Hi,
I have an '05 LR3 with 79k miles. Recently the engine light came on and when I took it to Meineke for a diagnostic I was told there were 3 error codes: 2 are related to the engine coolant temp and coolant performance and the 3rd is the catalytic converter performance.


I did some research and in speaking with the tech they stated that there is NO leak, the engine temp gauge is in the middle (normal) and my heat is working fine. The Meineke tech told me if the thermostat was bad or stuck open like I see in some forum answers it would affect my heat (which like I said is cranking fine). He cleared the codes to see which came back and 3 days later the engine light came on again


Any ideas? I'm about to take it to a local mechanic this week for a coolant flush... should I?

 

Based on description, the coolant fault is probably a P0128, and will most likely be fixed with a new thermostat, the seal tears, and is perceived open.

For the cat code, P0420/430, nothing but low cat efficiency can throw this fault code, but that is usually caused by an outside cause on this engine, such as poor fueling, incomplete combustion or burning oil.

How's the oil level? When was it changed last?

 

Would there be other symptoms with needing a new thermostat? My heat is working, the vehicle isn't over heating at all so Meineke didn't think it was a thermostat but I was going to replace it anyway since I see that they can be a problem (and look relatively easy to replace yourself).


As for the catalytic converter- the day I brought my car in to get the error codes diagnosed I also had the oil changed and I am religious about having this done every 3k miles, the levels have been fine and I don't see any dark exhaust like oil would be burning. I did have them reset the codes and am taking it back again so I'll see if that code came back (right now I don't know which codes came back, I just see my engine light on).

 

The symptoms related to failure, both burning oil and a stuck open thermostat that you mention don't have much bearing on this vehicle, and are based on older engines that don't have anywhere close to the monitoring and ability to compensate as this one does.

If you are positive that you have not been burning oil, based on consumption, not the lack of smoke, then you may be due for a tune up, as incomplete combustion (which will cause improper fueling) is also another major cause of cat efficiency being low.

The t-stat is being perceived as stuck open, that doesn't mean that the engine is not getting up to temperature, just that it isn't in the correct amount of time, based on various other inputs. There is a very small chance that the OCMV is failed(secondary t-stat for the oil cooler) but you are most likely looking at a failed thermostat.

 

To my mind, the thermostat is not easy to change. The link below is a good one in that it shows the second try to get it right. It seems LR fixes always have a bit of a twist to them. Also getting the air bubbles out can turn the refilling process into a multi hour task and use the opportunity to pour in all new coolant.

How To: Replace your Thermostat

If you are looking for an easy way to change your thermostat, install as below the complete assembly, LR part number LR005631. It solves two problems, getting the thermostat install correct and also the plastic ages so new plastic solves the cracking problem that shows up with time. Also the cost of the assembly is only a few dollars more than a thermostat by itself and the install labour is less and easier.

Also replace the bleeder tee, LR027661, as it is first to crack.

 

Yeah I just made an appointment with my local mechanic to get it done professionally I have an '05 4.0 v6 and it looks like the ones you listed are for a v8? I bought one that's an upper/lower hose assembly that has a thermostat as well as it looks like that's what I need. I'm also getting the front air suspension filters/beads replaced as that just went as well!

 

Yes, you are correct; the jpg is for the 4.4 litre V8.

I do not know much about the V6 other than it is a good engine.

I am not so confident about the new engines that Land Rover is now introducing as their contract with Ford to build engines has now expired.

Replacing the air dryer is a good move. My view is that most of the Hitachi air compressor problems are really air dryer related and that the air compressor itself is usually still OK.

The complete air dryer part number is VUB 504700 but may have been discontinued by Land Rover as they now stock only the AMK compressor.

Aftermarket bead replacement kits are available however.