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Briefly, Demian - you do not have the 8:1 compression, it’s closer to 10:1… :
*…‘losing coolant’ may just be the leaking expansion tank. Besides, one must not confuse ‘leaking coolant’ with the legitimate ejection of an overfilled coolant system - correct level assessment must be adhered to…
…‘hard blips on throttle produces smoke’. Fuelling is very enriched during sudden pedal increase - this may be carb adjustment issue, but is not alarming. Also, if the valve stems seal are deteriorating - oil is leaking into the cylinders. Particularly after dawdling; sudden throttle increase will burn off this oil - grey smoke…
…'dry dark, oily mud in radiator header tank cap may indicate coolant contamination - but oil in the coolant is virtually impossible without coolant getting into the oil…
As a probable aside, while the knocking does not sound like engine pinking - nevertheless; the high compression requires 'backing off ignition timing compared to standard specs, to fit octane available.
Sort out ‘easy, obvious’ while musing and driving the car, Demian…
If you wish to be highly technical, there are ways of determining unwelcome metallic particles in the oil.
DIY. Remove the oil filter after any oil has been run for a while.
Cut it open. Use a glass, fingers or even a magnet to examine.
Some is normal. That is the function of the filter.
Find a professional shop to do that with far better methods of detection and even measurement. I’d start by asking the operator of a large truck fleet.
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…‘closed off header tank’, Demian - does that mean that there is no coolant exit from the cooling system…? In which case this is ‘not good’ - expanding liquid needs somewhere to go, or something will burst…
I’m somewhat confused on your set-up. Three different coolant systems wee used; the smaller engines (2,8 and possibly the 3,4) had indeed an overflow tank, placed across on top of the radiator matrix, with a filler cap. The early big engines had indeed a header tank, mounted to the front of the engine, with a sealing cap - and a separate thermostat housing. A separate expansion tank was fitted to the left side in the engine compartment. On later 4,2 engines there is a thermostat housing in front of the engine, no cap - and an expansion tank, again at the left side in the engine compartment…
Standard Jaguar practice implies that the 4,2 engine can be fitted with either the header tank or the plain thermostat housing - each with it’s bespoke expansion tank. However, if you do have the overflow tank, over the radiator, used with the small engine - I’m not sure if this set-up is directly compatible with the bigger engine. So if you you have the overflow tank we speak at cross purposes…
Does not mean that it is impossible to get effective engine cooling with a hybrid - but some careful thoughts are required…
It is the “earlier big” engine you describe w header tank at front of intake/water jacket rail and separate expansion tank on left fender.
There was bit of hose bypassing/closing both tube exits at header tank.
Yes, i know, you are right on, that pressure needs to go somewhere, and i don’t run it for long…just testing yet and haven’t driven more than 10mins.
It leaks anyway so some pressure relieved and it hasn’t overheated as i keep eye on it while testing while running and shut it down first.
I am replacing blanking cap w pressure cap. Plug one of those exits, and run other to an antifreeze jug for now as i just can’t stand running it at all anymore as it was.
Yes, something to consider, running s3 setup, but filler must be at highest point, and i want to try to maintain original looking engine bay.
Though I need to replace/rebuild radiator.
Cost of new ones online are as cheap as can be, but they are s3 radiators.
That fitting connection on my original radiator at top left that goes to header tank has been blanked off…
To restore radiator would exceed new s3 one no doubt.
So adopting later s3 system is a serious option now.
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Using a pressure cap on the header tank may be OK, Demian - providing either of those hoses is open when the pressure cap opens.
With a full system, the fluid starts expanding immediately - and enclosed liquid will immediately start to increase, the resulting pressure can be measured in tons/si rather than psi - and something will leak at an early stage in response …
In the original system, the header tank cap is indeed a blanking cap. Venting hoses is one to the top of the radiator and one to the expansion tank. Which has the pressure cap - and a separate venting at the neck, opening to free drain or into an unpressurized recovery tank. After initial fill, all refills and level checking is done at the expansion tank - filling is not at ‘the highest point’…
Incidentally; the series 3 expansion tank will work on the earlier system - but with some rerouting of vent hoses…
Yes, a pressure cap on the header tank (surge tank) will be fine for now.
Yes, filling point is always at t\he highest point of cooling system to purge air from system…fwiw.
Once filled and bled at surge tank filling is only necessary at the overflow tank thereafter.
The S3 has no surge tank, nor direct radiator fill either.
The system has been simplified on this (and modern cars) mostly, where fill-up is only necessary at overflow tank, which is again at the highest point of cooling system.
This should have its separate thread though I suppose as this is unrelated.
in fact I have a question and will post it within new topic if I cannot find searching.
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I think it is somewhat important to use the ‘factory’ names for the various parts of the cooling system components, Demian - for united understanding…
The ‘header’ tank not the ‘surge’ tank and the ‘expansion tank’, not the ‘overflow tank’; both are catching the expansion of the coolant within this set-up - not relating to system overflow. Genuine system overflow on ‘our’ Jaguars are caught by an atmospheric recovery tank - when fitted, otherwise just lost on the ground.
The level of the expansion tank will fluctuate with coolant temp, and is not at the highest point in the system. The important function of the expansion tank is to contain an air cushion at the filler neck lid - maintaining desired system pressure. Where the header tank is fitted on the ‘big’ engine - the lid there is a blank…
As the coolant cools and contract - coolant is forced back into the engine and radiator through the vent lines. And eventual air collected which will migrate to highest points in the engine/radiator, where the ventlines are connected - to be flushed back into the expansion tank as the coolant heats and expands…
