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Radiator upgrade?

73K views 269 replies 27 participants last post by  VernDiesel 
#1 ·
Over the years the issue of a bigger radiator for us, to replace the little dinky one we have, has been discussed on and off. Did anything come of those discussions? Did an aftermarket larger radiator ever become available?

I see that folks have been fiddling around with oil coolers. But if we could just keep the coolant cooler, we wouldn't need oil coolers.
 
#3 ·
Attempting to cool oil is no way to cool an engine.

1) Oil doesn't exchange heat very well. Not nearly as well as water. So engine doesn't xfer heat to it well, and air flow doesn't extract heat from it well.

2) Water cooled engines are designed to xfer heat to the water, not to the oil. Look at how the engine block and head are designed such that the water jacket surrounds the entire cylinder and almost the entire top of the combustion chamber.

Te objective of cooling oil is to limit the peak temps of the oil. This extends oil life and keeps viscosity changes under control. Cooling the engine is not an objective. A feckless dribble of oil thru a little oil cooler, the oil resistant to giving up heat energy, is no way to design a cooling solution capable of significant load.
 
#4 ·
I see that folks have been fiddling around with oil coolers. But if we could just keep the coolant cooler, we wouldn't need oil coolers.
I disagree. I've never had an issue with high coolant temps when towing heavy. Can't say the same for oil.

Since installing my oil cooler my oil temps are much cooler, and thus my coolant stays cooler as well due to the lack of being heat-soaked from the oil.

A feckless dribble of oil thru a little oil cooler, the oil resistant to giving up heat energy, is no way to design a cooling solution capable of significant load.
Apparently you haven't seen my oil cooler lol.
 
#5 ·
I disagree. I've never had an issue with high coolant temps when towing heavy. Can't say the same for oil.

Since installing my oil cooler my oil temps are much cooler, and thus my coolant stays cooler as well due to the lack of being heat-soaked from the oil.

Apparently you haven't seen my oil cooler lol.
Re. coolant temps vs. oil temps. Those are different issues. The engine is putting lots of heat energy into the coolant, and not much into the oil. The OEM set up has the radiator to extract heat from the coolant, but nothing to extract heat from the oil. Isn't surprising, therefore, that our oil runs hot.

What people in this forum tend to call an oil cooler, isn't. It's just a heat exchanger to allow quick warm up of the oil in cold climates. Easy to do when coolant is 200deg and oil at 0deg. That's a 200deg delta. But when the coolant is at 225deg and the oil at 240deg, it's only a 15deg delta and w/o much surface area to xfer heat between fluids, it won't do much.

Just the fact that people are calling the OEM heat exchanger an "oil cooler" should cause everyone to be wary re. oil cooling opinions here.

Unless your oil cooler is huge, it's not going to do much. Remember that oil doesn't xfer heat well so oil coolers have to be really big to xfer noticeable thermal energy. Otherwise all they do is cut off the peak oil temps. Some oil cooler that is maybe 1' by 2" isn't going to dump enough thermal energy to matter. Remember, the coolant thermostat is a dynamic flow control device. It will attempt to keep the coolant at it's designed temp by changing the valve's position and therefore flow rate. So the larger oil cooler will not change the temp of the coolant until the heat load goes beyond what the fully open thermostat can handle, call it 225deg. Beyond that, the engine can use all the help it can get. So the way to tell if the oil cooler is helping is not lower engine temps, but lower incidents of coolant going >225deg, all else being controlled to be equal.

There is no "thus my coolant stays cooler". At least not w/o rigorous experiments. One of these days find a way to get your hand behind an oil cooler with hot oil in it. Blast air at it's face. You will find that the air hitting your hand isn't warmed much at all. Oil does not xfer heat well and there isn't much oil moving thru the cooler. Therefore not much thermal energy dumped.

The flow rate thru the oil cooler is the flow rate of oil out of the pump. At 35 or so PSI, it's the kind of dribble you'd expect from water pouring out of a 1/2" hose. No matter how big the oil cooler, you won't get more oil flow rate.

