4.0 SOHC Chain Tensioners
 

Hey guys, you may have seen my thread in the other ranger forum. Basically, I have an 06 with around 90,000 miles. I had an intermittent timing chain rattle at startup, mostly when it was pretty cold and never more than a second. I replaced both front and rear tensioners with genuine, "new" rotorcraft tensioners. I say "new" because the rear tensioner has blown out in three months... I pump it full of oil, I can squeeze the tensioner once and all of the oil will come out. Today, I re-installed the old tensioner because it still holds oil pressure when primed, and the rattle is not as bad. Am I doing something wrong, is the guide and cassette worn beyond repair or what? When I installed the "new" tensioner, the rattle was quiet for a day or two but as it lost it's prime, the start-up rattle got louder and louder. Any thoughts or ideas are welcome.

Once you have the rattle noise the guides are damaged, so you will need to pull the engine as it gets worse.

The fault with the 1997 to 2003 4.0l SOHC tensioners was the springs inside, they would loose tension or break over the years allowing the long chains to bang against the guides on start up, guides would be damaged and even with good oil pressure the chains would start to rattle, even after startup.

You shouldn't be having this problem with 2006 4.0l SOHC engine, so there may be an oil pressure issue, which is why the "new" tensioners didn't correct the issue.

Ford quit using real oil pressure gauges back in the late 1980's, they use an oil pressure switch on the engine, under 5psi it is off, over 5psi it is on
So oil pressure gauge is either off or on, any changes in gauge level is electrical and not related to oil pressure unless it drops under 5psi.

I would install a temporary oil gauge in place of the switch and see what your actual oil pressure is, cold and after warm up.
Could be your problem came from failing oil pump or a bad oil filter in the past

Some have reported synthetic oil quieted down the chains for awhile.
But I think in the long run you should plan on pulling the engine

I think that's just as reasonable a hypothesis as mine about not getting a new tensioner. It is very frustrating, as I know this engine is supposed to have the issues fixed, or at least far fewer issues. I purchased with 81,000 miles in August, and the rattle started to develop as the weather got colder. Any idea where the oil pressure switch is located on the block?

Oil pressure switch will be on drivers side, lower block, towards the front, just in front of motor mount.

I don't think the tensioners are designed to hold oil pressure when they are out of the engine. They have a spring in them that is supposed to provide some tension at start up and then as the engine oil pressure builds up, the oil pressure also builds up in the tensioner to provide more tension on the chains.

I replaced my tensioners at around 100K miles as preventative maintenance and at nearly 230K miles they are still working well. I know my guides are worn at this point but I am getting no indication that I need to replaced them yet.

Yes, +1 ^^^

These Tensioners work much like hydraulic lifters do
They have springs inside for start up tension then the oil pressure takes over

The 1997 to 2003 tensioners had a problem with the springs, loosing tension or breaking
So like a collapsed lifter when they failed

I figured as much- honestly, I'm scrambling to try to find a solution before the guides are too far gone and the timing has to be done. In case my last gasp install of one more different new tensioner fails, I was quoted $1400 at a trusted mechanic for the complete timing job, parts and labor.

What really frustrates me in the intermittent nature of the rattle- last night and this morning, around 30 degrees, zero rattle on startup. Yesterday afternoon, around 40 degrees? Light rattle.

I tested my oil pressure in my shop- around 7 psi cold idle, 5-6 psi warm, and 43 psi at 3000 rpm.

I do believe that the "new" tensioner was used, and has a very worn spring- whether or not that is the root of why the rattle got WORSE when I installed it is yet to be determined. The original one that is back in the block is doing a fine job, just a light intermittent rattle on startup here and there.

You can do what I do each morning on my almost 400k 4.0l OHV
I use the Clear Flooded Engine routine to pump oil thru the engine BEFORE I start it up

Turn key on
Press gas pedal down to the floor and HOLD IT DOWN all the way
Crank engine over for a few seconds, it should NOT start, fuel injectors are off, thats Clear Flooded Engine routine
Then release gas pedal and start engine

If engine fires/starts with gas pedal to the floor then you need to do "Throttle cable mod"
Google: ranger throttle cable mod
Very simple fix

I may try that this afternoon- the throttle cable mod was definitely one of the very first things I did on this truck lol. The new Motorcraft tensioner should be here tomorrow or Friday... we'll see what happens.

Unbelievably, I am 99% sure the new tensioner solved the startup rattle- I know the guides are worn, but not enough to have any kind of rattle. I'll cross that bridge when I come to it.

This new guide definitely had the stiffest spring of all of them by far- AND it shipped in a bag sealed from the motorcraft factory, stamped "made in Italy". The "new" one I installed in late October came in a beat up motorcraft box and was dinged up. In any case, I'm going to keep my fingers crossed for a little bit. But I am confident that this has solved the rattle.

You guys aren't going to believe this, and I definitely feel like an idiot.

I did in fact have a very, very light rattle which was fixed when I changed the tensioners. However, this mysterious rattle continued.

A couple nights ago, I woke up in a cold sweat. I remembered that the bendix on the starter can sometimes rattle on the flywheel if it does not disengage all the way or quick enough. So I held onto the starter when my buddy started the truck, and lo and behold, I can feel the rattle within the starter. I pulled the starter off, and I can see the wear in the teeth of the bendix. Installed a ford shim, which is just a spacer, and boom. Absolutely no noise. That's why this rattle was intermittent- when the truck was hot or stone cold, there would be no rattle because the truck would get going slow enough for the bendix to withdraw. But every once in a while, I would hold the ignition for a couple milliseconds too long, and the flywheel would be spinning too fast for the bendix to withdraw and disengage completely, causing the rattle. Unbelievable.

Good work

Thanks for the update and fix

My ranger does same thing. I doesn't do it every time, but sometimes, and it's pretty noisy when it does, i have 202k with no engine work at all.