Checking a suspect timing chain

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  #1  
Old 01-21-17, 08:31 AM
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Checking a suspect timing chain

My 2003 Explorer won't start/run and I suspect a timing chain. From what I am reading it seems I have to at least pull the valve covers to see anything that indicates the timing chain(s) operation. Even this appears to be more involved than I have time for today.

Before I go pulling things apart, is there a simpler way to check?
 
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Old 01-21-17, 09:07 AM
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Someone else might prove me wrong, but I can't imagine any way of diagnosing a bad timing chain without accessing the ca shaft. Or it could be bad tensioners rather than the chain, but I believe that you would still need to be able to see what the camshaft is doing in relation to the crankshaft.
 
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Old 01-21-17, 09:19 AM
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Maybe Yukon could pull a Plug and see/feel if he's completing a compression stroke ?

Unlike Timing Belts, I don't recall Timing Chains breaking all at once; not skipping a tooth as they reach retirement.

When I've been around an engine with a broken timing chain, it made a lot of metallic noise, or was jammed up.
 
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Old 01-21-17, 09:24 AM
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I suppose if you think the chain is actually broken you could pull the plugs and see if you get compression on all the cylinders. Depending on where the cams stopped you might get compression on 1 or 2 cylinders, but not on all. Obviously you would have to turn the crankshaft to check. Not sure that's less work than pulling a valve cover.....

Not sure on a 2003, but if you have a large breather hose into one of the valve covers, pulling that might let you see enough to tell if the cam is turning....
 
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Old 01-21-17, 11:54 AM
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Thanks for the comments. My other vehicles are all older and smaller and have easy to reach covers or peep holes, but this one definitely does not. The nearest thing is the oil filler port, but I am not sure if what little I can see through it is a moving part or fixed. I did not see any motion there in any case, so need to look further. Anything beyond that means intake and a variety of tubes, cables, fittings and brackets just to get to the valve covers. Well, a few more hours of daylight, so maybe I'll keep going...
 
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Old 01-21-17, 11:54 AM
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If the starter will crank it (I'm assuming you've already done that trying to start it), just the sound to a trained ear will usually be enough.

I would be trying other possibilities because as already noted a broken timing chain (un;like a belt) is not a common occurrence.

Fuel pressure and spark, for starters. Maybe the inertia switch is simply tripped.
 
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Old 01-21-17, 12:07 PM
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A quick way to check would be to get a compression gauge which is fairly inexpensive, remove all the spark plugs and see what is going on in each hole.
I speak from experience when I say that a timing chain can jump a timing gear when it has a lot of miles on it.

I think it was GM that used fiber gears to reduce engine noise and created a timing chain replacement industry!

Edit:
Opps!: I see a compression test was already suggested.
 
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Old 01-21-17, 12:25 PM
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Yes; and on a cooled off engine (which won't even start) you can use your thumb to check for varying pressure in just one cylinder; WITHOUT worrying about the precise PSI.

That'll be enough to verify that the camshaft is still being rotated by the Timing Chain, and that at least one lobe is opening and allowing valves to be released and closed.

If that Camshaft and Timing Chain is functioning well enough for that single test, and baring any noticeable acute and recent damage to the engine, I think you'd be safe in concluding that the other cylinders are being dealt with similarly, and that the Chain is not broken . . . . maybe stretched, maybe worn; but not broken !

Just a thumb !
 
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Old 01-22-17, 07:19 AM
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I don't think it's timing chain.
It will be rattling or making cold start slapping noise. Both are pretty loud and noticeable.
It all needs to start with basics:
air
petrol
spark
timing.
"I think it's timing chain" simply does not work without eliminating ALL the usual suspects first. Only leads to haphazard guesspairs and tossing money at it.
 
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Old 01-22-17, 08:35 AM
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"My 2003 Explorer won't start/run and I suspect a timing chain."

That is a very precise statement to make without telling how you came to that conclusion ....
Why do you think the chain is bad/broken ??
 
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Old 01-22-17, 11:05 AM
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  #12  
Old 01-22-17, 02:48 PM
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First, let me make sure I understand, as I never quite got the hang of cam timing... If no cam rotation, then most of the cylinders will have no compression because one or other valve is likely to be partially open? It may be one or two cylinders are fully closed and would show compression? Not sure if I can reach the spark plug hole conveniently, but may look into it next chance. I do have a compression gage somewhere, which actually may be simpler. I will mention that with the air cleaner hose off the intake, I did get some suction, if that means anything in and of itself.

History: last 4 July I got an emergency call from my daughter who was almost home from wherever saying the car stopped and would not restart. Been sitting since, until yesterday. Fuel pressure checked, cranks over fine (when I keep the battery recharged), no current "crunching" noises. Did ask her yesterday if she remembered any noises when it happened. She said it made some grinding sounds and then quit. Getting good fire on #1 plug, but didn't check others.

Discovered that this engine has four timing chains, and the plastic guides apparently have history. This makes it easier to speculate as it has something like 254,000 miles on it.
 
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Old 01-23-17, 10:52 AM
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"speculate" is the key word. You read my post #11, didn't you? Btw, it is good it has 4 chains instead of one VERY LONG. And those are good chains. Stronger design.
Why does it seem you have your mind set on timing chain and do not want to look into more plausible options? Not saying it is not the cause, simply saying - it's likely the last on the least. Ford was always plagued with electrical issues.
That is a 4.0L V6?
Just trying to figure if it's interference or not... it's not on the list.

• 2.5L V6 Non-Interference
• 3.0L SOHC Interference
• 3.0L & 3.2L SHO Non-Interference
• 3.3L Interference
 
  #14  
Old 01-26-17, 06:14 PM
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Yes, 4.0L, V-6. Since I likely am going to sell it shortly, it had occurred to me that an interference engine would be, um, disappointing if it was the chain.

Not set on it. It's just where I had landed for the moment. Was just asking for a simpler way to check and eliminate. Won't have a chance to do the compression check until next week now, though.

Forgot to mention, borrowed a code reader but it showed no codes at all. Thought it strange. Does disconnecting the battery erase codes? Will have to borrow it again to follow up.

Did verify fire on all plugs, though. Since electronic, is that dependent on cams or crankshaft signals? As I mentioned, fuel pressure at the rail tests good. Way to test injectors? What might be next in electrical checks?
 
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Old 01-27-17, 06:19 AM
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I don't believe the 4.0L SOHC is an interference engine so a timing chain failure won’t bend the valves. But it would create a pretty expensive repair for you, even if you did it yourself.
 
  #16  
Old 01-28-17, 06:47 AM
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Thanks to those suggesting the compression test. Checked one cylinder on both sides and got zero compression on both. Just have to decide now about repairing...
 
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