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03 explore sohc driving me nuts!


April 16, 2012
Reaction score
City, State
harrisburg, pennsylvania
Year, Model & Trim Level
2003 explorer xlt
ok this is my first thread in this forum i wasnt making out too good on the other ford forums i belong so i signed up here.. Hi everyone!
Here we go..
I just bought this beautiful 03 expy with 4.0 sohc with 106k on it. the fella i bought it from told me upfront his mechanic determined it needed a new engine because the timing chains are bad. He started it right up for me and other than a brief clatter that went away immediately it was a quiet smooth engine. he told me showed up worse at 2500 2700 rpm under load sounded like pinging. i bought it for very little money i thought at 1500. i towed it home
after alot of research i decided to try new tensioners front and rear. no change..clatter at cold start then smooth until you rev it to 2700 then a metallic pinging could be heard. I finally got time enough to get her in my garage and open the engine up. I found the left cassette in good order no pieces missing but the rear cassette was gone! so bad that the chain had been slapping the upper guide bolt and had worn it flat. I pulled the engine and ordered a new rear cassette from the local ford dealer. I have built loads of ford engines over the years including degreeing camshafts on race cars. so i figured this would be something i could do. I didnt have the extra cash to buy the otc kit. so i made my own camshaft lockdown plate by welding up flat stock parallel to the head with the slots on the low side. i compared it to left side and tool i made fit perfect at top dead compression #1. my kit came in so installed the tool on right cam and used the flywheel to hold the crank solid by using flat stock bolted to flywheel and block. no movement either way. i changed out cassette following all the posts i could find step by step. and tightened everything down, also i made my own dummy tensioner tool by using the old tensioner i welded the plunger to the body. i rotated everything afterword several times to be sure of my work i double checked the camshafts with my tool and everytime they were dead on. so i put the engine back in. fired her up and UGGH it sounded worse than it did with the old cassette in. it had a steady knocking in the right rear terrible. i removed the valve cover and checked my timing again..dead on. and the chain looked taught. so i thought maybe my tensioner hadnt filled with oil yet. so i buttoned it back up and fire it up. still knocking after idling a minute or so.
the only thing i came to is when i was installing the new cassette i screwed the dummy tensioner in only about 1/2 way cause i figured that was enough tension on the chain. after some thought i realized that by not tightening it in the whole way had compromised my cam timing with the jackshaft. so i just redid everything tonight by screwing the tensioner in the whole way it moved my camgear backward about 1/8 inch so that could be it? and im gonna wait till tomorrow to fire it up. does anyone have input i would be glad to hear what your thinking. sorry for the long post but i wanted let you know what my deal is. do you think it could be the front chain/s causing the rear chain issues. bear in mind i never removed the front timing cover cause i figured with broken rear guide that was the problem. thanks all

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primary tensioner?

Often mid range engine speed rattle is associated with a failed primary (crankshaft to jackshaft) chain tensioner. Your 3rd generation has the improved 6 leaf tensioner but they still can fail. I would have pulled the front cover when the engine was out to replace the rear cassette.

Not tightening the right tensioner would make the camshaft off a few degrees which would make the crankshaft off twice that. It might be enough to affect performance but should not result in clatter. Are you sure that #1 cylinder was on the compression stroke (and not exhaust) when you timed the right camshaft? It is possible to time the camshaft 180 degrees off - the engine will start and run but not well. The camshaft position sensor "nub" on the left camshaft should be above the camshaft axis when #1 cylinder is at TDC on the compression stroke.

Hey streetrod! thanks for the input. do you realize in the last 3 days of my posting on diffrent forums you have been the first throw your hat in the ring!
ive read many of your posts over the last few days since starting this project you are quite the guru of the 4.0 sohc engines. glad to have your input.
Yes on engine timing i can assure you. i checked and double checked.
first before i tore anything down i brought the harmonic balancer up to zero.
then i checked both cam relationships. the right side(rear cassette) both notches were on low side of cam parallel to the head. left side exactly the same with camshaft position sensor nub up just inside the cove.
I think you probably correct on 2 counts first off i should of had my a@@ kicked for not removing the timing cover and further inspecting lower shafts and chains. and i do believe the noise is coming from the jackshaft chain cause she really jingles at 2500 to 2700. i ran it this morning and not much change engine performance is quick and smooth with no missing etc..
im gonna let her cool down and tear back into it. i just really thought when i found that rear guide in a million pieces that was the problem for sure.
thanks for your input. im sure i will be needing your help soon.

