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03 4.0L Timing Chain Noise?


dsturch1

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So before I get flamed for not using the search button and people posting the infamous 'google that' link, I would like to start by saying that I have read tons of posts on here and am just trying to confirm what I have found.

I have a 2003 with a 4.0L motor. I have all of a sudden as of the past week or so noticed a rattling noise under load, but only from about 2500rpm's and upwards. I have noticed the noise is almost not existent at lower RPMs and there is no noise at idle. When I rev the engine, it sounds like a rattling noise as if something is stuck in my intake manifold.

If I have figured this out correctly, without actually pulling anything apart - it seems as if this is the infamous timing chain issue with the Explorers. Are there any other surefire signs of the timing issue? If so, and this is the problem I have - is it okay to continue driving the truck? I am mechanically savvy, but not savvy enough to pull a whole motor out I don't think - does anyone know roughly what shop rate is to fix the issue including parts and labor? I am hoping to not lose an arm and a leg to fix it.

Any help is greatly appreciated - thanks in advance!
 

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2000StreetRod

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00 Sport FI, 03 Ltd V8
cold or warm starts?

If the sound is absent on cold and warm engine starts then it is probably not either camshaft timing chain that is rattling. However, it could be the primary (crankshaft to jackshaft) chain rattling. The 2002 and later engines have an improved primary tensioner which should last 200K miles if the periodic maintenance is performed. How many miles are on your vehicle? Replacing the primary chain tensioner and guide can easily be done with the engine in the vehicle and does not require retiming the camshafts.

If you have 4WD the sound could be from the balance shaft chain rattling. It is difficult to replace the balance shaft tensioner with the engine in the vehicle because the block cradle is normally removed.

I suggest that you remove the serpentine belt to eliminate the accessories as the source: water pump, alternator, power steering pump, A/C compressor, belt tensioner and belt idler pulley. If you only run the engine for less than a minute without coolant flow it will not overheat. As I recall there is a rev limit of 3,000 rpm on your model when in Park or Neutral.

You can also try to use a mechanic's stethoscope or a length of flexible hose to locate the source. I did not have any luck with either when my rear cassette broke. If the noise is generated internally it is very difficult to isolate.
 


rainbow9

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run synthetic Mobil 1 in it...245,000 on my last 4.0 no problems
 


RicketyExplorer

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Ask any shop it's a common problem with that motor you can get it replaced with a new and improved timing chain and gears set.
 


dsturch1

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If the sound is absent on cold and warm engine starts then it is probably not either camshaft timing chain that is rattling. However, it could be the primary (crankshaft to jackshaft) chain rattling. The 2002 and later engines have an improved primary tensioner which should last 200K miles if the periodic maintenance is performed. How many miles are on your vehicle? Replacing the primary chain tensioner and guide can easily be done with the engine in the vehicle and does not require retiming the camshafts.

If you have 4WD the sound could be from the balance shaft chain rattling. It is difficult to replace the balance shaft tensioner with the engine in the vehicle because the block cradle is normally removed.

I suggest that you remove the serpentine belt to eliminate the accessories as the source: water pump, alternator, power steering pump, A/C compressor, belt tensioner and belt idler pulley. If you only run the engine for less than a minute without coolant flow it will not overheat. As I recall there is a rev limit of 3,000 rpm on your model when in Park or Neutral.

You can also try to use a mechanic's stethoscope or a length of flexible hose to locate the source. I did not have any luck with either when my rear cassette broke. If the noise is generated internally it is very difficult to isolate.

I have 174,000 on the motor, I haven't had time to pull the belt off and check but it doesn't make the noise at start up and is much quieter when revved up to around 3000rpms when cold. Is there a sticky with instructions on how to change the tensioner? How long about does it take?
 


2000StreetRod

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replacing primary chain tensioner & guide

I'm not familiar with the 3rd generation nor do I know of a thread describing replacement of the primary chain tensioner & guide. If it's like the 2nd generation you have to remove the cooling fan, radiator, intake manifold, alternator, power steering pump and harmonic balancer to remove the front timing cover. The A/C compressor can be unbolted and set aside without disconnecting refrigerant lines. It's probably a weekend project.
 


dsturch1

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I'm not familiar with the 3rd generation nor do I know of a thread describing replacement of the primary chain tensioner & guide. If it's like the 2nd generation you have to remove the cooling fan, radiator, intake manifold, alternator, power steering pump and harmonic balancer to remove the front timing cover. The A/C compressor can be unbolted and set aside without disconnecting refrigerant lines. It's probably a weekend project.
Once all of those are removed, do I need to remove anything else? The sound seems like it is coming from the front side of the motor, so I am assuming this would be the chain tensioner in the front? The sound was prevalent after a warm start, but only when revved up from the 2500-3200ish RPM range. Still sound like it is probably the front tensioner? Do I need any special tools in order to do so?
 




75ohm

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Starts with the guides... at 143K my rear guide was in such a bad state I'm surprised I didn't lose the valves -- the chain was so sloppy it wore a moon-shaped groove in an adjacent bolt head. Had a local mechanic and friend pull the engine and replace them all with the updated kit. Choose your battles.
 


75ohm

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you may want to check the cats before swapping engines. i had the same problem and the cats were busted in pieces and causing noise under load.
The guts of it rattling around?
 




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