Discussion on cooling system efficiency; what do you expect?

[mrk5]

I've been looking at a new radiator for my crewcab project. After reading several threads, I have been thinking about what I expect my cooling system to be able to do.

Right now I have the factory radiator. I assume factory because it doesn't have the plastic tanks. Lately our temps here have ranged from highs of 85° to 100° and lows in the mid 60°, giving me a lot of ambient air temps to use for "data collection". I have figured out the best my system can manage is a 130° differential.

So if it's 95° out, the engine temps will run about 225° on the highway. If it's down around 85°, the engine is at about 215°.

I guess since the truck runs a 195° thermostat, I expect it to run down the highway at 195°, or within 5° of that anyway. That means keeping the engine within 100° or less of the ambient air temperature on the really hot days.

Does this seem unrealistic? What do some of you expect?

 

[swettysblazer]

Stock Radiator, 180 degree stat, my truck will run around 180 all day in one hundred degree weather. Just drove 2500 miles with that set up and no problems at all.

 

[Carcinogen]

I expect 10-15 degrees above my thermostat rating.

 

[miniwally]

I've been looking at a new radiator for my crewcab project. After reading several threads, I have been thinking about what I expect my cooling system to be able to do.

Right now I have the factory radiator. I assume factory because it doesn't have the plastic tanks. Lately our temps here have ranged from highs of 85° to 100° and lows in the mid 60°, giving me a lot of ambient air temps to use for "data collection". I have figured out the best my system can manage is a 130° differential.

So if it's 95° out, the engine temps will run about 225° on the highway. If it's down around 85°, the engine is at about 215°.

I guess since the truck runs a 195° thermostat, I expect it to run down the highway at 195°, or within 5° of that anyway. That means keeping the engine within 100° or less of the ambient air temperature on the really hot days.

Does this seem unrealistic? What do some of you expect?

Scott

I spent way too much time planning and figuring out the cooling system for the Race Car. It comes down to Horsepower and radiator effectiveness.

Griffin rad. claimed that a 31"X19" dual pass radiator with a trans heat exchanger in it would cool our 400hp race car engine in Nevada in August. I disputed that claim and asked what happened when we had been in a silt bed for an hour straight with our foot flat on the floor, in traffic, and the rad was full of dust. They kind of got quiet.

We have a 36"X19" that only cools the engine in the car and you honestly can hold your foot flat on the floor in a silt bed in Vegas to Reno for an hour straight in traffic while passing guys cause they are over heating. We were told that was crazy and we would never need that but I see now the standard in the Ultra 4 world is moving towards that large rad. Mainly I suspect for the 16" dia spal fans but still it's more common now.

IMO it isn't about the ability to cool today it's how will it work in three years when it's full of dust and bugs. Bigger is better for the most part. If I was you I would look at the largest physical size rad that you can fit in the stock mounts. Meaning a big direct fit unit, keeping in mind that the more cores it has doesn't always mean it's better. Generally speaking a 2 core is better than a single core but not by double, because the second core has heat load from teh first. Also a double pass isn't as effective as a single pass because the second pass the temp difference (delta) between the water and the air is less.
Cooling is all about the delta between the heat and cold and the rate you move the water. Don't over look adding a higher flow water pump, the more 225 degree water you push past the 100 degree air the better your engine will cool. Provided there is no cavitation at the pump and or the water in the radiator you literally can't move the water too fast in the system.

Cliff notes;
Big surface area rad. Multiple cores but keep in mind the surface area is more important,
Good water pump
Good air flow, don't obstruct the rad with things like winches, lights etc. OR if you do you need to add size to the rad to take this into account.
clean your rad. look how much dust and debris is on an air filter after 10,000 miles. Your rad had that same air run through it too.

 

[nvrenuf]

I expect 10-15 degrees above my thermostat rating.

Agreed. No reason a healthy system can't do that (unloaded).

 

[mrk5]

Sounds like mine is lagging. It's about 25 minute drive home and I feel like on the 90°+ days if I drove further the coolant temp would just keep climbing.

