XJNKY

Alright guys, I've been trying to info on this, and came up fairly empty. I've seen several posts of guys putting automatic radiators in manual Jeeps (XJ or otherwise) and just capping off the transmission lines. My question is, what's the harm in trying to run oil lines into the transmission cooler section?

I'm really researching for a buddy who has a 96 3 door, 5 speed. It has 313K on the clock at the moment, and surprise surprise, it runs hot during the summer. The previous owner wired the electric fan to run anytime the key is on, so it has obviously been having this problem for a while. The fan clutch is a little loose, but not terrible. Last fall, we flushed the cooling system (impressive amount of crap was flushed out, chunks of things I can't begin to identify). We also replaced the water pump, coolant, and removed the thermostat. We even installed a redneck hood vent (it's actually a floor register from Lowe's, screwed into the hood, with an ABS hood scoop from autozone flipped around backwards to cover the vent. You can still reach in to open or close it, it works pretty well, and you can't see that it is just a floor vent).

On our fist 90+ degree day this year, it was still running hot. Not in the red, but hot enough to make me nervous. I have a used radiator for an automatic, and I've been thinking about switching it into his Jeep.

So is there any reason not to use the transmission cooling section as an oil cooler? Is there any problem with doing that?

Will it have any real effect on the overall engine temperature? It can’t hurt, right?

Any thoughts are welcome and appreciated.
-XJNKY

Turbo X_J

Where do you plan to tap into the engine oil from a filter adapter & flex lines? (probably $100 right there & while your at it you could move the oil filter somewhere else) Then after that you realize your adding yet another source of heat to a situation thats already bad. Why not run the engine oil through a cooler separate from the rad?

ETA: What is the condition of the used radiator is it clean? If not a new stocker is like $100.

djb383

Yep, $100 spent on a new radiator would get better results.

XJNKY

First, I thought I had fixed my typo in the title of this thread. Apparently not. If any mod's see this, and could change "Eadiator" to "Radiator", that would be awesome.

Second, I was planning on using one of the oil filter sandwich plates with the tapped outputs. As for lines, I have a spare set of transmission lines that already have the proper quick connect fittings on it. I figure they could be spliced and fitted to the oil outputs relatively easily (they're already bent to go around the correct side of the engine). I figure if the lines are suitable for the pressure and heat of transmission fluid, they would probably work for oil. So it wouldn't be a huge investment, mostly just the adapter plate and a few fittings ($40-$50?)

The "new" used radiator isn't pristine, but it's in good working order, and much better shape than the one he has. Obviously the trans cooling section, and the lines, would need to be flushed out before hand, so it's not putting transmission fluid in the oil.

I'm fairly certain I could do the whole thing on the cheap. Also, I'm not sure where you guys are finding $100 radiators, unless they're single core. I've been down that road, and it's about as effective as leaving the bad one in there.

The goal was just to do an upgrade for him using the spare parts I have laying around, with minimal financial investment. I agree, that if it ends up costing more to retro fit a used part than it would to buy a new one, I've lost sight of the real end goal. I just don't think it would be that expensive to fit it using all my spare parts.

besides that, the real questions is if an oil cooler is really going to help the overheating issue any in the first place.

djb383

Most OEM modern radiators are 1 (very wide) row aluminum core. Strength, efficiency and light weight have pretty much made them the norm replacing old school copper/brass multi-row rads. One 1" wide row is more efficient at dissipating heat than two 1/2" wide rows. OE style at Autozone is $110, life time warranty.

A oil cooler will cool oil, not prevent motor overheating.

5-90

Putting a radiator for an automatic transmission into a manual transmission-equipped vehicle works just fine, just leave the "cooler" plugged off.

For cooling engine oil, you're better off doing it right:
- Sammich adapter to go between the oil filter and engine
- Thermal bypass valve to allow the oil to heat up relatively quickly
- Standalone oil-to-air heat exchanger for more efficient cooling.

The thermal bypass valve should work better to keep the oil at a more optimal temperature than the oil-to-water heat exchanger (the idea behind the in-tank fluid "cooler" for the transmission is to heat the fluid up quickly first.

