442 Guatemala

Hello im thinking on removing the thermostat from my 66 442 with 400 engine because i just rebuild my engine (street/strip) and im running too hot like 200-210 farenheit, its safe to remove it?? there is any problems??

for cooling system im using an aluminum 2 row radiator that supose to handle up to 600hp??? new aluminum watter pump, flex fan.

thanks

70 cutlass s

What temp thermostat do you have now. Is it running over 200 at idle, high way speeds or both.

442 Guatemala

I have a 160 high flow. at idle like 190-210 (depending if is a suny day), if im runing like in highway at 50 MPH constantly my temp goes from 180-190.

my fan blade is very close to the radiator, and also to help my temp go down I install an electric fan pusher in the front, but steel the same. Im not using a shroud for now

Olds64

Hmm... the temperatures don't seem too high. Perhaps you should try a standard flow 160. Maybe the coolants is going through the radiator too fast to get properly cooled.

Eric Anderson

I agree w/ the above. Removing the thermostat will make it run hotter.

Lady72nRob71

Removing the T-stat is never a good idea.
It is best to find the root cause of any overheating problem instead. On a fairly stock setup i would use a 180* Mr Gasket / Robertshaw high flow T-stat.

When is it running hot? At idle? On the road? With A/C?

70 cutlass s

How close is close sometimes if to close then it will not work as well. I always recommend using a fan shroud, but not always needed. With a electric fan and flex fan you should have no problem with temp. Unless there is a blockage in the cooling system or a problem with a part not working correct.

442 Guatemala

before I use the 160 thermostat I was using a 180, nothing change. after I wift from 180 to 160 thermostat I leave my car without thermsotat and temp go down, so I decide to use the 160 hig flow, and having problems again.

I bought my watter pump from mondello it supose to by a high flow, so maybe like some of you say the watter is running to fast?? if that is the case how to solve the problem

my other question is what is the hottest temp i can run without damagin my head gasket that is what im worried about???

henryk8398

Don't do it. It will take forever to warm up. Make sure your timing is correct as well as your carb. calibration. Those can have a substantial effect on heating. How many miles on the engine? It's not unusual for an engine to run hotter when it's just been rebuilt. It's breaking in. Give it some time.

Things to consider:

-If you are running hot at idle and low speeds, it's typically a matter of a lack of air flow through the radiator. You might want to try a fan with a clutch instead. Is your shroud in place?

-If you are running hot at high speeds, it's a water flow issue. If you radiator is new, then you might have some air cavitation in the engine. Your lower hose could be collapsing, too.

jaunty75

Isn't it the opposite? The thermostat prevents coolant from flowing to the radiator until the temperature of the engine reaches the thermostat setpoint, and then it opens and allows coolant to flow through the radiator. Without a thermostat, the engine can take a long time to warm up as coolant is flowing through the radiator right from the start. If anything, removing the thermostat can cause the engine to run too cool. A common reason for a heating system that takes forever to blow hot air is a thermostat that is stuck open.


I'm not sure why 442 Guatemala is worried about this at all. Olds64 is right. The temperatures he's describing don't sound too high. A thermostat that opens at 190 doesn't mean the temperature will never rise above 190. It'll get a few degrees above that, and 200-210 doesn't sound inordinately high to me. After all, that's not even the boiling point of pure water at atmospheric pressure let alone the boiling point of an anti-freeze water mix that's at 15 lbs above atmospheric. At 1 atmosphere, a 50-50 mixture of water and ethylene glycol boils at around 225 F. But under 15 psi pressure, that rises to something like 250 or 260 F, or somewhere in there. I'm not sure of the exact value.

442 Guatemala

my engine has only like 550 kms on it. and my car and timming is not setting good, im waiting to reach at least 1000 kms to set properly

what is the total timming recomended for this engine?

442 Guatemala

the only thing im worried about is dont damage the head gasket and make it worse

Eric Anderson

I assume it allows the coolant to flow too quickly. I have seen people remove the thermostat on a few occasions and the outcome was the vehicle ran hotter than before. I agree on paper it seems it would be the opposite.

I also agree that a stuck thermostat will cause a problem with the engine coming up to temp.

jaunty75

Removing the thermostat would not increase the RATE of flow of coolant through the system. It would only start the process of the radiator cooling the coolant sooner than it should.

If removal of the thermostat did cause an increase in coolant flowrate (and it might a little bit, now that I think about it, because the thermostat itself, even when it's open, is an obstruction that the coolant has to flow through), the effect of the increased flowrate would be to INCREASE the heat transfer rate (think of the increased Reynolds number and thus the increased heat transfer coefficient). An increased heat-transfer rate would act to cool the engine, not warm it up.