10yrs ago I did some experimenting with oil coolers on my race car. I put in a big oil cooler, 12x18", and put in oil temp sensors before and after. I was getting a lot more air blast on that oil cooler than a truck gets because race cars are allowed to go much faster. The best temp delta I could get was 2.5deg between in and out sensors. Consider how miniscule that much thermal energy must be. Over time tho, it added up. As I said, oil doesn't xfer heat well, but that's a 2 way street. Consider that my entire oil load was probably going thru the oil cooler every 2min (that's a guess btw) and every time the oil went thru the engine, it gained only enough thermal energy to raise the temp 2deg. In that scenario the oil temp drops 0.5deg with every circuit thru the oil cooler. That's how oil coolers drop peak oil temps. But as you can see from that example, it wasn't pulling much thermal energy out of the engine.
 
#6 · (Edited)
Dodge Heavy Duty Cooling by CSF Radiators, the cooling experts.. Click the view button on 3738

It’s what Sasquatch sells. Basically quality stock replacements. Fwiw 1/2 the price a dealership charges.


No the oil cooler/heat exchanger is not for cooling the engine. That remains the radiators job. We are having foremost an elevated oil temp problem where in the computer can derate the engine by pulling back fuel. The two best oil cooler set ups to replace the heat exchanger are reported to help. First & foremost keeping the oil temps down so that no oil temp derate happens. The side benefit less load on the radiator from not having to cool the oil also helps to keep coolant temps in check which is also an issue when towing TTs in really hot humid weather.

So directly & in directly it helps with both issues. At least that is my understanding. A concern I had was that replacing the heat exchanger also takes away the heat exchanger for the transmission. Unless I am mistaken about that. Regardless nobody who uses one of the aftermarket oil coolers has yet to complain about elevated trans temps or uber slow trans warm up.

I’ve always though more “plates” in the existing heat exchanger might be the best all around solution. Well in conjunction with bigger radiator / tanks. Next generation with the incredibly strong 48 volt fan should help tremendously.

Edit ok FYI I typed this post prior to RGs last post.
 
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#9 ·
Oil cooler not written off. Oil coolers are a fine means to cool oil. They're just not an efficient means to cool engines. For cooling engines we have a radiator and water-based coolant. Even if the radiator is on the small side.
 
#8 · (Edited)
I think a better rad would be the proper way to remove engine excess heat , that is its main function . Remember we have a electric fan and there not as good a a viscous fan clutch unit . I rather spend my money on a rad then a $ 1000 dollar oil cooler setup with all the extra plumbing and the possibility of a blown line while driving .
 
#10 ·
During ascents while towing, why is it the oil temp climbs so quickly while the coolant doesn't? Where is the oil scavenging all the engine heat from under a heavy load?

VernDiesel said:
A concern I had was that replacing the heat exchanger also takes away the heat exchanger for the transmission.
How does this affect the transmission temps? I don't understand how the transmission comes into play between the oil and coolant interaction.
 
#23 · (Edited)
During ascents while towing, why is it the oil temp climbs so quickly while the coolant doesn't? Where is the oil scavenging all the engine heat from under a heavy load?

How does this affect the transmission temps? I don't understand how the transmission comes into play between the oil and coolant interaction.
Sorry, I don't have all the answers. Certainly the heat transfer issues involved are pretty simple, but in order for answers to be good guesses, the questions need to be pretty precise, and the conditions the symptoms were observed in, carefully controlled.

The coolant system has some ability to regulate it's temperature, but the oil system doesn't have that ability to add heat xfer capacity if conditions warrant. So under different demand, ambient temp, and air flow velocity conditions, load vs. temp behavior of the two systems is sure to be different. One can make pretty good predictions as to how the two systems will react differently to different conditions by looking at the heat xfer mechanisms.

