I have noticed an odd coolant leak from my newly rebuilt 390. After the car has completely cooled down since driving this past weekend, I noticed a small amount of coolant dripping from the very bottom of the bell housing inspection cover. I noticed this only one other time since the engine was installed over a month ago (and driven every weekend since). I do not feel any leaks around the cylinder head gaskets on either side. From what I can see of the core plugs just poking my head under the car with a flash light, they appear dry. From what I can see in photos, there are no coolant core plugs on the back side of the engine behind the bell housing. I was not able to lift the front of the car to fully crawl under it tonight, but the last time I was under there (about a week ago), all the core plugs looked dry. The other odd thing is that my add-on coolant catch tank (separate from the standard FE surge tank) filled up as the car got hot, but the coolant didn't get sucked back into the stock FE surge tank as the car cooled down. The catch tank was full almost to the overflow tube while the surge tank was only 2/3 full. I raised the overflow tank above the surge tank and coolant drained back into the surge tank OK. This has never happened before and I have had the add-on overflow tank for over a year.

I hope to crawl under the car later this week and check everything out. Any ideas or suggestions on where the leak could be coming from or what to look for? Thanks.

 

intake gasket near the back running down? i say this because i had the same thing with the overflow happen to me right before the gasket completly went out and dumped water into the #4 cylinder.

 

I can't see/feel anything that would indicate a leak from the top of the engine. There has not been anything (like white exhaust smoke) that would indicate a head gasket or coolant getting into the cylinders. It was only a very small amount of coolant. I know that I had overfilled the catch tank (a very small amount came out of the overflow tube after the engine was shut off). It may seem far fetched, but I am wondering if a small amount of coolant escaping from the overflow tube while driving could have gotten blown back on the underside of the engine by the air moving under the car.

 

It's possible there's a crack or pinhole in the back of the block. To see it, the bellhousing has to come off. Stop-leak will fix it right away but I know you'll hate doing that on a fresh rebuild.

 

Well, I found my coolant leak tonight. Actually found two. The first one was the lower radiator hose leaking at the water pump. I tightened down the hose clamp, gave the hose a squeeze, and no sign of a leak. I tightened all the other hose clamp just in case. The other leak may be more troublesome. The rear most core plug on the driver's side is leaking slightly. It does not appear to be hammered in as deeply as the others. I don't want to try and hammer it in more myself as I am afraid I will punch it all the way end and end up taking an antifreeze bath! As a temporary measure I cleaned the area around the plug with Simple Green and smeared a bead of red hi-temp silicone around the lip of the plug and block. Even if that doesn't stop the leak it will make it easy for my mechanic to find. I think this should be covered under S&S's warranty. I'll call them tomorrow to see what they say. Short of replacing the core plug, does anyone thing that a can of Bar's Stop Leak would do any good in the long term or should I just have the plug replaced? Thanks.