While you have the transmission out, I would suggest removing the oil pump and replacing the large o-ring that goes around the pump as well as the pump gasket and front seal. I've seen several cases of pump o-ring leakage on older 400's, in Jaguars and other vehicles. It is easy to reseal the pump now, but a whole lot harder once the car is back together. There are videos on youtube showing how to do it. The parts are cheap, as little as $12.99 on ebay.

 

OK, Andrew. Pics herewith:
Your mystery piece (your photo):

This assembly is a PRESS FIT into the oil cooler casting, as shown in my pics here:

Full Flow oil filter casting general view. Note huge threaded plug at bottom

Close up of internal oil relief valve. If the cooler gets blocked the internal pressure forces open this valve to allow high pressure oil to the engine.

Valve in closed position

Valve in opened position (pushed open against the spring)

Close up of valve in closed position. This valve assembly, as shown on its own in Andrew's photo (first photo in text above) has to be pressed into position in the casting by unscrewing the large plug, pressing in the valve, then replacing the plug.

In your original photos, it is clear that the valveless spring has just been placed into position, and as you guessed is doing nothing. The valve and spring assembly you have (your photo reproduced above in my post) has to be pressed into position in the FF casting in order for ANY oil at all to go into the cooler. No valve = no oil being forced through the cooler and probably not much pressure anywhere! Which may or may not have something to do with your engine failure....

On re-reading your post about this, if you are going to FF cooling in your new engine - it makes naff-all difference by the way - I am pretty sure that if you change the sandwich plate you will have to make an internal change to block off the oil pump inlet that was fed by the bypass system. On the FF there is only one oil inlet to the pump - from the pickup in the sump. On the Bypass system, there are two: one from the sump pickup and one from the oil cooler return via the front RHS of the sandwich plate. I am pretty sure (not 100% but pretty sure) that if you change the bypass to the FF sandwich plate, you will need to blank off the inlet to the pump that the oil cooler output flow was connected to - otherwise the pump will be trying to suck in air from the open inlet. All you need to do is leave the original sandwich plate from the bypass system and just blank off the inlet at the plate: ie instead of the cooler pipe going into the hole just blank it off with a plug. You can check this by looking down the hole in the sandwich plate that the bypass system flow enters, and if it leads straight into the pump just blocking it off at the sandwich plate will be OK.

As I indicated above, just keeping the replacement engine's bypass system would also be fine, as long as you can get the local hydraulic shop to reuse the cooler pipe metal parts you need to make up pipes to hook it up to your FF cooler. The theory being with the Bypass system - in non-racing applications anyway - that the cooled oil goes back direct to the pump, and thus to the engine, so the engine is always being fed mainly un-mixed-with-hot sump-oil cooled oil. I did some careful measurements and my Bypass system engine oil on a 35 degrees C summer day on a hot fast run, never got over 93 degrees C anywhere, and my cooler took 20 degrees C out of the oil across the cooler. So I never bothered to fit the FF system I had bought!

 

To add to Gregs snaps, these parts schematics may help also.

There is a large spring loaded valve in the top face of the Sandwich plate, full flow AND By Pass, and is the flow back relief IF there is a filter blockage. #12 in the last drawing.
1st drawing is the By Pass System.
2nd drawing is the Full Flow System.
3rd drawing is the Oil Filter Relief Valve drawing.


By Pass System
Full Flow System

Oil filter relief valve #12.

 

Both Greg and Grant,,, Jaguar shops globally should have y'all on retainer! Jus say'n... Makes me want to pull my engine - kinda, lol

And Greg, I have your post to my wheel spacer thread on my mind. Thanks for offering it... I didn't not see it, or ignore it - and I appreciate it The spacers are on the way and as soon as I place them, experience a little, and see what I got - I'll ask some questions,,, cuz I'll have them I'm sure.

Yeah, y'all are a wealth O info.
Many many Thanks 😊

 

Thank you both very much. Sorry for some reason it didn't alert me I had replies.