(Problem is, the "ideal" operating temperature for most lubricating oils runs, as I recall, 190-195*F. Engine operating temperature is more like 210-215*F - and running your engine oil cooler helps with oil service longevity.)

A similar setup is better to use for the automatic transmission than the OEM as well.

And, cooling the engine oil will help to eject waste heat from the engine, and oil-spray piston cooling is a known trick for turbocharged or high-compression engines.

Engine oil cooling is generally not sufficient to remove waste heat from the engine (which portion gets conducted into the metal, not pumped out the tailpipe,) but it does help remove a thermal load from the water loop - and can help to pull operating temperatures down.

XJNKY

I'm going to have to disagree with you on that one, both from the scientific side and experience. Either that, or I'm just a bad ME. My old 2 row did better than the autozone single row. My 3 core that's installed now coupled with a 160* thermostat keeps me running below 190 in the heat of summer, and under 230 when I've been stuck for 20 minutes doing my best to blow it up.

Agreed. but there's doing it right, and there's doing it cheap. Again, I have these parts laying around. I'm trying to determine the cost-benefit ratio of doing it with existing materials. Doing it with a dedicated oli-air cooler would be best, but the expense is not worth the return.
That's the goal, just to help pull the temps down an extra X%, even if "X" is relatively small. I know plumbing the oil through the radiator is clearly not going to fix the overheating problem. (To be fair, it doesn't really overheat anymore, it just runs warmer than I'm comfortable with, about 230 on a 94 degree day, stopped in traffic, down to about 215 on the highway).

Also, I believe some of the sandwich plates I was looking at had built in thermal bypass valves (?, need to double check)

I feel like I maybe didn't state the original hypothesis clearly enough. It's not "hey, I'm looking for the best way to cool the oil because I think that will solve the overheating issue", it's "hey, I have this spare radiator laying around, that I'm probably going to stick in anyway, what's the harm in running the oil lines to it"

I do appreciate the feedback guys, and I'm sure it will be a source of reference for the next person with the same misguided thought. I'm not meaning to sound like I'm arguing, just trying to direct the conversation back to my original intent.

djb383

You're the ME, I'm not, but look under the hood of just about any late model p/u and u'll find a 1 row aluminum/plastic rad and they tow 10K lbs. Somebody came up with that design to replace 3-4 row old school copper/brass rads, no?

XJNKY

Yeah, but that's not necessarily because it's more efficient that way, it's because it's cheaper. Aluminum is a better heat conductor than brass, and is a lot cheaper. Plastic end caps are there because it costs about 20% as much as a stamped metal piece, and plastic is cheap.

That argument is sort of like saying that plastic impellers are better in water pumps because more manufacturers do it these days.



Just an aside, I'd reference you to a website called Matweb if you're ever curious about material properties. Specifically here :http://www.matweb.com/search/DataShe...666c0e0&ckck=1 and here:http://www.matweb.com/search/DataShe...2f4c101c2a20e5

Looking at thermal properties,and generally pricing aluminum vs brass/copper, you can see why they use aluminum these days. In the next 20 years someone will come up with a cheap polymer that transfers heat as well as aluminum, but costs less, and we'll all have completely plastic radiators.

Also, look at the actual size of the grille on a modern truck, they're much larger than 10 or 20 years ago, so it's easier to get by with a large area single row radiator. And it's cheaper to manufacture one big piece than 2 smaller pieces and joint them together. Modern manufacturing is all about cost over function (ask me how I know ).

My OEM radiator(s) have 2 rows. Not sure about anyone else's, I thought that was the standard. We have relatively small grille openings, and a big chunk of cast iron behind them, with lots of thermal mass. I'd agree with you if these vehicles were originally designed to run a big single core unit, but they weren't.

