Just got back from an incredible road trip with my '00 XK8 Convertible.


I've had it for almost 5 years now - in this time I've performed a chunk of preventative work - a little bit of repair work in addition to a few upgrades here and there. Overall the car has been an absolute joy to own - it's never broken down or misbehaved in a serious way - never left me stuck by the side of the road or gone into restricted performance for a prolonged period of time. When I got back home I'd added 2,550 miles to the odometer - ~18,000 of the ~81,500 miles on the car are mine.

For these 18,000 miles the coolant reservoir has been an infuriating nuisance that I've been unable to address completely.

But first - pics!
-Wall, SD (some place that I was told I have to go to by ~650 miles of signage)


-Badlands National Park, SD



-Custer State Park, SD


-Mount Rushmore, SD


So what's going wrong with the cooling system? Well, the stupid thing throws "ENGINE COOLANT LOW". VERY FREQUENTLY. It's done this since I bought the car - and honestly I am fed up with it. I'm hoping there's a permanent solution to this system that seems to be designed to throw a low coolant alarm up if the level drops below 99%.

In case of a leak I've replaced just about every hose I could last year, the thermostat and tower were replaced right after I got the car, the big "T" junction that attaches to the thermostat tower was one of two leaks I found - the other was below the reservoir tank which I also replaced last year. The sensor was replaced with the reservoir.

Every day on this trip I would drive usually a few hundred miles - before leaving the hotel I would open the coolant reservoir and check the level - it was never lower than ~1/4" below the fill point but either way I topped it up and the stupid thing would still throw "ENGINE COOLANT LOW" if the engine got hotter than 210 - which it did with all the stop-start driving we did through the Badlands. My typical temps are between 199 and 203 for highway driving - once the engine got back into highway temps the alarm would clear. This is most common if I ever parked the car for a short period and then started it again (e.g. stopping for gas/rest area or to look at buffalo) presumably due to heat soak and the engine not cycling coolant while stopped.

So to recap:

• Every morning before a drive (engine stone cold) I would check the coolant reservoir
• Every morning there would be at most a drop to 1/4 below the bottom of the threaded bottle neck into which the cap screws
• I would then top up the coolant back to "full", jiggle the reservoir to make sure there were no air bubbles, and if necessary top up again. Never more than, say, a shot glass at a time.
• I would then drive the car - if the temperature got above ~210 that day I was pretty much guaranteed to see "ENGINE COOLANT LOW".
• Once temperatures return below ~205 the alarm would clear.

What I think is happening: There's another tank somewhere in the mix (if I remember correctly) - as the engine temperature gets hotter more coolant is required in the engine - this extra coolant is enough to drop the reservoir level below """coolant low""" level.

So you would think there'd be a leak somewhere except that on the day where I drove from Gillette, WY to Fargo, ND with only one stop (~585 miles) I did not see the alarm. I believe there's no leak for three reasons: 1). I maintained highway speeds for basically the whole drive, 2). The stop for lunch (and gas) was a long one, so the engine had a bit of time to cool down. 3). If there is a leak it's <30ml on days with lots of driving.

I'm not sure y'all are going to have much in the way of suggestions as to how to address this, I just hate this stupid warning, the stupid tiny reservoir and the anxiety I get from worrying about the stupid design of the stupid coolant system while I drive halfway across the bloody country. I'm wondering if anyone's ever replaced the stupid reservoir with a larger one from another car or something like that.

 

Oh and have a bonus pic from the rained-out Cars & Coffee last month

 

Excellent post. I thoroughly enjoy reading about trips to places I'm never likely to get to myself.

Low coolant warning but coolant is at the correct level. It has to be a sticking level sensor even though you mention replacing it last year.

Graham

 

I understand that theory - what makes me think it's related to the two tanks and not the sensor is that the alarm only appears to go off at hotter temperatures.
I went to the SNG Barratt Catalog and took a look at the cooling system parts and there is indeed another tank (the Atmospheric Recovery Bottle).



I'm not sure under which circumstances exactly coolant moves between the two bottles and the engine but to me it seems like - the hotter the engine, the higher the likelihood I will see the dreaded alarm.
If coolant is moving from the reservoir to the recovery bottle (when above 210) is it not possible that's when the level in the reservoir drops below the "low" point - and when it moves back (as the engine drops back below ~205) that the level is high enough again? I mean, I can replace the sensor again but I am pretty certain this is not going to fix the problem since I've already done it. Maybe I just have it seated wrong...?

