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How to: SOHC V6 Timing Chain Inspection & Repair

MNT2007

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2007 Mercury Mountaineer 4.0L

Thank you for pointing out the correct bank for cylinder No. 1. I had just recently done some work on my Chevy pickup 5.7 where cyl #1 is front driver side. Without even thinking to check it out I assumed the same for this engine. I had previously decided to try replacing the hydraulic tensioner on the left head...no change, although the old one was maybe slightly sticky as compared to the new one. It probably makes more sense now to at least pull the right one and check it out, in case it may be seized or otherwise compromised, at least to try before opening it up?
 


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2000StreetRod

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replacement tensioners

I advise against replacing the rear tensioner unless you're prepared to (immediately after) pull the engine to replace the cassette. If the cassette guide is broken there may be pieces lodged in the head that may move when the tensioner is removed. Also, in the last couple years replacement tensioners (even OEM) have weaker springs than the old original tensioners. I used to recommend replacing the tensioners every 75K miles but not anymore. The springs only matter when oil pressure is low. To my knowledge there is no significant piston/bore wear problem in the stock tensioners resulting in excess oil leak and reduced tensioning. Replacing the tensioners will probably only possibly correct a cold engine start rattle.

As I recall your valve covers are not that difficult to remove and if you use some gasket sealer there should be no leaks if you reuse the cover gaskets. I suggest visually inspecting the cassette guide rather than replacing the tensioner.
 




MNT2007

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Thanks 2000StreetRod.

If I have a failed rear cassette/guide assembly, and my obd codes indicating cylinder 1 misfire (sometimes; seemingly not constant), could this happen even if my right side chain has not slipped? Also, would I not also expect to see misfires on cylinders 2 and 3 also? Thoughts?

Thanks,

Jeremy
 




2000StreetRod

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cylinder 1 misfire

I suspect the PCM monitors cylinder 1 more than the others because it is used for spark and injector timing. As I recall when my rear cassette guide was broken I did not have any reported misfires.
RCasset.jpg

I was in the middle of a custom tune involving multiple WOT pulls to max RPM but my chain did not slip.
 




ef2764

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The saga continues

So I just finished replacing my front tensioner for the second time. When I went to start the engine back up I have what sounds like a rod knock coming from the front left bank. I pulled the valve cover to verify everything then reassembled the intake and ran it without the valve cover to watch what is going on. Chain runs smooth all the valves and rockers seem to be functioning fine. I tested the oil pressure and I have 50 Psi at idle so that isn't the issue. The tensioner is staying steady and not bouncing. I have no misfires and no engine codes.

Anyone have any final thoughts before I push it out in the street and burn it?
 




2000StreetRod

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hydraulic lash adjusters?

Does the "knock" sound like its coming from the upper part of the head? The oil in the hydraulic lash adjusters will frequently drain so there is valve clatter when the engine is started. It happened to me. It usually requires driving at cruise for 20 or 30 minutes for the lash adjusters to refill with oil.
 




ef2764

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Knock

Yes it is a wicked knock in the top end. What i was thinking is that when I was cleaning the plastic cheese gratings (from the guide) out of the heas I used brake cleaner. Then like a dumba$$ I didn't re-oil everything. I oiled before I put it together but I'm thinking something is sticking. I'm not used to working on OHC motors so I am not familiar with what the rocker arm lifter combination is supposed to do up there. I'll try to take a video of it later and post it.

I'm thinking of dumping some marvel mystery oil in the head to see what that does
 




Rick00100

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2004 4.0 timing chain cassette replacement.

I'm in the process of replacing the front timing chain cassette using the procedures outlined in this thread. I did not use the tool kit. On a side note, the lower cassette retaining bolt will not come out through the hole in the primary chain sprocket. It is a flanged bolt. Easy enough to turn and rotate to slide it from behind the sprocket but an absolute bear to get lined back up and screw back in. I got every thing bolted back up with all my marks lined up and thought I was on the home stretch. However I noticed that there seem to be a lot of slack chain on the lower side near the camshaft sprocket. I hand rotated the crankshaft and of course this took up all the slack. I am concerned that this slack could have somehow messed up the cam timing. Does any one have any experience and/or an opinion on this?
 




2000StreetRod

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check the timing

Around 2004 Ford changed the jackshaft front sprocket making it very difficult to remove the left cassette guide lower mounting bolt without removing the jackshaft sprocket. Ford also changed the head or block casting making it very difficult to remove/install the front cassette guide without removing the head.

If you have successfully replaced the cassette guide without removing the head I suggest that you check the timing. One of the advantages of using the timing tool kit is the precision tensioner keeps the chain taught. The spring in the standard tensioner is not strong enough to keep the chain taught.

I suggest that you rotate the crankshaft clockwise until piston 1 is at TDC on the compression stroke.
TDCPntr.jpg

Then check the traction side of the chain (outboard) to see if taught. If not taught, use locking pliers applied to the camshaft and rotate the camshaft counter-clockwise slightly to taught the chain. Then check the timing. The slot at the end (firewall) of the camshaft should be below the axis of the camshaft and parallel to the head surface that mates with the valve cover.
cam1.jpg

You can use an allen wrench fitted in the slot and measure the distance from it to the head.
AllenL.jpg
 




Rick00100

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Thanks will do.

