• Welcome to The Truck Stop! We see you haven't REGISTERED yet.

    Your truck knowledge is missing!
    • Registration is FREE , all we need is your birthday and email. (We don't share ANY data with ANYONE)
    • We have tons of knowledge here for your diesel truck!
    • Post your own topics and reply to existing threads to help others out!
    • NO ADS! The site is fully functional and ad free!
    CLICK HERE TO REGISTER!

    Problems registering? Click here to contact us!

    Already registered, but need a PASSWORD RESET? CLICK HERE TO RESET YOUR PASSWORD!

External oil cooler vs internal rad one....

A

Acesneights1

New Member
Messages
10,018
Reaction score
33
Location
Northeast CT
Just thinking out loud but those of us who have owned older Square Body 6.2's and then moved up to 6.5's know that in the older trucks the oil cooler was integral with the rad. My 93 has a 2 core rad in it and I want to put something better in it. As some of you have heard me speculate before, I still think a brass rad would cool better than the plastic aluminum ones the later trucks have. Since my 93 does not use a pressurized overflow and initial measurements look like a Brass 3 core from a CUCV would fit my 93 with no issue. Now...As we all know the GMT400 style trucks have poor airflow with all the crap stacked in front of the rad. What if I put the brass CUCV rad in my 93 and then made up some new oil lines (or used CUCV ones) and eliminated the external oil cooler ? That would not only give me IMO a better rad(brass) but now just got some more airflow to the rad by canning the oil cooler and using the integral one. I thought about doing this to the burb but it would be more costly as I would have to change the overflow tank. The 93 needs a rad anyway so I have nothing to lose....opinions ??
 
if you need a set of 6.2 style oil cooler lines i've got a full GM set(including the aluminum lines that go in front of the rad which are still a dealer only part).

No evidence of leaks either.

Also have a few 6.2 rads here if you want to borrow one to test fit it. That way if it doesn't fit, your not out any money.
 
putting the oil heat into the rad taxes the already marginal cooling ability of the rad. I haven't heard as many cooling problems with a manual trans . Do you really want to risk getting coolant in the oil through the internal cooler? I wouldn't.
 
I can tell you that without the auto trans in my K-5 it ran cold unless i really got on it. Then it would just touch 200*F before the 195* stat opened and the temp dropped like a rock down to about 175* or so on the gauge. With the auto trans it always sat just under 200*F, but that trans was slipping badly so it was dumping excessive heat into the radiator. That was with the engine still in N/A form.

I haven't had a chance to run it with the turbo setup yet, but i'll let you know when i do get a chance to drive it.
 
Max outside air temp before it hits the oil cooler is 121 out here. Coolant temp on the hot side of the radiator is 180 - 240 degrees. Oil will always exit the cooler hotter the the cooling air/water. The transmission oil cooler is on the cold side while the engine oil cooler is on the hot side of the radiator!

130 HP 6.2 NA was fine but required a oil cooler to prevent overheating the oil.
200 HP 6.5 with a turbo required a air to oil cooler to keep the oil cool enough not to require synthetic oil.

Point of fact as 6.2 NA was an option on 1993, so is radiators with both an engine oil cooler and transmission oil cooler. Obviously for the 6.2 NA option! My 6.5 radiators for 1993 do not have an engine oil cooler.

Thus, the turbocharger requires the oil cooler to be out of the radiator to stay cool enough.
 
WarWagon said:
Max outside air temp before it hits the oil cooler is 121 out here. Coolant temp on the hot side of the radiator is 180 - 240 degrees. Oil will always exit the cooler hotter the the cooling air/water. The transmission oil cooler is on the cold side while the engine oil cooler is on the hot side of the radiator!

130 HP 6.2 NA was fine but required a oil cooler to prevent overheating the oil.
200 HP 6.5 with a turbo required a air to oil cooler to keep the oil cool enough not to require synthetic oil.

Point of fact as 6.2 NA was an option on 1993, so is radiators with both an engine oil cooler and transmission oil cooler. Obviously for the 6.2 NA option! My 6.5 radiators for 1993 do not have an engine oil cooler.

Thus, the turbocharger requires the oil cooler to be out of the radiator to stay cool enough.
Click to expand...


If this were true wouldn't companies like Banks and ATS have added an air to oil cooler in with there several thousand dollar turbo kits?

They built the oil lines for the turbo supply so logic would have it that they would've supplied an air/oil cooler that would've probably just connected to the factory "lower" oil cooler lines before the threaded aluminum pipe assemblies.

Not to mention there are plenty of people running around with 6.2 turbos in OBS trucks that literally did nothing but bolt the turbo on.

Usually you want engine oil to get to around 210*F or so, because water boils off at 212*F that's the optimum oil temp area. Oil that's too cold with not boil off moisture, thus becoming contaminated with water.