The coolant system. Two factors dominate the coolant system's ability to dump more heat if needed. The first is the thermostat. As the engine produces more heat, the thermostat opens up more, so more coolant flow goes to the radiator. The more hot water to the rad, the more heat energy is dumped. This ability to increase heat xfer maxes out when the tstat is fully opened. At that point, much of the coolant system's ability to "add capacity" ends. This produces a significant "knee" in the graph of heat produced vs. ability to dump heat.

The 2nd issue is vehicle speed. With the exception of a steep hill pulling a heavy trailer, higher engine loads produce higher velocities. So the additional heat produced by the higher engine load is offset, to some degree, but the increased amount of airflow thru the radiator. That allows the radiator to dump more heat energy. The heat loss effect of vehicle speed is not as significant as thermostat opening because the size of the thermostat opening can vary a lot whereas the speed difference between towing at 60mph vs. 70mph, for example, isn't much.

The 3rd variable that has to be accounted for is ambient temp. Heat xfer is proportional to the temp difference. A 220 deg rad will dump about a 1/3rd more heat if the ambient temp is 40deg than if it is 100deg.

Cooling the oil. The oil has almost no ability to cool itself, excepting the heat radiating from the block itself. But we ignored that heat loss from the surfaces of the hot block for the coolant system, so we should ignore that for the oiling system. The oil/water heat xfer device on the engine block, erroneously referred to as an oil cooler, is fine for warming up the oil under cold conditions, but it's not going to do much at operating temps because there's just not enough temp delta between 225def coolant and 240deg oil, nor surface area, for significant thermal energy xfer.

You asked why oil gets hot. Well, it's because it spends time in hot places. The top half of the block is filled with coolant. The bottom half of the block can get pretty hot tho because there's no water jacket down there. The very top of the head can also get pretty hot because even tho there's water flowing over the combustion chambers, there's enough hot metal up there in contact with the combustion chamber that getting pretty hot is inevitable. And certainly the crank bearings eventually get warmed up by the connecting rods. So altho oil is not going thru voids expressly designed to cool the block, since the whole block reaches a pretty high operating temp, the oil eventually gets pretty hot. It just takes a while.

Re. Why is the oil scavanging all the engine heat when the engine is under heavy load? It's not. Don't confuse temperature with xfer of heat energy. The oil gets hot because some of the places it goes to is far away from the block's water jacket. But the fact that it's hot doesn't mean that it's xferring a lot of thermal energy, nor participating much in keeping the engine cool. Remember that oil doesn't xfer heat very well and with no oil cooler there's no way to dump that heat. Those that have an aftermarket oil cooler will dump a little heat out of it, enough to lower peak oil temps, but if they think they're xferring significant heat energy out of their engine, they're fooling themselves. Lousy heat xfer coefficient and low flow rate.

I mentioned earlier in this thread that at one point I had temp sensors before and after a big oil cooler in the race car. I also experimented with removing the oil cooler all together. I found that oil temps got really hot. Because even tho the oil cooler didn't drop the temp of the oil much due to oil being reluctant to xfer heat, the oil cooler did dump heat faster than the oil was absorbing thermal energy from the engine. That was the example I stated where the oil cooler seemed to dump as much as 2.5deg of heat, yet over time it added up because the engine was adding less with each circuit of oil thru the whole system. The difference in oil temp peaks were as much as 50deg. That is to say, the steady state in a Summer race might be 50deg cooler oil with the oil cooler. Pretty surprising since the oil was exiting the oil cooler only out 2 to 2.5deg cooler. The lesson there was that even tho oil cooler's don't pull much heat from the oil, they do result in dramatically cooler oil. If that seems a contradiction, pls go back and read this paragraph more carefully.

Another lesson I learned in those experiments was that keeping the engine cool had a big impact on oil temps. By putting in a bigger radiator, I was able to drop the coolant temp from 200deg(ish) to 190. My oil temps dropped a similar amount.

A word about thermostats. A cooler thermostat only changes the temp that coolant starts flowing. It doesn't create magic that increases the coolant system's ability to dump heat energy. So if my car's thermostat was fully open at 190, which is realistic, then the larger radiator dumped enough additional heat that the steady state temp dropped 10deg. But it couldn't drop much more because the tstat would have just throttled back flow.

