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TR4/4A TR4A Thermostat Bypass

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rlich8

rlich8

Jedi Trainee
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Should I be blocking this thing off??? I'm using a modern style thermostat. I forgot what I was told on this matter... My bad!
 
Look up the PDF on Bob Schaller's More BS on TR's. Someone said Moss has it on their site. he outlines the reason for plugging the bypass and describes the type of plug to use.
 
IMO no, you "shouldn't" be blocking it off on a 4A, at least not entirely. No circulation at all (even with the engine cold) leads to cracked heads.

BTW, the factory quit using those quaint sleeved thermostats some time during the TR4 run. The TR4-4A thermostat housing was redesigned to provide more restriction without the sleeve.
 
That's interesting, I'm still using my original sleeved 160 degree thermostat in my 1966 4A that I've owned since 1969. Low mileage when I bought it and I doubt that it was replaced before I bought the car. The housing does have a squared off bypass opening however. Wondered why it was made that way. It would provide some limited flow restriction.
 
Well, both the part number and the illustration in the factory parts catalog changed. If the Tstat didn't change, they went to an awful lot of work to create a mistake. I also believe the original thermostat was a 180F unit.

Check out TSB T-65-12, which talks about an alternate "pellet type" (so unsleeved since all the sleeved ones were aneroid) thermostat, 82C, for the TR4.

But I could certainly believe that someone, perhaps even the dealer, installed an sleeved 160 thermostat to make the engine run cooler. After all, "everyone knew" that was the right thermostat for a TR.
 
Temperature gauge on my car also has two dots where the gauge needle normally sits at 160 degrees. No numbers just a line which is red at the upper range. Almost seems like a calibration mark from manufacturing. I see that the SPC shows a non sleeved stst but I also know what came with my car. Can't say for certain that it was or was not changed however the car was barly used when I bought it. Just too coincidental.
 
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