Loud Knock with Cold Morning Start - What to do?

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bluemarket

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Hi Guys,

Recently my 2005 LS V8 has started to knock really loud when first starting in the morning. It's been about 30 degrees or so when I start it in the morning. It has about 112,000 miles on it.

It goes away shortly after starting, and seems to drive to work fine. After sitting 8 hours at work, and going to start it up again (at around 50 degrees outside), she starts up just fine. Plus if I start it up after turning it off on the way to work after it has warmed up, it starts up fine. Any ideas?

I'm debating taking her in to a dealer to get it diagnosed but guessing whatever it is will cost enough to make me faint.

As far what I have done in work recently:

I have replaced just about every temperature sensor on the car (while troubleshooting overheating issues)
Installed the new revision Ford coil on plug units
Sealed the spark plug well covers with black high temp silicone to prevent water getting in the wells (this happened too much in the past)
Replaced the intake manifold gaskets
Oil is freshly changed with Mobil 1 5w-20 and a K&N filter
 
check your harmonic balancer , mine is doing the exact time and it drives fine and I had recently put a new belt on it, had it checked out and it was my harmonic balancer going bad which making the belt spin bad and cause squeeking and thuds when i first start my car , after it warms up its fine
 
Hi Ghost. I looked into it further this morning. That does indeed look like the problem. How hard was it to replace yours? I've been looking at the crankshaft pulley section of information on http://deneau.info/ls/ and it's looking like the engine needs to be lifted.
 
easy to change problem is the part cost 1000 bucks and its dealer only
 
bluemarket said:
... How hard was it to replace yours? I've been looking at the crankshaft pulley section of information on http://deneau.info/ls/ and it's looking like the engine needs to be lifted.
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No need to lift the engine. You'll want to put the whole car on a lift, or just ramps or jack stands to raise the front of the car so that you can get under there. You can get the damper pulley for $700, but you'll also need a bolt, some seals, and a couple of special tools.
 
joegr said:
No need to lift the engine. You'll want to put the whole car on a lift, or just ramps or jack stands to raise the front of the car so that you can get under there. You can get the damper pulley for $700, but you'll also need a bolt, some seals, and a couple of special tools.
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If the 05 uses the same bolt as the 00-02 he'll be spending $30 and waiting for one to come in from Nevada. At least that was the case when I rebuilt my engine over a year ago. I think the dealer said only four were still left. In other words, people just reuse the bolt that is on there.

I got a harmonic balancer puller from autozone, and did the whole deal in 45 min. A new timing cover seal is needed, but I just used a really large socket or some stock black pipe and carefully tapped the seal in. The big concern would be breaking the outer plastic ring, pressing the seal in too far or twisting it; hence, going slowly and being careful.

Is there anyway to verify the balancer is the issue besides just watching it as the engine runs for any variance. $700 is a lot for a guess.
 
Broseph said:
...Is there anyway to verify the balancer is the issue besides just watching it as the engine runs for any variance. $700 is a lot for a guess.
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In my case, just watching it while idling in the cold with a cold engine removes all doubt. Mine is not bad enough yet to worry that it is going to fly apart anytime soon. It sounds like Ghost_Ls8's is in worse shape. Ford did make a bunch of bad ones of these, for several engines. I think the rubber or whatever it is between the inner and outer parts was bad.
 
yessir mine whobbles pretty noticably , drives fine , makes that noise when starts up and whines till it warms up
 
My 2006 does the same thing. How long can this be let go before it's a huge issue? What happens if I ignore it completely?
 
well i don't know how long mine has been going on for but if you ignore it it will become worse and eventually it will let go of the belt and the belt will come off
 
kaoss said:
My 2006 does the same thing. How long can this be let go before it's a huge issue? What happens if I ignore it completely?
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Eventually, the damper could fly apart and do quite a bit of damage under the hood. As far how long you can wait on it, I don't know. I've been watching mine for around two years now. I've had it since new, and it wasn't noticeable for the first five years.
 
My 2006 just recently started developing what seems like a slight knock in the morning that seems to quiet up after a bit. Guess I'll have to check the balancer and see if it wobbles.
 
I guess my 2003 didn't get one of the bad ones. Checked it this morning, 18 degrees out, and my balancer was spinning so smoothly it was almost as though it wasn't moving. This also rules out the HB as my problem.
 
thats good news man , check the other pulleys , otherwise your in the same boat as a ton of others saying their car makes a weird start up noise and can't pin point what it is
 
Telco said:
I guess my 2003 didn't get one of the bad ones. Checked it this morning, 18 degrees out, and my balancer was spinning so smoothly it was almost as though it wasn't moving. This also rules out the HB as my problem.
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My 04 is perfectly fine too. Wish the 06 was...
 
my friends 04 is in better condition than mine and it has 103k , must be an 06 thing :/ , i thought 06s would be bullet proof or close to it -.-
 
2006 LS 48k miles
Last summer idler pulley & belt were replaced due to squealing belt. It was happening again last week. Plus I had a similar knock noise (more on that below). Had belt tensioner replaced which seemed to have fixed the squeal. But the repair place (local Goodyear dealer) could not figure out the knock.

Cold mornings - at start up, there is a fairly rapid knock coming from the front of the engine compartment. The knock quickly slows in frequency and then disappears altogether within ~1 minute.
Is this consistent with the harmonic damper problem?
 
I dont think so but it is a factor because I changed my balancer and when it was freezing cold it made that noise for 1 second , not as much as before though
 
You can tell if it's the HB by popping the hood, then starting the engine then watching the HB with a flashlight. It'll either spin smooth or will have a wobble.

Weird thing on mine, I also have a cold weather knock for a few seconds. I heard the car start while near the back, and found that it's the exhaust near the rear that is actually making the knock. Still haven't gotten under there to find out exactly why, nor can I explain why it only happens when it's cold out. Nevertheless, there ya go. My knock sounded like it was under the hood, but noise can travel funny sometimes.

Seems the LS has a whole lot of different, totally unrelated sources for startup knock.
 
you might be right Telco, might not be engine related , do you have a squeak also when yours warms up ? once i start driving it disappears , i thought it was related to the harmonic balancer but it wasnt
 
I had this problem on my '06 at around 80k. I couldn't believe how much the HB cost! I got very lucky and found the right one on ebay for under $100. PS how can anyone justify $700 for that part?? It's just a crude piece of metal..nothing special about it.
 
my 06 it happened at 84k , called local dealership and they said 1200 plus tax , i ended up fixing mine for 180
 
Ivan_D said:
... It's just a crude piece of metal..nothing special about it.
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It's two+ pieces of particular metal (one at just the right weight) and a particular piece of rubber-like material. There is a little bit to it. However, I agree that it shouldn't be anywhere near $700. $100 would be high enough. It's one of the costs of having a car that they made very few of and that very few parts are shared with any other car.
 
Had a squeak, but the squeak went away when I replaced the tensioner and idler pulley. The startup rattle didn't.
 
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