"Engine Coolant Low" message appears (a common occurrence it seems with the X308); add water/coolant to expansion tank and message clears. Is there a "correct" level for the coolant in the expansion tank? How is the level measured with respect to the top of the neck on the expansion tank that receives the cap?

Thanks,
Al

 

Just below the neck. If you have to add coolant you have a leak. See if you can borrow a pressure tester from one of the auto parts stores. You'll have to pay a substantial deposit but it's refunded.

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Cheers, RJ. Nothing under the car, no wet spots under the hood, and a previous pressure test showed no leaks -- so it must be small. Anyone used a product for cooling system leaks, like K-Seal ST5516 HD Multi Purpose One Step Permanent Coolant Leak Repair (https://www.amazon.com/K-Seal-ST5516...p/B002BJEG3U)? What's the downside apart from the cost of the product?

 

Never use sealants. You can clog the heater core and reduce the radiator efficiency.

The more common leaks are the thermostat tower which will crack with age and allow small amount of coolant to run on top of block where it evaporates before dripping. Also from rear of engine the Norma connection of the octopus hose and several others that could evaporate before dripping.

Of course it could also be a head gasket.

What year is your car?

 

This is a 2000 MY. The deposit on a pressure tester is about $130 for up to 48 hours. Hopefully there is an adapter to connect it to the expansion tank neck. The pressure cap says 100 KPa so presumably the tester should be pumped up to about 14.5 psi. ' sound right?

 

First Welcome.
Can you be a little more specific? Is this an XJR or XJ8? Each one can have coolant leaks, albeit in different locations. If you are constantly adding fluid, you have a leak, usually when it comes to these cars.
Don't be surprised to not see anything dripping, there are several hoses in a position to have coolant pool up.
Unfortunately the gauges either read normal, or hot, there isn't really an in between. The AJ motor does not do well if overheated repeatedly. Are you seeing any bubbles or oil in the expansion tank? Or white smoke from the exhaust, especially on startup?

 

None of the AP store rental units that I have used have a Jaguar specific pressure tester kit adapter. All have an universal adapter that will work. An adapter that fits may not seal the vent to the atmosphere overflow tank.

Yes, 100 Kpa translates to 14.5 psi but I usually go to 20 psi which is usually about as high as it will go. Unless a headgasket the leak should show up.

 

Hi Allen,
These cars have a very good efficient cooling system.
The so called 'common' problem is only down to lack of maintenance or
not keeping a regular check on the system level.
For both the XJR and NA XJ8...the book sez coolant level should be at
the base of the filler neck but in reality, a 1/4 inch (6mm) below is normal
as the rest will just puke into the catch tank buried in the front left guard/fender.

How much did you have to add and how often have you had to do it?
If it's persistent, you will need to check for leaks.
When was the pressure cap replaced?
These need replacing every three years along with a complete drain and coolant change.

Sometimes the coolant level sensor can stick and this can be resolved by using a long thin rod or chop stick to give the magnetic sensor a poke up and down to clear to prevent it from giving false readings.

In regards to pressure testers.....the Jaguar uses a Ford type pressure cap
and will need a similar fitting to test the cooling system.
Quite often, a lot of connectors that 'fit' will not seal the top 'bleed off' port.
I personally prefer the 'bladder' style of connector which will fit any system
because you don't need a lot of fittings.
When testing, you need to be slightly higher than normal system pressure
to effectively detect where a leak is....usually around 18-19psi....tested either cold or half warm.

Looking at the pressurized expansion tank, take note of the correct fitment
of the three bleed pipes.
The highest one which is attached to the 'bump' at the top front goes directly to the right fender/guard and down to 'atmospheric catch tank'.
The second one on the front is directly below and heads off to the left, across the cam cover and joins radiators left top side....quite often these two are mistakenly crossed over leading to a constant coolant loss.
The third bleed pipe exits from side of tank and attaches to side of thermostat tower.

As the system ages, the most common places for leaks are:
1. The thermostat tower (plastic)....usually up the side and the plastic cap.
2. The plastic heads collector pipe which sends coolant to rad's passenger side LHD models.
3. Heater hoses both inlet and outlet but more often than not the
return hose which attaches to back of thermo tower at it's base.
Both of which run under the inlet plenum.
4. the water pump will only be a sauce of leaks if coolant has not been
changed on a regular basis, or it's still fitted with early versions which gave impeller trouble.
5. Thermostat....this should be replaced every three years along with coolant change!
Invariably these are ignored along with the pressure cap!

Less obvious places for leaks are the hoses from auxiliary pump and valve body situated directly below expansion tank and also the small hose that attaches to bottom of throttle body....often over looked.

It goes without question that the major hoses attached to radiator are replaced at least every four or five years....especially the short hose which attaches the thermo tower to the collector pipe....this is always overlooked
and if upon observation it looks like it has swelled....time to replace it
before it ruptures!!
Same applies to people reporting 'blow off' the return rad. hose where it connects to thermo tower bib....get rid of the crappy spring clip and replace
with two thin section stainless worm drive clamps to ensure security!
And don't forget the little crappy plastic drain plug at left base of radiator!

As with any vehicle if they are checked and maintained as per factory schedule you DO NOT have problems ;o)

 

Many thanks to all who responded. XJay8 made some excellent points and I will be quizzing my mechanic on at least some of these when I take it in for a pressure test. Hopefully others can also benefit from XJay's wisdom. BTW, one of my relatives had a Humber decades ago, probably a late 1950's MY.

 

Hopefully Allan. this will be of benefit to you and your mech ;o))

Humbers weren't all that common in the US so most likely a late fifties
MK1V Super Snipe or the series Snipes which came later ;o))

 

Alan,


Had a similar problem shortly after purchasing VDP. Except I would find a spattering of coolant on the cluster of hoses under the reservoir. Thought it was a hose, could find the coolant but couldn't find the leaking hose.



Turned out to be the reservoir cap; was dribbling out shortly after shut-down when well hot. (Missed clue: when completely full, never advanced coolant to the under-fender overflow tank)


New cap resolved issue.


I know a good mechanic avoids being a 'parts swapper', but if the cap is old it's due to start acting up anyway


NOTE: spend the coin for proper replacement. That $12 cap holds the fate of a many-thousand dollar engine in it's little plastic hands.