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Overcooling Healey 100

BobAH100

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I have a most unusual Austin-Healey: It NEVER overheats, even at highway speeds on a hot summer day, thanks at least in part to an alloy Wizard radiator, performance water pump, and D. Welch alloy head. Engine was gone through and rebuilt from the new steel crankcase and con rods on up. Yet, despite trying both the 160 and 180-degree F thermostats available from Moss and others (modern disc type), it runs too cool on a cool morning, even at 50 to 60 degrees F.

Aside from covering part of the grille (which a photo of Donald Healey in the prototype Healey 100 at Jabbeke shows was done back then!), might the original type sleeved/bellows thermostat work better? Thanks in advance for your thoughts!
 

GregW

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Are you sure your measuring equipment is accurate?
 
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BobAH100

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Will consider that. I’m just wondering whether it’s the design—modern disc vs sleeved bellows thermostat as original—that’s the issue.
 

John Turney

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Will consider that. I’m just wondering whether it’s the design—modern disc vs sleeved bellows thermostat as original—that’s the issue.
The heads have a bypass passage that recirculates coolant to warm up the engine faster. When the older thermostat with the sleeve would "open", the sleeve would block the bypass passage so almost all the coolant would go through the radiator. With a modern disc, coolant will continue to flow through the bypass passage and not go through the radiator. In summary, the old style is supposed to result in more cooling.

These cars usually tend to overheat when stopped or in stop-and-go traffic, not at highway speeds. When it's 75F outside, what does your temperature gauge read? On mine, once ambient reaches ~70F, the temp gauge reads about 100F above ambient.
 
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BobAH100

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Same here. As I said, cooling isn’t the issue. Since all the thermostats Moss and others sell are made in China, I will try a thermostat made in Germany from the 1970s—new old stock—to see if it lets the car run warmer in colder temps and heat up faster, which is what any good thermostat should do, without causing the engine to overheat in hot weather. Will report my results. Stay tuned ...
 
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CraigC

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Bob, you never did say what the temp was that you were seeing. Also, was the performance water pump sourced from the individual who rebuilds them on the east coast?

The heads have a bypass passage that recirculates coolant to warm up the engine faster. .....
John, this feature is specific to the 100-6 and 3000.
The bypass passage in a 100 is from the side of the water pump, directly beside the impeller, into the coolant galley that runs down the right side of the block. It is approx 1/4" x 3/4" and is always open.
 
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BobAH100

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Thanks guys! My Hundred runs between 70 and 80 c on the hottest days, which is great. But on a cool morning, where it’s perhaps 50 to 60 f outside, the gauge reads 50 to 60c (yes it’s a ‘53 so the gauge is centigrade). And the water pump is Denis Welch as is the alloy head, while the alloy radiator is Wizard. I’m about to try a different thermostat sourced from Germany (new old stock). Worst comes to worst, I’ll cover part of the grille as D Healey did on the prototype!
 

vette

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BobAH100,
My BJ7 has a centigrade water temp guage. (presumably because it was originally delivered to Germany). My temp runs at between 70 & 80* centigrade during most driving here in the northeast. That’s around 175 - 180* F. On really hot days meaning 90s and high humidity it will creep into the 90*c range in slow traffic. On really cool mornings the temp gauge will struggle to get above 70*c. My engine is a stock 3000 with a stock but cleaned out radiator. I’m running a Texas Cooler fan.
I suspect your wee bit cooler situation is do to the aluminium components installed.
 
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Just to be my usual contrarian self: Just because something is made in Germany doesn't automatically mean it's super quality. My '96 Ford Ranger has the 4L 'Cologne' engine--and thermostat--made in Germany, and the temp gauge would barely get off the peg from the time I bought it new (custom-ordered fleet sale). I finally got around to swapping in a Stant--AFAIK made in the USA--and the temp would get to mid-range on the gauge and stay there. Heard/read somewhere that all of those engines suffered that problem; i.e. a stuck-open thermostat. I still wonder if any damage occurred from running too cool for several years.
 

John Turney

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John, this feature is specific to the 100-6 and 3000.
The bypass passage in a 100 is from the side of the water pump, directly beside the impeller, into the coolant galley that runs down the right side of the block. It is approx 1/4" x 3/4" and is always open.
Thanks Craig. Always learning something here.
 
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BobAH100

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Thanks for all the suggestions! I have a vintage USA made thermostat as well and may try that as it’s rated at roughly 180f.
 
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