissy will react like that.

Dissy amps (modules) are known to partly fail, resulting in wooly running. I have seen it plenty of times. There is a Bosch module that is easy enough to adapt, I've probably done 50-odd of these. Details here:

Lucas ignition amplifier replacement by Bosch 024

Oh and your compression is probably adequate, there might be a broken ring somewhere but it won't actually cause it to misfire that badly.