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Getting hot at highway speeds -Solved?

You said that the temp at the right rear of the engine block is above 230*. It sounds like you measured that with an infrared thermometer, correct? Is that the only place on the block that reads that high or didn’t you measure any other place?
 
Both the TBI sensor through ALDLdroid and inferred.

The Autometer dash gauge also shows the same heat soak (normal front left GM temp sender port).
 
dyeager535 said:
I've never understood how a cooling system pressurized to ~16PSI could collapse hoses, but maybe that's just me.
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That is because there is a difference between static and dynamic pressures.
The system has 16 PSI at all points in the system when everything is sitting still. But when the water starts moving, you get varying pressures.
For instance, look at an AC system. When its sitting still, you have about 90 PSI in the system depending on the outside temp. When the compressor starts running, you can 180-200 PSI on one side, and 20 PSI on the other.
If the radiator of a cooling system has 16 PSI in it, but the water pump is trying to pull water out of it faster than even the 16 PSI can force it through the passages then the pump is going to pull a vacuum on the lower hose.
As soon as the hose starts to collapse, that puts more restriction on the suction side of the pump, causing more collapse, and so on.
That 16 PSI will kick in as soon as the engine is switch off or slows down, and will reinflate the hose instantly. Thus you will not see it unless you are looking when the engine is running fast.
Its not going to collapse instantly though. As the water flow through the natural restrictions of a radiator core faster and faster, the more apparent restriction you get due to turbulence.

On top of all that, the faster a fluid flows, the lower the pressure due to Bernoulli's principle. But I'm not going into that. I studied all I wanted to about that in college. I know how it works and how to use it, and that is good enough for me.
 
You've got an electric fan on that now, is there any shrouding on it? After about 50-55 the fans are useless, and actually impede airflow.
 
Infrared - just near the sending unit to confirm the reading.

I like the AC analogy, but the AC actually has a valve to from the high side / low side gas / fluid sections.

The flex a lite fans have two “ports” for a lack of a better term maybe to allow the airflow through, but that’s what my thought was too. The fans actually restrict air flow at highway speeds. I hate having the thought of running a mechanical fan again. I’ve done mods that I’ll have to change to go back to mechanical.

The fan covers the entire radiator core.
 
I did not catch the electric fans originally. I would hve started there. Make sure they are spinning the right way. Fixed an overheating issue on a 40 chevy. Wired backwards.

Picture of said fan shroud? If it one of the flat tight units, they are notoriously bad for blocking air at speed. Even with the flaps.

To prove it to one client, we drove his classic car to the freeway. Pulled into a parking lot and pulled the fans. Jumped on the freeway and it ran a little cool. Put the fans back on and changed nothing else, ran 30 degrees hotter. I did not think it would be that bad.

My dad claimed that it was like clogging the radiator grilles. No air moving. Made sense on that car. Moved the fans back one inch and built a surround to cover that 1 inch. Brought it done 15 degrees, enough to run it.
 
That’s exactly what happened with a set of real cheap fans. I went with the flex - a - lite after some reading on them.
 
Fordum said:
That is because there is a difference between static and dynamic pressures.
The system has 16 PSI at all points in the system when everything is sitting still. But when the water starts moving, you get varying pressures.
For instance, look at an AC system. When its sitting still, you have about 90 PSI in the system depending on the outside temp. When the compressor starts running, you can 180-200 PSI on one side, and 20 PSI on the other.
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The water pump is not positive displacement. There is nothing that acts as a valve short of the thermostat, and if it's closed, fluid isn't moving effectively anyway, so there will be little suction. There are various restrictions to flow throughout the system of course. There is vacuum relief built into the radiator cap, and depending on setup, those without valves on the heater line will help equalize pressure if going to the radiator. The lower hose is also larger than the upper, to help prevent a drop in pressure before the pump.

99% of us using aftermarket hoses would have overheating issues if a spring was a necessity, since almost none are sold that way. That spring was there from GM because they used a vacuum setup when they filled the system with coolant, and that kept the hose from collapsing as they did so. It's a piece used to assist assembly. The fact that so few have ever actually witnessed this happen, tends to indicate there is something else going on in those cases. That so many of us have never had an issue, with centuries of combined use, tends to make me believe that there has to be another cause.

A radiator cap that won't hold pressure (or doesn't stop the system from going negative), could certainly exacerbate/cause a hose collapse with no spring, if the pump can move enough coolant.

It's an easy test, in any case. Get the engine warm, and manually open the throttle. Watch.

FWIW, I thought fans would impede airflow too. If the incoming air is moving faster than the electric or clutched fans can pull, it will just turn the fans faster. Still a restriction, but its not as if air can't get through. Having seen fan effectiveness at highway speed first hand when my radiator was on its last legs, climbing a 5% grade for 5 miles in 90* weather at 55-60MPH, I could watch my GM LS1 fan (only one runs up to 240*, engine never got that hot) pull the engine temperature back to its set "off" temp, and as soon as the fan shut off, engine temp would rapidly rise, the fan would come back on at it's trigger temp, and the cycle would repeat. Others have seen this with the stock clutch fan as well, when you are really taxing the cooling system (towing, grades, heat), a proper fan setup, at freeway speeds, will pull more air through the radiator than you would via road speed alone. I suspect the fan shrouding and overall design of the front end is the cause of the fan being effective even at speeds where we would think speed alone would suffice. Same vehicle, under much less load, didn't need fans at all as long as I was moving.
 
