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Discussion Starter #1
Hi Everyone,

I had a shop replace the thermostat in my 2006 Range Rover Supercharged. 144k miles on the vehicle. Fault codes prior to dropping it off were P0171, P0174 and P0128.

Shop replaced the thermostat ($560 total) and stated when they performed a test drive P0128 came back. They cleared it and it didn't come back after another test drive. Drove 45 minutes home without issues.

I started it today and drive about 10 minutes and noticed the thermostat gauge never got above a little over 1/4, then the check engine light came on. On the trip home I was watching the thermostat gauge and it properly got up to 1/2 way showing what I believe would be normal operating temperature.

Any ideas on what would cause the vehicle to intermittently not get up to temp? I can't help but feel like I paid $560 to replace a thermostat that may have been fine?
 

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Discussion Starter #2
I've done some more reading and it sounds like PCH501310 - the thermostat to radiator hose might be to blame? Anything I could visually inspect on the hose to confirm or do I just have to buy it and replace it and hope? How hard is it to get to?
 

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2007 Land Rover Range Rover 4.4
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Hello I had this EXACT same issue! And even did the same thing as you and pay to have the thermostat replaced. After TONS of research it turned out to simply be this hose which has a second thermostat in it (part number: PCH501310)
 

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Hello I had this EXACT same issue! And even did the same thing as you and pay to have the thermostat replaced. After TONS of research it turned out to simply be this hose which has a second thermostat in it (part number: PCH501310)
Hi, thanks for the reply. I'm thinking I might as well order the hose and give it a shot. Did you install it yourself? I'm wondering how hard of an install it is. So there's an actual second thermostat in the hose?
 

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2006-2009 Range Rover MkIII / L322
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It's the thermostat for the oil and transmission coolers, and it does bypass some of the engine thermostat water flow so if it fails open you get an engine that takes a longer time to heat up (usually only noticeable in cold weather) and your transmission runs cooler than normal.
 

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Discussion Starter #6
It's the thermostat for the oil and transmission coolers, and it does bypass some of the engine thermostat water flow so if it fails open you get an engine that takes a longer time to heat up (usually only noticeable in cold weather) and your transmission runs cooler than normal.
Thanks! Any idea how hard it is to replace? I'm going to take a look today to see if I can spot it.
 

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Discussion Starter #7
I just took a look in my engine bay and not immediately seeing a hose which looks like PCH501310 coming from the radiator, so I'm assuming this isn't an easy hose to replace? Any suggestions for where to look to find it?
 

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Glad this post came as I get the same thing on our 04 which is of course BMW and I did not do the trans t stat yet so I see both have a similar set up. On ours it's of course tied in to the trans cooler so follow the pipes till you get the junction of at least 2 small hoses. I have not looked at our 08 to see a similar junction tube. I do know that the quick connect couplings can get jammed and need twisting back and forth sometimes fof them to release. Have the Dow Corning silicone grease on hand to lubricate the o rings and the joint on reassembly. Makes it sweet but always takes longer than you think. Clip all small hose back into the rad shroud to avoid potential wear thru failure. Btw if o cleared the 128 regularily the 171/4 ones did not pop up. I really must try it on our 04. Will likely have to pull the splash shield and go under. Will also need to drop the rad fluid first and then fill properly once reconnected.
 

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2006-2009 Range Rover MkIII / L322
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I think the oil and transmission coolers on the SC range rovers have their own air cooler coolers mounted out in front of the engine radiatior. So if its there its on the bottom of the left side of the radiator, there are two 2" hose connectors. The bottom one has what looks like a hard plastic elbow held on with a big clip that slides thru 2 slots on the elbow, and fits around a lip on the end of the radiator connector. The hose bends 90 degrees and there is a t tap off the side going to the oil cooler, and then another hose fitting straight ahead the connects to a hose that runs up to the thermostat housing at the front of the engine. Its tucked in just above the oil filter. The other 2" connector above that one (just a hose with a clamp) is the return from the main engine thermostat. At least thats what it looks like on a 4.4L 06. Should be the same on the 4.2L
 

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2007 Land Rover Range Rover 4.4
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Just thought I throw my 2 cents in again... if it’s pretty much the same as the 4.4 then it is very easy to do... I have very little practice with cars in general (working on gaining more practice) I did it in my garage... my only advice is to make sure you bleed the system properly... I also squeezed the upper rad hose to get some coolant in the system.
 
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