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TR2/3/3A Found my overflow problem from the radiator ,

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Jerry

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I am disappointed. I kept boiling over when the temp gauge said it was not quite hot enough (new rebuilt from Valley west). The cap I put on is only 3/4 inch so I had no back pressure. I would have thought I should have measured that prior to starting the engine. Too eager . Anyway, on the way to NAPA for a cap. Anyone know the numbers?

Jerry
 
You're not likely to find a 1" reach cap at NAPA. Stant used to have a listing for it, but the listing was wrong and the actual cap was only 3/4".
 
You are correct again Randall, NAPA listed one but did not have it in stock. I will put an old one on I found in the barn till I find a replacement.
Jerry
 
Probably have to order one from the usual suspects. Or, if you feel like driving over to San Rafael, you could probably pick one up at TRfest tomorrow.
 
Triumpfest will be good this year. I will be Sonoma Race track on Thursday for the Le Mans start. Also on Friday and Saturday, I will bring a spare with me. Hope to see you both there.
 
Sorry, I'm not going this year. Combination of family complications, no vacation time, and the TR3 is still wrecked.

I know, I could go without a Triumph, but I know from experience that I get to thinking "Why aren't I home working on the TR?"

But thanks for reminding me, I need to call someone about a front apron. Hopefully he hasn't left yet.
 
I asked a friend who knows a lot about radiators and caps. Here is what he wrote:

"The cap MUST match the depth of the hole. You should first order the cap that the manufacturer of the radiator suggests. Then you should measure the amount of 'squish,' that is the amount of spring so that you are sure that the cap can release and is not bottomed out. Lastly, a 4 lb cap is what I believe they recommend, but it is not as critical as the depth."
 
FWIW, I found it difficult to measure the cap accurately. The sealing end flops around, and is not flat; plus it's tough to measure accurately how far the top of the cap is from the top of the filler neck when installed. Ultimately it was easier for me to rig up a pressure gauge and Schrader valve (tire stem) on a tee to the heater valve fitting on the head, and inject small amounts of air until the radiator cap started to vent. Then I could watch the gauge to see how much pressure the cap would actually hold (and that I had no leaks). The gauge did drop a bit more overnight, but I think that was because the engine got colder during the night than it had been when I started.

More of a hassle if you have a heater (I don't), but might be worth considering if you want to know exactly what the cap is doing.
 
Randall, I don't think I follow you on the reported problem with measuring the cap accurately. If you measure the underside of the top of the cap to the sealing end, you should get the accurate measurement. I measured mine and it is exactly 3/4". My sealing end has a metal ring to stabilize it, so it doesn't flop around.

One of my problems is that nowhere in any of the descriptions of radiator caps for sale do I find depth measurement. All they provide is overall measurements and pressure. Seems to me they would want to distinguish 3/4" from 1" depth.... or perhaps they are all normally 3/4" now???
 
I will be at Triumphfest. Look for the TR3A in a Tangerine color. NO fenders, doors etc. It should be the only one there. It has lights, turn signals and such that I can drive it but the fenders and such needed repair from my painting experience. I have not decided if I will drive it to the Sonoma raceway, it does not have any break in miles yet. But maybe that will be a nice 18 mile drive that will be good for it.

Jerry
triumphfest 2013.jpg
 
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