<html><body><div>Went on my "heat of the day" test drive with a new radiator cap, it was close to 100. I live in the Santa Cruz Mountains at 2000' elevation. Drove down a fun winding road to get it up to normal operating temp, about 180. Then went up the main highway with the hammer down, keeping it in 3rd gear, going in and out of OD, and go it up to 210 degrees and change. Got off at Summit Road and down to my house, which is partly level and then a bit down hill so it cooled down a little. Pulled into the garage and it was a needle width below 210. Opened the bonnet and the radiator cap was snugly in place, no leak, no coolant in the catch bottle. Got my infrared thermometer and put the red dot on the top of the radiator, 205. So the gauge is pretty much spot on.</div><div><br data-mce-bogus="1"></div><div>So the culprit was the radiator cap. It does seem the car is running a bit hotter then I'd like, so I'll be exploring ways to improve it for extreme heat situations.<br></div><div><br data-mce-bogus="1"></div><div>Rye</div><div class="x-apple-signature"><br></div><div><br>On Jun 21, 2017, at 03:05 PM, Randall <TR3driver@ca.rr.com> wrote:<br><br></div><div><blockquote type="cite"><div class="msg-quote"><div class="_stretch"><span class="body-text-content"><br><br><blockquote type="cite" class="quoted-plain-text">In other words, it goes like a "bat out of hell".</blockquote><br>So did my Dad's TR3A (first one I had to maintain, over 40 years ago). It<br>would run right up to red line in 4th gear with no problem at all. But it<br>still had a severe overheating problem. I believe (in retrospect) that the<br>primary root cause with it was either worn fuel jets, or some ill-considered<br>carb mods by a previous owner.<br><br><blockquote type="cite" class="quoted-plain-text">From what I've heard from</blockquote><blockquote type="cite" class="quoted-plain-text">others, the cap should not come loose at 210 degrees, thus depressurizing</blockquote><blockquote type="cite" class="quoted-plain-text">the system,</blockquote><br>Yeah, I said that too. Cap should not come loose by itself, even with the<br>system actively boiling.<br><br><blockquote type="cite" class="quoted-plain-text">So maybe that's the area of questions. With everything being equal,</blockquote><blockquote type="cite" class="quoted-plain-text">engine timed and tuned, do you think in extreme heat and driving pretty</blockquote><blockquote type="cite" class="quoted-plain-text">hard uphill, that 210 degrees is acceptable temperature?</blockquote><br>Well, maybe. Depends on things like how accurate your temp gauge is, and<br>what kind of thermostat you are running. With no thermostat at all and an<br>accurate gauge, I would say that definitely indicates a problem. I can go<br>up Grapevine hill with my foot on the floor (as long as no cops around) in<br>100F heat, and the electric fan won't even come on.<br><br><blockquote type="cite" class="quoted-plain-text">When getting to</blockquote><blockquote type="cite" class="quoted-plain-text">that temperature range, or higher, would you expect the radiator cap to</blockquote><blockquote type="cite" class="quoted-plain-text">get loose, or blow off via the overflow hose?</blockquote><br>Cap should _never_ come loose on its own. It might play a tune for you, but<br>it should stay in place.<br><br>Depending on circumstances, you might lose coolant through the overflow; but<br>in general not at 210F unless the system was overfilled or you are at high<br>altitude (like 5000 feet or more). IIRC, 33% glycol, and a 4 psi cap,<br>should boil around 215F at 7500 ft.<br><br>-- Randall<br><br></span></div></div></blockquote></div></body></html>