I don't believe it, but it is a terrible idea to run without one. Sixgun has a bad fan clutch or a partially plugged up radiator.

Sixgun, when the engine is warmed up to normal, feel all over the surface of the radiator. If the temp is uneven, replace the radiator.

 

In all the motors that I removed the T-stat they would run hot if sitting at a idle for even a short time but would run cooler running down the road even when I would run a clutchless fan.

 

Yes Guru, your just afferming what i had suspected thank you.I had one give out already so i went and bought a used one at the local junk yard but that one was probably on its last legs to. ....Handyman,a thermostat will cause your truck to overheat if its stuck open and since i just replaced it not long ago and i'm over heating again ,i figued i got a deffective one and figured just to do away with it since i live in Fl..But it wasnt the problem and since it stays norm. on the highway and gets hot in town i'm sure its the fan clutch,Thanks guys

 

Why would you install a used thermostat? They are readily available at almost every automotive parts store in America!

You need the 'stat to heat up and maintain a constant temp in the engine. This makes it run efficiently and not allow water vapor to collect in the oil causing sludge, which will ruin an engine.

 

Yes, I agree Holmes with the constant temp but i took it out to pinpoint the problem and now i can rule Thermo out: on which i'll replace with a brand NEW one at the local American auto parts store like i did the first one........it was the fan i replaced out of another 86 from the junk yard.I'm learning its cheaper to pay the $50 for a new one(fan) then replace it once a year with used garbage

 

The thermostat controls the flow of coolant to the radiator. If it's not there, coolant will flow through the radiator as fast as the water pump will move it. At higher RPMs, it flows through too fast to cool it enough. And the engine will overheat.

I've seen more than one post from an FTE user saying that without a thermostat, their engine overheats.

Ok, I can't guarantee that it's the problem, but it's definitely a contributing factor!

 

Things like fan clutches do wear out. I never replace parts like that with used junkyard parts. In the case of something like an alternator that is used, The seller either has to guarantee the condition of the unit, or allow me to return it within a reasonable time. Guys willing to do that usually dont have any problems with their stuff. I know how to rebuild alternators from the frame up, and have only had to buy one unit at a store, and that was because the bearing froze and ripped the front half of the alternator to shreads. The same goes for starters. Parts like water pumps are another matter. I dont have the proper press to remove and install the bearings in these, and since the store offers a lifetime warranty, I've never had to pay for a second pump. Only had to replace one pump almost 12 years after I bought it, and since I keep the receipts, they gave me no issues.

I have replaced items like thermostats before that were good. My F-150 had a ground problem that caused the temp gauge to go to hot when the motor was running at normal temps. I'm glad I did, 'cause I found things like a water pump with a well-worn impeller, a thermostat that had a 1/16" gap when it was closed, and a temp sensor that was corroded enough for me to suspect it anyway. Now the truck runs fine, there's no problem with wild gauge readings, etc, and I trust the gauges. Now, the fuel tank sending unit is something else alltogether. I fill the truck when the gauge hits empty the first time. It usually holds about 11 gallons if I keep it filled this way. At least there is not as much gas price shock at the fill-up!!!

The bad engine ground was between the intake manifold, and the truck body. The connection at the firewall just beside the throttle cable where it comes through the firewall. It caused the previous owner lots of problems too!!!

 

Think of coolant on a molecular level as it flows through the block, heads and the radiator. The layer of molecules against the metal experiences drag so it moves slowly. The next layer moves a little faster and the next faster still. Each successive layer moves faster than the one below it until you get to the middle of the passage, furthest from the drag of the wall. This situation provides very poor heat dissipation. This is laminar flow.

Accelerating the flow combats the problem of poor heat exchange. Speeding up the flow creates, more turbulence putting more of the molecules in contact with the tube wall where the heat is dissipated better. Another way of creating turbulence is to use dimpled tubes, which also helps to break up the laminar flow.

This principle also has to be kept in mind inside the cylinder heads where most of the heat is generated. If the circulation is a slow laminar flow in the hotter areas, particularly in the area of the exhaust ports and valve seats this is where trouble starts. When the engine is under load and those areas reach temperatures above the boiling point of the coolant the molecules of coolant in contact vaporize and create a layer of steam, which effectively insulates the metal from the coolant which creates a deteriorating condition. Too much steam allows the metal to get continually hotter, creating more steam which forces coolant out of the overflow and then you are into a serious overheating condition. The way to prevent this is to speed up the flow to generate turbulence, which will scrub away the steam bubbles while they are still at the molecular level. Cooling passages are, or should be designed to shoot high-speed jets of coolant directly onto the surfaces that tend to get hottest. You know that if you are towing and your engine begins to overheat, you pull over and run your engine at a very high idle. What you are doing by stopping is generating less heat. The fast idle rushes the coolant over the hot spots, scrubbing off the steam, which allows the hot spots to normalize. Everyone has had the experience of seeing someone stop and shut off an overheated engine and remove the radiator cap only to have the cooling system go into a nearly explosive boil over. In that case, they didn’t cool down the engine by running at fast idle, so once the coolant stops flowing, the hot spots create a mass of steam. Opening the pressure cap lowers the boiling point so even more coolant vaporizes, and boom. Second degree burns.

