Any Bad Side-Effects of Running Engine Cool?

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Feb 16, 2006
A few days ago the thermostat in my Civic apparently decided to stop working in the "open" state. So now I would estimate that the coolant temperature is maybe 100-130 degrees, depending on the outside temperature and how fast I'm driving. Besides having no heat and getting bad MPG, are there any problems with operating the engine in this condition until I can get a nice warm day to work on it? Or should I just pay someone the $50 to install the new thermostat? BTW, I've got 5W-30 in the crankcase right now.
Well, you're in warm up mode. The fuel mixture in enriched. Your oil will get fuel dilution. The combustion byproducts that end up in the oil well as moisture/water, will have to be at that stated temp much longer to be purged.

..but I doubt you'll do more damage then the money that you're saving ..assuming that the next warm day is in a couple of weeks. Personally I wouldn't want to go without the heat.

Adjust your 200 mph tape to alter airflow. That's what they do on NASCAR TV

or try a piece of cardboard covering part of the rad. I really shouldn't recommend it ..but it is an option for the frugally minded as a stop gap measure.
I bought a v-8 kingswood that the owner had removed the thermostat from at 20,000km, and reinstalled it at 150,000km (for sale)..."cold running engines last longer".

I didn't know that he did this until I had the heads off, and saw the extreme valve guide and bore wear associated with cold running engines.

Short term, no problems.

Longer term, and you'll have dramas.
You're getting increased wear. Period.

I'd get a new thermostat ASAP.
it wont hurt anything in the short term. i know of people who have run engines for decades with no t stats, even in minnesota winters.

i would however get it reaplced because you will lose some mileage if the engine doesnt get hot enough to go into open loop.
Goldenrod, if his Civic's thermostat is in a location similar to my Accord's, then changing it will probably be a long, frustrating experience that should not be attempted outside on a cold winter's day.
Now come on people, I done my oil pump, crank seal, cam seals, oil pan gasket, and a few other objects a couple weeks ago lying in 4 inches of snow. Yeah it sucked real bad but it had to be done. Not trying to sound tough or anything like that. But I dont hardly see where doing a thermostat in the cold is going to hurt anything.
You Kentucky boys are tough as nails. I want to get me a John Deere hat, so I can look like a Kentucky boy. I already have the Carhartt bibs.
It will hardly make a difference for a month's worth of use. I have seen many old and modern cars run with a similar problem. The motivation to fix it quickly is to keep YOU warm. You can always duct tape the radiator for a temporary fix.
same thing happened to me shannow, pulled down a 308 with no stat and the front cylinder next to water inlet was way worn out, all others were ok though ...
There are people out there that needs to make a living too. Take your car to a certified mech.

I never work on any of my engines. I have better things to do with my time and I expect the mech to know more about the engine then me. lol
I do all the stuff I'm able to do. It's gotta be a **** of a job if I'm paying anyone $50+/hr to work on my bucket.

I'd wait for a warm day, but I wouldn't wait longer than a few weeks.
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