Where is my coolant leak?

[kawahonda]

I have a steady dripping coolant leak. About 1 cup every two weeks. It's enough to want to fix, for sure.

It's definitely coming from the driver's side.

It's definitely dripping from the bellhousing (first photo).

It's definitely dripping from the driver's side rear oil pan bolts (second photo).

It is definitely NOT dripping from any visible freeze plugs.

The exhaust manifold rear studs feel dry. It is most likely NOT dripping from those.

If you look in the engine bay, you will see the bottom of the block on the driver's side lime green, so it's hitting, or perhaps forming around there.

I cannot see any more of my dye from my intake nor from my heads, so I'm still at a loss on where this is coming from. I've used rotatable mirrors and I've gotten under the car and checked above the car from all angles.

Cracked block?

[GoodysGotaCuda]

I'd start with, what engine?

Second, I suggest renting a pressure tester and pumping it up, it should expedite the leaking process for you and you can poke around easier on a cold engine.

[kawahonda]

Engine doesn't need to be hot nor cold. This is from 2 weeks of it parked with dye...steady drip every 5-10 minutes.

340.

I've probably spent 2-3 hours of the course of a month or two looking.

I know of a really good shop that can find leaks way faster than me. I suck at finding leaks. I'm just wondering what you guys think based on the images. It's really easy to say "must be coming from heads or intake", but I'd like visible proof before assuming that.

[EV2RTSE]

Probably a rusted out freeze plug in the back of the block, I had one fail on an unrestored '73 340 car about a year ago. I pulled the engine and replaced all of them. PITA. Note the weep hole below the plug, see if the coolant is coming from there on yours.

[kawahonda]

Ah $hit.....there's a plug back there that I cannot see!?

I bet that's it, but I will say that my car is "relatively" rust free....

[Cuda Cody]

Pressure test it. 

[kawahonda]

Sounds like I need to take it into my shop for a pressure test to identify it.

God I hope it's not that rear freeze plug.

[Chryco Psycho]

my guess is exhaust stud , it would dry when hot & only drip when cool / sitting

[kawahonda]

Just got under the car and looked (again).

Luckily I arrived at the right time and I saw what is going on. It is not coming through the weep hole, but it is certainly coming from behind that area, running down the back face of the block behind the weep hole where it hits the oil pan, then drips on the bellhousing.

I think that means freeze plug.

That means pulling engine.

Or that means dropping transmission.

Now it's time to consider options.

1) Pull engine and do a full rebuild.

2) Pull engine and replace the plug

3) Drop transmission and replace the plug

4) Deal with the leak for a year (ignore it).

I think what I will do is 4), and then 1).

[EV2RTSE]

Yeah there's another plug on the right rear side so it could be that one then. It's probably best to pull the engine and replace all of them, there are I forget exactly but like at least 10 or 12 in all in the block and heads, if one is bad then it's likely that there are others that are not far behind. If the engine is otherwise ok you could just pull it and replace the freeze plugs, the whole set is cheap so the only thing lost is the time spent pulling the engine & putting it back. But yeah if it's close to needing a rebuild then...

I don't think I'd run it much longer as is, if the plug totally fails you could lose all your coolant in a hurry.

[kawahonda]

Another option...Barr's Leak stop....

Will it crud up my radiator, heater core, or my water pump?

Engine doesn't "need" a rebuild. Runs, drives, and starts awesome. If you're going through the effort of pulling the engine, I'd certainly want to do more than just replace the freeze plugs. That's a big job. Not something I was planning to do any time soon.

[RUNCHARGER]

If ones leaking the rest are close to leaking.

[BIGSHCLUNK]

years ago I had the dreaded back of block leak on a SB...   not a rusty block either.... had to drop the trans

[Rich G.]

It's a lot easier to pull the trans and replace the ones in the back then to pull the engine. Unless you plan on opening up that can of worms. Two schools of thought, rebuild it All and be done or if it ain't broke don't fix it!

[anlauto]

I would try Barrs leak first...I don't think it plugs up everything else.