I have a hi-flow pump to put in, but I ordered short when I should have gotten long. I also have a hi-flow thermostat.

I am leaning towards a Griffin. Actually the 31"x19" unit miniwally referenced.

The General had a diesel radiator that is 6" wider than a standard rad, I think that would be 34" wide on the core. I want to steer away from that because it made a couple of things difficult, namely radiator hoses and fan shroud. I'm planning to keep the mechanical fan for now so I need to keep something close to the size that fits the shroud.

I'm also looking hard at doing an LS swap in a couple of years so I want a good radiator for that.

 

[ryoken]

alum.. as big as you can possibly fit.. and as much as you are comfortable spending... as with headers, with alum rads, you tend to get what you pay for I've found....

this coming from a guy that likes and has had great luck with the big universal off-brand Northerns from Summit....

but some of the higher end stuff is outstanding... with BeCool being absolute top of the line imo.. but Griffin and AFCO both make a nice rad too...

 

[6872xtc]

The only thing I can add is that I had a Be-Cool in my '70 and in less than 4 years and 15K miles it started leaking at the header panel. (That truck doesn't get used real hard.) The company told me just have it epoxied as that's what they do for those repairs. Local shop did that and 6 months later more leaks. It is gone now...

 

[1leg]

My truck runs about 10' hotter then the T-stat. It will climb to 15' over if i'm climbing a long hill.

I want to go with a water pump pulley that is about 1/2" smaller to see if i can get some more flow out of my pump. this should help to keep it more stable.

 

[diesel4me]

Sometimes moving the water too quickly leads to problems with overheating too,like when someone removes a thermostat ,thinking the increased flow will help (and sometimes does),but racers found out some restriction to the flow is better ,it gives the water time to get cooled in the radiator before flowing back to the water jackets..

Moroso came up with restrictor plates to install in place of the thermostat ,after some guys used plain washers and noted it reduced the operating temps a lot..

So,I wonder if having a high flow pump and brand new radiator with nice clear passages really IS better or not......seems to me the factory setups worked pretty darn good in most cases..

.trouble is every truck is different,and will act differently in different climates and conditions...someone driving a truck in Denver might boil over ,while the trip on the east coast at sea level wont phase it at all..

 

[miniwally]

Sometimes moving the water too quickly leads to problems with overheating too,like when someone removes a thermostat ,thinking the increased flow will help (and sometimes does),but racers found out some restriction to the flow is better ,it gives the water time to get cooled in the radiator before flowing back to the water jackets..

Moroso came up with restrictor plates to install in place of the thermostat ,after some guys used plain washers and noted it reduced the operating temps a lot..

So,I wonder if having a high flow pump and brand new radiator with nice clear passages really IS better or not......seems to me the factory setups worked pretty darn good in most cases..

.trouble is every truck is different,and will act differently in different climates and conditions...someone driving a truck in Denver might boil over ,while the trip on the east coast at sea level wont phase it at all..

This is a widely argued topic all over the place. bottom line is tht's it's simple thermodynamics.

It all works off of the temperature differential between the medium being cooled and the medium cooing it. The more water in this case you can push by through a radiator with cool air blowing on it the more temperature you are going to loose in that system. leaving it in the radiator too cool off more doesn't "improve" the cooling ability of the system.

Also radiators depend on a certain amount of turbulence within the radiator to get the fluid moving and tumbling thus exposing more of the fluid to the cooling part of the radiator.

Where this whole thing falls apart is when you create cavitation within the system either at the pump or in the radiator. This is what causes issues when talking about the water moving too fast. When the pump cavitates it really stops pumping and thus you aren't moving water or if the water is cavitating in the rad it isn't being cooled as well. Hence the restriction plates.

 

[dyeager535]

I'll just chime in because I've been watching mine to try and see if *downsizing* my radiator will cause issues.

As has been said, application is going to make a world of difference. This thread is a good example of that http://coloradok5.com/forums/showthread.php?t=298869&page=10

A high HP motor, or towing two tons of junk, is going to be a completely different world of cooling, than a stock, unloaded truck doing the same trip. It's already been said, but I just want to +1 that thought...what works unloaded may not work loaded, or on hill climbs, etc.

