Coolant leak around oil cooler line fitting.
 

Hi folks, My father in law has a 2001 chevy blazer and it has a coolant leak around the top oil cooler fitting where it enters the radiator.
We have tried tightening the (hollow, slotted) nut around the fitting that is against the radiator and it stops for a time but will vibrate loose after a period of time and continue to leak coolant.
I do not know if this part is replaceable or not and after a lot of searching I still don't know what it is called or if I can replace it. LOL I am at a loss.
Once again to be clear, it is not an oil leak but a coolant leak where the upper oil cooler line attaches to the radiator on the driver's side.
Any help would be greatly appreciated.

Thanks....

If you have not gotten an answer by later today, I might have time to look at a recently replaced radiator I have that is in my garage where I can take a close look at it.

However, I think from what you described, you are doing what I would try. I can't help but wonder if something broke that would have prevented the nut from backing off. If so, I don't know what to recommend besides replacing the radiator itself.

Aha. I did not think of that.
 

I will check for something that may let it back off. I was also thinking of putting a gasket between the nut and the radiator with a little permatex and re tighten the nut. Mickey mouse I know but I am trying to save him some money although I have seen radiators for around $60. Thanks for your help.

Been there done that - Be forewarned you will prob. crack the cheap a$$ed plastic side cover - Mine may have had a hair line crack before but diff was cracked after .....

I've taken these radiators apart and fixed them. That hollow slotted nut isn't the problem. There is a C clip that holds the oil line to that fitting. Carefully remove the c clip so you don't lose it and disconnect the oil line from the radiator and move it to the side. You'll see what looks like a big serrated washer against the radiator. Behind this is a thin rubber washer that provides a seal between the washer and radiator, this is what provides a seal between the tank and the oil cooler. Remove that big washer and replace the rubber piece. You can pick one up from a radiator repair shop. When you replace the serrated washer DON'T over torque it, just snug it down. When the radiator gets warmed up it's going to help seal the rubber to the tank also.