Rattle at start up?
#2
08-04-2009, 11:11 AM
Gonna need a bit more info to help. Like where does the rattle sound come from? Under the hood, under the truck, front or back.
W/o any further info. a guess would be you have a loose exhaust manifold heat shield?
When the motor is completely cool, see if you can bend it further away from the exhaust so it cannot touch.
W/o any further info. a guess would be you have a loose exhaust manifold heat shield?
When the motor is completely cool, see if you can bend it further away from the exhaust so it cannot touch.
#3
08-05-2009, 06:26 AM
Check The Timing Chain Tensioner
If it only does it when you first start the engine after it has been sitting overnight, the problem is with the timing chain tensioner.
The tensioner is activated, that is it adds tension to the timing chain by oil pressure. When you first start the engine, until the oil pressure comes up, the chain will "slap" or rattle. This is a warranty repair.
What happens is, over time, the chain stretches. The tensioner has a ratchet on it that lets it move up to the next position to accomodate the slack in the now stretched chain.
The design tollarences are such that the chain can be loose enough to slap yet not loose enough for the tensiorer to move to the next position. This is a design flaw that HUMMER will fix.
The tensioner is activated, that is it adds tension to the timing chain by oil pressure. When you first start the engine, until the oil pressure comes up, the chain will "slap" or rattle. This is a warranty repair.
What happens is, over time, the chain stretches. The tensioner has a ratchet on it that lets it move up to the next position to accomodate the slack in the now stretched chain.
The design tollarences are such that the chain can be loose enough to slap yet not loose enough for the tensiorer to move to the next position. This is a design flaw that HUMMER will fix.
#4
08-06-2009, 08:41 PM
ok he also did not say what engine he had if it was an alpha or the 5 cyl. If he has an alpha the 5.3 get a bit of a carbon ring at the top of piston travel that can cause a tick or rattle sound, the sond quiets as the engine gets warmed up.
#5
05-20-2012, 12:27 AM
Albert
If it only does it when you first start the engine after it has been sitting overnight, the problem is with the timing chain tensioner.
The tensioner is activated, that is it adds tension to the timing chain by oil pressure. When you first start the engine, until the oil pressure comes up, the chain will "slap" or rattle. This is a warranty repair.
What happens is, over time, the chain stretches. The tensioner has a ratchet on it that lets it move up to the next position to accomodate the slack in the now stretched chain.
The design tollarences are such that the chain can be loose enough to slap yet not loose enough for the tensiorer to move to the next position. This is a design flaw that HUMMER will fix.
The tensioner is activated, that is it adds tension to the timing chain by oil pressure. When you first start the engine, until the oil pressure comes up, the chain will "slap" or rattle. This is a warranty repair.
What happens is, over time, the chain stretches. The tensioner has a ratchet on it that lets it move up to the next position to accomodate the slack in the now stretched chain.
The design tollarences are such that the chain can be loose enough to slap yet not loose enough for the tensiorer to move to the next position. This is a design flaw that HUMMER will fix.
Did they fix yours, and did the noise went away completely and not come back? I will be interested to know.
#6
05-20-2012, 06:55 AM
I also have the same noise when I first start mine. Mine does it worse when the engine is cold, but still will do it even when the engine is warm .And I have the 3.7. It is coming from the hood and it makes a sound of death sound for about 2-3 seconds.. but it is a loud, grating sound, that sounds like you are running a cement mixer with loose rocks kinda. I think Black Hummer hit it on the head. I will be taking mine to the dealer in the near future to see if they will can figure it out and fix it..
#8
07-16-2012, 10:51 AM
H 3 engine rattle/nose/knock cold start
Pay attentio if you have the infamous cold engine rattle/noise/knock when vehicle has been sitting for a few hours.
I am disapointed by the effort GM is making to convince H-3 owners that this in normal and their failure to provide a fix or a clear explanation of what is causing the noise.
I own two other GM vehicles with the Alpha engine and none of them make the noise.
SOLUTION: GM's lack of sincerity has led me to do the following at my own cost.
1- I am taking the vehicle to a GM dealer other than a Hummer dealer. It will be a Chevrolet dealer with certified technicians on the Alpha engines.
2- I am requesting an oil and filter change and having an oil and filter analisys for metal in the oil.