My cheapy aftermarket thermostat (before I knew better, but it's already 10 years old, so why change it?) keeps the engine to about 208* according to the ECM. it's the stock small block radiator (19x28" IIRC, it's not the shorter one), copper/brass, about 10 years old. Dual LS1 fans. No AC, manual trans, so less heat for the radiator to deal with than ones with.

I climbed two mountain passes the last two days (0-~5400ft and 0=~3000ft) in roughly 85* temperatures. Obviously thats an average since the temps at the bottom and top were different. Weight difference with gear/extra person was roughly 500lbs over normal, but temp never exceeded that 208*.

Were I towing a significant load, and/or not able to maintain the same amount of airflow through the radiator (slower vehicle speeds) who knows if it would climb above what I see now?

I would like to try a more efficient water pump, but without cooling issues I'm not sure I'd see a difference, which makes it a hard cost to justify.

With an unknown quantity radiator, it's pretty tough to tell where you are starting in terms of efficiency. If there is corrosion in the tubes (whether you can see it or not) efficiency is going to decrease, which is very hard to determine. I suppose an IR temp gun on the inlet and outlet sides should give you an idea of efficiency, but how that relates to a "good" radiator I don't know. Can't recall seeing charts that indicated what kind of heat loss you should see across the radiator if everything is up to par. *That* would be valuable, at least within the constraints of ambient temp, AC, additional coolers, radiator size, all the common variables.

 

[cybrfire]

Had some cooling issues in my crew cab when it was first put together.

In the end, put in the largest(surface area) Griffin alum. radiator I could. Twin 16" electric fans. Haven't had a problem since.... Except, it doesn't warm up very well in the winter.

Keep in mind, thermostats are not digital. They will open/close partially and control water flow. You can tune your system with the thermostat as long as the other components are up to the task.

 

[ktmoutfront]

Bone stock 5.7, stock fan, clutch and shroud. 4 row rebuilt stock radiator. 120 degree day in the dessert, it still ran 180 up hill in a sand wash for miles. I have never had a heating issue.

When I wheel with jeep and Toyota guys in the Rockies during the summer, they open their hoods when they stop. I Just leave mine running.

Now I probably will probably start having issues.

 

[1leg]

This is a widely argued topic all over the place. bottom line is tht's it's simple thermodynamics.

It all works off of the temperature differential between the medium being cooled and the medium cooing it. The more water in this case you can push by through a radiator with cool air blowing on it the more temperature you are going to loose in that system. leaving it in the radiator too cool off more doesn't "improve" the cooling ability of the system.

Also radiators depend on a certain amount of turbulence within the radiator to get the fluid moving and tumbling thus exposing more of the fluid to the cooling part of the radiator.

Where this whole thing falls apart is when you create cavitation within the system either at the pump or in the radiator. This is what causes issues when talking about the water moving too fast. When the pump cavitates it really stops pumping and thus you aren't moving water or if the water is cavitating in the rad it isn't being cooled as well. Hence the restriction plates.

Thank you, I thought i was going to have to explain it. you did a better job then i could.

I have a Meziere WP401 water pump. it shouldn't have a cavation issue until around 7500 to 8000 RPM(pump speed). My tow normal cruse speed is around 2500rpm(engine) 3000rpm(pump) I was think i could pump the pump speed up to about 3500.

I need to get out a measure my pulleys again to make sure.

 

[dyeager535]

In the end, put in the largest(surface area) Griffin alum. radiator I could.

Realistically, for a project, as far as I can see, there is no downside to using the largest radiator you can find/use, except cost.

At ~8.3lbs/gallon (for straight water), even four gallons of additional coolant capacity would be nearly insignificant in the long term for a large vehicle. In terms of keeping the vehicle cool, that would be huge over "normal" capacity though.

I would think that it always better to start out with a radiator too large, than buy one that doesn't quite make the grade in all situations, at least when starting out.

Since running other than your stock radiator requires modifications (fan shroud in particular) for a long term vehicle, it makes sense to pick a size and stick with it though.