I've got an 03 Land Rover Discovery Se7. It started getting really bad mileage (4.8 miles to the gallon). It was due for new O2 sensors, so I ordered them already. I was under the truck this morning and found that the weld on the back of the RH Catalytic converting is leaking. Do I need to replace the whole thing of can it be welded?

 

How many miles on the truck, you may have some warranty coverage left on them.
Yes, the cats will need to be replaced.

 

Sorry, forgot to mention that it has 90,500 miles

 

Too bad, out of both the state and federal warranty.
Get them replaced, then find out why you engine was running so bad it killed them, fix it, or it will happen again.

 

do you think it was caused by the engine. It's only the RH converter that seems to have a weak weld. The LH converter is fine.

 

With your mileage, you should replace both and yes, it was caused by your engine. How has it been running, when was it last tuned, has the check engine light been on at all?

 

Interesting. I've only had this LR for about a week. The previous owner had it serviced at 86,000 (plugs, cables, flush, etc) The "service engine soon" like did come on the second day I owned it reveiling a P1170 code (O2 sensors). I've already ordered replacement sensors and they are on their way.

 

Just throw in the new O2's when they get there and make sure that you use premium gas, drive it for a few hundred miles and see what happens.
Bad O2's will reduce your MPG. Check your air filter too. And your tire PSI, they can look good but still be under inflated.

 

Is it just the weld where the cat meets the back half of the y-pipe? If so, I'd say just to give it a hit with the welder and close it back up...might have just gotten a bum weld by someone on the Friday afternoon crew. A bad weld does not imply that the converter itself is bad...but you are getting close on mileage (I think 100k is the usual change point).

My .02c.

 

The service you have mentioned should have been done at 60,000 miles, they may be part of the problem.