3- I am having the timing componets examined for signg of scraping and if possible a cold engine start without the cover on to see what is happening.
4- If the above faile to show any problems we will proceed to an engine teardown and inspection of the lifter bores and piston to cylinder bore clearances. Acoording to some engine rebuilders (certified) that i have spoken to other causes for this type of noise are:
a- Piston slap due to excesive clearance between piston and cylinder walls.
b- Lifter wooble again due to excessive clearance between lifter and lifter bore.
I will be paying the dealer out of my own pocket and perhaps put the issue to rest and be able to advise all h-3 owners of the results.
Stay tuned Let me know.
I am disapointed by the effort GM is making to convince H-3 owners that this in normal and their failure to provide a fix or a clear explanation of what is causing the noise.
I own two other GM vehicles with the Alpha engine and none of them make the noise.
SOLUTION: GM's lack of sincerity has led me to do the following at my own cost.
1- I am taking the vehicle to a GM dealer other than a Hummer dealer. It will be a Chevrolet dealer with certified technicians on the Alpha engines.
2- I am requesting an oil and filter change and having an oil and filter analisys for metal in the oil.
3- I am having the timing componets examined for signg of scraping and if possible a cold engine start without the cover on to see what is happening.
4- If the above faile to show any problems we will proceed to an engine teardown and inspection of the lifter bores and piston to cylinder bore clearances. Acoording to some engine rebuilders (certified) that i have spoken to other causes for this type of noise are:
a- Piston slap due to excesive clearance between piston and cylinder walls.
b- Lifter wooble again due to excessive clearance between lifter and lifter bore.
I will be paying the dealer out of my own pocket and perhaps put the issue to rest and be able to advise all h-3 owners of the results.
Stay tuned Let me know.
#9
07-16-2012, 11:23 AM
Pay attentio if you have the infamous cold engine rattle/noise/knock when vehicle has been sitting for a few hours.
I am disapointed by the effort GM is making to convince H-3 owners that this in normal and their failure to provide a fix or a clear explanation of what is causing the noise.
I own two other GM vehicles with the Alpha engine and none of them make the noise.
SOLUTION: GM's lack of sincerity has led me to do the following at my own cost.
1- I am taking the vehicle to a GM dealer other than a Hummer dealer. It will be a Chevrolet dealer with certified technicians on the Alpha engines.
2- I am requesting an oil and filter change and having an oil and filter analisys for metal in the oil.
3- I am having the timing componets examined for signg of scraping and if possible a cold engine start without the cover on to see what is happening.
4- If the above faile to show any problems we will proceed to an engine teardown and inspection of the lifter bores and piston to cylinder bore clearances. Acoording to some engine rebuilders (certified) that i have spoken to other causes for this type of noise are:
a- Piston slap due to excesive clearance between piston and cylinder walls.
b- Lifter wooble again due to excessive clearance between lifter and lifter bore.
I will be paying the dealer out of my own pocket and perhaps put the issue to rest and be able to advise all h-3 owners of the results.
Stay tuned Let me know.
I am disapointed by the effort GM is making to convince H-3 owners that this in normal and their failure to provide a fix or a clear explanation of what is causing the noise.
I own two other GM vehicles with the Alpha engine and none of them make the noise.
SOLUTION: GM's lack of sincerity has led me to do the following at my own cost.
1- I am taking the vehicle to a GM dealer other than a Hummer dealer. It will be a Chevrolet dealer with certified technicians on the Alpha engines.
2- I am requesting an oil and filter change and having an oil and filter analisys for metal in the oil.
3- I am having the timing componets examined for signg of scraping and if possible a cold engine start without the cover on to see what is happening.
4- If the above faile to show any problems we will proceed to an engine teardown and inspection of the lifter bores and piston to cylinder bore clearances. Acoording to some engine rebuilders (certified) that i have spoken to other causes for this type of noise are:
a- Piston slap due to excesive clearance between piston and cylinder walls.
b- Lifter wooble again due to excessive clearance between lifter and lifter bore.
I will be paying the dealer out of my own pocket and perhaps put the issue to rest and be able to advise all h-3 owners of the results.
Stay tuned Let me know.
I could sarcastically say thank you for digging up a 3 year old thread again.
#10
07-16-2012, 05:15 PM
Before you tear down the entire motor. check the inside of the timing chain cover for signs of "slapping".