LMM: 08 LMM loud fan noise

[joshjudd1992]

Okay i have an odd problem i have a 08 duramax im the second owner it has 130,000 miles edge CTS programmer cognito UCA's firestone rear airbags, k and n cold air intake. Im in west texas right now this started happenig nearly two to three months ago. The truck randomly roars sorta like when you first start a diesel in the morning. I know thats normal and thats not what im worried about im worried about the squeal that comes woth the roar it will come randomly and when it does as i accelerate a buzzing/grinding sound comes with it. It dosent effect the trucks performance at all its just a grinding noise that only comes when the fan is working. It sounds like a jet in the cab of my truck. This is a random occurance and smsostly happens when its hott outside. Im posting a link of a video of it the sound almost sounds like a dirtbike or passing car but it is my truck. Please any infor would be helpful im wondering if its the fan motor or clutch fan.

https://youtu.be/9SOMq3L1-1M


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[Novak]

Have you checked your ps fluid? That what that sounds like. Hard to tell without peaking under the hood and being there but that whine sounds like cavitation.


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[joshjudd1992]

Have you checked you ps fluid? That what that sounds like. Hard to tell without peaking under the hood and being their but that whine sounds like cavitation.


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Yeah i checked it and it was a little low not much tho. The sound will not happen unless im driving so its hard to diagnose.


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[Chevy1925]

will it ONLY do it when the fan locks up? or all the time?

really check the cage that is behind the fan but infront of the engine. i have seen them come loose, suck into the fan and create a noise that sounds just like a power steering pump going bad. im betting thats what yours is doing. you may need a new fan after this too depending on how much it has rubbed it

 

[joshjudd1992]

will it ONLY do it when the fan locks up? or all the time?

really check the cage that is behind the fan but infront of the engine. i have seen them come loose, suck into the fan and create a noise that sounds just like a power steering pump going bad. im betting thats what yours is doing. you may need a new fan after this too depending on how much it has rubbed it

Yes it only does it when the fan is on never hear it when its off. I am going to look jnto that does the 08 have an electric fan motor? Or is it the clutch fan?


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[Chevy1925]

Yes it only does it when the fan is on never hear it when its off. I am going to look jnto that does the 08 have an electric fan motor? Or is it the clutch fan?


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it is a mechanical fan, no electric fan on it.

push on the cage all around it, look for any part that flexes into the fan or feels loose. that fan creates ALOT of vacuum and will suck it in with any kind of decent flex.

i had tried leaving the top mount off the cage on one truck, the mount went right back on after it did what yours is doing lol

 

[joshjudd1992]

it is a mechanical fan, no electric fan on it.



push on the cage all around it, look for any part that flexes into the fan or feels loose. that fan creates ALOT of vacuum and will suck it in with any kind of decent flex.



i had tried leaving the top mount off the cage on one truck, the mount went right back on after it did what yours is doing lol

I found the problem the rear fan shroud bottom left where it bolts to bracket broke off and is caused small chips in the blade. Going to get it fixed. Can i just take that shroud off? Idk if it serves a purpose or is it just to protect people from getting there hands caught in it?


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[Chevy1925]

I found the problem the rear fan shroud bottom left where it bolts to bracket broke off and is caused small chips in the blade. Going to get it fixed. Can i just take that shroud off? Idk if it serves a purpose or is it just to protect people from getting there hands caught in it?


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it serves a purpose. it helps create a better seal around the fan to pull more air through the shroud and help keep the truck cooler when loaded down and towing in the heat. you can take it off for now but i would put it back on. its a pain in the ass but it makes a difference if you tow decently heavy in the heat of summer.

btw, i have a brand new LBZ/LMM cooling fan sitting on my shelf at home i was going to try to retro fit onto my LB7 but im going a different direction. if you want it, make me an offer. just taking up shelf space.

 

[joshjudd1992]

it serves a purpose. it helps create a better seal around the fan to pull more air through the shroud and help keep the truck cooler when loaded down and towing in the heat. you can take it off for now but i would put it back on. its a pain in the ass but it makes a difference if you tow decently heavy in the heat of summer.



btw, i have a brand new LBZ/LMM cooling fan sitting on my shelf at home i was going to try to retro fit onto my LB7 but im going a different direction. if you want it, make me an offer. just taking up shelf space.

Is it stock a stock fan? Do you happen to have the shroud too lol


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[Chevy1925]

Is it stock a stock fan? Do you happen to have the shroud too lol


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yup, stock fan. no clutch, just the fan blades. i dont lol. actually threw away my brothers a couple years ago and thats when we realized how important it was.... i think rock auto or ebay had the best price on a new one. might be able to zip tie it back for the time being.