Coolant issues

  • 2015 JAGUAR XF
  • 3.0L
  • V6
  • 4WD
  • 12,200 MILES

I recently took my vehicle in for an overheating issue. When driving it, the engine light came on and indicated that the engine was overheating. I had it towed to the dealership for inspection and repair. I was initially told that the issue was related to the fan module. The plan was to replace it and all would be well. However, I reminded the technician that in the coolant reservoir there seemed to be an separation of the liquid occurring. The bottom 25% of the liquid appeared orange as the coolant should, the top 75% was clear like water. I had a theory of why that occurred considering the car was overheating but the technician said that without prior services records he cannot ascertain why this occurred and encouraged me to authorize a flush (which would not be covered by the warranty). I believe the issue to be a direct result of the engine overheating, causing a build up in the radiator which perhaps caused a back flow. In any event, I would have assumed that the Technician could get to the root of the problem before flushing the system, as that may not be the cause. Does any of this make sense? Can you weigh in with your expertise?

T. Young
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have the same problem?
Tuesday, July 24th, 2018 AT 4:00 PM

1 Reply

Hi and thanks for using

Based on your description, I too am stumped. Engine coolant, ethylene glycol, is completely miscible with water. Thus, once mixed, the glycol will not separate from the water. The only thing which can remotely cause it to separate is totally freezing, which is the opposite of what you experienced.

Now, this brings me to the next question, are you certain it was water? I ask because it does not make sense. The two would have mixed regardless of the overheating.

With that being said, I feel the shop needs to determine what was actually in the bottle. Please keep in mind, the overflow bottle should not be completely full once the vehicle cools. Are you sure it did not appear to have something in it when it could have been partially empty?

I do not know if this will help, but here is a link discussing how to replace a reservoir. As you page down to the refill section, it explains how to make sure it is full. Let me know if that may be what you saw.

I hope this helps and does not make things more confusing. However, once water and coolant are mixed, they cannot separate. Therefore, either the bottle was partially empty or something other than water was put in.

Let me know if this helps. I will watch for your reply.

Take care,
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Wednesday, July 25th, 2018 AT 8:29 PM

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