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2002-2005 Range Rover MkIII / L322
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Discussion Starter #1
In an attempt to bring oil pressure up at idle, I installed a lower temperature thermostat. This is a 2003 Range Rover with the BMW 4.4L, 166k miles. The stock thermostat is 105 deg C, I ordered an 87 deg C. Supposedly, some models/years/climates used 87 deg C stock, and the switch to 105 deg C was an attempt by Land Rover to increase mileage. We do a lot of towing, and having coolant 20 deg C cooler means the tranny and engine oil should also be cooler. I'm willing to sacrifice a bit of gas milage for longevity at this point.

At idle, with the engine hot, my oil pressure would drop down to 7 psi. I never had the oil light come on, but I would hear slight valve tapping when hot, mostly noticeable if I was driving next to a wall (drive thru). I would also get vanos rattle on start up if we had previously towed our trailer. Both Vanos have been rebuilt, I'm thinking if the engine had low oil pressure on shut down, it could be a contributing factor to the rattle.

The engine cold always sounds silky smooth and quiet. I just started noticing the noise after replacing chain and chain guides and thermostat. So far, after installing the 87 deg C thermostat, oil pressure is up about 4 psi, it doesn't drop below 11. I'm currently running Mobile 1 20w-50, but plan to switch to 5W-50 next oil change.


Old thermostat housing, and new thermostat sandwiched between mounting plates.

The thermostat kit includes several plates pinned together. Installing the kit requires cutting off the castings that hold the thermostat in place. Pic below shows one leg cut off.

Sanded down the two posts and snapped off the thermostat heater. The wires are potted in, so it should be water proof, I dabbed a bit of JB weld on top for extra assurance. So far I haven't had any check engine lights due to the thermostat heater being removed.

Kit comes with longer bolts to account for all the spacers.

Thermostat before

Thermostat after

Since the thermostat housing used an o-ring to seal, I installed both gaskets on the non-oring side.

Highly recommend this o-ring lubricant, especially on the clip on hoses.

2002-2005 Range Rover MkIII / L322
5,384 Posts
When I did mine, I found that coolant had been leaking past the heater element and out the plug on the outside. I removed it, replaced the O-ring, refitted it and filled it with epoxy as well.

Note that you will get a fault code on the heater circuit when you do a scan.

L322 Thermostat Connector 1.jpg

L322 Thermostat Connector 2.jpg

If I was doing another car, I'd just buy the BMW 740D 88 deg C thermostat housing (BEHR thermostat model TI 3288
They don't have the heater connection and it's a straight replacement.
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