97 XK 8 convertible purchased by me (Vin# SAGX2748VC012760) was filled, flushed and renewed for 17 years with Dow D-542 (JLM-20404) as recommended by Jaguar.

After purchase and from my reading on this forum, I was concerned that the plastic impellers in the water pump could fail.

In late 2007, at 32,500 miles I had the Jaguar dealer in Denver replace the thermostat, water pump and antifreeze. The Jag dealer also used JLM-20404. (D-542). No problems or issues. (Ironically, the removed components were in perfect shape).

Seven years (2014) later with 43.8k miles, a 'top' European shop that is not a Jaguar dealer, recommended a coolant flush as a routine service. I was having no problems, but I agreed. NOW, I notice from their invoice that it used JLM209722 (this is WSSM97B44-D). I have not experienced any issues since this last change except sometimes (intermittantly) during the past three years the message "low coolant level" appears . I checked the reservoir (at that time) and it was down from the top less than an inch. I added 2 oz (combo total) of Pentosin SF (pink) with distalled water 50/50. Perhaps one oz. of each (3 years ago). I realize that the top up of PentosinSF is WSSM97B44-D compliant.

Occasionally, I continue to get the intermittent 'low coolant' warning, but the reservoir is not low.

I want to flush and renew the antifreeze now (2023 with 50k) miles, but do not know which should be the correct antifreeze/coolant to use given the past change. Obviously, I will also want to get a flush of the system as well. Jag TSB's warn not to mix the D-542 with the JLM209722 or WSSM97B44-D specs, but that was done unintentionally, after a flush 9 years and 10k miles ago with the newer, long life JLM209722.

Advice is deeply appreciated.
97XK-8 Convertible

 

Your problem is most probably the coolant overflow tank situated behind the plastic liner in the RH front wheel arch to the rear. This must be half full or the coolant return will not work.
Once you have had a look you can fill it by burping the system ...fill expansion tank put on cap and compress the radiator hose. this pushes fluid into the overflow tank. Repeat until half full. Or take the pipe off the expansion tank ..the rear one with the rubber coupling and fill down that hole.
In UK we just check the antifreeze with a proper antifreeze hydrometer and if its OK leave it or top up with concentrate.

 

I would also replace the coolant reservoir cap with a new one. Properly-functioning caps are imperative for the required coolant flow process back and forth between the reservoir and the overflow tank....

 

I'd stick with the WSS-M97B44-D spec, especially if the change from DOW was done after a flush with no subsequent issues.

I did read some anecdotal evidence that it doesn't play well with the older composite head gaskets, but I made the switch about 10 years ago and have had no problems.

If you have to change the coolant reservoir at some point, the replacement will carry a sticker to the effect of mandating WSS-M97B44-D spec coolant anyway.

 

Thanks for your response. Perhaps my question was not clear. I am looking for advice on what coolant to use now, after a flush, given the fact that JLM20404 was unintentionally replaced with JLM20972 nine years and 10k miles ago.

 

Thanks for your input michaelh. I hope that this is the best choice for me.