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2006-2009 Range Rover Sport
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12 Posts
Discussion Starter #1
Hello friends,

Thanks for all the great insight in this forum. Quite helpful. I can't seem to find an answer to my overcooling issue.

The issue started with a CEL and P0128 code. The T-stat was bad (the seal was torn) and I replaced it and topped up coolant.

CEL light came back on same code...replaced the ECT sensor at the manifold...CEL came back on...replaced the temp sensor on the oil cooler...CEL came back on

Replaced all the coolant hoses, water pump, drained coolant, and replaced with Pentosin...went through the bleed procedure...CEL has come back on same P0128 code.


When the first started, the coolant never gets higher than about 160* F...I can do some driving then rev up the engine and get the temps up to 180-200*F to get the T-stat to open and you can see the temps going back down (via OBDII scanner).

2 T-stats, 2 ECT sensors at the manifold, 1 oil temp sensor, all new coolant and hoses...This is nuts!! Any other ideas here?

Local indy shop wants to replace the manifold...there are no leaks from there and the T-Stat and the temp sensor have been replaced, not sure how replacing the plastic crossover manifold could be to blame but that is literally the last thing in the cooling system to replace.

Onward,
J
 

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Registered
2006-2009 Range Rover Sport
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12 Posts
Discussion Starter #4
Great feedback...I did check the t-stat a couple times, first install it was crooked and definitely not sealing...i re-installed it and made sure it was seated...a new t-stat came in the kit with the coolant hoses so I may just replace it since it’s here.

The t-stats are all OEM LR brand from AB I believe they are 204*.

Checking the engine temps with the IR is a good idea.

Is there anything else in that coolant manifold other than a temp sensor and the t-stat??
 

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JACK'S GRANDAD
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9,244 Posts
You first need to confirm the temps with an IR temp gun. It's the first thing I do when a sensor is reading high or low temperatures. Saves a lot of time and money.
Far too many "techs" and owners alike, just want to look at the screen instead of doing a little actual fault finding. The owners I cant blame, they don't know any better, but the techs? Ugh
Shoot the IR gun near the sensors to compare apples to apples.

Martin
 

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2006-2009 Range Rover Sport
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12 Posts
Discussion Starter #7
All great ideas. I checked the t-stat and it was seated properly in the “bushing”/metal cup...I went ahead and replaced it since I had one on hand. Double checked the seat...looks good...see pics. I also checked with a laser thermometer and they temps seem pretty close.

Could there be an issue with the fan or fan ECU? The fan seems to kick on even at low temps (140*)...I just went on a 5.5 hour road trip in 55* weather and the coolant temp from OBD never went above 170*.

When I pulled the hoses off the t-stat side there was not a lot of spillage which leads me to believe the tstat is not stuck open spilling coolant through that side.
 

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JACK'S GRANDAD
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9,244 Posts
The fan theory is easy. Unplug it and see if it heats up or not.
Kicking on at such low temps tells me to check if there is air in the system first though.
 

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2006-2009 Range Rover Sport
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12 Posts
Discussion Starter #9
You may be right about air. I followed the bleeding instructions in the workshop manual. Steady stream of coolant coming out of the vent hose into the expansion tank. I did replace the plastic T under the housing with a brass fitting. I have seen people just do a brass coupling there but I can get coolant out the T so I wouldn’t think that would be the problem. But maybe?
 

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Administrator
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27,819 Posts
If you had air in the system you would be overheating, not underheating. With air, the cooling system can not pressurize.
 

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2006-2009 Range Rover Sport
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12 Posts
Discussion Starter #11
Team, this issue has not gone away...next thing to replace is the entire thermostat housing/manifold. That will be in this week.

This requires at least removal of the throttle body. Has anyone done this job? Anything I need to be particularly mindful of?
 

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2013-2015 Range Rover Sport
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480 Posts
no, no: what happened when you unplugged the fans? I would bet that module is bad and your fans are coming on too soon. Next step would be to try running it w/o the TST (you are getting pretty handy at changing them quickly!).
 

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2006-2009 Range Rover Sport
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12 Posts
Discussion Starter #13
Unplugging the fan did not do anything remarkable with the temps. The coolant stays around 160 degrees F. I noticed it would go higher after running and sitting and starting again. The fan still spins since its on a belt but does not kick into a higher rate. The same Thermo code is thrown. Net-net, no quicker rise and certainly no rise to 180-200*F which I assume is "normal operating temp".

What path are you going down with the removal of the T-stat? See if we see the same temps?
 

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2006-2009 Range Rover Sport
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Discussion Starter #14
Ok team..I think it’s fixed.

I replaced the Tstat housing and the temp sensor using the one that came with the manifold...I saw no difference between either item but something obviously fixed it.

I didn’t replace the whole manifold, that looked like a big project I was not ready to take on.

I used OEM tstats and sensors do not sure what fixed it...I may mess with it this weekend to see if I can nail it down...the not knowing is killing me.

Thanks for all the help!
 
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