Strange why the bits in photo are missing then wonder why and when they had been taken out. Its not as though they are small enough to dislodged and dissappear somewhere.

Yes as you say the piping is different inlets. As I am swapping over the oil housing the pipe is already blocked off. However on the underside of engine there is also an inlet on the engine which I also need to swap over as the engine I'm taking out has a blanking plate instead.

Just so I'm clear So that valve which is in first photo came out of the bottom of the bypass system as per fig 3 drawing. So that valve in full flow should be put in where you show in your photo by undoing the cap? Or do I need a different type of valve.


​

 

So in actual fact looking at the full flow diagram its 11 and 26 I seem to be missing. Not sure where 27 is supposed to go. You don't have the part number section for those diagrams do you?

 

OK, this is getting into real muddy water, AKA I dont bloody know.

The parts book, as per the schematics above, show that valve as IN the oil filter housing for FULL FLOW system, as per Greg, and C37888 is the Part #.

The 3rd schematic is showing the SAME part # for that valve in the top of the Sandwich plate, where you say you found yours, BUT for Relief oil cooler system only. AKA Canada, Japan, USA. We got By Pass as well but dont get a mention.

SO

My understanding, and based on NEVER seen, or worked on, a Full Flow System.

Full Flow has C37888 in the oil filter housing, #2 drawing above.
By Pass has that C37888 valve in the top of the Sandwich Plate.

NOW

Oil is pumped TO the oil filter housing FROM the pump.

The Full Flow diverts that oil to the cooler, and back to the housing for distribution to the engine. Before or after the filter has ago, I dont know.

The By Pass diverts oil to the engine from the oil filter housing, after the filter has filtered it, and some is sent to the oil cooler, where it is cooled and returned to the suction side of the pump via that fitting at the front of the Sandwich Plate.

My further understanding is:
BY PASS SYSTEM. This valve is a safety thing, so if there is a blockage in the cooler, filter, etc the engine is simply supplied oil direct from the pump, as normal, thus no starvation takes place, and this valve simply allows excess oil to dump into the sump.Because the cooler is blocked.
FULL FLOW SYSTEM It appears there is NO valve in the Sandwich Plate, and the relief is taken by the valve in the oil filter housing, and oil still gets supplied to teh engine and excess is dumped via a chamber in that oil filter housing.

BUT

You have found that valve in the Sandwich Plate, odd according to the Parts Books.that should not be so.

WAIT PLEASE

I have a factory Manual in the shed, and an actual Parts Book. Tomorrow, its 10PM here, I will take a few beers and have a read and come back with whatever I find.

 

Thanks for reply, we might be talking cross purposes here in the last bit I may not have explained properly . So the valve I found in the bypass is correct as per your schematic part 12. I found it on the bottom where in diagram I am assuming that is sandwich plate. What I found in my original full flow. Was just a spring inside where 11 and 16 go in the full flow diagram and where Greg mentions it appears that spring should be part of a valve also. So I wasn't sure if I could fit number 12 there as they had just moved it. Or if I needed a different one with the bits 11 and 16. From what you have said so far it would seem it is the same valve.

Anyway thank you, enjoy your beers, have one for me and let me know what you find! 😁

 

AHA< the mud clears a tad.

Looking at the Parts Listings,, 11 and 16 become one Part Number, C37888, so the seperate bits were very misleading.

I still see no reason for no valve at the bottom on Full Flow System, but then I am not privileged to the design of either system.

I will still study those books tomorrow.

 

So I don't want to deprive a man of his beer drinking whilst musing over the jag engine. So I'll ask you to drink beer instead in celebration you sorted it! 😁

After Greg confirmed there was supposed to be something there and you said it may be the same part number. I went and checked again and found that what I didn't realise was that in the hole was still the outer part of the valve cover held in by a clip. So I took that out and checked the spring and bottom cover to the bypass one I had and its the same. So what happened was at some point the spring retainer and the centre part of the valve have come off and probably disappeared inside the engine or oil sump. So the one from the bypass now fits in and is held in by the original clip. So many thanks one more issue sorted. Sure many to go!
J