Considering changing over to the S3 cooling setup on my S1. Use S3 radiator, overflow tank, etc.
Therefore remove the aluminum header tank/thermostat housing with the bung(blanking) cap off S1 and use the S3 simple thermostat housing and heater connector (I believe it is) .
Anyway, must use original S1 manifold obviously .
From images the S3 seems to have the same 3 bolt connection as the S1 …
Do the bolt patterns match? Simple plug and play?
Many thanks in advance!
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I’m almost certain the swop is a direct fit, Demian - it would be the Jaguar way…
However, it may not be an overall plug and play - the various hoses may not be directly compatible. You might need the specific SIII expansion tank as well…
Both cooling systems work well in their original configurations, but mix and match needs some consideration…
Frank
xj6 85 Sov Europe (UK/NZ)
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As mentioned recently, I’ve done this swap. But I also swapped manifolds–to a 420G. The S3 thermostat housing and water outlet fit the 420G manifold. I suspect they would fit the S1 Strangleberg manifold as well–I vaguely remember confirming this. There is a modification needed to the water pump though IIRC. The diameter of the bypass hose is much less, and requires that a different barb be fitted to the pump housing. I think that the large diameter S1 bypass hose was intended to add to the capacity of the smallish header tank. There was also some other detail that involved the pump–plugging an unused heater hose connection or something similar. I considered getting an S3 pump but wound up not doing so–can’t remember why but I know I wanted to keep my early S1 single pulley pump that I had fitted after removing the smog pump (to make removal of same less obvious).
You need to drill holes in the yoke under the radiator for the S3 version, and fit the S3 version of the sheet metal bracket across the top. It bolts right up, but its provision for cold air intake differs from the S1.
well, this is my experience.
the housing between the inake manifold (heater thingy) and the thermostat housing are the same.; however the bit that connects the hoses to the radiator and overflow tank aren’t. My series II has a fill location right off the thermostat housing between the upper radiator hose and the thermostat with a cap. The series III does not. that being said, the radiator hoses are different as well. I’ve included a couple of pctures.
Thank you (all) very much.
Dunno exactly what you are referring to above? …drilling holes in the “yoke” etc…
I would imagine the pump is from a series 3 … need to look it up for certainty, and actually I have a pic I wished to upload as I did wish to ask what this horizontal plugged connection is I have coming off my pump pointing towards the rear.
Received new radiator cap today and hoses so I feel more comfortable now starting it up.
Unrelated, but I do feel it is necessary to remove the head for my own peace of mind. A few studs have shims beneath the head nuts, so it is has been messed with and not done well anyway.
I am going to try and fabricate studs to remove the intermediate manifold too as I intended to remove the entire intake to clean anyway,and while there would prefer removing the intermediate manifold. Butterflies removed already as stated, egr removed and intending to plug properly, but hell, it is really a series of patchworks, and I would prefer removing it for reasons of thoroughness and professionalism.
PS: I would LOVE to replace my manifold with a 420G as you have. In time i will. Now I just want to get her running soundly.
Yes Mark, they are different, as Frank has written in great detail,as have I …within separate thread “engine knock”.
It needed its separate thread though.
Images are helpful though for those who don’t know, thanks…
Yes, mine is like your S2 with that header (purge tank) which is used for filling and where vapor is “purged”, then running to the lower overflow tank on the left inner fender.
What I am considering is removing that and installing the simple S3 thermostat end you have shown below the S2 image and running to the S3 type overflow and replacing original radiator with the S3 as mine should be replaced anyway due to sludge and all crap I’ve found.
Less expensive to buy new aftermarket S3 radiator than rebuild old one.
Anyway, simply creating a S3 setup for the S1 / S2 …
Thanks all for the thoughts and time. We’re not building a rocketship here, will genuinely consider it.
As Frank states, it is the Jaguar way, and as the 420G even fit apparently, certainly the S3 will too.
Not an expensive part or difficult to find.
Strangely the S3 parts engine I am buying does not have the thermostat housing of all things…damnit. But am certain I can find cheap online if I go that route.
Both the S2 and S3 radiators are designed to be electrically insulated from the chassis when fitted. On both, this is accomplished by supporting the radiator on two flanged rubber grommets. Studs (or pins) pass through the grommets to locate the radiator. Two similar pins/grommets locate and insulate the radiator on the top. For some reason, Jaguar changed the spacing of the pins so that to fit the S3 radiator you need to drill two new holes for the grommets (which remained the same part BTW) into the metal crossmember, or yoke, upon which the radiator sits.
Not sure if rubber grommets in Rad’s are for electrical insulation? I always thought it’s an anti vibration measure?
PS: This is the blanked off connection from water pump i was referring to…
Excuse the motor, not my neglect i assure you! Was ugly at that point!
Although I need to check the manual, if anyone knows where those 2 hoses run, and/or if I have a series 3 pump, do tell!!
Gotcha. Thank you.
Interesting, I never thought about need for electrically insulating radiator, however it makes sense.
Certainly a big unknown cause for faulty electrical radiator fans on later cars as it can effect the thermo switch. and perhaps issues related to electrolysis…anyway, never thought about that before.
Thank you once again.
I forgot I have this sitting in the garage. Not sure how. 
