OEM oil cooler block discoveries....

[rdezs]

Haven't ran across this in all the postings on the OEM oil cooler lines. A lot of them developing leaks and whatnot. Several references to the large plug facing the transmission being loose, and leaking.

I converted to an aftermarket oil cooler line block that mounts on the oil pan and went with steel braided hoses several months ago. I finally got around to dissecting the OEM oil cooler line block, and here's my discoveries:

1. I confirmed the rear facing plug is only sealed with an o-ring. Thread tape or some form of thread sealer would probably be a benefit. That is a 3/8 allen wrench in the photo, perfect fit.

 

[rdezs]

 

[rdezs]

I noticed with my aftermarket oil cooler line block, my engine oil ran 25 to 30° cooler. I discovered the OEM one has a small thermostat in it. Stays open by design until the oil reaches operating temperature. My thermostat was stuck open.... So most of the oil bypassed the cooler in the radiator at all times.

You can easily retrieve it out with needle nose pliers. Haven't been able to locate a part number so I'm assuming it's not considered serviceable without replacing the whole item.

 

[rdezs]

If you read the hundreds of postings on the oil cooler lines, it's frequently mentioned that the oil cooler increases the oil temperature from the radiator quickly.... And from then on it is used to cool down to 200° or so.

That is 100% totally inaccurate. Your oil cooler in the radiator is completely bypassed until that little thermostat opens up.... Probably somewhere around 200 to 220°.... And only then does it send oil to the cooler in the radiator. (This is how it warms up the oil quicker)

When that thermostat eventually sticks..... If it sticks open, most of the oil bypasses the cooler. If it sticks closed, all the oil goes through the oil cooler. I have no idea what the expected life expectancy is on that thermostat.

I do surmise though, regarding the common issue with the oil cooler lines seeping at the crimps? If the thermostat is stuck closed when the engine is started cold, you're sending perhaps 70 PSI oil through those cooler lines, stressing the crimp connection. Working properly with an oem oil pressure, oil would not be sent that way until it is hot, oil pressure in the mid thirties as an overall average.

That's my two cents worth before I throw this old cooler line set in the trash....

 

[rdezs]

..... I've also read many posts where people delete their oil cooler and report oil temperatures run the same. Most likely it's because that thermostat was stuck and no oil was going to the cooler.

With no oil temperature gauge on most models, this is a bit of an irritant. But if you use your vehicle to tow quite a bit, it can be a real problem.

Here's what I converted to last year.... Put one on the 2014 Escalade and one on the 2003 Hummer.

 

[mikez71]

Just to confirm this is transmission cooler lines/block?

And you're saying the cooler is bypassed until 200 degrees?

 

[rdezs]

Engine oil cooler line block

 

[rdezs]

Really makes me wonder.... is that without an engine oil temperature gauge, and towing a heavy trailer.... If this was the source of early bearing failure in some engines.

I find it hard to believe I'm the only one to open one up and investigate.... Just surprised no one has posted this before that I could find. I have no doubt the oil cooler lines are much more durable than that little thermostat, so how many are running around out there with a stuck thermostat not utilizing the cooling capacity of the radiator? Really no way to know without an oil temperature sensor. (Which I use on my Hummer H2.... Below is a photo from the gauges on the Hummer on a 96° day after coming off the freeway. This is with the aftermarket engine oil cooler line block )

 

[OBSandaNNBS]

Really makes me wonder.... is that without an engine oil temperature gauge, and towing a heavy trailer.... If this was the source of early bearing failure in some engines.

I find it hard to believe I'm the only one to open one up and investigate.... Just surprised no one has posted this before that I could find. I have no doubt the oil cooler lines are much more durable than that little thermostat, so how many are running around out there with a stuck thermostat not utilizing the cooling capacity of the radiator? Really no way to know without an oil temperature sensor. (Which I use on my Hummer H2.... Below is a photo from the gauges on the Hummer on a 96° day after coming off the freeway. This is with the aftermarket engine oil cooler line block )
View attachment 460911

I can't believe the timeliness of your post! I'm waiting for my line to come in from RA. TYF for the win!
The thermostat is in the line side of the block, correct? So it'll be swapped when I replace with the OEM line?
I have no heat issues, but it definitely seeps a bit. I'm hoping it's the line and not the rear main.

 

[Foggy]

Engine oil cooler line block

More Information for GM GENUINE 84828848

So that little thermostat is located inside the actual oil cooler line block that
bolts to the engine block, correct ???
My lines look great. No leakage. But I did have to replace the gasket between
the block and oil cooler block - really common...
But I never thought twice about whats inside.
Is the fix to just remove the hex plug and remove that little "thermostat" ????
I do tow , so you've got my ears perked up on this subject !!!

 

[Foggy]

..... I've also read many posts where people delete their oil cooler and report oil temperatures run the same. Most likely it's because that thermostat was stuck and no oil was going to the cooler.

With no oil temperature gauge on most models, this is a bit of an irritant. But if you use your vehicle to tow quite a bit, it can be a real problem.

