getting too hot!!!

[GT_Rich]

That's an interesting article Jason posted. It's informative, but who can say if every theory in there is proven?

I know for sure I had a thermostat sticking open last year and my F-150 ran 20 to 30 degrees hotter than usual in a steady state situation. What I posted earlier still makes sense to me. I'd love to see equations (that don't have ridiculous assumptions and take into accout inefficiencies) that prove no t-stat is cooler than a cycling t-stat.

 

[89SaleenGT]

91,
Installing a new fan clutch is cake. Four bolts and switch the fan to the new clutch and back in. You will have to remove the drive belt so if it needs replacing, this would be a good time.

I am at the same stage you are. My car is running hotter than usual and has benn gradually doing so over the past few months. I replaced my fan clutch several years ago but I noticed that the replacement clutch had been leaking and the engine is running hotter. Of course we are experiencing 100°+ temps in Cali right now so the extra engine heat is not helping how my car is running.

I have ordered a new Motorcraft fan clutch ($72.00 incl shipping at rockauto.com) but it has not arrived yet.

A source for an inexpensive radiator is from either Kragen (Parts America) or Rock Auto (rockauto.com). You can get a 2 core for under $100. If you want a 3 core brass radiator, then you are looking at $165shipped. I opted for the 3 core.

 

[vristang]

89 saleen i am still working on that, my fan will spin at least one complete turn if not two and it does seem to spin the same speed even when cold now that u mention it. how difficult would it be to take it out and install a new one.

Dude, I apologize for getting this thread so far removed from your original question.
I just can't turn down the opportunity to learn something this interesting.

Years back when my clutch went bad I put in a metal flex fan. Not ideal, but it has worked very well for me. It was pretty cheap too; about $25 for the fan and another $15 for the spacer. You will want the fan positioned so that it is just inside the fan shroud. Too far in or out will hurt the airflow.

jason

 

[vristang]

I am getting pretty frustrated looking for an appropriate equation.

Here is why...
All the heat transfer stuff in my Phys book assumes that the hot object and the cooler object are in contact until thermal equilibrium.

This is not the case for radiator coolant.
The coolant hits the radiator for a short period of time, then goes back to the engine block to pick up more heat energy. The coolant temp does not equalize to the temp of the air going over the radiator. Or does it? Maybe this is part of answer?

I would like to find a thermal transfer equation that does not assume thermal equilibrium.

This is the question I would like to answer...
If an piece of aluminum at 30F is placed in a cup of water at 98F for only 5 seconds then removed, what will the temp of the aluminum and water be? How about if the contact time is extended to 10 seconds?
We would need mass/volume values for the aluminum and water, but the point is that the amount of time the aluminum is in contact with the water would be a factor in the amount of heat that is transferred.

Maybe I am way off base in thinking that the above example would even apply to a radiator?

I feel so lost.
jason

 

[89SaleenGT]

I just read my comment to vristang,

I am basing my comment on the engine retaining a functioning thermostat.

The thermost does indeed regulate flow of coolant through the engine.

I have also experienced an engine without a thermostat that would overheat.

 

[vristang]

91whiteponygt,


One thing you may want to check is your ground wires. Missing ground wire tend to make the car run hotter. I recall a fix where one would actually slip a wire under the upper hose and into the coolant. One would then have to ground the other end of the wire. This was a fix recommended by Cadillac in the early 80's.

vristang,
Maximum cooling occurs when you have maximum coolant flow through the radiator.

Good Luck

I had completely missed this comment. My apologies for not responding sooner.
According to the article I quoted from, there is a upper limit to how high the rate of flow can get, before there is a negative impact on cooling efficiency. I still hold to this point. My question is... How do you determine that point?

I would never put a ground wire in contact with the cooling system. This is a sure way to increase corrosion on the radiator. Grounding to the block and aluminum intake is ok because (assuming proper coolant mixes) the resistivity of coolant is sufficiently higher than the metals, so there is no e- current flow through the coolant. Putting a ground in the coolant, or mounting it to the radiator will decrease the resistivities to a point where electricity will begin to flow through the cooling system.
If you look at our cars (in stock form) you will find that the radiator is insulated from the frame at all mounting points. This is one reason why. The other reason has to do with vibration accelerating corrossion in the thin radiator materials.

