OldSkool
Active Member
- May 8, 2010
- 4,360
- Boat Info
- restored 1976 SRV200
- Engines
- 188 Mercruiser I/O
Pressure test is to pump pressure into the coolant system and see if it holds. Some call it a leak down test because the result is pressure bleeds off if there is a leak. Pretty self explanatory don't you think?
Whatever you call it, you need to do it before pulling the head.
Now it is possible to have a leak due to a cracked block between an oil port and coolant port at the block deck where the head bolt down. This is rear but I've seen it happen. The crack will be very small and magna flux or dye is about the only way to check it. The crack will open up when hot then shrink shut when cold. Since water is not pouring into the oil pan you can rule out intrusion through the piston AKA bad exhaust manifolds. Your compression test proves that.
Cooler is about the only thing left.
As far as the cooling system. Since the temp is now regulating, either the crap pushed through and the thermostat is working or the thermostat finally freed itself from rust/contamination and popped open.
Just my opinion.
Whatever you call it, you need to do it before pulling the head.
Now it is possible to have a leak due to a cracked block between an oil port and coolant port at the block deck where the head bolt down. This is rear but I've seen it happen. The crack will be very small and magna flux or dye is about the only way to check it. The crack will open up when hot then shrink shut when cold. Since water is not pouring into the oil pan you can rule out intrusion through the piston AKA bad exhaust manifolds. Your compression test proves that.
Cooler is about the only thing left.
As far as the cooling system. Since the temp is now regulating, either the crap pushed through and the thermostat is working or the thermostat finally freed itself from rust/contamination and popped open.
Just my opinion.