I’ve just filled my cooling system for the first time, and have two significant leaks.
One is the drain tap in the bottom hose - the fibre washer is leaking. Tap and metal pipe are new, so not sure why that one’s leaking yet, need to investigate further.
The other is at the temperature gauge capillary bulb adaptor, part no. C.9621 in the diagram from XK140Explored. My adaptor has a copper washer between it and the aluminium inlet manifold, but the drawing shown does not seem to have anything. If there should be something here, should it be copper or fibre?
Doesn’t mention anything, just the adaptor.
So why, I wonder, does mine have a copper washer behind it? Anyone know if this is a tapered thread, or parallel?
Interesting! So, no washer on the 140, but present on the 150. I wonder when the change came in? Mine is the original inlet manifold to the car, May/June '55.
The 140 parts book gives the same number - C.9621 - but in Jag-speak I think that number just describes the part’s function, not any design changes. No mention at all of a washer and none shown in diagram F. If it’s a BSPT fitting, there should be no need for a washer (and indeed it wouldn’t work). It would need one if it’s BSPP, but the info isn’t clear. Time to try removing it and inspecting and measuring.
Steve, just a thought - on the 150, is there a washer between union and aluminium intake, or between union and capillary bulb, or both? I have both at present.
Hi Roger…the 150 parts catogue in the electrical section…guage…says 1 coper washer…i would expect the threads to be parallel going into aluminium…washer between union and manifold…the the bulb will have a flare nut i think holding it to the union…Steve
In the electrical section of the 140 book it simply mentions union for capillary gauge to inlet manifold. No mention of a washer - I’d expect BSPP into aluminium rather than a taper, too, which would surely need a washer. Odd.
Let’s hope the aluminium thread’s in good nick!
I think that as it’s coolant I could try PTFE tape and/or a thread sealer, probably with a new, annealed copper washer. I think the problem could be the very thin copper washer between the bulb flange and the adaptor, not easy to fix.
Plus, I have installed Evans and that, of course, finds all the leak spots. Encouragingly, there don’t seem to be any at hoses etc.
The adaptor is in a different place on the 140, Rob - it threads directly into the inlet manifold, not the thermostat housing. But the drawing I posted, and the parts book, do not mention a copper washer. Obviously it needs one as the thread is BSPP, not BSPT.
Unusually my drain tap conical tap is fine, it’s the washer that leaks.
Sorry I wasn’t clear, I meant the 3/8"-BSPP fitting should have a seal regardless of what engine it is in. Here is one in my '38 SS saloon 2-1/2 L pushrod engine, same fitting, same seal.
I think we’re all singing from the same hymn sheet here!
The only question I can see is why Jag put the washer in the 120 and 150 parts books, but not the 140. It also seems to have slipped past the XK140 Explored team, but that may be reasonable as their diligent research probably involved the factory parts book…
I agree that this should solve the leak, these washers are hard to find. I get mine new from West Valley Instruments who also supply them with their rebuilds of all 120-140-150 dual gauge.
I have experienced some seepage between the union and the manifold even with what appear to be perfect surfaces on both, I use aluminum sealing rings with a dab of permatex on the union and the sensor bulb.
Yes that is a nice washer that would certainly create a seal. I used neoprene ‘o’ ring…and didn’t crank down too much on the nut. Seems like it sealed enough to reveal a failing core plug under the Exhaust Manifold.