But I digress...

highmileage

when nascar starts using plastic tanked single core radiators so will I. Till then I'll stick with two and three core brass/copper ones (welded aluminum is just to pricy for me).

odgreen

Just a FYI. My 2 core new rad cost me $67 shipped to my door on eBay. I never overheat anymore.

djb383

Good read and here's some more. This place employs a bunch of ME's. http://www.stewartcomponents.com/tec...ech_Tips_5.htm U can recite thermodynamics til u r blue in the face.....all I'm saying is, there are numerous reasons why OE mfgs have gone to 1 row design rads....one reason is they cool better and a more efficient radiator design is one more reason why 1/2 ton p/u tow capacities have increased over the years. There may be some OE mfgs out there still using 3-4 narrow row copper brass rads but I bet they are few and far between.


Richard Petty may have been the last NASCAR driver to use copper/brass. LOL. Varoom, Varoom.

djb383

Here's a pic of a OE XJ rad.....it's a 1 row (1.25" wide tube or thick core) rad.

djb383

Another good read about modern radiator design (less number of but wider rows).

http://www.stockcarproducts.com/rad2.htm

XJNKY

More efficient cooling systems are both a byproduct, and a supporting factor in the advancement of engine efficiency. If you really want to look at towing capacity, you chould be giving more credit to more efficient engine designs. The ability to produce more power, with less fuel, in a smaller engine, has really driven the overall capabilities of modern vehicles, p/u trucks included. And guess what? More efficient use of fuel, from smaller engines, leads to less heat needing to be dissipated.

Cooling is all about surface area. One large piece has less surface area than two smaller pieces. It's like saying one cube of sugar will dissolve faster than that same volume crushed up into granules.

Now design specific considerations change the requirements. You can't just apply concepts from a modern 1/2 ton pickup with a more efficient fuel systems unilaterally. They're different animals. If you were to chart the benefits of tube diameter and number of rows (and fins just for fun), you'll likely find a standard distribution (bell curve if you will). If you start with one 4" tube with 4 fins on it, you can see how that's not going to work. Alternatively, if you look at some ridiculous design with 72 rows, 5,000 micro-fins each, and .005" ID tubes, you're clearly not going to get good results either. And the average of your bell curve is going to shift on this imaginary chart based on a number of factors, most of them design specific (what size engine, what material, what type of block, what level of efficiency, what size opening and the amount of airflow, etc). Automotive engineers take charts like this, reference them against cost-of-manufacturing numbers, and then decide what is "best" for each application. (hint, best doesn't always equal best performance, but best bang for the buck if you will).

Your links are interesting, but if you look, they seem to pay more attention, and make argument on the point of actual tube diameter, and it's effect on velocity of the fluid. Now you're really stepping into my realm. Of course you can pass more fluid through a larger diameter tube. You cannot necessarily pass the same amount of fluid through 2 tubes half that size. You're back to the surface area debate, and in this case more surface area= more friction= less velocity. Then there's the argument of what point the coolant reaches it's terminal dissipation point, or the point where it's already equalized temperature with it's environment (air in this case) and it doesn't really have anymore energy to transfer. If a passageway is sized too large, the fluid passes through without having enough time to adequately dissipate its energy. If it takes too long to pass through (like with too small a tube diameter, and too many rows) you're losing cooling system efficiency, and also velocity.

The point is, you can't just apply an example from one design unilaterally. Citing design from example A, with "Set A" of circumstances does not validate example B, unless example B is similar enough to warrant a comparison. Here, it doesn't.

I really didn't start this thread to squabble about radiator design, although I did learn some new things about radiator design in arguing the points, so thank you.

The original question was if anyone had ever used the unused part of the radiator for a makeshift oil cooler, and if it had any noticeable effect on overall engine temperatures.

I'm not sure how it turned into a referenced discussion on thermo-(and fluid)-dynamics.

So, I'm going to stop taking the bait. You can run a single core if you want, it's your Jeep. I've been down that road, had bad results, switched to a 3 core, never had another problem. That, to me, speaks more than our theoretical situations and examples.

If I do end up plumbing the oil lines, I'll update on any results, or lack thereof.

also...
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Surprisingly, that's an option I hadn't thought to look at. I've almost forgotten Ebay still exists. There's probably some gain to be made just switching to a radiator that doesn't have 300K on it, so I'll probably just do that anyway (I already have it), but if that doesn't help, I'll try to remember to go there first. I think i paid $130 for my 3 core from radiator barn 2 years ago.