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H3 Rattle near fan when idle and at normal operating temp. only

Doug

Probationary Member
Messages
1
Location
United States
2007 132,000 miles Hummer Service did head job, within a week a rattle began only when idle and when eng is at normal operating temp. That's to say when its cold and until the temp reaches normal, no rattle. Same if driving... no rattle.

The rattle comes from the fan/front engine upper area. Hummer can't diagnose it but says I should not drive it for fear of damage to lower engine. They suggest to replace the engine for $6,100. I said yes, next day I called to cancel the engine order and they went into a frenzy with every reason why I can't cancel the engine. Persistence brought them to offer the engine replacement for $4,100 and I declined. What's going on 1) with the rattle and 2) why such hard push-back on canceling the engine, and then a $2,000 reduction to replace the engine?
 

alrock

El Diablo
Staff member
Messages
10,426
Location
Scottsdale
Does it sound like the noise is internal to the engine, or outside, like an accessory, heat shield, etc?
 

Airborne

Just a regular dude
Messages
294
Location
Utah
2007 132,000 miles Hummer Service did head job, within a week a rattle began only when idle and when eng is at normal operating temp. That's to say when its cold and until the temp reaches normal, no rattle. Same if driving... no rattle.

The rattle comes from the fan/front engine upper area. Hummer can't diagnose it but says I should not drive it for fear of damage to lower engine. They suggest to replace the engine for $6,100. I said yes, next day I called to cancel the engine order and they went into a frenzy with every reason why I can't cancel the engine. Persistence brought them to offer the engine replacement for $4,100 and I declined. What's going on 1) with the rattle and 2) why such hard push-back on canceling the engine, and then a $2,000 reduction to replace the engine?

HUGE red flags. If you are able to drive the vehicle with no loss in power, no check engine lights are on, and the rattle goes away... That by no means says to me you need a new engine. I would run fast and hard from that shop.

The I5 is a "rattly" little engine. I have quieted a few rattles my self. The biggest problem is sometimes its really hard to tell where the rattling is coming from.
First places to check would be the heater hoses. That is usually the biggest culprit with the 3.7L "noise". They enter into to the passenger side of the body/fire wall. Two hoses about an inch thick. Zip tie them together pretty tight about 4 inches where the hose itself leaves the connector. Next I would check the exhaust manifold heat shield, air intake box connection points to the body, air resonator box might not bolted tight there are some others but I would start there. I am going to put money on the heater hoses though. It took quite a while to find out what my rattling was but based on what you stated it sounds like that is it.
Again it may sound like its coming from the "fan area" and it's really not.
 

Best4x4

Well-Known Member
Messages
1,042
Location
Vidor, TX
The waterpump on my 3.7L H3 made weird noises. From scratchy to small thump sounds. Best way to check it really quick is to take the serpentine belt off, and spin it by hand. It shouldn't have any slop in it, or movement up/down. If it does the bearing is toast and you need a new one. Quick and easy on the I5. With the right tools it can be done under an hour for sure.
 

USMC_TOP

Well-Known Member
Messages
491
Location
Muir Michigan
He did say he just got the head rebuilt. Maybe the fresh head with an increase in compression from valves not sealing or a leaking gasket put too much stress on the 100k+ lower end? That's worst case for sure but it can happen. Or maybe it's the timing chain? Do these i5's have chains or belts running the camshafts?
 

Best4x4

Well-Known Member
Messages
1,042
Location
Vidor, TX
Also if all of this started after the head work, take it back and have them fix it! Should have a 12,000 mile/12 month warranty at least. If it runs and drives fine besides the noise chances are they either bent a heatshield, left something loose, or they put it back together with a worn waterpump vs replacing it....

It really sounds heatshield related or it could be the transmission cooler lines rattling. I had a small rattle at start up and one of the transmission metal lines was out of it's clip behind the oil filter previous owner could have bumped it during an oil change or when they had the oil changed. I popped it back into place, and no more rattle. A cracked exhaust manifold can make it sound like valves ticking, and once it warms up and the crack closes the noise will go away. My 3.7L has a slight exhaust tick on a cold start up so I know I have crack in the manifold somewhere, but it's a common thing on most cars now days.
 
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