Hi All…I currently have a S1…in the service manual it gives a description of the oil filter housing pressure relief valve opening at 45-50psi…and gives spec for oil pressure as 40psi at 3krpm…Im after the same info for a S3 car…its a friends car and i dont have a S3 manual…my understanding is the oil pump is higher pressure? Here is a photo of the S1 manual page…do you have the same info for the S3 you could copy/photo…thanks…Steve
Should be the same (per my gauge), the pump is bigger so it delivers more oil which is especially important at hot idle. More top end pressure should not be needed.
If you want the S3 manual I can send you some parts of it tonight.
David
Hi David…thanks for the reply…my thoughts were the pump is bigger and the oil guage can read up to 100psi…if you can possibly look in your manual for me and see if there is a description with figures that would be much appreciated…Steve
I will but I think the manual is not very clear and gives something similar to 40@3000. And then there’s the old rule of 10 psi per 1000 rpm.
My gauge is sitting at about 40 psi when not hot and not below 1500 rpm. As long as the relief valve is limiting the maximum pressure and not the pump, things are fine. That is probably why the pump got larger. At the lowest possible idle the oil lamp should not come on and apart from that I really wouldn’t worry. No idea why the gauge goes to 100!
I’ll look for the manual tonight 
No info in the engine book. Assume that it‘s all normal.
David
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The gauge reads pressure after the filter and relief valve.
Increased pump capacity relates more to the amount of oil the pump can deliver - which also reflects the pumps ability to maintain pressure as leaks caused by bearing wear etc increases…
The relief valve offers no protection against low oil pressure - its exclusively used to avoid excessive oil pressure, which is counterproductive.
As the characteristics of the xk changed little through the years. As David says; the oil pressure specs given for S1 is likely OK for the S3 - though there is some ‘rumours’ that the relief pressure on the latter is some 60/65 psi…? Generally; Jaguar specifies 40 psi at 3000 rpms as an indications that oil delivery is satisfactory to supply the engine’s lubrication needs throughout. This has no significance with a properly working relief valve…
As an aside; when the valve opens, oil is diverted from the valve back to the sump - reducing oil flow through the engine itself. In cold weather, with thick oil and elevated pressure may open the valve, it means less lubrication while the engine needs it the most. Which is one of the reasons for thinner oil in cold weather…
Frank
xj6 85 Sov Europe (UK/NZ)
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Hi Frank…thanks for the reply…yes i fully understand what you are saying…im not questioning how the valve works…my question is about the description in the service manual of the S3 cars…the S1 manual shows 45-50psi operation of the valve…so what does it actually say in the S3 manual…you do mention 60/65psi…my thinking is that with the increased capacity of the S3 pump and that the oil pressure guage has markings up to 100psi on it then Jaguar possibly increased its figures for operating oil pressure and valve operation…so is there any info in the service manual to clarify this or anyone know of a service bulletin chang re oil pressure…Edit…possibly a S3 owners manual has oil pressure info?..thanks all…Steve
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I have found no reference to the opening pressure of the relief valve in my S3 manuals, Steve - though it doesn’t mean that specs do not exist…
The valve construction is different between the S1 and S3. And no actual test procedure for the valve is described - though it can be inferred…
Which doesn’t really answer the question…
Frank
xj6 85 Sov Europe (UK/NZ)
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Hi Frank…i do appreciate you looking…does it specify an operating oil pressure like the 40psi in the S1 manual…or do you havd the small owners manual that may have it…cheers…Steve
Just for info…i started looking for this info becaus useing a calibrated wet guage on a friends S3 we are seeing 65psi on cold startup…on my S1 i would expect the relief valve to open befor this…so does the S3 run higher…and relief valve open higher…Steve
I have a Series 3 oil pump in my E Type and a Series 3 spin on filter head. It’s just passed 5,000miles. On 15w50 oil it runs 45psi hot idle (about 700rpm) and seems to limit just beyond 65psi hot running. My Series 1 XJ6 runs same oil, same pump and filter head and has about 12,000 miles since rebuild. Similar oil pressure readings. Both have mechanical OP gauges (full scale is 100psi). FWIW. Paul.
