Using Radiator as an oil cooler?

[Dzimm]

So my 92 is a 5 speed, I just replaced the radiator with one designed for an auto trans so it has the fittings and passages to cool ATF or some other fluid.  Does anyone see an issue with using it to cool engine oil? 

 

I looked around at oil coolers and they seem to be very much the same as any other cooler so it got me thinking.

[Pete M]

does your engine oil need to be cooled?  cooling it down from operating temp changes its viscosity.  I have no idea how much so I don't know if it'd be detrimental.    I know that some vehicles come with them from the factory, but to me that implies the cooler was taken into account when the oil type was picked. 

[DirtyComanche]

20 minutes ago, Pete M said:

does your engine oil need to be cooled?  cooling it down from operating temp changes its viscosity.  I have no idea how much so I don't know if it'd be detrimental.    I know that some vehicles come with them from the factory, but to me that implies the cooler was taken into account when the oil type was picked. 

 

Almost everything modern has them, and the OEMs would not have done so if they didn't see a benefit that justified the added cost.  Cooler oil = longer life of the oil, and less chance of the oil actually reaching it's thermal failure point while in a bearing, so all around it's a better thing.  However, a thermostatic valve is used to regulate oil temperature, so you won't be pumping oil through the cooler when it's not yet up to temperature, and that is a critical part of the system.  Also, even more heat that is generated by the engine can be removed via the oil, although that is a bit moot if you're dumping that heat into the same undersized radiator used for the coolant.

 

That said I don't know if anyone sells an adapter with a thermostat that works with the 4.0L.  And I don't know if it would really be worth it to use the in rad setup meant for the automagic trans, it's not exactly the best setup.

[Dzimm]

Agreed it's not the best setup.  I see no reason for it on a stock 4.0 like Pete said, but I was thinking after a turbo, the oil outlet could run through the rad before going back to the pan to avoid heating the oil beyond the normal temperatures.  

 

This was really just a what if question, I was mostly wondering if the thicker oil would even make it through the rad.  I'm not sure how much thicker engine oil is compared to ATF.

[DirtyComanche]

2 minutes ago, Dzimm said:

I'm not sure how much thicker engine oil is compared to ATF.

 

Older ATF, such as our trucks were designed for, is typically about a 10W equivalent.

 

I can assure you hot 10W30 would have no problem flowing through that cooler.  But, you do NOT want to put a restriction of any sort on the return side of the oil from a turbo.  You will have problems with the seals leaking, and potentially premature bearing wear.  If you look at the literature on oil return requirements from most OEM turbo manufacturers, they make it fairly clear they want it to return to the pan via a large hose with as few bends in it as possible and with gravity doing all the work.  Low mount turbos often wind up with scavenge pumps because of this, which is a solution that's just looking to give you a problem, and to run the return oil from a turbo through a cooler you would need to do something similar.

[Dzimm]

12 minutes ago, DirtyComanche said:

 

Older ATF, such as our trucks were designed for, is typically about a 10W equivalent.

 

I can assure you hot 10W30 would have no problem flowing through that cooler.  But, you do NOT want to put a restriction of any sort on the return side of the oil from a turbo.  You will have problems with the seals leaking, and potentially premature bearing wear.  If you look at the literature on oil return requirements from most OEM turbo manufacturers, they make it fairly clear they want it to return to the pan via a large hose with as few bends in it as possible and with gravity doing all the work.  Low mount turbos often wind up with scavenge pumps because of this, which is a solution that's just looking to give you a problem, and to run the return oil from a turbo through a cooler you would need to do something similar.

This is really good to know.  That's a bit of info I hadn't come across yet in my research.

[75sv1]

My take is that the radiator is a bit undersized from the factory. Some of use put on an auxiliary trans cooler or two. My plan is or would be to put a separate engine oil cooler on. Possibly with a thermostat by-pass. 

[Eagle]

I think you're wasting your time. What you refer to as the "transmission cooler" in the radiator is there more to keep the auto tranny up to temperature in cold weather than it is to cool it. Remember, for the towing package Jeep added an external tranny cooler that attached outside of and in front of the radiator. The radiator for the 4.0L XJs and MJs is marginal at best. Throwing hot engine oil in there just means more heat that the already marginal radiator has to try to shed.

 

If you want an external oil cooler ... get an external oil cooler, and don't use the radiator.

[omega_rugal]

it´s a long way from the engine to the radiator for the oil to go don´t you think? if you really want to use those lines, how about routing the steering fluid there?

[Jeep Driver]

23 hours ago, Eagle said:

I think you're wasting your time. What you refer to as the "transmission cooler" in the radiator is there more to keep the auto tranny up to temperature in cold weather than it is to cool it. Remember, for the towing package Jeep added an external tranny cooler that attached outside of and in front of the radiator. The radiator for the 4.0L XJs and MJs is marginal at best. Throwing hot engine oil in there just means more heat that the already marginal radiator has to try to shed.

 

If you want an external oil cooler ... get an external oil cooler, and don't use the radiator.

Correct. 

[Jeep Driver]

2 hours ago, omega_rugal said:

it´s a long way from the engine to the radiator for the oil to go don´t you think? if you really want to use those lines, how about routing the steering fluid there?

I'm posting for general thought-

 

No, it's not a long distance, particularly for a high-volume pump. 

Cross-contamination, frankly it's foolish in my opinion and as a practical matter to mate any other cooler to the radiator, including the trans. There is always a risk of cross-contamination. 

 

Here is something to read-

 

https://www.moroso.com/pub/media/wysiwyg/Charts/OilSumpInfo.pdf

 

 

For those who, such as the guy who notched his pan (diesel) for the steering link.........dry sump cures interference problems with clearance of axles and steering. (also cures hood clearance issues...ie....LS swaps)

Also provides crank case vacuum which eliminates blow-by and increased ring seal. 

Provides for cooling, increase oil capasity, variable pressure adjustability and so forth. 

 

 

And it does not have to be used strictly for racing. 

 

 

Wet sump-

If the OP wants to properly set up for cooling and remove oil filter....etc...everything he needs is commonly available..........at a price, of course.