I have a peculiar and rare re-occurring problem which I have consultedmultiple mechanics and other experts on, and never resolved…
On very rare occasions, just 4 times in the last 5 years, our VolvoTAMD40B starts making a very loud banging sound. The rate/frequency of the banging soundaccelerates/decelerates with RPM, and occurs both in gear or neutral. At idle it’s imperceptible or almost imperceptible. It has occurred once after about an hourunderway, and 3 times when underway 2-4 hours. While our boat can run up to 14 knots at 3,600 RPM, we stick to hull speedat 1,700 RPM. We do some short runs, butfrequently do longer trips of 4-8 hours year-round. The engine/boat are 1985 with only 1,500 hours in the first nearly 30 years, and 1,500 of active use in the last 5 years. The engine is in excellent shape and has been very well cared for.
In all four cases, the banging has gone away on its own. Three times after just 1-3 minutes (while tryingturning engine off, low revs, etc.). Onthe fourth occasion in rough water it took almost an hour and finally resolved afterrunning the engine at normal RPM (1,700) and ignoring the banging for a minute or two. Acomplete mystery.
As the problem goes away by itself, it clearly isn’t a permanentproblem such as a damaged piston. Theoil and coolant are always perfect when changed and checked (both consistency and levels). Engine temp and pressure always run at normallevels.
The only outstanding possibilities that have been suggestedto me are that it could be either: a) fuel filter should have been replacedmore frequently, or b) a valve getting sticky, but then freeing up again.
It’s been a while since the problem last occurred, but I’dlike to get to the bottom of what it could be in case it happens again, or toprevent it from happening again.
I would greatly appreciate any ideas or insights.
Thank you.
On very rare occasions, just 4 times in the last 5 years, our VolvoTAMD40B starts making a very loud banging sound. The rate/frequency of the banging soundaccelerates/decelerates with RPM, and occurs both in gear or neutral. At idle it’s imperceptible or almost imperceptible. It has occurred once after about an hourunderway, and 3 times when underway 2-4 hours. While our boat can run up to 14 knots at 3,600 RPM, we stick to hull speedat 1,700 RPM. We do some short runs, butfrequently do longer trips of 4-8 hours year-round. The engine/boat are 1985 with only 1,500 hours in the first nearly 30 years, and 1,500 of active use in the last 5 years. The engine is in excellent shape and has been very well cared for.
In all four cases, the banging has gone away on its own. Three times after just 1-3 minutes (while tryingturning engine off, low revs, etc.). Onthe fourth occasion in rough water it took almost an hour and finally resolved afterrunning the engine at normal RPM (1,700) and ignoring the banging for a minute or two. Acomplete mystery.
As the problem goes away by itself, it clearly isn’t a permanentproblem such as a damaged piston. Theoil and coolant are always perfect when changed and checked (both consistency and levels). Engine temp and pressure always run at normallevels.
The only outstanding possibilities that have been suggestedto me are that it could be either: a) fuel filter should have been replacedmore frequently, or b) a valve getting sticky, but then freeing up again.
It’s been a while since the problem last occurred, but I’dlike to get to the bottom of what it could be in case it happens again, or toprevent it from happening again.
I would greatly appreciate any ideas or insights.
Thank you.