Clogged Exhaust manifold
Moderator: Jim Walsh
Clogged Exhaust manifold
Hi! I need help determining when an exhaust manifold is too clogged to be saved. Being this clogged, I have no idea how far into the engine I can expect the clog to be. Anyone get to this point and still salvage the engine and exhaust manifold? Thanks!
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Re: Clogged Exhaust manifold
This looks like the MD7 manifold, correct? If so, the large hole was intentionally blocked off at the factory and was welded shut so that is not of concern. If you make a hole in it, some water just will go thru the head and not the block first which you may waan to do if the block is clogged as well and you are not planning to pull the head and clean out both the block and head. The smaller hole is the trouble as that is the inlet to the block. It looks completely clogged which would make a hot running engine. There is another small hole near the top centre (shown in your photo on the lower right) which also must be cleared but that one is not so critical. Look carefully as you can miss it.
First remove and discard the gasket. Then use anything you can find (small screw driver, wire, drill and bits, etc. to clear the passages and get the water flowing. Use your garden hose at the inlet and keep working until you get a nice solid stream coming out everywhere it is supposed to be. Then, dump all the water out and inject acid (hydrochloric or supfuric work ok) and try to burn as much of the rust and scale in the chambers that you can't reach with your screwdriver or wire. Often, you get some big flakes trapped inside which need to be broken up and removed or they will vibrate free and block something. If you shake it, when dry, you can hear them rattling about. When all is clear, start on the passages to the head. They are not usually as clogged as the manifold. If the engine is out ofthe boat, you may find it useful to pull the head and clean both the head and the block as well. Mine had some of the passages between the head and block clogged.
In my experience, you will get another 3 -5 years or so out of the manifold before it needs another cleaning. As it ages, and corrosion sets in, it clogs up faster and faster. That said, if you can get another 4 years out of it at this point, it is a good investment of your time.
Good luck.
S.G.Bernd
First remove and discard the gasket. Then use anything you can find (small screw driver, wire, drill and bits, etc. to clear the passages and get the water flowing. Use your garden hose at the inlet and keep working until you get a nice solid stream coming out everywhere it is supposed to be. Then, dump all the water out and inject acid (hydrochloric or supfuric work ok) and try to burn as much of the rust and scale in the chambers that you can't reach with your screwdriver or wire. Often, you get some big flakes trapped inside which need to be broken up and removed or they will vibrate free and block something. If you shake it, when dry, you can hear them rattling about. When all is clear, start on the passages to the head. They are not usually as clogged as the manifold. If the engine is out ofthe boat, you may find it useful to pull the head and clean both the head and the block as well. Mine had some of the passages between the head and block clogged.
In my experience, you will get another 3 -5 years or so out of the manifold before it needs another cleaning. As it ages, and corrosion sets in, it clogs up faster and faster. That said, if you can get another 4 years out of it at this point, it is a good investment of your time.
Good luck.
S.G.Bernd
Re: Clogged Exhaust manifold
Yes, this is a Volvo-Penta MD 7-A. Didn't know the manufacturer blocked off that hole. Thanks! I also heard about a transmission company that can back flush engines to de-scale them. Hunting down that lead too.
Marcia Brown
CD30C "Leona Pearl"
Portsmouth NH
Marcia Brown
CD30C "Leona Pearl"
Portsmouth NH
Re: Clogged Exhaust manifold
Here's a better picture.
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