Hello All!

I have an interesting one here. Before I go ahead and start looking all over the cooling system, I wanted to seek some advice and to check if someone experienced this or have some guidelines.

Just a bit of context. We live within the Colorado front range, south of Denver, so we experience changes in temperature, altitude (and thus atmospheric pressure), humidity, etc, etc so our operational environment is far from sea level or textbook conditions. Our LR3 is our family travel vehicle, so it hauls people, bikes, camping gear and anything needed for a typical weekend outdoors.

This last weekend during our trip to Winter Park (yes we go to Winter Park during the summer to the Bike park) we experienced very drastic fluctuations in the operating temperature of the truck. Starting from home at the highway (I-25) it was as normal steady slightly bellow the half of the scale (for reference slightly below the 1/2 gas tank mark). At certain point on the I-70, the temperature wend DOWN (yes DOWN opposite to overheating). I thought that due to the fact we had our climate control in auto and the outside temperature dropped quite a bit and the heat went on, that the heater core was cooling down the coolant. The concern started when the needle went down almost to the point of 1/4 of the scale. Before turning into HWY 40 and starting climbing to the pass, the temp recovered almost to the normal, but still a bit below. Then, while climbing to the pass the temp went passed down the 1/4 mark and more or less stayed like that till we reached our destination. First thing I did was to check the engine bay, and surely the coolant hoses were warm (not as hot as normally), level in the expansion tank was over the cold level (as normal) but surely truck felt colder. Next day did a short run to a store, temperature went almost to normal, but definitely rising slower.

Coming back, the truck heated up normally climbing to the pass in the opposite direction, and then, same story. Temp went down, then went a bit up on the I-70, down again and then went up in the I-470. Running back on the I-25 temperature reached normal (slightly below the half mark) and stayed like that for the rest of our run till home.

So, truck is not overheating but getting colder, which I don't think is normal. Few weeks back, we went to Medano pass at Sand Dunes, no issues. Also for context, we haven't experienced yet a full feature Colorado winter with the newer to us LR3 because it was going through the repairs, previous owner neglected maintenance, fitting. So I have no full data of cold temp behavior.

Also for context, new radiator (also new oil cooler), fresh OAT Zerex Dexcool filled with vacuum refill kit, new expansion tank, most hoses changed. Never overheated (at least under our ownership). Engine runs steady, not rough, MPG on the high 17s on the highway (depending on if the gas is from Costco, Valero or Conoco).

Any ideas about what are we looking in here, dying thermostat, failing temp sensor, or some Land Rover feature that I'm not yet aware about?

Thanks!

Dario

 

These things are all but guaranteed to have air bubbles no matter what you do when refilling the coolant.

After your next drive try opening the t bleeder on top of the TB and the expansion tank bleeder to make sure. Also with the bleeders closed unscrew the expansion tank cap (with it running), that will burp any air as well.

Other thought is the thermostat stuck open or a dead/dying coolant temp sensor.

 

Thanks Blackngold. If my understanding of the design of the cooling system in the LR3 is correct, air in the system should be more consisting with overheating, not with running cold. So, I'm inclined to the theory of the thermostat getting stuck open. I thought about it, but the puzzling part is why all the sudden it goes back to normal consistent operation. It was like ... it didn't like a section of the road ... Do you guys recommend getting the whole housing and thermostat or just the thermostat? EDIT: Not looking to throw in money just because, but reliability while traveling with the family is of paramount importance!

 

If you have a GAP tool (or other scan tool) it's worth taking a drive and using it to see the live values of the coolant temp. If they're normal and consistent then you know it's a gauge cluster issue. If they're funky too then it's a system issue.

Before throwing parts at it I'd inspect your thermostat and give it the boiling water test to confirm it's shot. If you replace it I'd opt for getting the housing too. It's more costly but the thermostat housings in these love to crack

 

I've had the thermostat fail open before. In my case after enough time it threw a code. As other posters have suggested if you have a GAP tool getting live values would be my next step. If you want to blead air again from the system, there's a really good youtube featuring Doug from Atlantic British on how to bleed air out of the LR3 cooling system. His approach has always worked perfectly the first time for me, but does require staying with the car as it comes up to temp with the coolant cap off and then shutting off the car as soon as the thermostat opens (otherwise you'll get a mess).

Edit: oh one other thing to listen for is the fan noise, sometimes the fan electronics can fail sending the fan into "full on" mode when it is not required. I have had that error too.

 

Thermostat sticking open sounds rational to me. Definitely buy the whole housing and OEM or OEM equivalent. FCP sells an OEM one. I bought a URO thermostat assembly for my 07 and re-replaced it a year later. I was getting a DTC for not warming up fast enough with the URO model. You’ll also find that housing plastic is brittle like your radiator probably was too. It’s a good time for a water pump too! Sorry to pile on, but…