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The supercharged Jaguar XJ X350 models (the XJR and Super V8) have an electric pump which is used to circulate coolant around the intercooler, thus keeping the temperature as low as possible to ensure the charged air is cooled to maximise air density.
However this pump can fail, triggering a 'Restricted Performance' mode and a P2601 (coolant pump control circuit range/performance) DTC code, readable via the OBD diagnostics.
Note that sometimes this gets confused with the Auxiliary heater pump, present on V8 models - the aux heater pump is smaller and located halfway down the radiator, whereas the supercharger coolant pump is located underneath this, at the bottom of the radiator.
My understanding from reading lots of information about this issue is that the diagnostics code is not triggered by the pump controller detecting an abnormal current draw from the pump motor, but rather by comparing the input from different temperature sensors and establishing that if the intercooler temperature is too high, then the coolant pump must be faulty.
Below I shall describe the process I took when replacing my supercharger coolant pump after experiencing more frequent P2601 diagnostic trouble codes with my Super V8 going into Restricted Performance mode.
First job is to remove the plastic trim panel which covers the width of the engine bay at the front, covering the headlights and radiator grille
Remove the radiator grille and the two air deflectors on each side of the grille
Next unbolt the 'radiator splash shield' which is the plastic undertray at the front of the car.
You can then remove the plastic bumper cover, by pulling away at each side to release the clips. I find that spraying the join between the wing and the bumper with copious amounts of WD40 helps the bumper cover release much easier.
There is no need to disconnect the washer jet hose or electrical connectors, you can simply swing the entire bumper cover out of the way with everything still attached.
Underneath the radiators there is another plastic splash shield. This can be removed by pulling downwards - there is a wiring harness attached to a hole on the left side of the shield (as you look at this picture), which can be detached with a pair of pliers then you can put the shield aside..
Now you have access to the pump. You can see it at the centre of this image with the two coolant hoses connecting to it.
I think that my pump may have been replaced at some point in the past, as it's only attached with a cable tie which I'm not sure is the standard fitting method.
I chose to use hose pinch-off pliers to stop the coolant flowing out so that I could replace the pump without draining the coolant. I found that my pinch-off pliers didn't clamp the hoses sufficiently unless I added some extra plastic packing, so I lost a little bit of coolant while I found this out and solved it!
Once the hoses are pinched-off correctly, you can release the two hose clamps and disconnect the inlet and outlet coolant hoses.
At this point, I cut the cable tie retaining the old pump, and removed the pump by dropping it down, and rotating and manipulating it so that the outlet pipe cleared the air-conditioning line.
At this point I found that the old pump did not have a removable power connector, the cable was hardwired at the pump end - the other end was completely in-accessible and in fact I couldn't trace it at all, it disappeared into the engine bay somewhere.
So my only choice was to cut the old pump off, and hard-wire the new pump in a similar way, as I had no connector with the new pump.
The wire I chose was a little larger than necessary, but was a size I already had available that had at least the same current carrying capacity as the existing wire. I started by soldering the positive and negative wires to the pins on the pump body.
I then individually heat-shrunk both of these wires.
Next step was another larger diameter heatshrink covering the pump socket body, and then a slightly smaller diameter to reduce this down to the diameter of the two supply wires.
A couple of cable ties should make it sufficiently waterproof.
Then on the wiring harness where I cut off the original pump I repeated this again, soldering and heat shrinking the new pump wires.
Finally a larger diameter heatshrink over everything will keep the connections watertight.
Refitting the pump turned out to be a little trickier than anticipated. This is mainly because the new Bosch pump (0 392 022 002) has a slightly larger diameter than the original Hella pump. (It also has a higher flow, which apparently improves the cooling performance).
This larger size meant that it was a bit of a squeeze into position, but as the previous pump had already been attached using a cable tie, I used the same method. I believe that originally they would have been attached via a metal bracket, but don't know this for certain.
I would advise testing the pump before re-assembling - just switching on the ignition will activate the pump which you can feel, only let it run for a couple of seconds without the water hoses attached. I found after testing with the pump mounted back in place that it no longer worked - I had inadvertently broken one of my solder joints trying to manipulate the pump into the very tight space. Better to test and fix before everything gets bolted back together!
The plastic shield under the radiators (underneath the actual 'Radiator Splash Shield') needs a bit of modification as the new pump is larger than the old and so won't go exactly into place. A small adjustment with a saw solves that problem.
All in all it was a little trickier than I expected, mainly due to the large size of the Bosch pump vs the original Hella making the refitting pretty awkward, and the fact that the wiring harness did not have a connector to the pump so needed to be hardwired.
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