I purchased my 2004 XJ8 two weeks ago. It has 60K miles and both previous owners had all service done at their local Jaguar dealer (who is not local to me). I noticed I was getting less heat on the driver's side (left) than on the passenger side (right). Searching I see that this could be the auxiliary pump and/or the heater core. While I'm changing the pump (holding off on the core until I see if the easy fix works), I'd like to change any other troublesome coolant equipment. Searching I see this would include the reservoir and the thermostat housing.

According to the CarFax for the car the Jaguar dealer serviced the cooling system three times in the last three years. Is there any way to tell if the thermostat housing and/or reservoir have been changed? I'd rather not change them if they are less that three years old.

 

The only way to tell is if you have a receipt saying it was replaced. Otherwise it will be hard to tell when it was replaced. Odds are it will be in the heater core. You can change it without taking the dash out, but can be tricky. You could try checking the coolant pump, it is possible it could be faulty, but I've seen quite a few X350s with this issue and its ended up being the heater core.


I did have one where one of the flaps in the distribution box was stuck causing this issue. Luckily I was checking codes at the time for another fault and there was a fault logged for this. May want to pay to look up on both sides of the distribution box to make sure all the flaps are moving properly.

 

I'd try flushing the heater core, backwards and forwards (& repeat a number of times) before starting out to replace things.

 

An idea for using the old auxiliary pump. Collect the drained antifreeze in a large bucket, reverse the flow to heater core, using the old pump, connected to another battery, with lengths of hose, both going into bucket. Tap water is not good for ANY coolant, or interior motor parts.

 

I'm more interested at this point in trying to determine if the reservoir tank and thermostat housing are original and should be replaced before they fail or have been done by the dealer in the last three years and can be left in place. I don't mind spending money proactively just don't like wasting it on unnecessary parts.

The heater core I will replace if the auxiliary pump and a good back flush do not restore the heat. I plan to use the car as my primary ski vehicle and as such it could see temperatures as low as 35 below F in central VT, so I'll do what is necessary to get good heat.