I think everyone worried about valves is missing the point. I probably should not have used the AC example, but since pretty much everybody is at least partially familiar with those systems, I thought it would help.
When a closed liquid system is at rest, the pressure is equal at all points in the system. As soon as something starts moving the fluid through a closed loop, pressure differences start occurring. If they didn't, the fluid would not move.
I agree that the water pump on a vehicle is not a positive displacement device. But I think I can be fairly confident that gauges placed on the input and output side of that pump would show pressure differences.
If there is no difference in pressure, the fluid would not be moving. Especially with a non-positive displacement pump.

How much difference? No idea. I never measured it, nor do I remember seeing any data on the amount of head a regular automotive water pump develops.
But, there must be a significant amount, it moves a lot of water fairly quickly, and there has to be a fairly large amount of pressure difference to do that. Is there enough to collapse a lower hose? Again, no idea. But, people have seen it happen, so something
must be going on. I have seen older radiator hoses so soft and squishy they felt like boiled noodles, and others so hard that it felt like they were under pressure when empty. I assume different rubber compositions age differently. Of course, a lot of hoses
are different hardnesses right out of the box.
And, as for the suction valve on the radiator cap, remember its on the pressure side of the system, before the restrictions of the radiator. Any suction is going to occur between the radiator and the water pump inlet.

And BTW, veering wildly back to the AC, what valves? There are two valves in the compressor, but they only affect the movement through the pump. As far as I know, there are no other valves in that system. Its all wide open. There is a built in restriction in the form of an orifice tube, but its not a valve.
Admittedly the valves in the compressor do prevent the fluid from moving backwards through the pump when its shut off, as it could in an automotive water pump, make the compressor more efficient, and make the amount of pressure difference a matter of power of the motor rather than the clearance of the impellers.
So, in an automotive water pump, there is a limit to the amount of pressure difference that it can develop before water starts to try to run backwards past the impeller, but at the speed its spinning, and the velocity of the water would tend to limit that due to the inertia of the water.
I think all that makes sense. I'm running on next to no sleep. Went out and hurt myself yesterday, and did not sleep much last night.
 
Wes Harden said:
AC thermal expansion valve and POA valve have been/are used.
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I know, but I was hurting and tried to take a shortcut. In my opinion, the systems were much better when expansion valves were used. And not having checked into the newest crap gas systems that we are being forced to use these days, I don't know what is under the hood now.
But several years ago, most of the systems I saw were orifice tube. Maybe in the suburbans where you had two different evaporators, they used expansion valves again, but I know Ford has been mostly orifice tube since about 1985 or so.

Also, the crap I was referring to was the gas used, not the systems themselves. My new car uses the 1234YF gas and it cools very well. I just don't like the properties and handling procedures of the gas.

At least its not CO2. A lot of the refrigeration systems are going to that, and I think Mercedes tried to. I have no problem with the gas its self, or its cooling properties, but the pressures are going to be scary.
 
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Old original lower hoses were kind of flippy floppy.
The spring definitely made some sort of difference in those. The new hoses have all the strength built in and just don't need that spring.

The lower we took off of my kids 72 was much more pliable and felt thinner. When I bought the replacement I asked at the counter why it didn't have the spring. I was told then that they just didn't need it in the new hoses.


I wondered about fan rotation as mentioned above too.
 
Not sure where in the valley you're at but if you wanted to come by I'd eyeball it with you. I'm in Glendale by the Cardinals stadium.
 
Fordum said:
When a closed liquid system is at rest, the pressure is equal at all points in the system. As soon as something starts moving the fluid through a closed loop, pressure differences start occurring. If they didn't, the fluid would not move.
I agree that the water pump on a vehicle is not a positive displacement device. But I think I can be fairly confident that gauges placed on the input and output side of that pump would show pressure differences.
If there is no difference in pressure, the fluid would not be moving. Especially with a non-positive displacement pump.
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No disagreement there is a pressure differential. All the hose diameters would be the same otherwise. Point I'm making is that the system design can't have the hose on the ragged edge of collapsing, otherwise it would be a far more common occurrence. These systems are the same on nearly every RWD GM vehicle made from the late 60's up until the mid 90's.

And, as for the suction valve on the radiator cap, remember its on the pressure side of the system, before the restrictions of the radiator. Any suction is going to occur between the radiator and the water pump inlet.
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On this vintage cooling setup, the radiator cap is on the same tank as the outlet of the radiator, so pump inlet side.

How much difference? No idea. I never measured it, nor do I remember seeing any data on the amount of head a regular automotive water pump develops.
But, there must be a significant amount, it moves a lot of water fairly quickly, and there has to be a fairly large amount of pressure difference to do that. Is there enough to collapse a lower hose? Again, no idea. But, people have seen it happen, so something
must be going on. I have seen older radiator hoses so soft and squishy they felt like boiled noodles, and others so hard that it felt like they were under pressure when empty. I assume different rubber compositions age differently. Of course, a lot of hoses
are different hardnesses right out of the box.
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I couldn't find any either, I figured someone would find that information valuable and have posted results. Some rough calculations I was able to do with data easily found, is that a ~1.25" pipe, 2 feet long, between 10 and 16 PSI, will flow ~42-52GPM. Aftermarket pump numbers apparently aren't reliable, but Stewart Components "competitor" flow numbers put the number at 59GPM @ 3000RPM. With the restriction of the block, thermostat, upper radiator hose smaller diameter, and radiator cores, plus inefficiency of the impeller setup, I assume the amount of coolant moved through the complete system is less than what can be (or is) tested by manufacturers.
 
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