Bizarre Coolant Leak (Freeze Plug?) 1983 300D, failed plug rear engine block
 

Hello Everyone,

Went to change the oil today on my 1983 300D (w123) and noticed a large puddle of coolant underneath the car.

When I turn the car on coolant begins to steadily leak, dripping off the seam where the transmission meets the block. There is no indication of any leak around the cooling hoses that are between the block and firewall at the top of the motor.

From my reading around, this seems likely to indicate that the core plug on the back side of the block has failed, and that I'll have to drop the tranny to fix it. I just want to be confident that this is the problem before I through money at it, as I don't have the tools to get it done myself.

Also, I'm wondering if anyone reading this might know a dcent shop in Syracuse, NY?

Picture of the leak is attached (please forgive the horrendous state of the coolant).

Attachment 124453

I would get a small mirror and try to verify the actual source.

Attachment 124454

I did my best to get a decent photo but it's a tough angle. There are visible orange spots from coolant inside of the 3-4" hole shown in the photo (I wish I know the name of that part). While the photo doesn't demonstrate, if I crane my neck I can see trickles of coolant running down the rounded edge on the inside. I'm not sure where else it could come from besides a failed core plug.

If the leak is originating inside the transmission bell housing, it pretty much has to be from the closing plug on the back of the block.

I just dealt with that very same situation on a domestic vehicle. Plug leaked for no apparent reason.

Odd and having rust colored water, means that someone isn't running coolant...if the plug popped out....and there is no coolant....possible over heating comes to my mind..

I wouldn't leap to any conclusions...water gets blown around the engine compartment when the engine is running and the car is moving. Clean things up and get closer to the source.

Thought I would post back in here for closure.

I took the car to a shop (stopping every few miles to add more coolant), and a pressure test showed a gush of coolant running out of the bell housing with no access to the source. Removing the transmission revealed corroded freeze plug in the back of the engine block.

Smooth sailing after replacing the plug. Now dealing with the other plugs on the passenger side failing.

Always use brass or bronze freeze plugs...