Also your wrong about the cooler locations. The Engine oil cooler is on the cold side of the radiator. The trans cooler is on the hot side. The hot side is where the top hose comes in. That's the driver's side. The trans cooler lines go into the driver's side tank. The engine oil cooler is in the passenger side tank, which is the cold side because the lower rad hose that the coolant exits on it's way back to the water pump is here.

GM did put some thought into the setup. The aluminum "crossover" lines may look stupid, but they receive cooling in 2 ways. GM used aluminum for a reason. It sheds heat faster than steel. When these lines are right in front of a large spinning fan they are having air pulled over them, cooling the oil. Then the oil enters the cooler, and is cooled further(or the temp is maintained if the coolant is overly hot for some reason or another). Then the oil leaves the in rad cooler and crosses in front of the fan again, being cooled even further. Sounds like a good system to me.

If you run the truck hot, yes the system doesn't work well. However running a 6.2 hot, oil temps will be the least of your problems.

The 6.2 rads are huge. They make the 6.5 rads look tiny.

The 4 core i installed was so heavy and large it needed to be lifted by myself and a friend to lower it into the truck without damaging any fins on it. I'd estimate it's close to 45 lbs of copper and brass if not more.

I've never weighed a rad but perhaps i'll pull the spar 6.2 3 core i have from storage and see just how much it does weigh.

The reason the in tank oil cooler was ditched is because the smaller 6.5 rad couldn't handle cooling the coolant, trans oil, and engine oil together. The 6.5 rads are much smaller. Stand a 6.2 4 core next to a 6.5 rad and you'll see what i mean.

The copper and brass construction really sheds heat well, but they are more expensive to make(and they seem to last forever since they can be easily repaired with solder and a torch), which is why all radiators are now aluminum cores crimped to plastic tanks. They are junk.
 
Last edited:
well, dads 92 3500HD has the oil cooler lines in the radiator, and I am thinking about finding some brackets and going to air to oil. the only benefit I can see is for wintertime use, if one uses a block heater, it would warm the oil quicker, and keep its temp stable during cold trips, but for summer, I dont like it one bit.
 
1993's came with the OBS huge copper/brass radiator. I don't think the thickness changed as the replacement aluminum one and the one in my 1995 are the same thickness.

Every GM radiator I have seen has the trans oil cooler in the cold side making the transmission heat go through the engine before reaching the cool in radiator air. Part of the engine oil cooler in the hot side is indeed to boil off the water by higher oil temps. Both 1993 and 1995 have the trans oil cooler on the passenger side of the radiator as well as the lower radiator hose. Regardless of either side you are still dealing with hot coolant vs. cold air.

Aftermarket turbo's may have been more efficient or not tested to the extreme GM did. Oil temps are known to be ignored until something locks up in the bottom end during dyno testing or warranty claims for oil failure show up in record numbers. GM is a bean counter company and had a good reason to add a more expensive external oil cooler. GM is known to use/require synthetic engine oil in Corvettes to avoid having to install oil coolers.

You can overheat the oil and scuff a piston without excessive coolant temps. Getting coolant and the engine hot may crack heads. But loosing control on oil temps as well can do further damage to the bottom end than just cracked heads.

In any case these are just some ideas as to why GM would go through the expensive trouble to use more than a in tank oil cooler. Perhaps it was just a misguided attempt to solve the cooling problems a better fan and water pump did in later model years.
 
WarWagon said:
Every GM radiator I have seen has the trans oil cooler in the cold side making the transmission heat go through the engine before reaching the cool in radiator air. Part of the engine oil cooler in the hot side is indeed to boil off the water by higher oil temps. Both 1993 and 1995 have the trans oil cooler on the passenger side of the radiator as well as the lower radiator hose. Regardless of either side you are still dealing with hot coolant vs. cold air.
Click to expand...

I'm going off the OBS truck in my garage. GM must've done this one differently, because the oil cooler is definitely on the colder side of the radiator.


I feel the external oil cooler was added because the radiators were not as large, or as efficient in the GMT-400 truck. I"ll measure both my radiators to see if i'm correct or not.

The plastic tank aluminum core radiators suck compared to a copper and brass. They do not cool as efficiently.

Here's another example. There's a reason after market computer processor coolers have copper centers(where they physically touch the processor) and aluminum fins. Copper conducts heat better than aluminum.
 
