Cross reference for the Bosch spark plug (heat range 8) matches Champion 11, 12 (OEM spec). Reason I asked is because the insulators are so black that they might be too cold, but no. So, could be a fueling problem (running way rich, like Extinct mentioned above), or burning lots of oil. Either way, the plugs do not look good. Will take some investigation to track down the issue, could be O2 sensor related or MAF if running rich. Can you scan O2 sensors for real-time data, and long and short term fuel trims? That might help with the misfiring diagnosis effort, but might only be a coincidence.

 

Thanks... going to compression check it this weekend and hopefully get that off the list. I've overheated cars before and it seems extreme to blow a head gasket that fast. It's an old dog tho. Oil is clean, no coolant mixing, exhaust is clean. I'm going unhook all the O2 sensors and cleans the MAF. It should run relatively okay with the O2 unhooked which may give me some insight. I have a okay scanner... i haven't used it a lot of diagnosis. I am fairly okay with part trouble shooting normally, but this one has me up against the ropes. I'll hook that up see what i do.

Thank you all for the help. I purchased the truck and put a lot new parts in for maintenance and had it running really well, before my water pump seal blew. Like most of ya'll ... the Land Rover will be revived come hell or high water.

When i throttle is just bogs down...

 

UPDATE:

massive vacuum leak... my brakes are completely useless. I think i'm going to rip the intake off and install new gasket, check ignition system whiles in there area.

Failed seal on the intake would create a major vacuum issue extending to the break booster yes?

 

Yes, but seems unlikely it would be the upper one unless the bolts are loose. It is a metal gasket, extremely rigid structure with an excess of bolts. And no way would I get all the way down to the lower intake gasket and not do hg because at that point only exhaust manifolds and heads are left to remove.

 

Yeah that makes sense on the lower ... I'm confident going to the lower gasket, but I've never done a head gasket change on a car engine before, just smaller scooter engines. I suppose it's not too much more work as you said? I just did the upper months ago, prob go a lot faster this time. Is it standard to resurface the head if i pull it?

Appreciate the help extinct - your stockpile of Rovers says it all!

 

If it runs now at all you could easily find the general, if not exact, location of a vacuum leak with a quick spray of your favorite flammable liquid. I like using carb cleaner for that. There is also the smoke test. I like a little more certainty to my testing before I rip into things. I HATE redoing things because I failed to check out what I could have easily done.

Spray around with carb cleaner, and do your comp/leakdown test. You might learn that you have both a vac leak AND a need for a HG. Test first, wrench second.

 

i have a habit of wrenching first... never used a leak down tester - you tube is it.

 

If the brake booster is causing the vacuum leak, a simple test would be to cap that vacuum line and see if the engine idle changes. In general, capping all the external potential vacuum leaks (e.g. carbon canister, brake booster, PCV, FPR) is easy and will help rule out external problems. All those external devices are exposed to engine bay heat.

 

The engine overheated, blew my water pump seal. Fixed that and now have misfiring and sluggish running and bogs down when i throttle it.

I just noticed the brakes have zero pressure - not even working so which led me believe the one of the intake manifold gaskets blew. The vacuum pressure is leaking there so it can't push to the brake booster. I think Extinct is right on the lower intake manifold gasket. I've done this job on it before the upper intake gasket - just before the overheat. It's not too bad and i can get through way faster now... knowing my way around.

Some air leak in the manifolds seals.

 

Does not hurt to cap all the vacuum lines as John Zo suggest. Although rarely would an engine overheat affect brake booster or other engine vacuum devices, but does not hurt to test.