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Best alternative option to sleeved thermostat?


Freshman Member
After doing plenty of reading, it sounds like the OEM style sleeved thermostat is the preferred/recommended style thermostat. My question is, what is the next best alternative? Are you better off running a modern thermostat without the sleeve and lose 25% of your flow through the bypass, or are you better off running the block-off sleeve and no thermostat at all? The context of my question is relative to cooling efficiency - not for using the heater (since we all know heat is not hard to come up with in a Healey!)
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When I first bought my Healey__1978__there was nowhere near the parts availability that we enjoy today; I think my first Moss Healey catalog had about 12 or 14 pages.

In any case, we used what we could get our hands on! I used non-sleeved thermostats (160* to 180* ranges) or gutted thermostats for years with no known ill effects.

Nowadays, I used a sleeved thermostat__because I can__and figure here in Florida, I'd better give my cooling system all the proper fitments that I can.

Healey Nut

Luke Skywalker
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If I lived in Florida I would take the **** thing out and drive without it. We all know that Healeys run hot and if you do decide to take it out on a cool evening then a chunk of cardboard to block of a section of the radiator works like a charm.
Last edited by a moderator:


Darth Vader
Hi All,

As I understand, the thermostat not only controls internal coolant heat but also flow. When running without a thermostat, you will eliminate any control of both and therefore it will take longer for the engine to heat up as well and assume a temperature more conducive for allowing lubricants to be operationally effective. As a result, the period when engine wear is most prevalent will be extended as will the time before efficient fuel burn. Add to this condition is the fact that it takes a period of time in contact for coolant to absorb heat from the engine and give up heat through the radiator.

Therefore, without a thermostat the flow rate and volume of coolant will be fast moving and could pass through the engine and radiator at a rate that will be less efficient for heat transfer to and from your coolant. The result, a longer period of initial engine wear due to slower warmups and higher running temperatures due to fast-moving coolant at driving RPMs.

There are many issues with the Healey Cooling System's design, but I don't believe eliminating the thermostat is much of a fix.

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Luke Skywalker
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Ray is correct. There seems to be so much misunderstanding regarding thermostats with some people believing they control the temperature that the engine runs at, which of course they don't. Removing the thermostat would mean the engine takes longer to reach operating temperature and therefore is more likely to suffer wear. That is why in cold temperatures you need a higher temp rated thermostat and vice versa.


Darth Vader
Country flag
If I lived in Florida I would take the **** thing out and drive without it. We all know that Healeys run hot and if you do decide to take it out on a cool evening then a chunk of cardboard to block of a section of the radiator works like a charm.
I lived in Florida fir about 6 years. Taking the thermostat out didn’t help one bit as many club members there found out. A good cleaning of the radiator, correct timing, correct fuel mixture helped.


Country flag
Every car I know of, old and new, has a thermostat. The factory accountants would have made the engineers leave them out if it could be done without.

IMO the best argument for is DerekJ's - most of the wear occurs when the engine is cold: cold longer = more wear.
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