S-Type Normal Running Temperature

[YoungJagFan]

Good Evening Everyone,
I am a young classic S-Type enthusiast and I just purchased my very first after cutting my teeth on a Triumph Spitfire and Herald for eight years, 1965 3.8 S P1B77802BW.
Upon my first drive home with it yesterday afternoon, the temperature gauge registered between the 70 mark and 110 mark (it was 93°F in Los Angeles yesterday). It also discharged some coolant out the overflow pipe when I shut it down.
Is this a normal temperature range for an S-Type? The car does have an auxiliary electric fan and I used it the entire journey from the dealer to my home (20 miles).
As I'm new to Jaguars, I want to make sure I don't cook my beloved kitty! Thanks for your help!

[Orlando St.R]

Congratulations on your new purchase! And welcome to the forum.

My car typically runs at 70-75C. If the ambient temperature rises to 30C plus, which is rare in the UK, it will generally run a little hotter (c80C). These are figures for when the car is cruising at 60 - 70mph. If I encounter traffic, it will rise to maybe 90C in a traffic jam or very slow-moving traffic. My car doesn't have an electric fan. It does have a proper sleeved thermostat, which is essential.

Yours does sound as if it's running a little warm, especially if you had an electric fan running the whole time. As the system is only lightly pressurised, the coolant will boil at the top end of the range you describe. Though fitting a higher pressure cap is not the solution!

To satisfy yourself that everything is in order, I would suggest the flushing exercise described by Rob in this topic: http://jagstyperegister.com/forum_new/v ... 4555#p4555.

If that doesn't improve things, I would check you have the correct sleeved thermostat (covered in this topic: http://jagstyperegister.com/forum_new/v ... stat#p3074).

If neither of those improve things, I would look at the radiator. They don't last forever and the tiny pipes do get bunged up, especially if the car is run without antifreeze. Getting the radiator re-cored is not a particularly expensive job and is considerably cheaper than dealing with a blown head gasket.

Always run the car with antifreeze for its anti-corrosion properties. The recommended mixture is 50:50. And it's preferable to use distilled water if you can, as it has fewer minerals.

Coolant flowing out of the overflow pipe during heatsoak is a normal 'feature' of these cars and, on its own, should not cause too much concern. People often fill the radiator right to the top, in which case it will spew out coolant until it finds its proper level, which is about an inch above the bottom of the filler neck. Of course, the hotter it gets, the more the coolant expands, and the more will be ejected.

[Glyn Ruck]

Welcome to the forum. Heed Orlando's wise advice. My engine is newly rebuilt with spotless water jackets free from sludge & scale (chemically cleaned) & one of Barratts' uprated "tropical" radiators & the sleeve thermostat that Orlando mentions above which is OK for the S Type narrow bypass slot head. (no auxiliary electric fan)

My engine temperature settles at just under 70 deg C in normal conditions & just over 70 Deg C idling in traffic on a hot day.

Ejecting some coolant on shut down heat soak is normal for these old girls & IMHO can only be overcome by the fitment of a surge tank. That said don't overfill & leave an air gap below the cap.

Fiddling with new radiator caps because I seemed to be forming a siphon after shut down & losing too much coolant, my worse situation was caused by a 4lb cap which seems not to have sealed at all. Then tried a long reach 4lb cap and it is too long to operate at correct pressure. I now have a 7lb cap fitted that seals well, builds up pressure as designed & minimises coolant loss on heat soak. At present I have resigned myself to checking coolant level before each outing ~ I'm all ears if anybody has a better suggestion.

Don't use very high pressure radiator caps as other components such as the water pump seal were not designed for their use.

The best advice would seem to be check that your engine is in a decent state of tune ~ not running too lean & with correct timing. Flush the head & block with a decent cooling system flush or citric acid or similar ~ whatever your preference & re-core the radiator with a modern increased capacity core. Make sure you have a shrouded thermostat & good water pump. Also that you have the fan cowl in place.

Good luck & enjoy!

Pictures please when you get around to it!

