I am giving my newly acquired 1999 XK8 fluid changes. I am at the cooling system now, and will replace the original 13 year old radiator hoses as they seem a bit soft. The water pump, thermostat and housing were replaced a couple of years ago by the PO. After I flush the system should I replace whatever stuff is in there ( can't tell if it is yellow HOAT or orange OAT) with DEX Cool or use the original spec Yellow HOAT G-05 for my car ?
I have seen references on this forum to TSB's to change to from the Yellow HOAT to OAT DEX Cool and others recommending only to use the original spec coolant. I'm tempted to use the DEX Cool as I have used it in multiple cars with no problems, but there does not seem to be a consensus of opinion on the subject that I can discern. Any enlightenment on whether to use the original spec G-05 or the DEX Cool as the TSB indicates will be appreciated.

 

The important thing is to know what spec coolant you have in the system, ensure it's the correct strength and not to mix types.

As you are replacing the hoses and flushing the system, what type and brand of coolant you then use to refill is down to personal preference. With the recent water pump, thermostat and housing replacement and now new hoses, I'd take the opportunity to go for up-to-date spec OAT coolant rather than stick with the original.

Graham

 

Thanks for the info, I have no idea what is in the cooling system at the moment, looks like dirty pond water. I will give the system a good flush a few times and finish off with distilled water and 6 quarts of DEX Cool.
In the past I have used half a cup of Cascade dish washing powder as a cooling system flush, works great, but I'm not sure the Jag would appreciate the common touch.

 

As finicky as these Jaguar cooling systems are, I wouldn't pour any dishwashing detergent in there....

Be sure to check the condition of your plastic coolant reservoir. They are notorious for cracking and leaking as time passes, especially at the hose nozzles. Hairline cracks form at the base of these nozzles that can be difficult to detect until they snap off and ruin your day (and hopefully not your engine)....

 

Adding a strong base to the cooling system is NOT a good idea, seeing as the system is full of the proper oraganic acid film for bi metal protection. I don't know where this came from but don't sell this to anyone else.

 

Not for Jags, they are a bit too delicate.....
Used extensively on clogged or dirty cooling systems for trucks, cars and marine engines works great when a transmission oil cooler rupture has contaminated the cooling system or some idiot has mixed coolant types. Run for 30 mins and then flush 3 times with distilled water and then add an OAT coolant. If it can remove 3 day old dried on spaghetti sauce then a bit of coolant gelly is no match.
Better than when I used a gallon of white vinegar as a flush to free up a clogged heater core on my Audi S4.