I have tested: the commissioned by Moss-Europe.com sleeve bellows thermostat, part 434-156 107590, 160F, (71.11C) " Classic Gold: Authentic Reproduction," Made in China. It is currently priced at 87 British and seems not listed in Moss / Xks USA…but call. ?? The top lip diameter is 54.83mm and is ever so slightly too large for the 54mm lip recess in the XK120 housing. This can be easily revised by a fine file dress up around the circumference of the lip. The lip thickness is fine for the recess. The bellows is noticeably longer than the Smiths by approx 6.78mm however it is just barely in the coolant path and seems not to be an issue. The sleeve, at low position when cold, sits cold with its upper surface 17.1 below the lip, while the Smiths is 15.4. This made me wonder, will the sleeve rise enough to block off the bypass. The Moss sleeve is vertical dimension is 16.25…just a little more than the Smiths at 16.0 As it sits lower to start with, the sleeve does not cover any part of the bypass when cold. In hot water (I did not test the opening temp) the sleeve raises as it should in concert with the lid and did open fully to the stop, Then and when fully open I inserted the open thermostat, sleeve in raised position, into the XK120 housing. The sleeve did cover completely the bypass opening, as it should. The total lift of the thermostat top seemed the same as the Smiths. The Moss does also have the small poppet in the lid. So I conclude that the Moss sleeve bellows thermostat IS a replacement part for the XK120 and tho not tested in the 140 housing , the part operation should be the same and should be fine for the 140-150 as well noitn they all used the same original Smith’s part. Do note the slight dress to fit of the upper lid circumference, which is not a critical fit as long as it fits seated fully in the recess. (The Smiths fits a tiny amount smaller within the recess.) This thermostat is ONLY for 4-7lb max systems. This part is 434-156. Note that Moss part 434-155 is a wax thermostat for systems more than 7lb ( 4 lb is the XK spec, and more is not recommended for the XK systems) , and the sleeve is in the upper position cold, so moves downward to close the bypass port. It was neither tested nor measured but should work. Note that the 434 180 (inexpensive) and any similar are NOT applicable to the XKs, as there is NO SLEEVE, thus does not block the bypass at all. Cheers…Nick
I have tested: the commissioned by Moss-Europe.com sleeve bellows thermostat, part 434-156 107590, 160F, (71.11C) " Classic Gold: Authentic Reproduction," Made in China. It is currently priced at 87 British and seems not listed in Moss / Xks USA…but call. ?? The top lip diameter is 54.83mm and is ever so slightly too large for the 54mm lip recess in the XK120 housing. This can be easily revised by a fine file dress up around the circumference of the lip. The lip thickness is fine for the recess. The bellows is noticeably longer than the Smiths by approx 6.78mm however it is just barely in the coolant path and seems not to be an issue. The sleeve, at low position when cold, sits cold with its upper surface 17.1 below the lip, while the Smiths is 15.4. This made me wonder, will the sleeve rise enough to block off the bypass. The Moss sleeve is vertical dimension is 16.25…just a little more than the Smiths at 16.0 As it sits lower to start with, the sleeve does not cover any part of the bypass when cold. In hot water (I did not test the opening temp) the sleeve raises as it should in concert with the lid and did open fully to the stop, Then and when fully open I inserted the open thermostat, sleeve in raised position, into the XK120 housing. The sleeve did cover completely the bypass opening, as it should. The total lift of the thermostat top seemed the same as the Smiths. The Moss does also have the small poppet in the lid. So I conclude that the Moss sleeve bellows thermostat IS a replacement part for the XK120 and tho not tested in the 140 housing , the part operation should be the same and should be fine for the 140-150 as well: they all used the same original Smith’s part. Do note the slight dress to fit of the upper lid circumference, which is not a critical fit as long as it fits seated fully in the recess. (The Smiths fits a tiny amount smaller within the recess.) This thermostat is ONLY for 4-7lb max systems. This part is 434-156. Note that Moss part 434-155 is a wax thermostat for systems more than 7lb ( 4 lb is the XK spec, and more is not recommended for the XK systems) , and the sleeve is in the upper position cold, so moves downward to close the bypass port. It was neither tested nor measured but should work. Note that the 434 180 (inexpensive) and any similar are NOT applicable to the XKs, as there is NO SLEEVE, thus does not block the bypass at all. Nick
a look today at ebay.uk…several NOS sleeve bellows thermostats for the XK…item 273536660718 is an AC TF4 86C, nice cond in box 19.95UK, also item 223948511032 a Smiths 85025/80 80C at 82UK…pricey but offer? if you want a a Smiths for your collection or use. and another… the QH TF3 68C at 39.95UK item 143590541827 39.95UK All correct for XKs and XKE early series 1. As mentioned above the Moss Europe thermostat…also avail. I’d think a 68C would run open…all the time after initial start up. I doubt you’d see your coolant run as low as 68-70C anyway…but if it did…it is a few D below the optimal run temp. It would have to be a cold day…or a really exceptional XK cooling system !! Remember…they used 80 to 86C stats in winter…to reach optimal op temps. so don’t just think…colder is better. .Nick
I was just having a look at the Moss UK website to check out the various options you mention vs what I see on the Moss XK Unlimited US website where is shop; I have ordered the C3731/1 aka 434-156; the thermostat I took out was a 82C without a sleeve; hopefully this, coupled with a new water pump, a system flush and a new 4 lb cap will help me out!