I am not sure why Cadillac would recommend such a thing.
Maybe at the time this knowledge did not exist?

jason

 

[RaceDvr50]

RaceDvr50 - Just taking some classes in physics doesn't mean you know everything about the t-stat. I have took three years of spanish, but I'm not going to try my luck at Mexico.

It is not a good idea to not have a t-stat. If you sit in traffic, the radiator is not being used so to speak. The coolant will flow in and out and not have time to be in a "cool" radiator...the temps will slowly rise, and overheat.

Ok well maybe if you had studied three years hard at a college level you wouldn't have a problem in Mexico.


Also no it won't cause an overheat, read a book or something. We covered this, the coolant does not sit in the radiator waiting to be "cooled" Without a thermostat a car with a properly working cooling system will NEVER overheat. The more the flow the better PERIOD. Read the whole post and maybe you can follow this. Your coolant in your engine is getting hot while the radiator is sitting full of coolant waiting to be "cooled" you must be kidding me right. The job of the radiator is not to cool the coolant but to transfer heat absorbed from the engine by the coolant to air. The faster you move the coolant through the radiator, the faster the process takes place. Thermal transfer occurs fastest at greater temperature differentials. Don't argue I'm trying to teach you something.

 

[RaceDvr50]

What rpm is the "40 gallons per minute" on the water pump? 600 or 6000rpm?

Details on an Edelbrock water pump

SMALL-BLOCK FORD CIRCLE TRACK PUMP #8833


Pump RPM Left Flow (gal/min) Right Flow (gal/min)
2000.............16.03.....................16.16
3000.............24.07.....................24.11
4000.............32.31.....................32.51
5000.............40.12.....................40.08

 

[RaceDvr50]

I am getting pretty frustrated looking for an appropriate equation.

Here is why...
All the heat transfer stuff in my Phys book assumes that the hot object and the cooler object are in contact until thermal equilibrium.

This is not the case for radiator coolant.
The coolant hits the radiator for a short period of time, then goes back to the engine block to pick up more heat energy. The coolant temp does not equalize to the temp of the air going over the radiator. Or does it? Maybe this is part of answer?

I would like to find a thermal transfer equation that does not assume thermal equilibrium.

This is the question I would like to answer...
If an piece of aluminum at 30F is placed in a cup of water at 98F for only 5 seconds then removed, what will the temp of the aluminum and water be? How about if the contact time is extended to 10 seconds?
We would need mass/volume values for the aluminum and water, but the point is that the amount of time the aluminum is in contact with the water would be a factor in the amount of heat that is transferred.

Maybe I am way off base in thinking that the above example would even apply to a radiator?

I feel so lost.
jason

The above does apply but working 66 hours a week I don't think I'm gonna have the time to get those equations for you. I'll see what I can do. Basically this is what I was talking about when I said that thermal transfer takes place the quickest at greater temperature differentials. Say you put that piece of aluminum at say 180 degrees under 70 degree water. In 5 seconds you might get it down to 130 degrees a 50 degree drop but leave it another 5 seconds and it will only drop another 20 degrees. This is less than 50% as efficient of heat transfer. This is why more flow is better because you are quickly replacing the coolant with more coolant from the engine thus the highest rate of thermal transfer may be achieved. This is why the thermostat works, it's only mode of operation is to open more and more as the engine gets hotter and will not start to close until the coolant temperature drops below its heat rating.
Basically what the article you found said was that the higher the coolant flow rate the better up until the point of cavitation or disruption. I would assume that the water pump on your engine could never reach this point, basically what it is saying is that if you start to move the coolant too fast, eventually the coolant will stop flowing properly through the engine or radiator and cause a problem.

 

[vristang]

The above does apply but working 66 hours a week I don't think I'm gonna have the time to get those equations for you. I'll see what I can do. Basically this is what I was talking about when I said that thermal transfer takes place the quickest at greater temperature differentials. Say you put that piece of aluminum at say 180 degrees under 70 degree water. In 5 seconds you might get it down to 130 degrees a 50 degree drop but leave it another 5 seconds and it will only drop another 20 degrees. This is less than 50% as efficient of heat transfer. This is why more flow is better because you are quickly replacing the coolant with more coolant from the engine thus the highest rate of thermal transfer may be achieved. This is why the thermostat works, it's only mode of operation is to open more and more as the engine gets hotter and will not start to close until the coolant temperature drops below its heat rating.
Basically what the article you found said was that the higher the coolant flow rate the better up until the point of cavitation or disruption. I would assume that the water pump on your engine could never reach this point, basically what it is saying is that if you start to move the coolant too fast, eventually the coolant will stop flowing properly through the engine or radiator and cause a problem.

