Engine Oil Cooler Question

[Bigblue90]

I have a question regarding the factory oil cooler and doing an oil change.

My 1990 GMC C1500 came with the factory heavy duty oil cooler. I didn't know when I bought it and I did my first oil change (5 quarts Mobil 1 High Milage Full synthetic, MicroGaurd Select Oil Filter, ZDDP additive) without doing anything different from my cars that don't have an oil cooler.

I noticed that after changing the oil it seemed a little bit overfilled. It wasn't by very much so I decided to just run with it.

I later discovered that I had an oil cooler while crawling around under the truck. I checked my Chilton Manual and it has a very brief mention that one must also drain the oil cooler when doing an oil change.

Is it possible that there was extra oil sitting in the oil cooler that I didn't manage to drain out?

I'm planning on doing another oil change soon, so I have a few questions

1. Is there a drain plug on the factory oil cooler that you need to remove to let it drain fully?

2. The owners manual doesn't list a different oil capacity for models with an oil cooler. Will it still only need 5 quarts?

3. Should I be running a ZDDP additive in my oil or should I try to get Diesel oil with higher levels of zinc in the bottle? Or should I just forget about it and run with just straight motor oil?

4. Is it possible that I damaged my engine running it slightly overfilled for a few months? I did notice it sometimes would smoke on a cold startup, even during the summer.

 

[Supercharged111]

I don't know how you'd drain the cooler, and the oil in it has no bearing on what the pan holds.

 

[Bigblue90]

I don't know how you'd drain the cooler, and the oil in it has no bearing on what the pan holds.

That's a really good point. Maybe it won't actually affect the engine under operation. However, if there was an extra quart in the cooler it might drain back down into the pan after sitting for a while, giving you an overfilled measurement on the disptick.

 

[Supercharged111]

My truck has the factory oil cooler in the radiator. I drain the pan, refill with 5 quarts (and change filter of course), and the truck is at the appropriate level. Do you have an air to air cooler? Not that I feel it'd make a difference.

 

[Schurkey]

There's no drain plug on the (OEM) cooler, and probably not on an aftermarket cooler. Forget it exists as far as oil changes go.

No need for ZDDP additive.

Slightly over-full is not likely to harm the engine. IF (big IF) the oil were high enough to touch the crankshaft as it sloshes around in the pan, you would get some aeration with a corresponding reduction in oil pressure.

Is the dipstick accurate? Wasn't replaced with some aftermarket/generic/incorrect dipstick at some point?

 

[thinger2]

These days you need to be a bit suspicious of anything you read in a Chiltons manual.
A lot of the vehicle specific info has been removed and the only thing left is text that may or may not apply to your engine.
And those manuals include information dating back to the 1970s.
A chiltons in the 80s was about an 1.5 inches thick and specific to that particular generation of vehicle.
A chiltons is now about 5/8ths and shrinking and covers the same make and model but the years covered are expanded to include vehicles that are the same body but dont really have much to do with each other.
And the type specific text is gone.
They are also full of errors and typos.
Especially on torque values.
There are Buick torque typos that call for 215 foot pounds on a 3.8 instead of inch pounds.
Same on some Mopars on the crank pulley.
If you dont catch that some pumpkin with the best of intentions will playdoe saltwater taffy the bolts holding the crank pully on.
Those are all gaurenteed to make to the first freeway onramp beyond the shop.
Ive never heard of draining the factory oil cooler.
I suspect bad text or wrong text in chiltons.
Or maybe so complicated because of bad editing that it has become difficult to figure out which section of the text actually applies to you.
That is really common.
One of my Chiltons comic books covers all GM trucks from 88 to 98 and has the same cartoons about how to read plugs as my 68 chiltons for the olds.
Same text and pictures in my 1963 Chiltons.
You pretty much have to take a highliter pen to the text and figure out what actually applies to you.
Chiltons online is somewhat better.
Mitchells online is still not perfect but it is a huge improvement though Im not a fan of the layout and the interaction.
They are both subscription services.
But, in pretty much every major library system in the US you can access those databases for free by having a library card.
Chiltons online seems to be readily remote accessible.
Mitchells may be "In Library" only and only at certain branches.
Some libraries still have racks of the Mitchell repair manuals.
Use the library computer while the wife and kids have a blast getting to take home books.
Print what you need for 10 cents a page.
Buy some pizza on the way home, read some stories to your kids.
Tell your wife that know way in flying hell are you going to eat that imatation quina gluten free tofu lobster muffin recipe she found in that library cookbook.
Fix the truck.
Easy.

 

[_rgk]

I'll eat your wife's lobster muffin, if you don't want to.

 

[Erik the Awful]

Chilton's doesn't even work well as toilet paper. You're fine, there's no need to drain the oil cooler.

As far as how much oil drains back to the pan, causing it to be overfull, that's not a problem. It doesn't work that way. When you shut your engine down, wait 30 seconds to check your oil and you'll be fine. There's no "perfect" fill level for your oil, rather there's a range between underfull and overfull, and it's pretty broad. The fill level marked on the dipstick leans towards overfull, but there's room for stuff like the oil cooler draining back.

 

[Supertex]

I'll eat your wife's lobster muffin, if you don't want to.

Pure gold, right there