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My 235 engine "Sings"! Why?

Posted By: Joe S.

My 235 engine "Sings"! Why? - Sat Jul 20 2019 08:59 PM

Friends:

My 235 sings a constant musical note while running, when idling and running down the road. It is the same kind of sound you get wetting your finger and rubbing it around the rim of a glass. It is continuous and the tone and intensity stays the same regardless of engine speed. ! What is the cause? It is difficult to isolate to a specific part of the engine but seems louder on the distributor side. The only thing I can guess is the lip seal on the timing gear cover. I have no oil leaks.

Regards,

Joe
Posted By: Wrenchbender Ret.

Re: My 235 engine "Sings"! Why? - Sat Jul 20 2019 09:14 PM

Take the fan belt off & try it. If it goes away then spin the water pump & Gen. by hand & see if makes a noise or turns hard.
Check the dist points to see if there is a small amount of grease on the cam. I've seen this make a squeal when the rubbing block on the points are dry.
George
Posted By: Joe S.

Re: My 235 engine "Sings"! Why? - Sat Jul 20 2019 09:22 PM

George,

Thank you for the reply. The distributor points were lubed recently. When I installed the water pump, it did not turn freely in the sense of spinning but otherwise exhibited no excessive play. I attributed the stiffness while turning to the seal which would normally be lubricated by the coolant. I had the generator apart and the bearings were lubed and fine.

Joe
Posted By: Volfandt

Re: My 235 engine "Sings"! Why? - Sat Jul 20 2019 11:14 PM

If it weren't for it staying constant and not varying with rpm I'd say air rushing through the air cleaner or a vacuum leak around the carb, intake or even the vacuum wiper motor under your dash (if so equipped).
But it's loudest on the dist side, hummm, maybe a leaky vacuum advance canister?

I've seen electrical circuits vibrate at frequency's that could be heard, if you had a radio and heard it the capacitor/condenser in the dist could cause that. Might try replacing the condenser just for GP.
Good luck
Dave
Posted By: Joe S.

Re: My 235 engine "Sings"! Why? - Sun Jul 21 2019 12:07 AM

Thank you Volfandt, I DO have the air cleaner off. I will check it with it on and the vacuum advance, the truck's performance is as if it were not working.
Posted By: Jon G

Re: My 235 engine "Sings"! Why? - Sun Jul 21 2019 02:14 AM

I've seen this with a failing vac advance diaphragm. Same thing with air pressure regulators for compressors. Sounds like a tuning fork, doesn't it?
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