Troubleshooting a loud whine (2GM20F)

SebastienL · #1 (**permalink**) 08-30-2011

While coming back to my slip last sunday, a loud whine came from my engine (2GM20F). The noise goes up in intensity with rpm and is faint and intermittent at idl. (It really sounds like rubber slipping on metal.) While manoeuvring to my slip, everything went well, so I'm assuming there was no power loss. There was no smoke to be seen, but a burned rubber smell was noticed by everyone onboard. Once stopped, I opened the engine compartment and it felt hotter than usual, but this is rather subjective.

After docking, I had a few things to prepare for Irene's arrival and didn't have time to look into the engine issue. I'll be going back to my boat tomorrow (Aug 31st) to troubleshot that.

I'm planning to start by checking belt tension, oil level (engine + trans, wasn't done recently

) and any apparent damage near the shaft seal. I then plan to start the engine at idle and listen... If I can't find nothing, I plan to change the impeller as it wasn't done this spring (was done last year)...

I'd really welcome any suggestions on other things to check or wild guesses at what could be my problem.

(I've got nearly no hands-on experience with diesel, but have taken a theoretical class and read books)

PaulfromNWOnt · #2 (**permalink**) 08-30-2011

Belt slipping. Either alternator, or water pump.

FarCry · #3 (**permalink**) 08-30-2011

Probably a belt.

SlowButSteady · #4 (**permalink**) 08-30-2011

Engine belts tend to get loose with age.
Sailors' belts tend to get tight with age.
Go figure......

arf145 · #5 (**permalink**) 08-31-2011

A loud whine could be heard on our boat yesterday, but it turned out to be me trying to put the pins back in the swim ladder joint

SlowButSteady · #6 (**permalink**) 08-31-2011

Quote:

Originally Posted by arf145

A loud whine could be heard on our boat yesterday, but it turned out to be me trying to put the pins back in the swim ladder joint

A bit of ethanol, chilled with some ice, will take care of that.

arf145 · #7 (**permalink**) 08-31-2011

Quote:

Originally Posted by SlowButSteady

A bit of ethanol, chilled with some ice, will take care of that.

Had none--that's why I was whining

patrickstickler · #8 (**permalink**) 08-31-2011

Not sure what kind of whine you heard, but once I had a whine like noise from my old Volvo and it was a blockage in the raw water cooling passages (of all things).

So if no other source presents itself.....

75R20 · #9 (**permalink**) 08-31-2011

Also check the brackets and bolts holding accessories to the block or head. Cracked or loose bolts could allow the belt to be noisey. Check the idler pulley's if they or present.
Best of luck
Kary
S/V Mariah
#49080

SebastienL · #10 (**permalink**) 08-31-2011

Thanks for all the suggestions.

Upon arriving today, I noticed both belts (sea water pump, alternator + freshwater pump) being quite loose and quite worn out. I changed both and retensionned.

I briefly started the engine and saw that the freshwater pump seemed to emit some clunky sounds and sometimes it would jam in place for a few seconds, forcing the new (and well tensioned) belt to slip and emit its (now typical) squeal. I stopped everything, removed the belt and inspected the freshwater pump pulley. I noticed significant movement from the pulley suggesting a problem with its bearing, I also saw accumulated rust hiding behind the pulley.

That's where I humbly pull the plug and call up a pro. I'm kinda of assuming a new freshwater coolant pump is in order...