Just thought I'd share a helpful tip that could prevent a debacle. This pertains to the P300, but I image the head casting on the P400 is similar. Besides the annoying placement of everything blocking access to the fourth plug, where "fourth plug" refers to the plug furthest from the front of the vehicle, there is something else DIYers should be aware of. The hole (not the threaded hole the plug screws into) to access the spark plug seems to be tapered. The 14mm socket I had on hand fit with plenty of clearance at the top of the hole. But before it reached the plug it got stuck. It was a pain getting the socket out of the hole. Which involved a great deal of frustration directed toward the idiot that designed this. Maybe the taper this there for a reason. But it sure would have been helpful if the hole was the same diameter from top to bottom. Which would immediately let you know that your socket has too big of an O.D. The socket that got stuck had an O.D. of 20mm. I found another with an O.D. of 19.6mm, but wasn't brave enough to try it. I purchased a magnetic thin wall 14mm spark plug socket with an O.D. around 18mm from O'Reilly. This fit without issue. I've attached a pic of the plugs that were removed. They look fine to me, but I was replacing the PCV valve assembly and figured I might as well do the plugs. Note that the wet got some WD on it after removal.

 

I have the P400 engine and just had my spark plugs changed at 63,000 miles (as is recommended in the Owners Manual). For the P400 3.0L 6-cylinder engine, the spark plugs are in a really inconvenient place. In order to access the spark plugs, you have to remove the inter-cooler (which is a process apparently). And for the 3.0L engine there are 6 spark plugs -- which total $297.18 at the dealership (but I did have a 10% off coupon to apply). Unfortunately, I am not a DIY guy and had the Land Rover service department do the job....but parts plus labor was not cheap. Luckily this only has to be performed every 63,000 miles. I know there are cheaper options, but I like the convenience of the dealership and the free loaner cars.

--Tucker

2023 RRS Dynamic SE P400 Giola Green (Current)
2020 Defender 110 First Edition Indus Silver (Current)
2020 Discovery HSE Luxury Si6 Fuji White (Former)
2015 RRS Autobiography Fuji White (Former)
2011 RRS Supercharged Fuji White (Former)
2008 LR2 Fuji White (Former)

 

I don't mind paying for the difficult jobs. I just had the transmission flushed and new filter/fluid. The shop recommended doing the PCV and plugs after I mentioned some occasional misfire symptoms. I got the plugs online from LR Virginia beach for $24 each and it seems to be the same part # for the P400. I always get the part # from the diagram and search the web for the best price.

 

Great info. Thanks for sharing. I'm not close to this yet but it always pays to learn from others. Much appreciated.

 

I can see what came out are NGK. What’s the plug number?

 

For the P300 NGK SILZKAR8G7Y (93710)

 

Did I read the title of this thread right? Are you at 93k miles? If yes, you must be one of the highest mileage Defenders out there. How has the reliability been so far?

 

Yes, just over 93k miles. Though I purchased it around 80k miles. Here is a list of current issues. Some of these are common defender issues. My new 21 p300 had the leaky air suspension - replaced under warranty.

1. Software fails to update. While charging, with a new odyssey battery, wifi connection, etc. all fail.
2. Left rear door hard to open
3. Front air suspension leaks and lowers over night
4. Passenger door lock is inoperable - at least the alarm goes off when it is opened
5. Misfire (most common using cruise control) - will trigger limp mode.
6. Rear diff clunk when pulling off - this has been a feature all my e-diff equipped rovers.

I replaced the spark plugs and PCV valve in an attempt to resolve #5. So far so good. I have a 1600 mile road trip this weekend, so I'll find out for sure.