69 C10 396 Coolant leak behind the engine

[1SG.Rob]

First time poster here. 2 days ago I lucked into the C/10 that I've been looking for since I can remember. Only 75k miles and has been covered in a garage since 1990. I knew when I bought it the rubber parts would all need to be replaced soon. Yesterday it started leaking coolant and I assumed it was the hoses. Upon closer inspection I saw that it's coming from the rear of the engine on the passenger side. I can't get in close enough to see it directly, but I am guessing it is the intake manifold gasket or maybe even head gasket. Does this make sense to you guys? It only leaks when the engine is running and has warmed up a bit. I won't be able to get it on a rack until next week to take a closer look. Any advice or tips would be most appreciated. My apologies if this has been posted before.

[geezer#99]

Never assume the leak source is at the back.
I've had water pump leaks that travelled along the pan rail and showed up on the starter.
Clean your motor off and then investigate.

[hugger6933]

Welcome to the site lots of good help here, I think your leak could be a freeze plug. There is one in the back[ one on each side of the motor] and if your luck is like mine [probably not since you found a big block truck] but the trans will have to come out to fix it. Or you could pull the motor and change all the freeze plugs and possibly gaskets while it is out for cleanup. A perfect time to detail the motor and the engine bay

[1SG.Rob]

Thanks for the advice! Honestly, I hope it's the water pump. That's a much easier change for me to take care of at this point.

[Steeveedee]

Originally Posted by hugger6933

Welcome to the site lots of good help here, I think your leak could be a freeze plug. There is one in the back[ one on each side of the motor] and if your luck is like mine [probably not since you found a big block truck] but the trans will have to come out to fix it. Or you could pull the motor and change all the freeze plugs and possibly gaskets while it is out for cleanup. A perfect time to detail the motor and the engine bay

Sitting that long, I'd agree that it's probably a freeze plug, but could be a head gasket. Either way, it would be easier to do out of the truck, and cleaning it all up with the engine would be easy, too. I've been there with freeze plugs, and try to just change them all if I don't know the history.

For the OP- you can pull the flywheel dust cover off and look at the freeze plugs at the back of the block. You could get a rental cooling system pressure tester from Autozone or O'Reillys and pressurize the system cold, so you don't burn your pinkies while checking for the leak.

[1SG.Rob]

It ended up being a freeze plug. Put it up on a lift and it was easy to spot. Unfortunately that's not something I can do myself so the shop is taking care of it for me. Also replacing the rear main seal and oil pan gasket while it's all apart.

[MARKDTN]

That can end up expensive "while you are there". Oil pump, front seal, timing chain, intake gaskets, water pump.....

So they are doing all the freeze plugs? Or just the ones at the back?