So removing the thermostat could cause the engine to run cooler than it should for two reasons. One is that coolant flows through the radiator right from the outset, rather than after the engine warms up, and the other is that removing the thermostat potentially increases the coolant flow RATE slightly.

Eric Anderson

One incedent I can recall was a contractor I used to work for was pulling a skidsteer with an 87 dodge he was running a little hot most of the time, he took the thermostat out the next time he ran the truck pulling the machine the truck overheated(steam rolling out from under the hood), put a new thermostat in and it solved the problem. Why? I have no idea, it's just what happened. One other time was a guy I used to know with a Pontiac did the same thing with the same results. Mabey it was just a fluke.

jaunty75

Well, who knows. There may have been other issues besides the thermostat. All I know is that a thermostat that's stuck closed will cause overheating, and one that its stuck open will cause the engine to be slow to warm up. I assume that not having a thermostat present at all is similar to having one that is stuck open.

Eric Anderson

Yeah, I don't know, I will concede to any expert opinion( I don't even know what the heck the Reynolds number is...) like I said I've just seen this a couple of times could have been the truck was just a POS dodge and would have overheated anyway.

jaunty75

Never too late to learn!

You need this

http://en.wikipedia.org/wiki/Reynolds_number


and this

http://en.wikipedia.org/wiki/Nusselt_number



In short, for constant fluid density, fluid viscosity, and pipe diameter, Reynolds number increases linearly with fluid velocity. The Nusselt number, which is dimensionless heat transfer coefficient, increases with increasing Reynolds number, but usually not linearly.

Isn't this more than you ever wanted to know!

Eric Anderson

Pretty much

wmachine

Definitely do not run it without the thermostat. Yes, it can run too hot without one, *and* take too long to warm up. There are not any Olds engines that in stock to somewhat modified good running condition that cannot be adequately cooled with stock equipment.
Part of the function of a thermostat is to control/restrict the flow of the fluid. It is definitely possible to push the fluid through the radiator too fast and not give it time enough *in the radiator* to properly dissipate the heat.
So yes, the Mondello pump *may* be part of the problem. You shouldn't have any trouble with a proper 180 thermostat, stock pump, radiator, fan, and shroud. In fact, '66 400s without AC went without a shroud. But a shroud could help and wouldn't hurt.

442 Guatemala

I have another question: I install a new aluminum oldsmobile pulley set that supose to fit olds 350-455 engines (but whe I buy them I think they appear like for the 1970,s). the measurements are cank pulley is
4 3/4" diameter, water pump is 5 7/8", Alternator pulley is 3 7/16".

Can this changes affect my temp? I lose my original polleys so I dont know the diameters to compare if I change the realtion between them??



thanks Again

greenslade

be sure to check the rad cap,it should hold its rated pressure to prevent boil over.

compedgemarine

yes removing the thermostat can make it run hot. the thermostat when open provides a restriction so the flow rate is correct. too high a flow rate and the coolant is not in the radiator long enough for the heat to be drawn out. too slow and the engine puts more heat in the coolant than the flow rate can move to the radiator. on cars that do not run a thermostat you put restrictor washers in place of the thermostat. you have to keep trying ones with different openings till you find the correct flow rate. personally I would ditch the flex fan. they are rarely good, the have a habit of coming apart and they do not cool as well as the stock thermostaticaly controled fan. you should also install a shroud as mechanical fans will pull from the area of least resistance, i.e. around the sides of the fan verses through the fins of the radiator.

silverriff

My 1972 455 ran hot since the day I got it. Even on a fairly cool day, at idle it would get up to 205-210. After replacing the fan shroud that was missing, I do not get above 175 deg. It made all the difference in the world.

stevengerard

after having two thermostats go bad within weeks of replacing them I finally replaced the thremostat with a restriction type washer, I don't use the thermostat anmore, the car does take awhile to warm up in early spring late fall but I never have to worry about overheating or a thermostat that will stick closed. Anyone else use this item I think I got it from Mondello.

captjim

OK, couple of things. One, the coolant moving too fast through the radiator to cool is an old myth. The laws of thermodynamics dictate otherwise. However, removing the stat can cause a problem because the pumps are engineered with a restriction as part of the equation, as compedgemarine and wmachine alluded to. But, it is cavitation, not moving too fast, that causes the problems.

IMO, any car that runs cooler without a stat has issues that removing the stat is masking. Flex fans are not efficient. Get a shroud and quality (Delco, NAPA, etc) clutch or shroud a good electric fan(s).

skryla

How are you measuring the temp? It could be a bad sending unit, a miscalibrated gauge or both.