This is a '86 Series III 4.2l and I’m not sure why the PO decided to paint it burn orange. Supposedly this is a fresh rebuild. It doesn’t look like it to me. ANYWAY…
Here’s a couple of pictures of the water pump and thermostat housing from a North America non-smog (meaning not from California) 4.2l
Water pump and thermostat housing straight on
Thermostat Housing - and yes those are transmission cooler lines - I was lazy and didn’t want to deal with the mess when I pulled the engine. don’t judge me. 
I do have a question though, in your picture how come the vacuum line for the power brake booster is plugged?
Hah, you forgot? Yes, definitely sign you have too much stuff…
Funniest thing someone would paint it those colors, the blow by housing at front too!
Most bizarre thing.
Anyway, thanks…I see it is that connection below at thermostat housing is where the hose goes, …sigh…I was not aware of.teh additional S3 connection there…sigh.
Obviously I have a S3 water pump.
What is it for? Heater? grrrrr…uncertain what to do now with that plugged connection from water pump??
The manual does not show the hoses set up (strangely). Perhaps I can find online.
Ah, the other is where the brake booster is supposed to go on the rail?
I connected it nearer the rear.
Thanks
Did you say your car was a manual? my series II is an auto, and the vacuum in the back is where the auto trans mission modulator valve is connected. Is your car a f/i S 2 or carborated? Manual choke?
Ya, the PO was obviously color blind. I like the orange. on a Pontiac GTO, lol
No, it’s automatic…
Yep you’re correct, it is where vac modulator for trans goes…that’s another thing to get to.
Carbureted, manual choke…thank god.
I just trailered mine to the local pre electronics all British repair shop. To fix the carbs.
I believe its a bypass of sort. When I took mine apart, there are (if my memory serve me, there are several small passages, one keeps circulation so the water pump doesn’t cavatate and I think one tiny passage bypasses the thermostat, too. I’m use to working on old Chevy mouse and rat motors, so these fancy British engines have been a real mind bender.
I think about the American Iron, and what they were producing in the 70’s and 80’s, it blows my mind on how may decades they where behind the technological curve.
Seriously, a double overhead cam L6 in the 60’s. Pontiac attempted a single OHC in the 64 tempest, and it was an epic fail.
Defeated eh?
Well update how it goes…
Thank you for info.
Kind regards
PS…i just looked at your profile. Holy smokes! You have quite a collection!
I suppose it’s nice to be able to choose what to drive everyday…
Washington must be beautiful this time of year.
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On the SIII the plugged water hose goes via the transmission cooler (automatics) to the bottom of the radiator, Demian…
So what is connected to the radiator ‘out’ - for circulation; the radiator must somehow be connected to the water pump…
The brake booster requires manifold vacuum from somewhere, doesn’t really matter how - but since you have not commented on your brakes, booster must be ‘active’. If not, the braking effort would be superhuman…
Frank
xj6 85 Sov Europe (UK/NZ)
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Thanks for your reply and thoughts as always Frank…
Strange the original S! XJ6 manual doesn’t have a diagram of cooling system I can upload.
Again, it is a S3 motor, and apparently water pump, within an otherwise standard S1.
While sitting in a LHD car…
I see you have a S3 Frank…dunno how good your memory is.
Attached a parts image from XKs Unlimited I found.
That plugged hose I have within photo above is IMAGE 9 within diagram …
IMAGE 8 would be the short/fat squatty hose connected from pump to lower header tank I have (which is just shown at top right corner of my image above, and apparently incorrect type)
However I still don’t know where hose #9 connects on a Series 1 (as shown within the XKs diagram).
Kind regards
PS: As a note, to be thorough and avoid confusion and back and forth replies.
IMAGE 5 connects to front of header tank. IMAGE 6 connects to lower water pump.
IMAGE 10 connects to intake manifold.
All connections at back of manifold are plugged (by PO). no heater connections,etc.
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The diagram is more confusing than clarifying, Demian…
It doesn’t help that the differences in hose set-ups between the header tank and the plain thermostat housing is not shown - and that the numbers do not describe actual connection points. In fact, most diagrams shows separate items and their connections, but not the overall picture of the various set-ups. In fact, I’m equally guilty; I never had the need to do a detailed examination of the overall layout of my own SIII…
Briefly; thermostat housing connected to radiator top. The bottom radiator hose to the pump (via the transmission cooler on automatics - a plain tube on manuals)- which also has a connection to the thermostat housing, open with the thermostat closed to ensure continuous circulation through the block with the thermostat closed. The heater ‘in’ is connected from the water rail, the heater ‘out’ connected to the pump. The main point being that the pump, in all versions, forces coolant into the engine block - all differences are in how the coolant is returned to the pump, and the vent hose set-ups.
The central point to remember; all hoses at the pump is ‘in’ to the pump - the only pump out’ is into the block…
From the block the coolant flows through the block and head into the water rail, closed by the thermostat during warm-up - then circulates through the radiator. The heater flow is controlled by the water valve - and cooled coolant returned to the pump.
In your case, and contrary to my previous assumptions; your blocked hose is then likely the heater connection - and the PO blocking of the heater hoses seems to confirm that…
This is basically the SIII layout description and the only touches some of your hose connections - the original, SI set-up may differ in detail, and the probable use of the SIII water pump may further cause some confusion. The outlet dimensions (and locations?) may not be compatible with the original SI set-up…
How to sort it out is a different kettle of fish…
Frank
xj6 85 Sov Europe (UK/NZ)
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