GM went to aluminum/plastic to save money. I agree with Dave that the oil cooler went external because the puny aluminum rads could not handle yet another thing. I SCORED bigtime at the junky today. 4 core Brass rad in a 93 6.5TD...YES !!! and I got the overflow tank to boot so I will be swappng that rad into the burb and see what happens after I have it tanked first. Unfortunately it does not have the oil cooler but if I see an improvement in cooling capability with this swap I can then move on to trying the oil cooler and get a different rad or swap the one out of the CUCV. Air coolers CANNOT and never could cool as good at integral coolant ones. Many transmissions overheated by guys who disabled the internal tranny cooler and used and external, myself included with that. I learned a valubale lesson. Now if one were to route the oil cooler through the rad and an external cooler, that would be interesting but I believe integral coolers will always work better. Luckliy I have all three kinds of trucks here and can swap parts around and experiment. If i am wrong I will post the findings as well as if I am right but I gotta know. It's been bugging me since the days of my Tahoe to try and after the fiasco last winter with the aluminum heater core vs Brass I am more convinced than ever brass is better. I expect to have hard data with 2 weeks max. I am picking up the rad Tuesday and I want to tank it so probably won't install until next weekend. Although I am selling my camper anyway I will still do some trial runs just to see. I needed another rad regardless as my 93 has a gasser rad in it so if my experiment proves successful, the aluminum 3 core from the burb will go into the 93 as that truck will never tow anyway.
 
Copper and brass radiators don't last forever in the salt and other highly corrosive road chemicals. The copper rads were only lasting 2 years or less around here if they weren't washed at least once a week.
If copper and brass was so great ,don't you think there would be a huge aftermarket of replacement copper rads?
The high end rads on the high perf cars are aluminum with aluminum tanks. Hot Rod or Car Craft did a comparison a while back and the aluminum won if I remember correctly. I'm pretty shure Nascar uses aluminum too.

Yes, liquid to liquid is the best way to exchange heat but. Size constraints in the rad tank make it impossible to get as big of btu cooler in there. A separate thermostatically controlled liquid cooling system for just the oil would be ideal.
My olds diesels had the engine oil cooler on the cold side of the rad. The oil lines came out of the engine on the passenger side also.
 
The brass radiators will also clog with calcium. The aluminum ones don't seem to have that problem,but we see so many cracked plastic tanks and leaking seams at work,mainly because a lot are made in china. I'm planning on using a 2 core aluminum 350 gas radiator in my 6.5 Tahoe. It also has internal oil coolers. I have also done aluminum heater cores, none diesel and they worked the same or better than the original brass,even though the core was thinner.
 
Well I used a replacement aluminum heater core and it sucked. I had to recore the original brass one. I plowed all winter with the windows open.
 
bk95td said:
Copper and brass radiators don't last forever in the salt and other highly corrosive road chemicals. The copper rads were only lasting 2 years or less around here if they weren't washed at least once a week.
If copper and brass was so great ,don't you think there would be a huge aftermarket of replacement copper rads?
The high end rads on the high perf cars are aluminum with aluminum tanks. Hot Rod or Car Craft did a comparison a while back and the aluminum won if I remember correctly. I'm pretty shure Nascar uses aluminum too.

Yes, liquid to liquid is the best way to exchange heat but. Size constraints in the rad tank make it impossible to get as big of btu cooler in there. A separate thermostatically controlled liquid cooling system for just the oil would be ideal.
My olds diesels had the engine oil cooler on the cold side of the rad. The oil lines came out of the engine on the passenger side also.
Click to expand...
I disagree. I live in the Northeast where they use stuff that rots the chassis on 5 yr old trucks and the rad in my 1986 CUCV is original and still works fine. I plow with that truck.
 
FWIW Organic acid and Hybrid Organic Acid technologys A/F's such as Dexcool and the other high mileage ones out there are corrosive to old school copper/brass rads. It eats them up. Only good old Green Inorganic (silicate, phosphate) belongs in copper rad's as far as I am concerned. For me work wise this is of crucial concern for marine engine heat exchangers which are by nature copper brass set up's. Dexcool/High Mileage A/F's should be no where near a boat with this style technology as far as I am concerned.

Cheers
Nobby
 
Well picked up a nice clean CUCV rad today but the tranny lines are on the wrong side...:mad2: The lines are bigger on the burb than the CUCV rad. I can get adaptors but I am wondering if the intergral tranny cooler in the CUCV rad is sufficient for the 4l80e. Hmmm, this might be a snag. Rad was like new and I got it cheap so I may chuck it in my 93.
 
I'm gonna look at a factory 93 brass/copper rad which has the lines on the right side but no oil cooler. I may have one of those recored. I just returned a leaky one to the junky. I'll call him tomorrow and see if I can buy it back cheap for the tanks and then have it upgraded to 4 core. I really wanted to lose that oil cooler up front too though. I still think getting rid of stuff in front of the rad will make a huge difference. I worked on 2 6.5td owned by someone I know. One is a 94 and the other a 2000. Both are 1 tons and pull heavy equipment trailers. All stock same for PMDs. Stock exhaust everything and neither truck has ever had any overheating problem....why ??? NO A/C in either truck. No condensers...Coincidence ?
 
You must log in or register to reply here.
Back
Top