ok.. i just finished up for tonight. i pulled everything back off the motor, including intake, valve covers, all the upper stuff that ive removed for the
4th time now (im getting pretty good at) lol..
i removed all the necessary stuff to get the timing cover off. wow just like you thought the primary chain was dangling on left side looking at it.
there was a plastic gizmo with about 6 layers of spring steel that fell down and hung up on a bolt. what a joke. i cannont believe in this millenium thats the best our Blue Oval boys can do, Henry Ford would be ashamed..
looks like the little tensioner on the balance shaft took a dump too. Im just gonna get a complete kit like i should have from day one. and do all the chains and tensioners the right way. even though the front cassette looks good who knows when that bad boy will give up too.
I will keep you all posted on the progress.
I came up with a way of keeping the balancer tight while breaking the crankshaft bolt loose without the special tool. i wrapped a chain around the balance behind the belt area and put a bolt and washers through it and drawed the chain tight and took the loose end up to a head bolt where the alternator bracket goes. worked great the crank didnt move a bit backward i intend to implement this for tightening too. Is that crankbolt a torque to yield bolt also? :eek:

Hmmmm.... Interesting. So it seems as though it was the front crank to jackshaft tensioner causing the pinging all along. But I can tell you now that with the rear guide completely missing, that camshaft would have been over 10 degrees retarded relative to everything else, causing performance problems.

When I snapped my rear guide after I hydrolocked my engine I retimed the camshaft to suit instead of replacing the guide. I found the original tensioner had enough travel in it to fully tension the rear timing chain without the guide.

Be sure to remove the oil pan and check the oil pickup, the rear guide can break up into plastic squares that are small enough to jam up inside the oil pickup. This will cause a drop in oil pressure at higher rpm's due to the restricted oil flow.

Oh, and yes the crankshaft bolt is of the torque to yeild type.

balancer holder

. . . I came up with a way of keeping the balancer tight while breaking the crankshaft bolt loose without the special tool. i wrapped a chain around the balance behind the belt area and put a bolt and washers through it and drawed the chain tight and took the loose end up to a head bolt where the alternator bracket goes. worked great the crank didnt move a bit backward i intend to implement this for tightening too. . .

I've used a chain as a holder for other applications but never thought to try it on the balancer. I bought an inexpensive chain wrench but its difficult to hold the 1/2 inch drive breaker bar attached to the chain wrench and the torque wrench at the same time.

I tried an 18 inch pipe wrench but the jaws aren't deep enough.

You may have solved my ongoing problem.

It's important not to damage the teeth on the balancer that the crankshaft position sensor detects.

I used a Load strap wrapped around the balancer and hooked into the front diff housing to hold it in place. I used a cheaper torque wrench to undo the bolt as I found that the skinny breaker bar handle was hell to push on in such a tight spot. I thought it worked quite well indeed.



yeah the chain trick worked great today at the junkyard too. i was getting a better balancer mine had drycracks in it.

Ok about the explorer.. i put the new tensioners on up front.
I dont get and pinging at 2500 to 2700 anymore.
However.... I still have a nasty knocking coming from the right rear im telling you it is driving me crazy. ive had this motor apart 5 times now hunting the problem..
The rear cassette is brand new Ford item. heck it cost me 130.00 for just that.
The knocking is very reminisant of a dry lifter. its a hollow knock.
Now bear in mind this engine ran smooth before i messed with the rear tensioner. it only had the pinging at higher rpms.
now i got rid of the pinging and still have this nast knock. Im not really sure it is the rear cassette related. im gonna open her back up tomorrow and have a look at the lifters and check the followers. somethings making that noise
I did notice when i was using the ratchet to turn the engine over and listening and watching things there were times when the rear chain would be tight and times it was rather slack. is that normal ?
I know this knock didnt just come out of no where.
something else i wanna share too. when i removed the original cassette i couldnt hardly get the chain and sprocket to come out i had to carefully move it around something was catching down inside i couldnt see.
after i got it out i stuck my finger up in the lower jackshaft access and it felt like a bump sticking down. after mirror work and flashlight i realized it was the torx head long bolt sticking down through the head and protruding into the cassette cavity. after putting everything back together i did reinstall that bolt i still really dont know what that bolt does but i figured it had a job.
is that an alignment bolt for the guide setup?
i dunno just putting that out there.
thanks for the help guys

The Torx bolt you are talking about, the lower one near the rear jackshaft sprocket holds the rear timing chain cassette at the scissor point.

