I have a Series 3 XJ12 (1988, Canadian import), and am trying to change the coolant. The Haynes manual describes a drain tap on the upper right side of the radiator, which my car does not appear to have. I can’t really access the bottom of the radiator without removing the fascia surrounding the lower small grill (beneath the bumper), and 2 of the screws to remove that fascia are really hard to reach, I can feel the bolt but can’t see it directly. I guess I could take off the hose coming off the water pump, but that wouldn’t fully drain the radiator. Am I missing something here?
I assume the reference to “upper right” is for the drain tap handle, the drain itself is certainly not at the top of the radiator.
If that handle extension is missing you may have to get under the car and access the rear RH of radiator to operate the tap. It will not be accessible from front.
If you remove the radiator undershield you can loosen the lower radiator hose at the radiator to drain the coolant. Awkward. Messy.
The bolts for the undershield needn’t be removed. Just loosened. The undershield is seen in the illustration below, part number C45019
Cheers
DD
Forgot to mention that Jaguar stopped installing the drain tap sometime in the early-80s, it seems. On USA/NA cars, at least. I’ve never seen or worked on one that had the drain tap, FWIW
Cheers
DD
My Canadian 86 V12 has a drain plug and the lever at the top right side. Thankfully!
**
As Doug says, Steven - the drain tap was omitted for all markets at some stage…
The only way described to drain the coolant is to disconnect the bottom radiator hose. Awkward and messy, but that’s it…
Frank
xj6 85 Sov Europe (UK/NZ)
But, much better to flush out andy sediments.
Carl
It would be if the lower radiator hose was at the bottom! Unfortunately, it is not, it’s several inches up from the bottom. Only too likely sandy sediments will stay put.
The best way to drain coolant would be through a large diameter drain at the bottom right corner. It needs to be large diameter so the sediments will come out. If a tiny hole, the coolant would come out and leave the sediments inside. Unfortunately, the OEM draincock on the earlier XJ-S was a tiny hole and it was eliminated altogether on the later models!
If you ever have the radiator out, I recommend adding a hose barb at the bottom right corner. You need to check very carefully where to put it, because things are tight down there. Ideally about 3/8", I think. Then fit a length of hose to this barb, route it out the bottom of the car, and plug the end of the hose. It suddenly becomes dead simple to drain the coolant; just remove the plug from the end of the hose. And a 3/8" hose is big enough to clear out most of the sediment along with the old coolant. The length of hose even serves as a “dirt leg”, collecting sediment and keeping it out of the flow path.
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Cleanest way is to remove banjo bolt on top of the radiator and suck all the coolant with a long peace of tubing. I use either small hand pump which is used for syphoning fuel or small electric pump which is for syphoning eingine oil.
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Thanks to everyone for all the advice! You’re right, awkward and messy. I pulled the lower radiator hose to drain the coolant (no drain tap on the right on my car), and followed the directions in the Haynes manual on refilling, i.e. filling the overflow tank, running the engine to warm it up, then releasing the bleed bolt on the upper left side of the radiator, then adding more coolant to the overflow, etc. I repeated that about 4 times. Maybe next I’ll think about changing spark plugs. . .
I use a method similar to what John suggests when draining coolant from our V12 equipped 1990 XJ-S convertible and Canadian market 1990 V12 Vanden Plas. After the engine has cooled, I remove the bleeder on the top left of the radiator, insert a long piece of clear vinyl tubing as far down into the radiator as it will go, and siphon out as much coolant as I can, (which turn out to be quite a bit). Inevitably I must remove the large lower hose, but this can be done in a more gentlemanly fashion 
with very little coolant remaining in the engine.
Paul