Topping the engine coolant off after a run

[Neil1624]

Hi all.

I have a series 1 4.2 litre car that during a run pushes coolant out from the system to the extent that it requires roughly just over 1.5 pints or just under 1 litre to top it back up again, this to the bottom of the filler neck in the header tank, this being both filled and replenished when the car is cold.
I am running a 7lbs cap on the header tank and have a large Spall electric fan mounted behind the radiator to keep things under control when in traffic etc (the engine is tired and is due for a re-build in the near future. The car had been stored in a barn for a large number of years and I suspect there is still a fair amount of accumulated crud in the water ways - this has been removed as far as is possible but will be fully dealt with on re-build) I use a coolant mix of 50/50 blue glycol antifreeze and distilled water, there is no visible contamination of the engine oil or coolant that might indicate head gasket trouble.

Is this just par for the course given the engine requires an overhaul ? Your thoughts and experiences would be most welcome.

KR Neil

[malcolm]

I think you are filling it too high. There are level markings on the outside of the header tank, and they show full as being about half way down. When hot, the water will expand to the neck. If you fill it there to start with, it will just all flow out when hot. The litre you are adding is probably nearly the difference between filling to the neck and filling to halfway.

[Heuer]

Agreed, the coolant finds its own level and constantly topping up should not be necessary. Any excess will be pushed out and adding water will only serve to dilute the coolant.

[Neil1624]

Hi Malcolm, David.

I suspect you are correct in terms of the header tank being roughly up to the half way point - I have followed the instructions re filling in the original handbook which states " check the level of the coolant in the radiator header tank and if necessary top up to the bottom of the filler neck"
So this begs the question, did Jaguar have the filling level incorrect knowing that fluid would be pushed out of the system through expansion but a full header (with frequent checks) was better than one which might require coolant to be added ?

In terms of level marks on the exterior of the tank, I don't think I've ever seen these, I must admit my tank is a modern replacement the original having rotted through. One of my concerns in posting this question was the coolant height in the header tank and it's potential for having a negative effect on the otter switch (i.e. not covering the switch) which on my car triggers the Spall fan albeit through a 70amp relay, such an outcome would be unwise........

KR Neil

[Heuer]

More info: viewtopic.php?t=7622 and viewtopic.php?t=6325

[cactusman]

On longer runs I take a two litre bottle of ready mixed antifreeze with me....just in case.

[PeterCrespin]

I have followed the instructions re filling in the original handbook which states " check the level of the coolant in the radiator header tank and if necessary top up to the bottom of the filler neck"

You are quite right. If ever there was an example of the harm that can accrue from sloppy technical writing and proofing, the above is it. That single section is probably responsible for years of bad reputation for Jaguar and still causes endless confusion today. Thousands of careful owners have looked in their handbook, followed instructions and thereby become concerned at overheating. Even assuming dealers delivered cars correctly filled halfway (there are no external marks) it would only be a matter of time before an owner would look at the gorgeous engine, unscrew a few caps and top up the fluids as per the book - which in the case of the coolant will result in your present predicament. Pre-internet, you can imagine someone miles from a dealer being fed up of his 'overheating' car.

At least the answer is simple: Do nothing and it will sort itself out. Whenever it gets hotter than it has been before it may puke a little extra, but basically just watch the gauge and look at the level every so often to check you still have an inch or two of coolant visible in the bottom.

Pete

[rfs1957]

Is 3.8 experience relevant ? Different cap and header tank or the same ?

Mine still uses the early 4lb cap and the concertina hose so is maybe even more prone to coughing up any excess.

I found that it wanted to find a natural level within the tank that was right on the height of the horizontal baffle, so with your finger you never knew whether you were feeling wet brass with a dangerously low water level hidden way below it, or wet brass kept wet by a correct water level.

Having attached the first 1L plastic bottle I could find, with a zip tie, to the RH wishbone area, I realise I have unwittingly produced a system that has now worked perfectly for a couple of years.