One technique that has been used to deal with the problem of hot spots in the heads is to replace the thermostat with a restrictor plate, which builds up the pump pressure inside the block and heads. Never do this. It works up to a point simply because it further increases the boiling point inside the engine. It is never a good idea. Coolant speed is the ideal cure. And every street engine needs the proper thermostat.

The steam from the hot spots, (and all IC engines have them,) are the reason that we have “degas” bottles in the cooling system. Or, “liquid/vapor separators,” or “surge tanks.” They help to insure that the steam is what gets ejected when the system is heat driven into an overpressure condition.

It is the common belief that the cure for a hot running engine is a radiator with more rows of tubes. It does work in some cases but not all. In an unmodified engine, the stock radiator is of adequate size. If the engine is running hot there is usually a defect that needs to be corrected.

In the event that a turbo is added, or other modifications are made that increase horsepower to any significant degree, the cooling system will require upgrades.

The first thing to consider is to go to a water pump that will increase the flow. When a high volume pump is employed, it is a good idea to use a cross-flow radiator with the pressure cap in the tank on the low pressure side, (the side with the lower radiator hose attached.)

A well-designed fan shroud, as opposed to no fan shroud, can increase cooling effectiveness as much as fifty percent.

Also in the interest of airflow, moving any other coolers away from in front of the radiator will improve airflow and remove the heat load of the other coolers.

If you are running a turbo, devise air exits to get the heat out of the engine compartment. This also creates a more negative pressure behind the radiator, increasing efficiency.

If it proves necessary to increase radiator capacity, try to get one with a larger surface area rather than adding rows of tubes. Also, there are very effective high performance radiators available with one or two rows of deep tubes and louvered fins. These increase efficiency without adding 'rows.'

If you go from two rows to four rows, you double the volume flowing through it. If you double the volume, you reduce the rate of coolant flow through the radiator by half, getting back into laminar flow which reduces the heat dissipating ability by a large percentage.

 

I was told by a local circle track engine builder that the thermostat actually holds the coolant in the engine longer to give it time to absorb the heat which is then dissipated in the radiator. The race engines he builds use a restrictor, similar to a washer with a seal to do the same w/o a thermostat. Just a thought but it makes sense.<?xml:namespace prefix = o ns = "urn:schemas-microsoft-comfficeffice" /><o></o>

 

That engine builder is wrong. The restriction created by the thermostat or the "washer" that he uses is to increase the pressure (between the pump and the restriction, ie in the engine itself,) which serves to raise the boiling point of the coolant. This helps to prevent "hot spots'' that tend to occur in the heads around the exhaust valve seats. When you have hot spots the coolant starts to vaporize which creates a steam pocket. In that case the heat will not transfer from the heat source into the coolant and the situation just deteriorates from there.

The greater the difference in temperature between the engine and the coolant the better it transfers the heat. So you do NOT want the coolant hanging around in the block, you want it speeding through to keep lower temp coolant coming in constantly. That is why a typical V8 water pump can pump as much as eighty gallons per minute (unrestricted at 2400 rpm) so it pumps through very rapidly.

 

When I put a new thermostat in mine it run hot. I tested mine the old fashion way.

Pull it out, drop it in a pan of boiling water and watch. You can see it open. My brand new thermostat did open but only a tiny bit.

Got a replacement and tested it before I put it in. Opened completely in the boiling water and the engine ran fine with it.

 

Sorry I missed this earlier. If the engine overheats without the thermostat, which I admit is possible, it is because there is inadequate pressure inside the engine, lowering the boiling point of the coolant and it begins to boil around the hot spots.

 

Let me confuse this "no thermostat" deal even more. This is the explanation I read one time that I believe.

It was mentioned in a previous post above that the pump builds pressure on it's output. That is true, and the pressure will build at the most restricted point. This is normally the thermostat. If the thermostat is taken out, the next area of restriction is the top of the radiator where the coolant has to enter the tubes. This means besides the pressure building up by the coolant getting hot, there is also pressure from the output of the pump. This is too much for the cap, and the cap lifts and lets coolant spill out.

One way to confirm this sometime is when someone takes the thermostat out, and the engine "overheats", if they have a real gauge on it, they may find that the engine is not really that hot, but it is puking coolant out the overflow tube which gives the impression that it's overheating, when it may not be. It may be the cap is just being overwhelmed by too much pressure on top of the radiator.

 

If that were happening, the coolant loss would lead to overheating.

The pressure in the cooling system will be different any place you take a measurement. That is why the lower hose, (the pump intake side,) is reinforced to keep it from collapsing because the pump can generate a strong negative pressure on that side.

I would say if the pressure is so great that it overcomes the pressure cap it is most likely due to steam pockets developing inside the cooling passages in the heads. Again, the thermostat will increase the pressure in the engine (as opposed to NO thermostat,) which raises the boiling point so you don't get those steam pockets.