On the Series 3, based on the area of the piston in the bypass valve and the spring pressure at the relevant heights, valve movement theoretically starts at 55 psi, and the bypass ports are exposed from 65-73 psi.
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The question is then is the pressure increases further as rpms increase, Steve. If not; the 65 psi you are reading is indeed the relief pressure…
Which also means that your friends engine is at or above relief pressure with the engine cold. How cold, and what oil is he using?
By other posts it seems reasonable to assume higher relief pressure on the S3 than the S1. However, the S3 valve is adjustable. It’s conceivable that Jaguar upgraded the pump and relief valve based on experience - but it does not mean that S1 set up is not viable…
And, sorry, I have the S3 owners manual - and I need it…
Frank
xj6 85 Sov Europe (UK/NZ)
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Hi Guys thanks for the Replies…Colonial…where did you get the information to come up with your figures…i dont doubt them just interested in the results…Frank…oh yes i wasnt asking for your handbook just if there was a specified oil pressure in it…Iv since seen a S3 handbook and it says "no less than 40psi at 3krpm…slightly different to the S1 manual "40psi at 3krpm…Friends engine cold(6degC) 20/50 oil…we havent let it run yet till we can find some good figures…I didnt realise the S3 valve is adjustable…question now what figures to adjust it to…Unfortunatly i now just have this need to know what the actual Jag spec is…all the best…Steve
Me neither! Only way I see is dropping in a shim or two so the spring gets compressed.
Which is accepted practice, at least I’ve seen it done. My 40-45 psi at everything above 1200 are sufficient though. If it is a RHD, leave it be, unless you have a lift and time. The steering is in the way.
Steve - this was done by measuring the spring height implied by various valve positions in the housing (while it was in pieces), and measuring the spring pressure at those heights, and dividing by the area of the valve that the oil pressure acts on.
The parts manual suggests this would be do-able for S1 as well?
Anyway it’s great to see my fish scales verified by Paul’s gauge, and the calibrated mechanical gauge on your friend’s S3 - or is it the other way around…?
Simon
Or not, as it looks like the valve mechanism is a single component…
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I ‘think’ the 65 psi quoted repeatedly for the S3’s relief valve can be taken as gospel, Steve - based on observations by listers, even if not stated in manuals. And I’m equally sure that the 45 - 55 psi you quote from the S1 manual is equally so.
The difference between the two valve specs is as yet unexplained. But Colonial’s input may imply that your S1’s manual states the ‘start’ of the opening - while lister experience shows ‘fully open’ relief pressure…
Which would be highly satisfactory; no actual difference between the S1 and S3 engines’ oil pressure requirements - which makes perfect sense.
Notice that the minimum oil pressure, 40 psi at 3000 rpms, is the same. And the relief pressure is of less interest - and is not mentioned in later manuals.
Frank
xj6 85 Sov Europe (UK/NZ
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And yet I‘ve not yet seen an XJ6 with 65 psi on the dial. Paul Novak‘s shows about 55. mine might do 50. I‘m certain that 40 is all you‘d ever need on a not just rebuilt engine.
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The gauge pressure basically shows the flow resistance within the engine (and filter), David…
The valve opens when this internal resistance is high enough for the relief valve to open. The point is that with proper choice of oil viscosity the relief valve will not open. Ie, the valve must be specifically tested to verify its opening pressure…
Though experiment; if the oil is too thick to pass through the bearings - the relief valve dumps all oil back into the sump. To wit; you may alter oil pressure at will by altering oil viscosity - one solution with worn bearings; increase viscosity…
Without Jaguar specs for the S3 we are none the wiser…
Frank
xj6 85 Sov Europe (UK/NZ)
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Hi All…thanks for getting involved its been a good discussion so far…So we know the S3 has a larger o/p oil pump and a different oil guage and relief valve but we dont have any Jaguar figures?..over on the UK E forum we have Old Jag Service Bulletins that specify build changes etc…I have look but cant find much re these later XJ6 models…anyone out there have similar bulletins for XJ6 models…Cheers…Steve