OK, upthread I stated my combo and said it ran hot and that I was going to take the thermostat out to see what happens. Well, it runs cooler. Before when it would be at 190+ it was a shade under 170. And one thing I noticed was the amount of increased heat the radiator was shedding at idle. Granted, it was hot here yesterday but there seemed to be a big increase of heat being pulled by the fan. It did creep to 190 in traffic, but no higher (just tells me I have to work on my fan-shroud combo).
In the race car we did not run a thermostate. If we had a problem with it running hot we would restrict the lower radiator hose which would hold the water in the radiator longer and it would run cooler. It worked for use. The 58 rambler I have did not have a thermostate in it when I did some changes like a chrome Chevy water neck and upper hose I did not put one in. The car ruins at 190 driving it and if you go up a hill it does climb to 210 but as soon as you level out and go down the road it goes back to 190. I have let the car set and idle to see what would happen just in case I got stuck in traffic and it never got above 180. Now the Ford 351 Cleveland with out a thermostate will push the water out of the motor and overheat.
On one of my daily driver trucks I put a gutted thermostat in and even with a larger radiator from a bigger truck the temp gauge ran higher when I took it on a long trip,it got a thermostat when I got home.
For what it's worth: I've got an old daily driver from the eighties with a thermostat that's hard to pull (you'd have to remove the pullies, distributor belt, water pump and a lot of plastic crap on that side of the engine) and that thermostat is defunct. When I'm driving my car never gets to working temperatures, it's always way too cold. Except when driving slow in warm weather or when I'm stuck in traffic. My first thought was that this would be because of a filthy cooling system (especially the radiator) because I've never heard of the thermostat myth. Would it make sense that when the myth is true a car with a defunct (or maybe even pulled out thermostat - I don't know for sure if it's even got one in) thermostat would overheat in traffic jams and busy city driving but not while driving normally?
Well, I really didn't know what I was getting into when I posted a message on this old thread the other day. I never imagined it would come alive the way it has. When I go back and review the whole thread, it started with a degree level engineer, working in the thermodynamics field, telling us how it bugs him that some people don't get the fact that circulating cooling water too fast doesn't make an engine overheat. A couple of other knowledgeable people wrote in agreement with him and by this point that myth should have been well and truly busted and no longer a live topic. The debate should then have moved on to "If some engines really do run cooler with a thermostat in place, why do they do it?" and some contributors, chuckspeed in particular, came up with some plausible explanations for why that might be so. The extaordinary thing is the number of other posts the thread attracted, mostly off-topic and some just off the wall, about thermostats and cooling systems in general. If you pick through all the distractions there have been some pertinent points made about the original subject and it looks like, if we are to learn much more about why some engines overheat without a thermostat, someone has to do some testing. Is one of the people who has such an engine willing to take it on? You would first have to take the 'stat out again to prove the engine would still overheat without it, then fit a flowmeter in the top hose and measure the flows at high rpm with and without the thermostat in place. The results of those tests would inform any further debate on this topic. One detail that hasn't been described on this thread in words of one syllable and which seems to confuse some people is that a thermostat can have more than one function in an engine. The primary one, as many contributors have mentioned, is as a temperature regulator. It restricts coolant flow until a pre-set temperature is reached, at which point it starts to open and allows coolant to flow through the radiator. There is no good reason to run without a thermostat except in special cases such as race cars which run in such a narrow range of conditions that temperature can be easily regulated by other means, such as a fixed restrictor to coolant flow or air flow or by limiting radiator area. The other function, and the one which is pertinent to this thread, is to act as a restrictor even when wide open. People who fit restrictors in place of thermostats are simulating this function, not the temperature regulating one. Read chuckspeed's post on cavitation again to understand how this works. Bort62, if you're reading this, maybe you shouldn't be too surprised that some people just refuse to believe the truth when its shown to them. I'm told that a significant proportion of the US population don't believe Americans walked on the moon.