 

My next move would be to replace the existing coolant reservoir cap with a new OEM cap. When these caps begin to fail, they often allow coolant to move from the reservoir (in the engine bay) to the recovery tank (in the wheel well), but then they do NOT allow coolant to move back from the recovery tank to the reservoir. That leads to a slightly low reservoir and usually sends the unsuspecting owner on a fruitless search for hose leaks. A new cap has always fixed this issue for me. In more than 9.5 years of vehicle ownership my wife's 2006 XK8 is on its second reservoir but its fourth cap....

The aftermarket caps can work for awhile, but they are of inferior quality. Sometimes they are bad right out of the box. I am currently running a September 2017 aftermarket reservoir with a 2015 OEM cap. Not a drop of coolant loss thus far....

Did you happen to visit Devil's Tower National Monument when you were near Gillette, Wyoming? Ever since "Close Encounters of the Third Kind" was released in 1977 I have wanted to visit that park and hike around the tower. Maybe one day....

 

Thanks for the recommendation - I'll give that a shot!

No - unfortunately we ran out of time. Really killed me - but it gives me an excuse to head back that way another trip!

 

The correct coolant level (COLD) is to the base of the Expansion Tank filler neck. As the engine warms up, coolant expands and passes through the transfer piping to the Atmospheric Recovery Bottle which is behind the RH wheelarch liner.

The Atmospheric Recovery Bottle has a much greater capacity than the Expansion Tank and can easily take the excess coolant.

As the engine cools down after switching off, the coolant in the system contracts again and fluid is drawn back from the Atmospheric Recovery Bottle to the Expansion Tank to maintain the correct level.

I would follow Jon's advice as the Pressure Cap is a regular failure. However, you should also remove the wheelarch liner to check the Atmospheric Recovery Bottle is not leaking or it's cap is not displaced.





There is normally an inch or two of coolant in the Atmospheric Recovery Bottle with a COLD engine.

Graham

 

Are you familiar with Shanya Twain?? "Wide open spaces!!" As to your problem I concur with all the advise given here, which is better than saying "What he said". But it's just like he said.
Good to see the old girl being driven. TM

 

it has been my experience with the same frustration to replace the float / tank and sensor. I then found it was a combination of the float sensor plug and a saturated float that would sink.

 

I'm certainly no expert on Jaguars but in my younger days on older vehicles if we had similar problems we would change to a thermostat with a lower temperature rating. Of course those vehicles did not have any electronics to monitor the engine so it may not be possible on these.

I changed my thermostat housing from the OEM plastic to a metal one from Barrett due to a very slight leak, my mechanic told me to not use the metal filler cap that came with the housing but to use the plastic one instead. I haven't had any problems for the last two years since that was replaced but I haven't taken any long trips either.

 

Thanks for sharing
I encountered my first Engine Coolant Low on my 2002 XK8 with 36K miles after driving from Pueblo CO to Rye CO
Ambient temperature was in the low 90's
Stopped and opened the hood, nothing visibly wrong, nothing dripping.
Started back to Pueblo and the Warning went out.
Then it was on and off all the way back.
Will investigate and see if the coolant is actually low or possibly something else. Nothing leaking from the car onto the garage floor.

 

Good to see one of us driving their cars on a long trip. You are doing the right thing, replace needed parts and keep an eye on the system. I just replaced every hose on my daughters Mustang. We bought it new in 2007, now has 165,000 miles. All radiator, by pass, heater hoses (4) thermostat housing, as well as the serpentine belt and tensioner. Should be good for years. I've got to do that job on my XJS or i'll never take it anywhere.

 

I have a 2018 E-Pace, which signaled that the coolant level was low.....Dealership Service said that is because the sensor is in the reservoir bottle, and as soon as I added a small amount of water, the light went out....

 

you need a new tank with integrated float or sensor

both need to be working or it will keep annoying you

 

Thanks for the post and awesome pics. Thumbs up on the recommendations to replace the expansion tank and cap; cured my aggravating coolant loss immediately!

 

Rock Auto has the proper tanks and caps in stick generally. I replaced mine and have had no problems since


great writeup on the trip. My wife and I do long rodd trips as well. best GT car ever built IMO