If I had put in a colder thermostat, that wouldn't have changed the behavior any. The coolant would have started flowing at a lower temp, but the same steady state temp would have been reached. Thermostat's don't add cooling capacity.

Back to oil temp. Finally what I did was duct a lot of air flow at the race car's AL oil pan. That reduced oil temps a surprising amount. I tested that idea a lot and ultimately left the oil cooler off. Unexpectedly, as long as I ensure there was lots of air blast on the oil pan, I dumped as much thermal energy from my oil as my oil cooler did. And since "simple"= "reliable", leaving the oil cooler off was a net gain.

How this affects transmission temps. Well, mostly it doesn't. I think that the transmission fluid also goes thru a heat exchanger so that warm coolant can speed the warming of the tranny fluid. But we have no tranny fluid cooler. As long as your tranny fluid is in good shape, it should stay a fair amount cooler then your coolant. If you're getting tranny temps >200deg, I'd immed change your fluid. The idea that tranny fluid is a "lifetime fill" is one of the lies of our age.
 
#15 ·
I'm running my winter front cuz my oil cooler is a little too efficient. My oil temp is running about 20° cooler at highway speeds than idling at a stoplight. The 20° drop, coupled with the minimal airflow, tells me the oil cooler is fairly efficient for my needs.
 
#17 ·
There are at least 3 things that affect heat exchanger performance:

1. Size. The bigger, the more heat can be exchanged.

2. Design. Most HX have their plates specifically bent to create turbulent flow, which makes HX more efficient. Different thicknesses, different materials.

3. Flow. Flows on both sides. If oil is pumped like crazy, but coolant is too slow, no heat exchange will occur.
 
#21 ·
We moved the charge air cooler from in front of the radiator to a low mount unit in the bumper. This was very effective in dropping coolant temps as the radiator received cooler air. This allowed us to pull Eisenhower pass with loaded trailer without thermal management issues.

FYI, the heat rejection on this engine is higher than industry standard.
 
#22 ·
I used to subscribe to Scientific American. I soon learned how dumb I was. Was also smart enough NOT to renew.

My coolant run hot. My engine oil runs hot. My transmission runs hot. The whole mess is just that, a hot mess. Something is seriously wrong with the design and/or capacity of the cooling system - oil, water and transmission.

Facts are facts. The Ram Ecodiesel is a hot mess that holds back it's towing capacity to way below ratings. It is the #1 reason I will not keep mine much longer.
 
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#25 ·
I wouldn't.

Ask yourself what you're trying to accomplish.

My truck is a 2014 so I've had time to do a lot of towing with it. I was annoyed at my summer towing temps so I ditched my Laramie grill for a Tradesmen grill. That made about 3deg difference which was the difference between me being at the top end of what the tstat could control, vs being a bit beyond. I was pleased with that, but I'm not sure that me being annoyed with the towing temps was entirely logical. Sure, with coolant temp at 230deg I'd gone beyond the normal operational temp range, as defined by the temp range that the thermostat operates, but I was only maybe 5deg beyond, so not really a crisis. So it was a little hard for me to be sure that I was dealing with a "real" problem, vs. a problem that was mostly imaginary. But in the end, it irritated me so I got the grill the flowed more air.

Our engine is designed to run hot. This is easily deduced by the fact that our thermostat operates in a higher temperature range then most cars. The reason for this is probably related to emissions controls. So we should be wary of getting too excited re. how hot our engine runs. The way heat kills engines is that head gaskets fail. This is because AL heads expand more than iron blocks. Has anyone heard of EcoD HG's failing? I've not.

Oil temp. Modern oils will operate at pretty darn high temps. Back in the 80's and '90's there were air cooled Porsche's running 275deg and no one cared. Our oils today are better than what they had. Cars with oil cooled turbos heat the oil up really hot. Hotter than the car owner realizes. Because the oil temp sensor is usually AFTER the oil cooler.