Ken Parsons

Think back about 60 years, the old Ford flat head V8s with twin water pumps. Those things would melt down if they didn't have the thermostats in because the water didn't have time for a good heat exchange in the radiator. Don't take that thermostat out.

83hurstguy

Exactly. This is about the most overdiscussed and misunderstood topic on all car forums... if the water isn't in the radiator long enough to cool, it shouldn't be in the engine long enough to "warm up" either. It's all the same loop.

wmachine

But that is exactly the point! There isn't enough time for the thermal transfer to take place *period*, so the engine overheats!!

Eric Anderson

Would it be cavitation in the pump itself that would cause the problem? With the large pumps we run at work if you cant keep pressure on the discharge side of the pump you loose the prime on the pump pretty easy. Also with the too fast of a flow idea could it be there isn't enough pressure to get the coolant through the whole engine it just blows through the major passages, and allows hot spots to build up? Similar to the idea of putting your thumb on a garden hose .

jaunty75

It seems quite clear that there is a rampant lack of understanding of fluid dynamics and heat transfer on here.


First, how could fluid "blowing through the major passages" be caused by NOT ENOUGH pressure? It would be because of TOO MUCH pressure that this would happen. And "too much" pressure wouldn't cause this anyway. Rather, the higher the pressure, the faster the fluid would flow through ALL passages, big and small.

I don't quite understand your garden hose analogy because there is only one path for the water, and when you partially block it with your thumb to get the water to come out faster, it's not like there is another path the water could take to get out of the hose.

Second, it's a complete misconception that coolant flowing "too fast" through the engine and radiator doesn't give the fluid enough time to pick up heat in the engine nor reject it in the radiator. Heat transfer from the engine to the coolant and from the coolant to the radiator is in direct proportion to the fluid flowrate. It is counterintuitive I know, but it is not residence time in the radiator that matters. It really WOULD be better to have the fluid flowing through the cooling system at as rapid a rate as possible.

But there is a limit to this, too, because there are actually TWO heat transfer steps that have to occur, in series, to get the heat from the hot coolant to the air, and only one of them is controlled by the coolant flowrate. One step is what we've been talking about, which is the transfer of heat from the liquid coolant to the metal radiator. This is controllable by controlling the coolant flowrate, and the faster the better. The other is the transfer of heat from the metal radiator to the air flowing past the radiator fins. THIS heat transfer rate is also influenced by the rate of "coolant flow" (in this case, air) past the fins (which is why there is a fan for when the car is at idle), but the rate of air flow is determined by the car's speed, and there is a maximum to this.

So we can get the first of the two heat transfer rates (liquid coolant to radiator) as high as we want (in theory), but we can't increase the overall heat transfer rate because the second one (radiator to air) is limited. Thus there is no reason to increase the coolant flowrate beyond a certain point.

Remember, also, that a secondary concern in increasing the coolant flowrate is that doing so requires higher pressures, and there is a limit to the pressure that the cooling system can withstand. But, in principle, higher flowrate = higher heat transfer rate.

Eric Anderson

Right Jaunty lets accept the fact that that no matter how fast the coolant flows through the system heat transfer will occur. My thing with the thumb on the garden hose is sort of a path of least resistance idea, if resistance is low through the large passage the water will just flow through the large passage and won't to flow through the smaller ones. To prove my idea go poke a hole in your hose turn on the water will just run out the end and you will hardly notice the hole put your thumb on the end of the hose and the water will shoot out of the hole in the hose, see what I'm saying here? Despite any rampant lack of understanding here obviously I'm not the only one who has seen that removing the thermostat can cause an engine to oveheat.

jaunty75

This is correct and is a major reason why cooling systems fail. If passages in the radiator are blocked by crud, less fluid flows through them, so less heat transfer occurs, and less heat transfer also occurs because the crud itself is generally a poorer heat conductor than the metal of the radiator.

But if I poke a hole in my garden hose, water will ALWAYS flow out of it, just not at as high a rate. There is never a situation where the water is flowing so fast past the hole that none of it comes out. So, yes, if there is pinhole in my garden hose and I partially or totally block the end of the hose, the water WILL come out of the hole at a faster rate. But your first example didn't mention anything about there being a hole elsewhere in the garden hose when you blocked the end with your thumb.


Now you can call me stupid here, but this I just don't get. All the thermostat does is control whether or not coolant is flowing to the radiator. When it's closed, coolant is not flowing to the radiator. When it's open, it is. If the thermostat is missing altogether, then all that happens is that coolant is flowing through the radiator right from the moment the engine is first turned on, and all that that causes is that the engine takes longer to warm up.

