OK folks, looking for some experienced person to help out again. I removed the exhaust manifold and thermostat cover on my MD7a. It appears that the "bypass" hole in the manifold is blocked with a tarry substance (carbon??) I tried some solvent that did a great job on the rust and scale but the passage is still plugged. It appears to ba a erght angle (or pretty close). Any ideas on how to clear this passage out? Flexible wire bursh on a dremel? Boiling vinegar? Nuclear weapon? Any input would be greatly appreciated. Thanks.
John D
S/V Mariah
john_dupras@hotmail.com
Carbon removal
Moderator: Jim Walsh
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Larry DeMers
Re: Carbon removal
John,
I have no experience actually doing this -yet. But if that material is soft-like or tarry as you said I wonder if that isn't unburned diesel that has lost it's volatile fluids, leaving just the gooy oil base. This would be dissolvable in diesel fuel I suspect, but maybe even carburetor cleaner or Gunk Out would help break it up. Turpentine also would be in the same 'family' of chemicals that would probably work on it.
Usually carbon in the exhaust is a dry flaky buildup, sometimes it gets a glaze over it and becomes brittle hard. It all depends on what temps the diesel is at, and how old it is etc.
Let us know what worked for you. This is a problem for all diesel owners.
Cheers!
Larry DeMers
s/v DeLaMer
Cape Dory 30
demers@sgi.com
I have no experience actually doing this -yet. But if that material is soft-like or tarry as you said I wonder if that isn't unburned diesel that has lost it's volatile fluids, leaving just the gooy oil base. This would be dissolvable in diesel fuel I suspect, but maybe even carburetor cleaner or Gunk Out would help break it up. Turpentine also would be in the same 'family' of chemicals that would probably work on it.
Usually carbon in the exhaust is a dry flaky buildup, sometimes it gets a glaze over it and becomes brittle hard. It all depends on what temps the diesel is at, and how old it is etc.
Let us know what worked for you. This is a problem for all diesel owners.
Cheers!
Larry DeMers
s/v DeLaMer
Cape Dory 30
John D wrote: OK folks, looking for some experienced person to help out again. I removed the exhaust manifold and thermostat cover on my MD7a. It appears that the "bypass" hole in the manifold is blocked with a tarry substance (carbon??) I tried some solvent that did a great job on the rust and scale but the passage is still plugged. It appears to ba a erght angle (or pretty close). Any ideas on how to clear this passage out? Flexible wire bursh on a dremel? Boiling vinegar? Nuclear weapon? Any input would be greatly appreciated. Thanks.
John D
S/V Mariah
demers@sgi.com
-
Dale W
Re: Carbon removal
I've worked through a variety of issues with my exhaust manifold, thermostat housing, and corresponding orifices to the block. I've experienced some overheating and some underheating (i.e. the temp gauge never shows normal operating temperatures).
Most of my problems have come from running the engine too much in the slip where there's shallow water and soft, silty bottom. The 'gooey' stuff which also hardens and is black is mud.
Carbon, per se passes through only large holes. The small holes are water passages where all sorts of stuff goes through. There's a small hole in both the block and the manifold near the upper portion between the exhaust ports. If this is the hole you are concerned with, I've found that the awl on my swiss army knife gets the holes cleared out, I've then gone in with small flat screw driver blades to get to complete cleaning. There's no danger of hurting anything. I've experienced gunk in this hole that somewhat matches your description.
The other trouble spot I've experienced is in the thermostat housing by-pass circuit. Here I've used a length of stainless wire and done some fairly incessant poking and probing until I broke through. Once through I doubled about a quarter inch of the wire back on itself and poked through and pulled back.
I also went through trying to make one of the new style thermostats work and never got things balanced until I took the Volvo tech advice of using the older style thermostat that's made for the MD-11 engine and which requires a small bit of enlarging the manifold opening to make it fit.
Hope you get the system working without too much ado.
majortest@earthlink.net
Most of my problems have come from running the engine too much in the slip where there's shallow water and soft, silty bottom. The 'gooey' stuff which also hardens and is black is mud.
Carbon, per se passes through only large holes. The small holes are water passages where all sorts of stuff goes through. There's a small hole in both the block and the manifold near the upper portion between the exhaust ports. If this is the hole you are concerned with, I've found that the awl on my swiss army knife gets the holes cleared out, I've then gone in with small flat screw driver blades to get to complete cleaning. There's no danger of hurting anything. I've experienced gunk in this hole that somewhat matches your description.
The other trouble spot I've experienced is in the thermostat housing by-pass circuit. Here I've used a length of stainless wire and done some fairly incessant poking and probing until I broke through. Once through I doubled about a quarter inch of the wire back on itself and poked through and pulled back.
I also went through trying to make one of the new style thermostats work and never got things balanced until I took the Volvo tech advice of using the older style thermostat that's made for the MD-11 engine and which requires a small bit of enlarging the manifold opening to make it fit.
Hope you get the system working without too much ado.
majortest@earthlink.net