I'm an engineer too (went to school...had thermodynamics and all that jazz) but before that I practically lived in the shop in my back yard. Sometimes things that look good on paper don't accurately model what's really happening with a real life system. This is a fine example of that.
This is a great thread with lots of information that I've never seen in one place. I've only run and observed 2 cars without thermostats for any length of time, as it never seemed to make any sense to me. These are my unscientific, uneducated observations. I finally got my 99A flathead drivable this spring. Edelbrock heads, unknown mild cam, Mallory electronic crab distributor set a about 2° BTC, no thermostats, late '30's generator mounted type fan, Walker Z series radiator, 16lb cap, no shroud, 50/50 antifreeze mix. It never overheated in this configuration during the last 3 weeks of mid 90° temps, warmed quickly to 160°, never reached 200° during normal stop and go in town, cooled in 5 minutes or so at highway speeds (60-65 MPH) to 160°-175° and kind of drifted around that range, dropping to 155° at highway speeds on cool (70°) evenings. My conclusions were that it had adequate coolant flow, fan and radiator capacity, was running too cool, and the near 50° temp fluctuations seemed to kill any chance at thermal efficiency. Last week, I moved the fan closer to the radiator core (about 1"-had been about 2"), and fabricated a 17" square shroud. I tested it yesterday in low 90° mid day traffic and and out on the road. This change slowed the warm up a bit, and lowered the around town idle temps to a max 190°. I then added two small 180° thermostats from O'Rielly. The engine warms quickly now, runs between 180° and 185° in traffic, right on 180° at highway, under 190° on a long uphill grade (23 miles total driving). The most noticeable change, other than more stable operating temperature range, was the lack of clicking and gurgling sounds when I shut the engine off-it may have had hot internal spots that were boiling, and the thermostats seem to have cured this. In the past, the temp due to heat soak would exceed 210° during shut off, but cool quickly on starting. Yesterday it barely reached 200°. This is my first flathead V8, and I was definitely concerned about overheating, and have paid close attention to temp readings. As I sort this thing out, I'm becoming more confident in it's ability to run dependably cool. Although I saw lower temp gauge readings without a thermostat, I also saw higher readings. Is it running cooler now with them? Overall it seems to be. We shall see.
Same here...drove my 2000 Ford Focus for 6 months with the themostat open...NO engine temp without a chunk of cardboard in front of the rad. Winter broke...threw in a stat..running at temp ever since. Also had a 46 Mercury panel with a 350..had a 160 stat, always overheated...changed to 195, ran there from then on.
I seriously question 52gph being an accurate number. Unless GPH means Garage-fulls Per Hour..... For all the folks who haven't read this entire thread, but are asking the question repeatedly, the PRIMARY reason that the manufacturers put thermostats in engines is to get them to operating temperature as quickly as possible, and to KEEP them at operating temperature. And then again, for all the folks that haven't read this entire thread, chuckspeed has posted the correct answer. It absolutely and completely answers the question as to why SOME engines will run hotter (at higher speeds) without a thermostat, or without some other form of restriction between the engine and the radiator.
From experience it depends on the design. When the Ford V4 engines were popular here. If the the thermostat was left out of a Transit van it would probably overheat, but if you left it out of a V4 car (same engine) they usually ran cold. At the time I was rebuilding engines for a living, and we were doing this engines all the time
Well here's something I would never have believed. Our daily driver is a 1993 Jag, I drove it to work and my friend asked if the temp gauge worked. I looked down and it was on cold the whole time driving and would only get about half way up to the normal temp if that at idle. Well the stat had stuck open some time since the last time I drove it. My wife drives it every day. I replaced the stat and at the same time checked the oil. It was down a quart and so when I took the oil filler cap off, the filler tube that comes out of the engine was filled solid with a gel off brown milky sludge. I scraped it all out just so I could fill it with oil. I never had a problem with this happening before or after replacing the stat.I will always run a stat after seeing what can happen running too cold. The engine and filler tube is also all slunk.um that could have helped with the condensation build up.i
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