Generally, if you run hot under load, suspect radiator efficiency. This assumes a good pump, etc. On the freeway (high load) you have sufficient air flow...

 

Your conclusion is wrong. Both should have the same flow rate at fully open condition. Also, this is not correct "The only difference in the tstats is that the 195 is designed to restrict more water flow than the 180." Both should have the same flow rate when closed and open, the 195 is meant to restrict the flow until the coolant becomes hotter.

This topic has been beaten to death almost as many times as the "is it OK to restamp your engine" topic. If I put a 220 degree thermo in my car, it will likely run at around 220 somewhere. If I change it out for a 195, my car will run cooler. Change to a 180 and it runs cooler still. Change to a 160 and it still runs around 180. I can put a 140 in there, and it will run around 180. I can take the thermo out, and it will run around 180. I've done this on my cars (well, not the 220 part) and that is how it works in real life.

 

NOT true.

The temperature rating of a thermostat is the temperature at which is OPENS. Once it OPENS, it's up to the radiator and Fan to keep the temperature DOWN. When the temperature drops below the rating of the thermostat, the thermostat closes (to warm the water UP again), and so on.

REGARDLESS of the temperature rating of the thermostat, you want one designed to FLOW the MOST. Flow does not factor in to the temperature (unless there is an obstruction IMPEDING the flow of water which will make things too hot) It doesn't matter whether you run a 160 or a 190+ degree, they should flow the same. Some of the best designed thermostats (ie. Robertshaw which is also branded as Mr. Gasket) are designed for maximum flow but it has nothing to do with the temperature rating.

 

So why do we NOT want to run without a Thermostat. If we didn't need one, the car companies would save the money by not installing one. It can't just be to quickly get your motor up to operating temperature, can it ?? I understand needing one in the winter to be able to get heat into the motor to run the heater....., but why would one need a thermostat in the summer. Just asking why as I've always used one...........

 

That’s exactly what I said in much simpler terms


That’s called “modulating”.
The tstat is just a crude temp based flow control valve. The newer cartridge type can also redirect flow, but that doesn’t apply here.
That is also why there ar different size restricter disks, same purpose, reduce/increase flow, thus temp.
Of course it is limited to the upper and lower limits of the system it is installed in. That’s not the issue.



If you guys think that all thermostats flow the same rate, then what magic makes them different temperatures.

BTW, I’ve been using Rshaw tstats for many, many years and also different pumps and have yet to have any cooling issues.

 

by removing the t stat entirely you run the risk of water flowing at too great a rate for the rad. to cool it properly by exchanging heat. that is why most competition engines that don't run a t stat use a restrictor ring in the t stat housing. and no..a t stat does NOT control temperature by restricting coolant flow but by a different calibration built into the stat itself. always run one on the street for fast warmup and consistent engine temps....that's what they are for...good luck.......

 

Originally, thermostats had one purpose...allow the engine to heat up more quickly in cold weather so you could get heat in the passenger area sooner. After the EPA got involved with car production, the thermostat temp was raised to 195 deg....the maximum the auto mfgrs. would consider...so that more hydrocarbons burned off at idle. The engine does not need a thermostat...period. The cooling system is [or should be] designed to stabilize at around 180 deg F. That seems to be the best operating temp for a 4-stroke internal combustion engine..taking into accout fuel economy, engine performance, and engine life.

This is why I suggested that you remove the stat completely and run your car at steady-state at several speeds (ie, 30 mph, 45, 60, 70). Determining the equilibrium temperature for your car's cooling system at each speed can help diagnose what is happening within your cooling system.

[P.S. I'm content with ignoring the other discussions going on with this thread.]

 

ALL factory cooling systems are designed around a t-stat, that in turn should not be ignored..jmho

 

Yes. Modern engine manufacturers are required to operate their engines at 195F. Early autos didn't even have a temp control system on their engines. The thermostat allowed heaters to be installed in passenger compartments...and kept coolant temps regulated. And your point is.... ?

 

we recently did a valve job on a 35 buick straight 8 and the original t stat was stuck closed. had to call a buick restorer to find one....is that modern enough for you???.......im just trying to help on the original post which was tell me about t stats i believe.....there is much more i could add with my 40+ years experience..but why waste it on you???...anyway i hope i helped answer the question as to why to run a t-stat for other posters and since gm cooling systems were designed around the t-stat at least since 1935 i guess they were modern even back then.....see ya!!

