Howdy boys,
I have a 1989 Mercruiser 320 EFI sbc, built by Mercury Racing. Last summer I had a local machine shop rebuild it to the point of being a long block. They put the heads on. They're a reputable shop and do lots of boat motors for local marine dealers.
The engine sat on the stand for a year, now I'm finishing it to replace a motor that just went south on me on one of my other boats. I've built it all the way up and it's about ready to drop in. Just for good measure, I did a pressure test on the cooling system. First to 20 psi then 15 psi. It slowly leaks. By slowly, I'd say it drops about a 1 psi every 3 to 5 minutes. After about 20 minutes it's down about 5 or 10 pounds (starting at 15).
So i sprayed all around the engine with a very very soapy water. What I see is foam forming around the head gaskets. But it's weird, it's like the air is coming through the gasket, not on the top or the bottom. And it evenly leaks most of the way around, on both heads. And, I see the exact same thing on the thermostat gasket housing. It's like the gaskets are "breathing" some air.
Is this normal? Or should this thing hold pressure for hours? I find it hard to believe this shop did a crappy job sealing the heads on. Would sitting for a year matter? Or do the gaskets behave differently with water than the do air? I suppose I could just pull it all apart again, but Id rather not chase something that's not actually a problem.
thanks!
Stan
I have a 1989 Mercruiser 320 EFI sbc, built by Mercury Racing. Last summer I had a local machine shop rebuild it to the point of being a long block. They put the heads on. They're a reputable shop and do lots of boat motors for local marine dealers.
The engine sat on the stand for a year, now I'm finishing it to replace a motor that just went south on me on one of my other boats. I've built it all the way up and it's about ready to drop in. Just for good measure, I did a pressure test on the cooling system. First to 20 psi then 15 psi. It slowly leaks. By slowly, I'd say it drops about a 1 psi every 3 to 5 minutes. After about 20 minutes it's down about 5 or 10 pounds (starting at 15).
So i sprayed all around the engine with a very very soapy water. What I see is foam forming around the head gaskets. But it's weird, it's like the air is coming through the gasket, not on the top or the bottom. And it evenly leaks most of the way around, on both heads. And, I see the exact same thing on the thermostat gasket housing. It's like the gaskets are "breathing" some air.
Is this normal? Or should this thing hold pressure for hours? I find it hard to believe this shop did a crappy job sealing the heads on. Would sitting for a year matter? Or do the gaskets behave differently with water than the do air? I suppose I could just pull it all apart again, but Id rather not chase something that's not actually a problem.
thanks!
Stan