Here's what I converted to last year.... Put one on the 2014 Escalade and one on the 2003 Hummer.
View attachment 460893

Do you have a part # or specific description of this and how you set it up.. I could not
find it on derale website

Update: I found it !
Part #35611 without thermostat $103 at summit
Part #35621 with thermostat set at 180* $205 at summit

 

[rdezs]

Yes, that little thermostat is inside the oil cooler line block where it bolts on the oil pan. The round plug on the side of the cooler line block, that faces the transmission is the access to it. (And just has the o-ring to seal it)

Removing the thermostat would cause the oil to follow the path of least resistance.... And skip the cooler. When that thermostat opens, it connects both the in and out oil port to bypass the cooler. When the thermostat closes, all oil is diverted to the cooler. So stuck open is a problem if you tow. Stuck closed with a cold engine and thick oil might be a problem if the OEM hoses can't handle 70 plus PSI. (They should be able to, but for how long can they do that reliably?)

That hex plug that often leaks on the side of the block facing the transmission, actually retains the thermostat in position. If I didn't have the aftermarket Dorman oil cooler block, I would probably machine something out of aluminum with an o-ring to replace the thermostat, and just have the oil always go through the cooler. I always run 5W30, that shouldn't be too much strain on any cooling lines when the oil is cold and the pressure is high.

 

[rdezs]

Do you have a part # or specific description of this and how you set it up.. I could not
find it on derale website

Update: I found it !
Part #35611 without thermostat $103 at summit
Part #35621 with thermostat set at 180* $205 at summit

Yes, I've got the one without the thermostat. With what I discovered about the OEM thermostat hidden in that block, I don't want anything to do with the thermostat in the oil system. With the oil cooler in the radiator, the oil is going to heat up just fine and I don't see a need to bypass the cooler.

 

[Foggy]

Yes, I've got the one without the thermostat. With what I discovered about the OEM thermostat hidden in that block, I don't want anything to do with the thermostat in the oil system. With the oil cooler in the radiator, the oil is going to heat up just fine and I don't see a need to bypass the cooler.

What fittings did you use to go from the Derale block ? Did you go with #8 or #6
AN line ? And What did you use to adapt to the radiator itself (to convert to AN) ? \
I mostly drive in warm weather so I'd like the oil to go into my Mishi Radiator
Oil Cooler ALL the time. And no way to "fail"

 

[OBSandaNNBS]

Yes, I've got the one without the thermostat. With what I discovered about the OEM thermostat hidden in that block, I don't want anything to do with the thermostat in the oil system. With the oil cooler in the radiator, the oil I'm is going to heat up just fine and I don't see a need to bypass the cooler.

This line of thinking (pun intended) makes sense to me. Do you think I should take the thermostat out of the new GM genuine line before install?
Or would that bypass the cooler on that design?

I'm having a hard time visualizing because I'm not holding it...

Basically the benefit is shielding the crimp connections from extra high pressure on cold startup?
And it keeps cold oil out of the cooler if that's a benefit, I don't know.

 

[rdezs]

If you remove the thermostat you'll always be bypassing the cooler.

I went with 8AN stainless steel braided line. You can match the threads either on the OEM radiator, or an aftermarket oil cooler with an AN to ORB fitting of the proper thread size.

The only challenge is routing the stainless steel braided lines down the left side of the engine block and securing them so they don't rub anything. Fabricated an L bracket, ran both hoses through a large rubber hose where I attached to the L bracket with a metal zip tie. Similar to what you would use on the drive shaft boot.

 

[swathdiver]

If you remove the thermostat you'll always be bypassing the cooler.

I went with 8AN stainless steel braided line. You can match the threads either on the OEM radiator, or an aftermarket oil cooler with an AN to ORB fitting of the proper thread size.

The only challenge is routing the stainless steel braided lines down the left side of the engine block and securing them so they don't rub anything. Fabricated an L bracket, ran both hoses through a large rubber hose where I attached to the L bracket with a metal zip tie. Similar to what you would use on the drive shaft boot.

Thanks for being curious to discover this and share the information with us. I've replaced these lines in all three of mine and never questioned the purpose of that plug!

I wonder if the thermostat could be flipped around "Flip the pill" inside the housing like the K2s with their transmission thermostat? This would keep the oil flowing properly while bypassing the requirement for the temperature to get hot for it to work.

I scoured AllData and my pdf shop manuals and no mention of this item. Not just that, they say the oil temperature is controlled by the coolant in the radiator, which I reckon is only partially true.

Replaced a leaking gasket on the oldest truck a few months ago, wonder if they leak when they seize up?

Do you think we can replace the plug on the oil cooler adapter block for a temperature sending unit?

I learned something new today, thanks!

 

[rdezs]

Thanks for being curious to discover this and share the information with us. I've replaced these lines in all three of mine and never questioned the purpose of that plug!

I wonder if the thermostat could be flipped around "Flip the pill" inside the housing like the K2s with their transmission thermostat? This would keep the oil flowing properly while bypassing the requirement for the temperature to get hot for it to work.

I scoured AllData and my pdf shop manuals and no mention of this item. Not just that, they say the oil temperature is controlled by the coolant in the radiator, which I reckon is only partially true.

Replaced a leaking gasket on the oldest truck a few months ago, wonder if they leak when they seize up?

Do you think we can replace the plug on the oil cooler adapter block for a temperature sending unit?

I learned something new today, thanks!

Not enough room to utilize those threads. Plus, that plug holds the thermostat in position.

 

[rdezs]

Flipping it.... would reverse everything. It would send hot oil to the engine, and cold oil to the cooler. (Plus it wouldn't fit backwards in the recess)

 

[rdezs]

If I didn't have the Derale, I would machine a piece of aluminum to fit the recess, with an o-ring, and long enough for the plug to hold it in place.... effectively blocking the oil from going anywhere except for the cooler.