 

I don't agree. And it's not the same thing as what I said only simpler, because what you have written above is wrong. Where you are going is exactly as I have predicted, you are straying from "all other things being equal" and are talking about high flow stats compared to standard ones. Among standard GM stats, the 180 and the 195 allow essentially exactly the same flow rate when open, the 195 is only there to restrict the flow until the coolant is 15 degrees hotter than the 180, nothing more. Said another way, there is no difference in restriction, only the temperature at which it is relieved.

To the other poster wondering if we even need a thermostat, the answer is most of the time we don't NEED a thermostat. For a variety of reasons, especially when the weather is cold, it is nice to have one, so one is included in the car. Now I said "most of the time", and I can imagine the posts about winters in Alaska and what not, to that I will not respond.

For the curious: I had a 160 stat in my car last year because I had an overtemperature problem. This past Sunday, I replaced it with a stock 180 stat. Why? Because when the system is right, things just work well like that. But, I don't recommend changing thermostats ***** nilly. EVERY time I consider putting a different thermostat in my car, I test it in a pot of hot water with a candy thermometer so that I know at what temperature that specific stat opens. You should try that at home.

 

So you're saying the restricter ring (controlling flow) can control the coolant temp, but the tstat works by some kind of magic.

Ever heard of wax pellets?

Here is an quote from an SAE publication written by C Burrows and S Tomlinson, Univ Of Bath

 

noonie, you are correct that the T-Stat governs the coolent flow as per your article. However, the flow is either on or off (except while opening and closing for a second or two) It is the size or composition of the wax that determines when the stat opens and closes. Try the experiment PKguitar refers to... put the T-Stat in a pot of water, boil it and measure the temperature with a thermometer. You can watch it open. Take it out and it will close. Get a different rated T-Stat and it will open and close at a different temp. No magic

 

Are you sure your advance curve is set correctly and the vacuum advance is working? By 3000 rpm the advance should be "all in". Retarded timing at cruise speeds will cause your car to run hotter.

Just an idea......

Tom

 

Have tested dozens and dozens of tstats over the years.
Some of the better ones do open and close gradually and when at their designed temp are not fully open physically so that compensation can be made for an overtemp situation. Wax pellet type tstats do also have a slight problem of overshooting that can result in a slight delayed temperature ocillation. A lot is dependant not only on the wax pellet, but the rate of the spring it must work with.

Also have done quite a bit of a/c, which is a complete other can of BTU's

 

Most old cars up until about 1930 did not have thermostats, many early ones even didnt have water pumps. By the mid thirties, water heaters became common and most were equipped with thermostats. Higher end cars tended to have them first. Ford didnt have them until after the model A`s but Cadillac had them much earlier. I think the use of thermostats were two fold, one, heating the passenger compartment, and two, getting the engine temperataure to a good operating temperature for fuel evaporation. Early cars were designed with some very strange preheating devices to aid in fuel mixture control. Interestingly, lots of early thermostat systems didnt control the water flow, but operated shutters in front of the radiator. Both my `31 and `33 Cadillacs have this type shutter operated heat control.

 

umm, no...

a 195º t-stat doesn't restrict flow any more or any less than a 180º unit does. The only difference is the temp the units are designed to open at to allow coolant flow thru the system.
Once a t-stat is fully open the coolant flow is the same regardless of it's temp rating.

 

Hey, quit trying to solve Gingerbreadman's problem.
We got a good thermostat argument going on.

 

A thermostat simply regulates water 'flow' (essentially ON or OFF) depending on the temperature of the water. The amount of the passage (restriction) is of no real consequence, as long as the passage size is adequate for the cooling system design. I do appreciate wombvette's confirmation on the factual aspects of auto thermostat history.

Perhaps the original poster now can get on with solving his cooling system problems.

 

I know I'm working on cooling problems after I built my engine up above stock and changer the rear to a 3.70. When stock it never ran above 180 degrees. Now with a 160 or 180 stat it runs up to 215 degrees at 60 mph+ and 180 under 50 mph. I took the stat out and it ran cooler at all speeds. So I think if you have a GOOD cooling system the stat is there to maintain the temp of the stat. for heating the inside of the car and keeping the engine running at the stat temp. With out a stat and at idle my 77 ran at 150 tops and around 200 at 60 mph. I think if you have a cooling problem that is what it is a problem in the cooling system. Radiator not doing its job to small or clogged up or not enough air flow over the radiator. I think I have a cooling problem radiator not moving enough water through it clogged up. I can take off the cap and see some of the tubes are nor moving water. I'm going to flush it tomorrow and see if it make a difference if the flush work it should.