Elegant it is not.



The 5/16 overflow hose goes right to the bottom of this overflow bottle, and when the car spits out any excess - apparently only ever when the heat surge comes to the fore after shut-off - it just stays in the bottle, then as the car cools down and the system pressure goes negative, the lower pop-off valve on the filler-cap must open and the car noisly sucks back in everything it has just spat out.

Not only does it give one some idea and some visual as to what is going on inside the car's cooling system, it puts the coolant level back to a height you can feel with your finger before the next run, and the burps the car makes are reminiscent of someone drinking a beer and expressing their appreciation - which always seems highly appropriate and reassuring.

Please will someone now find a more elegant and appropriate container.

[PeterCrespin]

I agree an atmospheric catch tank is a nice system but at present you are under-exploiting its potential. On the S2 system the volumes and plumbing are configured such that there should never be any tidal air introduced into the working parts of the cooling system (brass radiator top tank, thermostat housing / cylinder head etc. Even at stone cold with every mL pulled back down the pipework, the open end in the expansion tank should still be under coolant. The air never gets further than the head space above the expansion level and that tank is brass.

In your system, if the milkshake slurping noises are any guide, when the last bit of contraction happens new oxygen-rich air enters the header tank and does what oxygen, water and metal do when mixed. Happily, this isn't too bad for brass, copper or aluminium but we know there are ferrous parts in the cooling system too - including the expansion tank on S1 cars (if yours is brass as you mentioned, it is aftermarket).

If you make sure there is enough space and always a bit of coolant in your atmospheric catch tank like on modern cars, you'll run with a brim-full inhibitor-protected header tank and 'improve' the system and cut down on the slurping noises after shutdown.

The 4lb cap issue just means the whole performance is shifted lower down the temp scale and you have less protection against boil-over. But don't plonk another cap on without checking/upgrading the hoses or that top one especially may burst. Personally I would leave an S1 as-is, especially if it had a brass, alloy or stainless header tank. The S2 system is better but the S1 is OK if you don't mind checking level occasionally and replacing a steel header tank once in a blue moon. It rots from half the insides being uncovered and not protected by corrosion inhibitors in even fresh coolant.

Slurp, slurp...

[Duckham]

I found that it wanted to find a natural level within the tank that was right on the height of the horizontal baffle, so with your finger you never knew whether you were feeling wet brass with a dangerously low water level hidden way below it, or wet brass kept wet by a correct water level.

Rory -
The natural level in my tank is the same as your.
My even simpler solution was to drill a finger-size hole in the horizontal baffle so that my digit-al sensor always register correctly.

Joe

[rfs1957]

Some great ideas there - yes Peter, will go for the fully-full option and report back ; but I will miss the burps.

Whilst on this subject, probably treated elsewhere, what would be a good South Of France-and-never-left-outside mélange ? I have Motul MotoCool anti-freeze, Water Wetter, Distilled Water ...............

[rfs1957]

Starting with the header-tank totally filled, I used 500ml on a recent 1.900 km run, and it all came out of the overflow bottle at my feet at the first stop.

I reckon this means that my 1L catch tank just needs to be 1.5 L for the whole system to remain air-free and autonomous, expelling and inhaling water to its heart's content ?

Anyone got any ideas for a suitable container ? The French way would be to use a 2L Period Oil Tin in appropriate Total, Elf, Yacco maybe, or Motul colours, and fit it to a suitable support within the wishbone area but it won't like water long-term and I'd rather find a plastic one that I can hide somewhere so it doesn't look incongruous in the engine bay.

[JagWaugh]

Rory,

Have a look in a cooking supply shop (I'm guessing you'll find one in France), and examine the selection of stainless vessels on offer. You can usually find a something of a suitable shape and size which, with a bit of silver solder and some strapping results in a suitable container. I've made puke tanks, Reservacs, Expansion and overflow tanks this way.

Andrew