Hello!

This week I was cruising along in my '98 XK8 when suddenly the dreaded "Low Coolant" light came on. It went away after a few minutes, and would come back on when braking to a stop. Upon returning home, I opened the reservoir cap and noticed still plenty of coolant in the tank.

I filled the tank up to the neck and no longer got the warning light. So my 1st question is -- what is the proper level of coolant in the tank? Do you always fill it up to the neck?

I checked but did not find any leaks. However, I had to top off due to "Low Coolant" warning only 1500 miles ago.

So, my 2nd question is -- Is this normal? How often do you top off your coolant tank? What would be the likely cause(s) for low coolant? Do you consume more coolant with the a/c on?

Thanks!
Wolfy
Los Angeles
1998 XK8 Converitble, Titanium/Oatmeal, 72000 mi

 

wolfy, before I head to bed, I'll tell you my experiences with the coolant level.

It does not magically disappear. If you've had to keep filling it up, there is sadly a leak.

Potential leak sources:

1. Water pump failing, weeping out coolant (yup, happened on mine)
2. Thermostat housing cracked (another yes, only recently I had to replace mine) Your MY has a $70 aluminum replacement kit available. Mine does not, had to go OEM plastic.
3. Expansion tank (the reservoir you speak of) cracks on the bottom where the large hose connects, and other spots. (first thing to go on my car when I got it used, and leaked like a sieve)
4. heater hoses, the octopus, a large group of hoses you can see from one side of the engine to the other, going under the throttle body. (of course I replaced this, the connection at the goofy looking clamp leaked)
5. radiator hose, most often the upper one, if old, can get a bubble, but if it bursts, it won't be a slow leak. Just keep an eye out for odd bulging on them near the t-stat housing. (mine was suspect for a bulge, so didn't take any chances... hose replaced)

If I missed anything, someone will let you know.

 

You obviously have a slow leak. Look for signs of dried coolant around the places H20boy identified or 'rent' a pressure test kit from one of the auto parts stores that do such a thing.

 

I recently had that issue. A slow leak that caused the low coolant warning every couple thousand miles. Turned out to be the crossover pipe.

 

I just got thru fixing a low coolant leak. It was the coolant pipe as well as the res tank. I got these parts from Car Quest, coolant pipe and replaced the plastic housing filler neck with aluminum from URO thru Car quest. A warning about the filler neck from URO the cap seal is crap. Mine leaked after about two days. I ended up buying a new cap from Jag $7.95. Do not forget to look under the res tank. You will probably see coolant on top of the header. If so then the sensor is leaking and there is no way to seal it up. A new tank from the dealer I think was a couple hundred bucks.

Just look for the orange stains!

 

I am also monitoring the coolant level on my 2001 XK8, because sometimes I can smell some coolant after parking my Jag. Since the engine is hot and the coolant is under pressure, there should be some orange residue to identify the leak. I have also had several hoses & pipes already changed.