TR2/3/3A Question on TR3 thermostat from TRF

The online TR3 catalog at TRF has only 2 choices of thermostat for TR3...the original bellows type and what is described as "modern type". The catalog says that the "modern type", p/n GTS104, can be used if the bypass hose to the radiator is blocked. I currently have a copper plumbing plug in my bypass hose, however based on information I got from some forum, I drilled a small hole in the middle of the plug (1/8" or 3/16" as I recall). Based on the TRF catalog statement, to use the TRF thermostat, should I replace the bypass hose plug with one that has no hole in it? Thanks!
Bob

The plumbing plug with the hole will work just fine.

M.

IMO, no, not unless you drill a hole in the thermostat.

With the bypass blocked and the thermostat closed, there is almost no water circulation. But there is still the usual amount of heat put into the water around the exhaust valves, so the coolant there can get a lot hotter than the thermostat setting, even boil, before the water at the thermostat gets hot enough to open it. Then when the thermostat finally does open, there is a rush of still-cold water (potentially below freezing in cold weather) into the near-boiling (or even higher) cast iron cylinder head. The sudden thermal shock can result in cracks.

The GTS104 type thermostat actually became the standard thermostat later on, and is listed as a factory-approved supercession for the earlier type. The thermostat housing was slightly redesigned, mostly I suspect to make it easier to cast, but the new casting did have a slightly smaller bypass passage.


I've experimented several times with my own cars; I found no real-world difference in cooling between fully blocked and fully open.

My current cooling system is not stock (mostly electric fan and an overflow bottle), but I have no cooling issues whatsoever even in 115F ambient temps, with the bypass fully open. (The driver overheats before the car does, at 115F I start looking for someplace cool to wait for the sun to go down.)

I use a sleeved thermostat which I believe they came with and with that I have a tropical fan. I also have a bellows thermostat that I took out of car that was a barn find which is made in England and maybe original. I can tell by looking the sleeved one is going to do what they are both designed for which is blocking the bypass hose for warm up more effectively. Not sure which one is truly correct. If you are having over heating problems, it is probably the fan. If not the fan, the radiator has plugged lines.

The TR Register has a nice list of items to check in cases of overheating: https://www.tr-register.co.uk/forums/index.php?/topic/58689-4-cylinder-hot-engine-causesanswers/

Something else to consider is using a "fail safe" type thermostat that stays open if it should fail: https://motorad.com/motorad-catalog/parts-locator/part/?pid=7200-180

Moss sells them but you find them at your FLAPS or on-line cheaper.

Yeh I saw the movie ---Fail Safe---I always call Moss motors with my problems, but we seem to be on different pages.

Thanks for the responses!!
Bob