I appreciate you coming back.
I understand your busy, so no biggee. I'll keep looking.

Another aspect that we have not brought up is that there are 2 heat tranfers going on. We have discussed the heat transfer from the coolant to the radiator, but haven't really talked about heat tranfer from the block to the coolant.

I am not sure how this impacts the discussion, if at all.

jason

 

[RaceDvr50]

91Whitepony you said that you have problems on the freeway too? Then you are probably not looking for a fan problem unless you have a really built engine or really steep rear gears your cooling system should be able to keep up going down the freeway without engaging the fan clutch. You asked about the orientation of the thermostat, did you check it? Is the spring end set into the intake manifold? Is your coolant full and clean? When was the last time you flushed and refilled your coolant? Does your heater produce heat? If not you might have a blockage. I assume that you are using the green stuff for coolant, if not the dexcool can create major problems. Let me know........

 

[RaceDvr50]

Jason, yes there are two heat transfers going on here, I think that is part of where other people have gotten hung up. The fact that as the coolant is transferring its heat to the radiator, the coolant in the engine is absorbing heat and needs to get back to the radiator. Heat transfer from metal to water (i.e coolant) happens faster than transfer from metal to air. That is why the radiator has fins to disperse the heat over a much greater surface area in order for the air to cool it. There is a possibliity that 91Whites engine could be experiencing a partial blockage in the water jacket of the engine which could slow the flow though the engine and decrease the efficiency of that heat transfer. Is this where you were headed with that?


Also he could be running too much coolant and not enough water, this would decrease efficiency as well since water does the bulk of the work in cooling.

 

[5spd GT]

Ok well maybe if you had studied three years hard at a college level you wouldn't have a problem in Mexico.

Maybe so, but don't let everyone assume that since you have taken a couple years of Physics that you know exactly what you are talking about.

Also no it won't cause an overheat, read a book or something. We covered this, the coolant does not sit in the radiator waiting to be "cooled" Without a thermostat a car with a properly working cooling system will NEVER overheat. The more the flow the better PERIOD. Read the whole post and maybe you can follow this. Your coolant in your engine is getting hot while the radiator is sitting full of coolant waiting to be "cooled" you must be kidding me right. The job of the radiator is not to cool the coolant but to transfer heat absorbed from the engine by the coolant to air. The faster you move the coolant through the radiator, the faster the process takes place. Thermal transfer occurs fastest at greater temperature differentials. Don't argue I'm trying to teach you something.

So what size water pump you putting on the car?

How often are we at 5,000rpm?

Does that Edelbrock flow the same as a stock one?

Air passes over the radiator. Air cools the radiator. Coolant is in the radiator. Coolant cools down. T-stat cracks or opens fully. Cooler coolant goes into engine. Engine cools or stays cool.

An electric fan simulates air passing over the radiator, cooling the coolant. My car runs cooler on the highway. Wonder why?

LOL @ your "physics for 3 years"...Oppenheimer, Galileo, and Einstein all shouldn't have passed you up...

 

[5spd GT]

Details on an Edelbrock water pump

SMALL-BLOCK FORD CIRCLE TRACK PUMP #8833


Pump RPM Left Flow (gal/min) Right Flow (gal/min)
2000.............16.03.....................16.16
3000.............24.07.....................24.11
4000.............32.31.....................32.51
5000.............40.12.....................40.08

Now that is a stock pump if I have ever seen one.

 

[RaceDvr50]

Air passes over the radiator. Air cools the radiator. Coolant is in the radiator. Coolant cools down. T-stat cracks or opens fully. Cooler coolant goes into engine. Engine cools or stays cool.

An electric fan simulates air passing over the radiator, cooling the coolant. My car runs cooler on the highway. Wonder why?

