Hey everyone,



I recently tackled the massive job of replacing the passenger-side valve cover due to a broken PCV outlet. No idea how it broke, but it did — and while I was in there, I figured it was the perfect time to upgrade the cooling system since the supercharger and most of the cooling components were coming off anyway.

Here’s what I ended up doing:

• Installed RXK’s black metal front coolant pipes
• Fitted the EuroAmp rear metal crossover tube
• Replaced the water pump with OEM new.
• Installed a metal oil cooler crossover pipe
• Swapped in a new brass fitting on the water pump

Now, I should mention — I’m working with a smashed up spine and limited physical ability, so this was a huge undertaking for me. It took about a week of evenings and two full Saturdays (plus a Sunday), but I got it done.

Sort of.

Today, I finally got everything back together. Vacuum-filled the cooling system — held 24 inHg for over 10 minutes with no issues, so I felt confident there were no leaks. Topped it up, double-checked everything, and fired her up.

Immediately got a Check Engine Light. Shut her down, and noticed the radiator fan kept running for about 30 seconds — while the engine was still cold. That’s never happened before.

Scanned the code and got P0118 – Coolant Temp Sensor Voltage High.

My scan tool shows the coolant temp sensor is stuck at 4.99V — not moving at all.

Now here’s where I am really not happy: I fear the coolant temp sensor is located on the rear metal crossover tube from EuroAmp… and I’m pretty sure I didn’t transfer the OEM sensor from the original plastic unit.

So, my main questions are:

1. Is the coolant temp sensor located on that rear crossover tube?
2. Can it be replaced without removing the supercharger? Because honestly, I’m dreading the idea of pulling all that off again.

As a side note — I did install a VAP symposer delete during the job. I’m hoping that might be the saving grace if the cross over is where the sensor is and that extra room will allow me to get it done without re-disassembling everything for a second time.



Any insight, experience, or suggestions would be hugely appreciated.

Thanks in advance!

 

1. Yes
2. Yes

I found it hard when I changed the rear water manifold with the SC on. Cursing and such! The temp sensor takes a good bit of force to twist it out and re-install it. You may need to remove the entire rear water manifold to get to the sensor? Not sure it's possible to twist it out in place?
I don't know I installed the manifold with the sensor already in place. Very little room.
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Hey Kevin,

Yeah. This manifold had the sensor pre-installed by EuroAmp. Since it was a new sensor in a new metal manifold, I didn’t see the need to swap my 79,000 mile temp sensor.

I’ve emailed EuroAmp to see if they have anything to say…

What I suspect has happened is a non-OEM / JLR / Bosch or whatever the OEM sensor is wasn’t installed show she’s throwing a hissy fit - like always.

I just cannot pull all that stuff off again… ugh. Time to practice on the plastic one I tossed in the trash.

 

Watch this video may help,the sensor can be removed without removing the supercharger or heater manifold

 

Yeah. I looked at my plastic manifold that’s not on the car last night to see how to do it. The problem is I can see the sensor from the drivers side of the car. I can see that it’s plugged in etc just for the life of me I cannot get my hand / arm down that low to even get a finger tip on it.

You video did show me that there’s two sensors that both look the same. I don’t know if the problem is in the rear crossover or the thermo housing.

I am also not sure how to check it.

Interestingly enough - my temp gauge in the dash display still works. It rose to working temp while I was letting her run yesterday. That means that one of the two is working correctly. Just not sure which one.

 

If the sensors look identical I'd be tempted to swap your old sensor out with the one in the thermostat housing first.

I don't see how you can undo the rear manifold without removing the supercharger and symposer piping. Just the fuss of trying to work around it would be worth pulling the blower again.

Did you reattach the ground from the harness to the passenger side valve cover bolt?

 

I’ve already swapped the sensor on the front thermostat housing, and it made no difference—so it’s definitely the rear sensor causing the issue.



I don’t have a symposer installed, but the mounting bracket is still in place since the wiring loom bolts to it. If that bracket wasn’t there, accessing the sensor would be easy. I might just remove the bracket first and then try tackling the sensor again—need to take another look at it.



And yes, the ground harness is connected. Just another one of those small, annoying things. LOL

 

I have done the rear water manifold with the SC in place. It's entirely possible but a really terrible job! I also removed the Symposer with the SC on. Again terrible job to do.
If possible removing the SC will allow many other parts to be replaced. Think of it as a grouping the repairs to avoid duplicate work if something else fails or leaks.
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That’s exactly why I’m so irritated. Since I had to replace the passenger valve cover, I went ahead and replaced all the cooling hoses and upgraded every single cooling pipe to metal. I did everything by the book—LOL. I even capped off the symposer port at the firewall with a nice silicone cap and hose clamp, since I did the VAP delete kit.