The larger bolt at the top holds the top of the guide part of the cassette.


"Picture courtesy of StreetRod"

If I read your previous post correctly and you did not install the timing chain cassette with the lower torx bolt at the scissor point, then I would have to say that would be what is giving you the dull knocking sound, metal cassette on the side of the head or the block perhaps.

As for the chain being tight or slack sometimes. If you wind the crankshaft clockwise the oil pressure pushes against the timing chain tensioners. If you then leave it for a while, the oil pressure will eventually bleed off. If you wind the crankshaft in reverse the oil will move backwards away from the tensioners, slacking of your chain. This is normal.

Here is the amount of slack in my chain while fully slackend off with no guide, just by rotating the crankshaft backwards.



And this is what it looks like fully tightened, also with no guide part of the cassette.


valve spring pressure

As you manually rotate the camshaft only the weak spring pressure in the tensioner is pushing against the guide assembly since there is no oil pressure. During manual rotation the chain tightens and slackens because of the valve springs. That is normal. The valve spring pressure against the camshaft lobes sometimes opposes camshaft rotation and sometimes aids it depending on which valves are open.

When I reassembled my engine after replacing the camshaft timing components I had a noise that sounded lilke a stuck hydraulic cam follower. On a test drive I ran the engine up near 6,000 rpm and the noise stopped and never returned.

The green arrow in the photo below identifies the casting that receives the transmission to engine bolt. The red arrow identifies the barely visible guide assembly bolt below the casting.

I had trapped pieces of the cassette in the area marked with red arrows in the photo below.


I pride myself in mechanical ability im sure much as you all do too..
I take my time and try to be very thorough and neat and clean about what im doing around my engines. being in race car pit crew and being the engine man makes you this way. Heck ive been known to feel myself getting aggravated about something and just stop and start cleaning my tools down and neatening up my workspace and snap on tool cart.. that being said just wait to you hear this one!! im almost embarrassed to say it. but i want others to gain from my mistakes too thats what makes these forums stay alive and well..
If your familiar with the 4.0 sohc motor then you are aware of the hollow tube that runs across the top of the camshaft to oil the lobes.
that tube is not supported at all cam towers. apparently while i was in the building/removing/installation i must have leaned or put my hands on it to balance myself. if was bowed down to the point of striking the cam lobes on # 2 exhaust and intake. to the point of actually starting to make wear line in both spots i saw this with my dental mirror. i bowed it back up.
I actually sat down on my stool upon seeing this and laughed my A@@ off at myself in embarassment and achievement both at the same time.
I sure hope this helps someone. we should make a sticky about this issue as it is so easy to do. particularily if your strapping the engine down in your truck.
shes running now.. smooth as silk and what a learning experience
I thank you for the help.
Oh by the way i must confess!!!
I found this idea out by another fella who had the same knocking after installing new cassette in his engine. apparently he broke his tube and had to reweld it. I think you know of this instance. i believe you were part of his success. it was on this forum.
Thanks again.. Bob


Those oilers are rather fragile and the mounts are flimsy. If care is not taken when loosening the camshaft bearing cap bolts the mounts can break. Some members have found them broken when removing the valve covers. I'm glad you found the problem and it was a simple fix! Thanks for posting the solution. Hopefully your SOHC V6 will provide many more years of dependable service.

Well fancy that, Cam lobe hitting the oiler rail. Glad to hear she is purring like a kitten again.;)

Has anybody tried replacing a 4x4 SOHC 4.0 engine with a 2WD OHV 4.0 on an explorer? I heard somebody in an autoparts store say it was possible.