So if you're dying to spend money on your truck, sure put in an aux oil cooler. It's a boy's right to spend money on their car/truck so no one will begrudge you that. Just don't expect it to make any difference in your engine's longevity.
 
#27 ·
My oil cooler setup works excellent coolant temps no longer hit over 230 even when towing at 70+mph up a 6% grade. Oil temps max out around 240 when towing under similar conditions but can be pushed to 264 with extreme abuse. With the stock oil cooler coolant would hit 243 oil would hit 270 and then the fun ends as I crested hills at 50 mph because the truck derated and thats just trying to maintain 65 mph. Also my coolant and oil runs within 20 degrees empty 185 oil and 205 coolant.
 
#31 ·
So, now we have chicken and egg situation.... what cools what.

No wonder, you added air cooled oil cooler, this took some BTUs from oil otherwise dumped into coolant via HX.

You actually increased overall cooling capacity.

The original posts didn't mention increased coolant temps. You (HD users) all said coolant was all great and not too hot at all.
 
#30 ·
and finally, two more fun facts. The more heat you reject from the engine the poorer your fuel economy will be since you are using fuel to make that heat in the first place so you just want to get rid of enough which is the philosophy Ram used in its design. They either made some errors in the complex calculations or their design case did not include the long, hot, fast and heavy trailer tows some users do. ANother source of heat rejection is the exhaust gas, which is less on a turbocharged diesel than a gas engine but still is there.

ANyhow, a fun but complex engineering problem and I hope everyone can keep their cool while discussing it.;)
 
#37 ·
I will ask HD users one more time:

This questions are all about stock radiator and stock oil heat exchanger (before adding any extra oil or coolant coolers)

1. From your HD user experience did you notice coolant temp climb up while heavy/long/fast towing/high ambient temps or all together ?

2. Our normal coolant tem is around 220 F. Did this coolant temp go 10 or 15 or 20 degree up while towing?

3 What oil temps did you see while HD towing?


Please be specific if possible.


The reason for this questions is simple:

Do we have enough cooling capacity while HD towing considering only stock coolant system: radiator/fan/thermostat ?
 
#38 ·
All the trucks are different. Mine runs 201-206 under normal driving most of it around 203 on coolant temps. Oil runs from 203-210 depending on outside temps and how fast I'm driving.

During heavy use water and oil temps climb, but oil climbs at a faster rate. I could easily see getting to the oil de-rate temp, but I don't think it would ever happen on the coolant for me.
 
#39 ·
Who else?



I can't share my own experience because I didn't tow hard yet.

I am trying to figure out if our coolant cooling system is big/efficient enough?

If out coolant system is enough for HD towing, then we can use upgraded HX for oil and it will be great, simple and we don't need to kill active shutters.

If at the end we figure out that our coolant system is not enough, then we have no choice other than make bigger coolant system or add air cooled oil cooler to help even coolant system by rejecting heat outside rather than into coolant..
 
#41 ·
We are talking about oil cooler, but you are right if somebody installs air cooled oil cooler in front of everything the heat will get everything behind it.

Just checked derale.com they have very compact air cooled oil coolers with electric fans.

https://derale.com/products/fluid-c...engine-oil-cooler-kit-sandwich-adapter-detail

This unit or even 2 can be installed behind our huge bumper or even under belly behind engine compartment. (I got this idea from GDE post above, so I am not trying to be super smart here)

The oil thermostat will need to be added and they have them also.

https://derale.com/products/fluid-coolers/thermostats-1/remote-mount-in-line-thermostats

https://derale.com/products/fluid-coolers/thermostats-1/fluid-control-thermostats

This cooler is not too expensive also just a bit over $200 not bad at all We can add 2 or even more if really needed.

Derale 15865: Remote Mount Fluid Cooler Assembly -10AN Inlets | JEGS
 
#46 ·
This guy added power fanned transmission cooler from Derale on his Ram. Because of the power fan he installed cooler under the belly and not in front of the vehicle.

We can use the same idea and add air cooled power fanned engine oil cooler behind and save active shutters in place for faster warm up and winter.

 
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