[YoungJagFan]

Thank you Orlando & Glyn for your excellent advice! I will definitely look into flushing my cooling system and recoring the radiator/replacing the thermostat if necessary.
Is the radiator relatively simple to remove? I've done a radiator in my dad's TR4, but that is a completely different animal
Also, during flushing, is there a particular connection point where I should hook up my hose?
Thank you both again and I will post up some pictures of my new cat soon!

[YoungJagFan]

I forgot to add two points, I kept the heater on the while on the freeway to keep things in check, and the engine had a bit of run-on (dieseling) when I shut her down.
This leads me to think the engine is running too lean. In any case, I had the car towed back to the dealer and requested the car be rechecked and gone through again...they'll be doing that this week.
The car also has the original Artic-Kar air conditioning from the 1960's (with a new Sanden compressor added), but I kept it off to avoid stressing the engine.

[Orlando St.R]

Hi again. Rob's post in this thread covers both the flushing and radiator removal: http://jagstyperegister.com/forum_new/v ... 4555#p4555. Radiator removal is more awkward that difficult and having four hands definitely helps. .

Re the radiator cap, I use a cap that I've tested at 8lb. It seems to me that the 4lb caps (or the ones I've tested, anyway) never meet their specification. Unless you have an original alcohol-filled sleeved thermostat, a 7lb cap should be fine and usefully increases the boiling point over the 4lb cap.

[Glyn Ruck]

This cap issue is interesting Orlando. I got Barratts to send me 4lb, 4lb longer reach, 7lb & 9lb. I have not tried the 9lb which is the highest I would go because the 7lb made such a big difference. Subsequently got a spare 7lb.

Let me know if you have any further findings in this regard. Maybe regular top up is something one has to learn to live with or fit a surge tank. I've done a combustion by-products test in the coolant & there is non so the head gasket is fine.

[Orlando St.R]

This cap issue is interesting Orlando. Let me know if you have any further findings in this regard.

Well, as you know, Glyn, I have been tinkering with caps for a while and a year or so back bought a Sykes Pickavant 318 cap tester used from ebay. Of the half a dozen or so caps I have on the shelf, only one met its specification. For example, I have two 4lb caps - a new one and a NOS AC one; the new one is actually 2lb and the NOS is 0lb. That's how I ended up with the 10lb cap I'm currently using; it measures 8lb on my tester, so that was as close to 7lb as I could get without buying another half a dozen!

I only really lose coolant down the overflow now after I've 'over'-filled it - ie. gone above the '1 inch below the bottom of the filler neck' point. As you say, I think there will always be some loss, but I don't feel the need to check mine before every journey.

Clearly with ethanol in fuel and none of us (except Alan) having the original under-bonnet insulation, under-bonnet temperatures will be higher, esp in countries where the ambient temperature is frequently 30C+, which can only exacerbate the heat soak/coolant loss issue. Maybe yours will settle down after you've put a few miles on it. Mine certainly did.

Cap tester:

sykes-318.jpg (286.78 KiB) Viewed 2821 times

[Glyn Ruck]

Yes ~ it was your advice that made me suspect the 4lb cap as culprit. A friend has a tester & sure enough you were right ~ 0lb

I think I'm still overfilling the system & should leave it to find it's own level which irritatingly seems just out of sight. The car never gets over hot on the gauge ~ ever! So I don't have an overheating problem. I've checked the gauge against a calibrated Fluke contact thermometer & it's pretty accurate. Sender is also new. What I don't know is at what point the sender might find itself in an air space due to low coolant level.

You are certainly correct that the engine should run cooler once fully run in. Many years spent in Dyno rooms inform this.

These uprated radiators while having an authentic pattern top tank are actually thicker back to front than the stock OE item so hold a little more coolant.

[Orlando St.R]

It's probably fine, Glyn. Famous last words! But I do know what you mean and I have worried about subjectively how hot mine gets (although, as you say, all the indicators are fine).

Re how the gauge would read if it were in air, I did once have a holed coolant pipe on my Subaru and all the coolant drained out. The gauge dropped to cold.

Are there any photos on here of your tropical radiator? I guess if it holds more coolant, it will need more space for expansion of said coolant, so the natural top-up level may be slightly lower than on a standard radiator.