LOL @ your "physics for 3 years"...Oppenheimer, Galileo, and Einstein all shouldn't have passed you up...

An electric fan simulates air passing over the radiator?? Mine actually moves air

You car runs cooler on the highway because more air passes through the radiator and your engine runs under a continuous low load condition. So the engine produces less heat and the radiator is able to exchange more heat to the air. If you think you're being smart now go back to jr. high where you can be around people who are your mental peers.

Too bad you are too thick to understand thermal transfer and how it applies to a closed loop system with a constant heat source.

 

[RaceDvr50]

Now that is a stock pump if I have ever seen one.

Well that non-stock pump flows over 80gpm at 5000 RPM a stock one is probably in the range of 60gpm at that speed. What's your point? The coolant can still cycle through the entire system several times a minute assuming the thermostat is open. If you knew anything about this subject you'd shut up now.

 

[5spd GT]

Well that non-stock pump flows over 80gpm at 5000 RPM a stock one is probably in the range of 60gpm at that speed. What's your point? The coolant can still cycle through the entire system several times a minute assuming the thermostat is open. If you knew anything about this subject you'd shut up now.

You talked about numbers on a stock pump, then posted an aftermarket pump.

 

[5spd GT]

An electric fan simulates air passing over the radiator?? Mine actually moves air

Yep, but it passes air, as if driving down the highway. That is why many experience there a/c is a bit cooler on the highway, along with engine temps.

You car runs cooler on the highway because more air passes through the radiator and your engine runs under a continuous low load condition. So the engine produces less heat and the radiator is able to exchange more heat to the air. If you think you're being smart now go back to jr. high where you can be around people who are your mental peers.

Too bad you are too thick to understand thermal transfer and how it applies to a closed loop system with a constant heat source.

So tell me this, am I producing more load at idle (overheating because fan isn't big enough) or cruising at 2,400 rpm...(no overheating)...radiator is getting cooled...air is passing over it.

Let me know this obvious answer Galileo

So how often are we at 5,000 rpm? I'm going to start reving my engine to 5,000 rpm when my car is getting hot...according to your theory on how much it will flow...I might need to take advantage of that flow by revving and letting them impellers start working eh?

 

[vristang]

So how often are we at 5,000 rpm? I'm going to start reving my engine to 5,000 rpm when my car is getting hot...according to your theory on how much it will flow...I might need to take advantage of that flow by revving and letting them impellers start working eh?

In the past I can remember having coolant overheat issues which would diminish when I disengaged the clutch and blipped the throttle. I cannot say if the drop in coolant temp was due to purging an air pocket or due to increased coolant flow.
I have suspected a coolant pocket until this thread.

I get the distinct impression however that a particular member of this community is being attacked because he has a different point of view.
This does bother me.
Personal slander, and degrading comments should not be allowed, from either party.

Keep things tech and we will all be happier.

We may actually learn something.

*steps off soapbox*

jason

 

[smittyb]

Alright, after watching this thread, I am just gonna add food for thought. First, regarding the grounded wire in the radiator, it all depends on the type of material used as to whether it will promote or inhibt corrosion. In power plant heat exchangers, zinc anodes are used as "sacrificial annodes". They corrode away instead of the heat exchanger tubes.
Next I will simply state I have had thermodynamics classes, although that was some time ago, and will not claim to be an expert by any means.
As for the flow rate, we all know Q=McdeltaT. However for a closed loop flowing system, cooling will increase with coolant speed, up to a certain point. Again I can point to nuclear reactor experience where increasing coolant pump speed will decrease core temps. I say up to a point, b/c I believe the heat transfer function will act as a bell curve. Up to a certain point, it will increase, and after that it will decrease. I believe the water pump manufacturers have taken care of this aspect for us, as you never really see a wter pump (sbf) with a flow rating of over 65gpm.
As for the t-stat sticking open and temp effects, Summit and Jegs used to sell "flow restrictors" to help cooling. They were nothing more than washers that took the place of the t-stat. I have heard of t-stats sticking open and causing overheating.
Also another thing to consider when figuring t-stat operation into account is that they do not open and close quickly like a solenoid. They actually take quite a while to fully cycle. This can be seen by placing a t-stat in a pan of hot water.
Like I said just food for thought. I am not going to call anyone stupid for disagreeing.