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m35a2 whistle noise
- Thread starter joho
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Jones
Well-known member
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From the sound description and the trouble starting I'd say a vacuum leak in the intake system. Either a bad gasket at the intake manifold to cylinder head connection or a cracked intake manifold.
You may be able to pinpoint the problem by starting the truck and spraying WD 40 or some other brand penetrating oil along the intake and head joint. A change in RPM will often result from the engine drawing in the oil at the site of the bad spot in the gasket.
If nothing shows up there than do the same with the intake manifold itself.
As always: Be safe and careful when spraying anything flammable around a running engine
A second trick would be to use about 2 or 3 feet of thin wall conduit as a stethoscope; one end to your ear and the other close to the suspect area(s). (Earplug in other ear for best results).
You may be able to pinpoint the problem by starting the truck and spraying WD 40 or some other brand penetrating oil along the intake and head joint. A change in RPM will often result from the engine drawing in the oil at the site of the bad spot in the gasket.
If nothing shows up there than do the same with the intake manifold itself.
As always: Be safe and careful when spraying anything flammable around a running engine
A second trick would be to use about 2 or 3 feet of thin wall conduit as a stethoscope; one end to your ear and the other close to the suspect area(s). (Earplug in other ear for best results).
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Diesels don't make vacuum, there's no restriction in the intake...carb or throttle body baseplate. Is the noise a solid squeal or a chirp or loud tick noise? Is there any oil leaks at the front, rear or between the heads?
Jones
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True, no vacuum like a gas engine makes; but just enough so that some air falls into the cylinders when the intake valves open.
And you're right, nothing but air in the intake so the possibility of leaning out the mixture wouldn't hold true here.
Said I had some ideas... didn't say they were good ones.
And you're right, nothing but air in the intake so the possibility of leaning out the mixture wouldn't hold true here.
Said I had some ideas... didn't say they were good ones.
Wolf.Dose
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These trucks usually do not have a silencer. This limits the problem. Normally these sounds come up if there is a failure in the muffler (broken interior). But without muffler...
So my idea is that somewere downstream the exhaust manifold is an edge in the exhaust where the exhaust gas is braking and producing the kind of whisle. Or simply a leaky gasket where the exhaust gas is bowing out and producing the noise.
Summery:Somewhere at the exhaust side something is producing the noise to my opinion.
Wolf
So my idea is that somewere downstream the exhaust manifold is an edge in the exhaust where the exhaust gas is braking and producing the kind of whisle. Or simply a leaky gasket where the exhaust gas is bowing out and producing the noise.
Summery:Somewhere at the exhaust side something is producing the noise to my opinion.
Wolf
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I had a noise like that once. It was a section of exhaust manifold gasket vibrating like a reed. If you can reproduce the noise while running the engine with the vehicle in the shop, you will be able to listen around the motor and deduce the location.
Hope this helps.
Rick
Hope this helps.
Rick
FreightTrain
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Not the airhorn is it?The valve might be leaking causing just enough air to leak into the chambers to vibrate the diaphram to squeel but not fire.
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It could be a bad alt/waterpump bearing (rather unlikely) or a leak in the air line (also unlikely). Loose belts can also squeal. The non-turbo does have a muffler next to transmission, but loose baffles seem to rattle more than whistle.
Jones
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All these may explain the noise but not his complaint of loss of power and trouble starting.
Now I'm thinking back to intake or exhaust systems. If not a leaky gasket then maybe one that's broken and part of it has fallen into the air stream and is blocking flow.
The mystery continues.
Now I'm thinking back to intake or exhaust systems. If not a leaky gasket then maybe one that's broken and part of it has fallen into the air stream and is blocking flow.
The mystery continues.
FreightTrain
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wonder if a fuel filter might have colapsed from crud blockage?They COULD in theory cause a vibration/whistle if everything lined up right.Long shot but worth investigating.....
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I had a bearing fail on the mower deck 2 weeks ago. It made a horrid screaching noise and [because I kept mowing] finally seized and stalled the 14hp engine. Things got mighty hot.
Hard to diagnose with what little info the author offered. Anyways, I just thought to add along a different line of thought.
Joho, Welcome... Please commentn t when you find out.
Hard to diagnose with what little info the author offered. Anyways, I just thought to add along a different line of thought.
Joho, Welcome... Please commentn t when you find out.
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RE: LMTV in cab turbo 'whistle'...
I have a similar issue. On boost only, I am getting a 'whistle' noise that sounds like a teapot on boil. It only occurs when it is on Boost. At a steady throttle, it does not happen. I have a stethoscope noise finder and I will begin my search under the dash. I'm just wondering what would be under there, and in the cab, that would react to high pressure in the intake manifold?
Performance is not effected and I just replaced the charge cooler boots on the up side of the cooler..
Pointman
I have a similar issue. On boost only, I am getting a 'whistle' noise that sounds like a teapot on boil. It only occurs when it is on Boost. At a steady throttle, it does not happen. I have a stethoscope noise finder and I will begin my search under the dash. I'm just wondering what would be under there, and in the cab, that would react to high pressure in the intake manifold?
Performance is not effected and I just replaced the charge cooler boots on the up side of the cooler..
Pointman
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Continued diagnosis of this 'whistle' indicates the sound coming off the top of the engine. I is louder with the dash vent open.
I'm hoping I do not have a leak in the charge cooler..
Pointman
I'm hoping I do not have a leak in the charge cooler..
Pointman
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Check and tighten all the clamps in the induction system. Look for a little soot around the hoses.
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Whistle gone!
After popping the cab over the weekend to do a fuel filter and oil change, I re-examined the hose clamps on the charge cooler that were changed when the fan clutch was repaired. I moved a few of them around, and now the mysterious boost 'whistle' is no more..
Pointman
After popping the cab over the weekend to do a fuel filter and oil change, I re-examined the hose clamps on the charge cooler that were changed when the fan clutch was repaired. I moved a few of them around, and now the mysterious boost 'whistle' is no more..
Pointman