4Winnsboater wrote:
I have a 1997 5.7GLi. For the past 4-5 years when I winterize the engine, I disconnect a half inch hose fitting located just below the port side head on the engine block. When removed, water and particles of black rust immediately come out of the engine block and hose. Most of it looks like coffee grounds, but when I insert a screw driver or wire into the fitting or hose, larger pieces (1/4") come out. I collect it out of the bilge with a magnet and the amount would fill a shot glass half full.
The boat is primarily used in the fresh waters of the upper Chesapeake Bay. I winterize the engine with
-50 degree RV antifreeze.
Any idea what might be going on? Risers? I haven't noticed any temperature problems...yet.
Any thoughts/ info is appreciated!
Thanks!
Are you referring to draining the block or the exhaust manifold? In either case, it is normal to get rust flakes out of the drains, when cast iron rusts it flakes off. And a 22 year old boat (if orginal engine) will have a lot of internal corrosion even in freshwater. Its just the nature of cast iron. If you are not having overheating problems or any sign of water in the oil I would not worry about it as of yet.
On the other hand, if you see any sign of rust trails emanating from the joint between the exhaust manifold and the exhaust elbow, then it is time to take the exhaust apart to check the manifold and elbow. The gaskets between these 2 parts are known failure points on Volvo and older Merc (Pre-dry joint) exhaust systems. What can happen is if that gasket leaks, water from the outer cooling passages (separted from the exhaust gas passage by just about 3/8s" of cast iron mating surface) can leak into the center exhaust gas passage. This can put water in a cyl via an open exhaust valve and that will cause low compression due to rusting valve stems and seats. Volvo Penta has revised those gaskets a few times. The other thing is the sealing surface gets eroded over time (rust under the gaskets) and even new good gaskets may not seal. You can remove them and have the sealing surfaces re-surfaced at an automotive machine shop if you don't feel comfortable doing it yourself. It is also possible to have leaks from the cooling passages in either the elbow or manifold, and this can also cause raw water leaks back into the engine. I take the exhaust off at 5 years (salt water) and fill the manifolds with acetone, it will find any small crack or hole faster than water will. Usually we replace between 5-7 years here. In fresh water they will last longer but keep in mind, those rust flakes used to part of your exhaust! If they are orginal it may be time to replace. See what the cooling passages look like when you take em apart.