Cylinder#6 Misfire & Coolant Leak

[tskim2024]

Hi all,

I have a 2003 Discovery SE with 54,000 miles. I've been wrestling a misfire and coolant leak for the last month and was looking for some guidance. I'm especially hoping that Elemental might be able to chime in and give me his thoughts. It's been a long battle, but let me lay it ALL out there.

Within 1 minute of starting my car, the check engine light blinks and then stays on. Afterwards, it drives beautifully for the rest of that commute. When scanning computer, it always reads P0306 - Cylinder 6 Misfire. Occasionally, I'll also get P0300 and P1300. At first, I thought it was just on cold starts but if I run into the shop for a minute and start it again, it will exhibit the same behavior even though the engine is now warm.

In a first attempt to troubleshoot, I changed the plugs and wires. That hasn't fixed the problem. Meanwhile, my car is losing some coolant and I'm getting the sloshing sound. At first, I thought the misfire and coolant problems were disconnected, but I got a coolant pressure test done and the results showed no external leak.

There was starting to be some coolant smell in the exhaust, so I went to an independent Rover mechanic for a cylinder leak down test. He told me that the test was conclusive of a leak in cylinder #6. Here's what I'm not so sure of...

The mechanic said, "Because of the location of cylinder #6 (being on the inside), a head gasket failure is not an option. If the head gasket were failing, one of the outer cylinders would experience a misfire first because the water ports are on the outside of the engine. More than likely, the engine liner has slipped and needs a new short block."

Needless to say, I freaked at the $7000-9000 repair job. He says that he's never seen an engine this young with a slipped liner, but all the symptoms are pointing that way. If I'm going to repair it, the next step he suggested was to pull apart the engine and make sure, but that would cost an arm and a leg.

Is his diagnostic credible and trustworthy? I'd appreciate any help or guidance anyone might be able to give. Thanks.

Side note: I'm not sure if this is important, but there were a few days in Chicago when the weather became unusually warm and humid - in the 60's. That was the first time the check engine light went off and did not misfire on any starts during that time.

[tempestv8]

On Christmas Eve 2007, my V8 slipped a cylinder liner on cylinder number 5.

I'm not sure how the cylinder number scheme goes, but I would imagine that cylinder 5 is on one back and (your) cylinder 6 is on the other bank, but in the same V, if you know what I mean.

My engine, which had 190,000 kms on it, suffered a cylinder liner slip, and for a couple of weeks prior to the failure, I've noticed sloshing sounds inside the cabin, as if there was air trapped in the HVAC heater core.

Since my block had to be replaced, I bit the bullet and ordered a tophat sleeved block and fitted a 4.6 crankshaft and camshaft. So I now have a fully rebuilt 4.6 V8, plus new water pump, thermostat and radiator. I even fitted new O2 sensors, just to be sure.

It's cost me AUD$8400 all up, so I hope my Disco will last at least another 200,000 kms. Its been a very expensive Christmas for me.

Sorry to hear about your woes, but it really doesn't sound too good. BTW, I did not have a scanner so I can't tell you if my cylinder number 5 ever reported a misfire. And Aussie spec Discovery II do not have a "check engine light", as far as I know.

Why don't you do something simple like pull out the spark plugs and check the condition? If cylinder number 6 has a much cleaner spark plug than the others, then there's some coolant leak into the combustion chamber, and the moisture is steam cleaning your plug tip.

Hopefully when you pull the spark plugs out, they ALL look the same. Then it's a case of tracking down the leak. Perhaps its the troublesome little hoses that connect to the throttle body, underneath the butterfly. These tend to leak badly and you'll see a build up of crusty dried coolant. The fix is a kit which is available from LR spares.

Maybe it's that simple. I hope so for your sake.


Lawrance Lee
Melbourne, Australia

Good luck with your search.

[tempestv8]

BTW, a slipped liner tends to cause a BIG leak. A failed headgasket would be a smaller leak. From the sounds of your symptoms, it might be a headgasket leak, rather than a slipped liner. How does one tell? I don't really know, I'm sorry.

I think it may be worthwhile to start looking on eBay for a slightly used V8, as it may be cheapest just to do an engine swap.

When I had to replace my engine, I wish I saw this ad sooner:

LAND ROVER DISCOVERY MOTOR SERIES 2 2001 V8 4 L LOW KM - eBay, Land Rover, Car Parts, Cars, Bikes, Boats. (end time 09-Feb-08 22:09:18 AEDST)

[XtremeMarine]

I believe it would be in your best interest to place this query (cut and paste) in the DII section. A lot more people will notice it, and you'll get a more informed answer a lot sooner. Good luck.