I really don’t want to go back in and do it all over again. I think I can remove the symposer mounting bracket to get access to the sensor—that's what’s blocking me right now. The mechanical side of it is what it is. The sensor needs to be replaced, and I’ve got a new one on the way from JLR. If I’m opening it back up, I’m not dropping in some old part.

I was hoping it was just the thermostat sensor that failed, and the timing just sucked. But EuroAmp confirmed they’ve had multiple sensor failures before—and apparently mine is the first one of 2025 they’ve seen. Definitely not a factory JLR sensor. Probably a Chyna-special, if I had to guess

 

chinese heater manifold came with a chinese sensor..... not to be that guy but you did it to yourself

 

Aaron (SuperChargedXJR) got me thinking about temperature sensors and why there are apparently 2 identical sensors on the 5.0L SC engine? What do they control?

I have both the front and rear sensor sitting on my bench and they are OEM Jaguar parts. The first thing is there is no information or markings of any kind on either sensor! What stumped me for a while is the front sensor is NEVER mentioned by Jaguar anywhere! In fact the front sensor comes with the lower radiator hose only. Kind of like what they did with the radiator as with that you can't order the drain plug separate. It ONLY comes with a complete radiator.

Again note that nowhere in the parts description of this hose assembly does it note that is ALSO contains a temperature sensor!

Here are the two places the sensors are mounted. Again note they have identical electrical plugs and I even measured the resistance and they appear to be identical too and both read around 27K-29K ohms at room temperature. Does anyone know what they should read at different temperatures?

One is black and the other grey plastic.







We do know that the dash board gauge is run by the front sensor and the computer is using the rear sensor from Aaron's testing and problems. So we think the P0118 code points to the rear temperature sensor. I did find a post where an after market scanner came up with temp sensors 1 and 2 but he never got any replies on how to identify which was #1 and which was #2.

I wonder what SDD would show if the front sensor was bad?
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Interesting.

Both of my OEM sensors are black. The sensor that came in the EuroAmp housing is gray.

I’m still waiting on JLR to deliver the new OEM sensor so I can swap’er out.

My Foxwell scanner gives no indication of sensor location when pulling DTCs. ALLDATA does not help with my code on location either.

 

As mentioned, both sensors are identical. The rear sensor is ECT 1 - Engine Coolant Temperature 1 - and the front is ECT 2 - also referred to in the workshop manual as Radiator Outlet Temperature Sensor.
ECT 1 (rear) drives the coolant temperature gauge on the dash and together with ECT 2, provides the ECM with some of the the information it needs to keep the engine operating efficiently..

If you monitor the ECT 1 and 2 values via live data using a suitable diagnostic tool, you will see the ECT 1 values increasing after starting the engine while ECT 2 remains fairly constant (around ambient temperature if staring from cold) until such time as the thermostat starts to open. ECT 2 will then start to increase. Once the engine is at normal operating temperature, ECT 1 will remain in a narrow band and ECT 2 will fluctuate depending on air flow through the radiator and thermostat opening.

If one studies the coolant flow diagrams together with the thermostat description in the workshop manual, it will make more sense.

It gets more complicated when the car it fitted with the electric thermostat but thats for another topic.

 

Interesting and great info. Aaron had a error code P0118 for the coolant sensor BUT his dash gauge was reading and acting OK? From what you said I "think" that error should make the dash gauge act up too?

Does SDD have different error codes for each sensor?
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I wonder if the connectors got mixed up on the rear ECT. The symposer electrical connector is identical to the ECT connector and is quite a common mistake. Not sure if that will give you the P0118 code but its worth a look especially considering the symposer delete.

From the workshop manual

If there is an ECT 1 fault, the ECM adopts an estimated coolant temperature. On the second consecutive trip with an ECT 1 fault, the ECM illuminates the MIL (Malfunction Indicator Lamp).

 

That is great information and thanks much!

It would explain some odd things too. I was curious and looked up the symposer plug and yep it's identical to the temperature plug! I had never looked before.
And they are close together as GT40 said on the rear water manifold.

I posted above the two temperature sensor plugs and they look like this.





Then the symposer plug that's left over after removing the symposer.





It's kind of an accident waiting to happen if you don't know this. If the plugs got swapped would it set code P0118? I think it would.
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this MUST be what happened. New sensor in. Same error. Still reading -40.

I MUST have the wrong plug.

 

Confirmed.

You CAN mix the two plugs. If you do a symposer delete - while doing the rear crossover don’t mix them up.