Worst case scenario, if the Allen wrench is NOT parallel to the head do I loosen the cam sprocket and line the Allen wrench properly the re tighten the sprocket bolt?
 




2000StreetRod

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why replaced?

Why did you replace the front cassette? Was the guide broken? Was the engine still running properly before disassembly? If the engine was running properly then the timing was probably correct and as long as you didn't loosen the jackshaft sprocket retaining bolt the timing for the right camshaft should still be correct. However, it is probably a good idea to check the right camshaft timing in addition to the left. It is more difficult to check because when piston 1 is at TDC the compressed valve springs on other cylinders in the bank tend to rotate the camshaft clockwise making the chain slack on the traction side.

If the right camshaft timing is correct and the left is a little off then loosen the left camshaft sprocket retaining bolt, rotate the camshaft to the correct position and then tighten the camshaft sprocket retaining bolt while making sure neither the crankshaft or the camshaft rotates. Have you already installed the front cover and the harmonic balancer? If not, it will be difficult to accurately determine TDC and difficult to keep the crankshaft from rotating.
 




Rick00100

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Front cassette

Both the front cassette and the primary chain tensioner were destroyed. The cassette had no plastic left on the outboard side and the primary tensioner had zero plastic left on it. Actually I had reinstalled the valve cover and the upper intake manifold and was about to replace the timing chain cover when I started to over think the slack chain issue. Trust me I do not relish the thought of having to get those back two bolts on the manifold off again.
 




ICoull

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Caution about the harmonic puller bolt size

A crankshaft balancer puller is required to remove the balancer. Do not attempt to use a gear puller. A gear puller will damage the rubber like material between the inner and outer sections of the balancer. Crankshaft balancer pullers usually come in a kit that includes various diameter and length bolts to attach the puller to the balancer. Because of the depth of the balancer the standard puller kit bolts will be too short. They may be long enough to engage but will strip when force is applied to the center puller bolt. Suitable bolts are M8-1.25 of 90mm or 100mm (preferred) length. Some members use the stud bolts that attach the A/C compressor to its mount.

My 2003 Explorer 4.0 SOHC does NOT have M8 x 1.25 threads in the harmonic balancer. The A/C bolts shown in the picture worked fine; but on mine they are in fact 5/16 NC 18 threads. Using M8 x 1.25 bolts would 'almost' work but they bind up after a couple of turns and would likely strip out. On mine, the correct bolt thread would appear to be 5/16 NC 18 [same as the stud end of the A/C hold down studs shown].
 




nlareau

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Just wanted to say "Thanks" for all the information in this thread. I'm replacing the timing set due to the right side failing and you guys have saved me more times than I can count. :chug:
 




Frank trac

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I have an 05 4.0SOHC with almost 90,000 miles on the clock. Is this something I'm going to have to get fixed in the future? I don't have any noise problems as of yet and the motor seems to be running fine and always has. I've been vigilant about oil changes and my local Ford Dealer has done all of my service work except the most recent replacement of the air filter element and I also replaced one of the front wheel bearing hub assembly's and shock absorbers were all done by me. This vehicle is in my opinion very good condition and I'd hate to have to part with it for something stupid like timing chain guides. I read that Ford made engineering changes after 2002 and that my 05 should be fine. What do any of you think? Is this BS or what?
 




laker82

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Finished rebuilding last summer but did not put back on the road until this spring. First 600 miles were great, then lost power at 50 mph but drove it 10 miles home. Snapped right timing chain and main tensioner. All new parts, little baffled, just bad parts or something else. Which would have broken first ? Torgue was fine on all timing bolts and still ran on the left bank.
120 lbs compression in 1 and 3 cylinders did not test #2 as I did not want to chance a valve hit being untimed from broken chain. planning on leak down of #2. to check exhaust valve.
 




laker82

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[

2000StreetRod,
Reread your post at #117. The kit I bought to replace the broken Right chain included the 0012 kit. Is that kit only for earlier models than the 02 Vin E? Any theory on why the chain and main tensioner broke?
 




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Here's what I don't understand....why did all of my chains break at only 90k miles? Was it not getting enough oil?
 




2000StreetRod

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The plastic cassette guide assembly is the weak item in the camshaft timing. The chains, except for the balance shaft chain, are very strong and seldom break. Usually, one of the timing chains slips because there is inadequate tension due to a broken cassette guide. Sometimes a piece of the cassette guide will get jammed between the head casting and the chain causing the chain to break. Low oil pressure can result in weak tension from the hydraulic tensioner but I think that is uncommon. How many pistons have dings? If only three then only one of the camshaft chains slipped. If all 6 have dings then the crankshaft to jackshaft chain slipped. That is usually due to broken leaves in the spring tensioner.
 


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The plastic cassette guide assembly is the weak item in the camshaft timing. The chains, except for the balance shaft chain, are very strong and seldom break. Usually, one of the timing chains slips because there is inadequate tension due to a broken cassette guide. Sometimes a piece of the cassette guide will get jammed between the head casting and the chain causing the chain to break. Low oil pressure can result in weak tension from the hydraulic tensioner but I think that is uncommon. How many pistons have dings? If only three then only one of the camshaft chains slipped. If all 6 have dings then the crankshaft to jackshaft chain slipped. That is usually due to broken leaves in the spring tensioner.
3 have dings on passenger side. Just noticed that my jack shaft bearing has scratches in it due to debris
 




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