If people observe overheating with the lack of a thermostat, then there must be SOME OTHER effect of removing the thermostat, such as a change in the overall coolant flow pattern through the engine.

wmachine

Are you including yourself with your finger pointing?

Sure it is "counterintuitive", as you admit but don't really explain why.
And you've totally ignored the heat transfer from the engine to the coolant. Let's get the complete picture here.


Yes, in principle, but there is more involved here because it is a closed loop system.

There are known situations where an unrestricted system overheated and *only* adding a restrictor in the thermostat housing worked to cool the engine down. Would you care to explain why? Or do you think that didn't happen or was due to other inadvertent changes?

Eric Anderson

Right I see that now, sorry about that, it was late and just got home from taking 2 kids to Sesame street live what can I say?



Not at all, just trying to get to the bottom of this


Exactly what I'm thinking, either due to cavitation in the pump due to a lack of back pressure, or to the altered flow causing hot spots in the smaller coolant passages.This is what I was getting at from the start about the coolant flowing too fast or mabey a better term would be unrestricted.

jaunty75

I didn't explain because I thought it was obvious. It seems reasonable that if the coolant is moving more slowly through the radiator, it spends more time in the radiator, and thus has more time to eject its heat. But this is exactly the opposite of what happens, and this is what's counterintuitive.

I ignored the heat transfer from the engine to the coolant because I assumed it was not a rate-limiting step in the overall heat transfer process, but you're right, if there is crud in the coolant passages or some other reason that fluid flow is restricted, this can be a cause of overheating no matter how efficiently the rest of the cooling system is operating. But the rate of heat transfer from the engine to the coolant will also be increased if the coolant flows faster.



True, but presumably the system is designed so that the coolant is able to accept heat from the engine and reject it at the radiator at a rate sufficient to keep the engine cool. The faster the coolant circulates in the system, closed or open, the more efficient the heat transfer rate at any step involving the coolant. But, yes, there is a maximum heat carrying capacity of the coolant because the amount of it is fixed, and that's why having your cooling system less than full can cause overheating. Again, this should all be taken account of in the cooling system's design.

My '73 Custom Cruiser came from the factory with a "heavy-duty" cooling system. The radiator is larger, and the total coolant volume is about 50% more than the standard cooling system. The larger radiator (more heat transfer surface) increases the rate at which heat can be removed from the coolant, and the larger total volume of coolant means that more heat can be held by it.


I can't explain why because I don't know why, but I do not think it has to do with the flow restrictor simply making the fluid flow more slowly through the system even though it's called a "restrictor." A better term for it might be flow "diverter" or flow "changer."

I would think it has something to do with changing the overall coolant flow pattern as I said earlier about why removing the thermostat could cause an engine to overheat. We had a discussion about this in another thread about how the service manual for my '73 makes a point of pointing out that that it mattered how the thermostat was oriented in the housing (not upside down versus rightside up, but rather rotated in the plane--something which would seem to be irrelevant) because the thermostat opens in a non-symmetrical way. So the thermostat is not just controlling whether or not coolant flows to the radiator at all, but it also affects HOW the coolant flows through the system.

Putting in a flow restrictor, which will slow the fluid flowrate, will not make heat transfer more efficient. But it could cause the fluid to flow at different rates through the different passages in the engine, just as the garden hose example showed. Partially plugging the end of the garden hose with your thumb (your thumb is a "flow restrictor") changes the fluid flow pattern through the hose, with more of the fluid coming out of the pinhole.


No. First because I'm not pointing a finger, but rather making a general observation, and second because the principles of heat transfer are independent of the system for which heat is being transferred. That people do not often understand the principles that govern heat transfer is evidenced by many of the statements made in this thread. You get a lot of "we've always done it this way" and "I know a guy who had this happen" type arguments, but these are all anecdotal, and the person making the argument doesn't know WHY what happened happened. Sometimes the reason something happened is not the reason that seems obvious.

Eric Anderson

I'll have to disagree with this statement, if it was observed that the removal of the t-stat caused the engine to overheat and the reinstallation improved the situation it is not anecdotal it's observed. The exact cause may not be known by the observer but the result of the action is known. Someone sees that grass is green they may or may not know why it's green but it doesn't change the fact that it's green.

jaunty75

I've never said otherwise. If someone claims they saw something happen, I don't deny that they saw it. My claim is that the REASON they gave for what they saw might not be right.

Undoubtedly the removal of the thermostat DID cause the engine to overheat. But WHY doing so caused the engine to overheat is another matter altogether.

wmachine

I know it will be pointless to say any more than I do not agree with your assessments. Nothing personal, but your answers do not explain anything beyond general theory.