Hi Nickolas, I have been shopping at XK Unlimited in the US - this is presumably where you saw the $100 option? what other suppliers are you looking at?
and what part of Canada are you in? I’m in the hot and sunny Okanagan in BC
Cheers,
I’m in Niagara, Dave. We relocated here from Mackenzie, BC, just a little north of you … like 800 km or so little. Almost bought a building lot just north of Kelowna 14 years ago but then got transferred here. Decided to stay. I have done most of my sourcing for my E and 120 from SNG.
I can tell you the C3731/1 I bought for my 140 did NOT do the trick…mainly because the blocking sleeve moves away from the mounting flange as it opens. Be sure to check all of the measurements after you receive yours…could be a different configuration than I received.(I hope)
the C part number…3731…was a Jaguar part number…for a thermostat…made by Smiths…with a Smiths number on it…that Jaguar “C” number .it is now used…as a part number for several thermostats of current manufacture that are NOT necessarily what was original or that will work. So…don’t rely on that old C part number from a current manufacturer…it could be anything. For the XKs…the thermostat must be: a bellows-sleeve type…that fits…and whereby the sleeve does what it is supposed to do…open coolant path to the bypass when cold (and the path to radiator is closed) , …and as the coolant reaches the thermostat opening temp…the sleeve closes the bypass hole (xk120) or slot (XK140)…when the thermostat lid opens path to radiator. The old C part number tells you ZERO…even the old originals…did not have that number on the thermostat…they were Smiths numbers…or QH, AC, ReMax.
the correct bellows sleeve must LOOK like the ones in the photos…
the overall shorter one is like the Smiths, QH, ReMax. in the photo. The overall longer is the current Moss…the extra length makes no difference. Both have the sleeve that moves upward…as the lid opens…thus the sleeve closes the bypass port. The only other type that works…is the type with sleeve at top when cold…the sleeve moves down to close the bypass port. With no sleeve…the bypass (means coolant bypasses the radiator)…remains open …and a lot of coolant circulates back thru the engine without ever being cooled…so becomes even hotter.
The “top down” style (C3731/1 I received) will not work on either of the 140 manifolds without modification…not even close. You will need the “bottom up” type(bellows type)…as pictured above. But as Nick sez, the original “C” number does not really tell you much with respect to these (WAY) after-market pieces.
IF this is what you receive, either modify it or try again.
I believe you Lee…I know you have had a 140 housing to test…an bottom up…was what was original…there are still plenty avail on ebay UK of various temps…and the new made Moss would seem to be OK…as I noted tho…the overall length…at the bottom…is different-longer, as seen in the photo of both…of no consequence in the 120…how bout the 140? Nick
As long as the sleeve comes to within about .23" of the mounting flange when open…good to go. The other issue COULD be the OD of the sleeve as the part I bought is about 3 or 4mm too small.
well… the part that XK Unlimited shows on their website looks like the “top down” style that Lee140FHC shows in his photo; but the part that arrived in the box (with the correct / same part number on it?!) is a “bottom up” style such as the 2" tall one on the left hand side of Nick’s photo, so I think I may have done better than expected… yet to be installed etc… a quick test shows its a little bit big and will need a small amount of filing to get it to sit into the manifold correctly…
Hi Dave…so seems you have received the relatively newly produced, for Moss Europe, now avail in USA Moss-XKs…the thermostat part 434 156 which is a bottom up …sleeve…it should have imprinted on it…160F Made in China. Moss commissioned the build. .I too found that the circumference of the upper lip edge was just a tiny bit too large for the recess…easily fixed with a fine file…all the way around. See my post above…You might want to test the unit in hot water prior to install just as a precaution…so that you KNOW it is operational. Yes…the stat on the left in my comparison photo is the Moss 434 156. It just became available in USA-Moss-XKs a few months ago…so may not show in the catalog, or on line yet. I hope it works for you. Nick
That is AWESOME news…gotta check on availability for myself now…
New thermostat is in, took little trimming to make it fit, new water pump as well… now cruises at @ 75° vs previously at 90++ with a dip of the charts over 100!
is the “trimming” you mention…to the outer rim of the top surface…as i described earlier…and that it is the Moss thermostat…odd that it would be that tiny bit too large…as nearly all thermostats of the day were of the same size OD size…but Moss did at first specify it for Healy and others…not the Jaguar XK…anyway…it is a slight trim…nice that it works well…runs at proper temp. Nick