I discovered how to easily drain the oil cooler! (on my 91' at least)
 

It seems that everyone accept that the oil in the oil cooler does not get changed during a routine oil change. Did you know, according to the FSM, that the oil cooler holds 2 quarts of oil, about 20% of the oil in the engine?

Determined, I figured out how GM solved this problem: The oil cooler has a drain plug that is easily accessible on the passenger side of the car, aft of the center front spoiler, in the center of what appears to be a large grommet with an allen screw in the middle! Mine was covered up by some type of sealant or adhesive, which is easily removed. The grommet is actually the lower right mount that sandwiches the oil cooler/air conditioning condenser assembly in the front cooler assembly housing.

I am sharing this because it seems to be accepted practice that you don't drain the oil cooler at oil change time. I would be astonished if I were the first to discover this, or at least to post it on this forum.

Re: I discovered how to easily drain the oil cooler! (on my 91' at least)
 

Interesting but I would be concerned draining all the oil out of the cooler. In my mind you risk a possible dry start as it may take a few seconds after startup to replenish the oil in the cooler.
Rich

Re: I discovered how to easily drain the oil cooler! (on my 91' at least)
 

Thanks for that! I have new oil cooler lines that I need to install to stop the dread oil seepage where the metal fitting is crimped to the hose. I was wondering how I would pull of the cooler inlet/outlet and not get oil all over the place. Now I know!

I tend to think the few seconds to refill the cooler with oil on re-start is not a concern. Everything internal stays coated with oil. Some larger oil filters can hold a half quart, and you cannot always pre-fill them when you change your oil because of the way some are positioned, like on a ZR-1!

Thanks for posting that info.

John

Re: I discovered how to easily drain the oil cooler! (on my 91' at least)
 

Easy enough to prime without starting. Cool! I'll have to look for that. Changing 80% of the oil has always bugged me.

- Jeff

Re: I discovered how to easily drain the oil cooler! (on my 91' at least)
 

Rich I would agree with a fresh motor but would there not be enough oil to still be coated all over the surface? I agree it maybe a risk.

ON another note what size fikses are you running? 18s?

Re: I discovered how to easily drain the oil cooler! (on my 91' at least)
 

I believe the "conventional wisdom" needs to prevail here because the plug the OP mentions isn't meant to be a "service port". I don't know the thread size involved here but for any thing other than maybe it's use to drain the oil for a cooler change seems maybe foolish. Any conventional engine oil drain plug uses a gasket or seal to prevent seepage and I'm quite sure this could only be some sort of an NPT plug and that's not a conventional method used for engine oil service ports.

Re: I discovered how to easily drain the oil cooler! (on my 91' at least)
 

When draining coolant for a flush, I've always held a Shop-Vac to different openings to try to pull the juice through to some place it would drain.

Seems to help a little; I hear the leftovers sloshing around when I do, and some additional DOES drain out...

Re: I discovered how to easily drain the oil cooler! (on my 91' at least)
 

I serviced the engine to nine quarts, the FSM says the engine requires about 10.5 with filter change and cooler drain, I started the car and the oil pressure came up at the same time period (actually a little faster, used Amsoil 10W-30 instead of 5W-30). Drove it around the block and I will check it tomorrow. Weird, but I believe I had less chain chatter using the 10W-30, or it was my imagination. I didn't like doing an oil change and the oil immediately turns dark when it mixes with those last two quarts.

Re: I discovered how to easily drain the oil cooler! (on my 91' at least)
 

The cooler uses the same plug as the rear differential drill/drain kit that CorvetteCentral has. I bet it could be screwed in too far and be stuck inside the cooler, I was thinking of replacing it with a bolt instead, maybe next oil change. As far as not being a service port, the FSM gives oil refill quantities if you drain the block, block and filter, block and oil cooler, block and cooler and filter, and engine overhaul.

The big thing I didn't like is that over time the acids and whatnot that break down an oils additives, it is nice to get as much of the old out as possible. Going over the Amsoil site and reading their monthly newsletter is really informative info for the gearhead.

However, the FSM doesn't really explain what is involved in a 'routine' oil change, so I guess we will all have to make up our own minds if you want to mess with the cooler.

Re: I discovered how to easily drain the oil cooler! (on my 91' at least)
 

I had my oil cooler out when I swapped in my new motor and it did not have any kind of plug like the OP mentions.