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Re: [GMCnet] Fan Clutch [message #61566 is a reply to message #61560] Sun, 25 October 2009 11:52 Go to previous messageGo to previous message
emerystora is currently offline  emerystora   United States
Messages: 4442
Registered: January 2004
Karma:
Senior Member

On Oct 25, 2009, at 10:30 AM, Roger P. Gleason wrote:
>
> Now for a question, several have lowered their engine thermostats
> from the recommended 195 degree to 185 degrees, what is the purpose
> of this? The newer gasoline’s are formulate where it takes
> higher temperatures to burn them completely some of the newer
> engines are using as high as 210 degree thermostats to accomplish a
> complete burn. Engines I have seen torn down with too low of
> thermostat leave unburned deposits in the heads leading to
> catastrophic failures.
>


Roger
I agree with you totally on this. I think that many have put in lower
temperature thermostats thinking that they would result in less
overheating. This perhaps is an attempt to mask a radiator problem or
other such engine problem that has resulted in their overheating.

I first posted this back in 2003:

> In the old days thermostats used to all be 160-180 degrees. Now they
> are 20 or 30 degrees hotter. Why was this done? Its fairly common
> knowledge that heat is the worst enemy of engines and oils. -- right?
> It's true that heat can be hard on an engine, but in the opinion of
> most automotive engineers, the benefits of hotter-running engines far
> outweigh the negatives. Engines burn fuel more cleanly and
> efficiently at higher temperatures. With the coolant at 195 degrees
> (instead of 160 to 180), you'll get better performance. less
> pollution overall, and greater fuel economy.
>
> While 30 years or so ago, using a 195 degree thermostat might have
> shortened the life of an engine, oils have gotten better. Now they
> perform much better in extreme heat, and give the engine plenty of
> protection without breaking down. Especially with the Mobil 1
> synthetic that you are using. Modern big block engines such as the
> 403 and 455 are optimized to run at 195 to 200 degrees and at that
> temperature no harm is done.
>
> Race cars are designed to run at even hotter temperatures with the
> result that higher compression ratios are possible as well as more
> aggressive ignition advance curves and leaner mixtures for greater
> fuel efficiency. While our GMCs are certainly not race cars, the
> same fundamentals apply.
>
> I will continue to use my 195 deg. thermostat. I rely on a 50/50 mix
> of antifreeze coolant, an operating 9# pressure cap (these usually go
> bad within two years) and a clean radiator and engine block to keep
> me from overheating. If your cooling system has problems, using a
> 160 or 180 thermostat will only give a very slight edge to slowing
> down an overheating problem. The engine can quickly pick up 30 or 40
> degrees when under load at high speeds or up grades.
>
> Another potential problem with running too low an engine temperature
> is that any condensation in the engine block must be evaporated by
> the heat of the engine to prevent the water from floating around in
> the oil pan and being picked up by the oil pump and getting into the
> bearings, etc. Water is not a good lubricant. It also will rust
> parts in the engine block.
>
> All engines will pick up water. When an engine cools the air in the
> crankcase shrinks and air is drawn into the block. Air contains
> water vapor which will condense into the engine. Most people that
> live in cold climate areas use higher temperature thermostats in cold
> weather to keep their heaters putting out enough heat to the
> interior. People in warmer climates often feel that they don't need
> as high a temperature thermostat but those living in the south where
> there is high humidity or even in the humid north still have water
> condensate in their engines which must be dried out. A hotter engine
> will do a better job of quickly evaporating this water before it does
> any harm.

Emery Stora
77 Kingsley
Santa Fe, NM


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