The rattles of a 2002 4.0 V6 SOHC 4x4... | Ford Explorer Forums - Serious Explorations

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The rattles of a 2002 4.0 V6 SOHC 4x4...


Active Member
February 1, 2008
Reaction score
City, State
Jackson, TN
Year, Model & Trim Level
2002 4WD
Okay, I have been here for a while and thought I knew what I needed to about the "death rattle" in the SOHC 4.0 V6. However, a recent thread here -> has thrown me off. Can we get clarification once and for all on the rattles of a 4.0 SOHC V6 WITH the 4x4 jackshaft?

Here's what I thought was correct:
  • Number of chains: 4 (primary, jackshaft, two cams)
  • Number of tensioners: 4 (one on each chain)
  • Number of cassettes*: 2 (one on each cam chain, right below the head
Chain locations:
  • Front - (Cam chains, primary chain)
  • Rear - (Jackshaft chain)

* Now I am hearing there are cassettes in the rear?

Symptom: Rattling at 2500-2800 RPM, no rattle at start up
Probable issue: Primary chain tensioner failure or jackshaft chain tensioner failure

Symptom: Rattling at startup
Probable issue: Camshaft chain tensioner failure (stops rattling when oil pressure builds up)

Symptom: Engine interference
Probably issue: Camshaft chain failed (no other chain can cause this, correct?)

Difficulty of changing tensioners:
Primary chain tensioners: Engine in, front timing cover off
Camshaft chain tensioners: Special ford timing tool, timing cover off
Jackshaft tensioners: Engine out

What do I have wrong here? I suspect quite a bit. Needless to say, I have run over 60K miles with a rattle that has not changed, so I am trying to determine what is broken and how easy it would be to fix. I called my shop a few months ago and they said it wasn't worth it to pull the enginer to replace the tensioners that were broken. They said they have never seen a SOHC 4.0 come in that had that problem or even a worse problem. Not that this is a bad shop, they are probably the best in town.

Sorry if this is a repost, flame me if you must. I will gladly take an internet flogging to get the correct info out there and possibly stickied.

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Timing chains

The timing chains for a 2WD are:

Primary (crankshaft to jackshaft) located in the lower front
Front camshaft (jackshaft to camshaft) located upper left
Rear camshaft (jackshaft to camshaft) located upper right

In addition a 4WD has a balance shaft chain located in the lower front right

All of the above have tensioners. The camshaft tensioners use spring/hydraulic pressure. The other two use leaf springs.

A cassette is the combination of camshaft chain, guide assembly and sprockets.

A failure of the primary timing chain or either camshaft chain can cause the valves to collide with the pistons. If the primary chain fails collisions can occur on both banks.

Replacing the rear camshaft tensioner requires removal of the inner fender flap.

Replacing the front camshaft tensioner requires removal of the upper intake manifold of 2nd Generation but may not on 3rd Generation.

Replacing the primary chain or tensioner requires removal of the front timing cover.

Replacing the front camshaft cassette requires removal of the left valve cover and front timing cover.

Replacing the balance shaft tensioner and guide requires removal of the front timing cover and I believe the upper oil pan.

Replacing the rear camshaft cassette requires removal of either the engine or transmission.

Since you have run 60K miles with the rattle at a steady state level (correct me if that is not the case), it may be worth it to try and reduce any new wear with a cheap remedy. In my 2002 V6 I had the timing chain rattle under some load conditions in the 2200-3000 RPM range.

I found that when I used an oil with a high HTHS (high temperature high shear) value the rattle was reduced to almost zero. There was a very dramatic difference in the rattle magnitude and frequency of occurrence between conventional oil 5W-30 (Walmart brand Supertech and Pennzoil Yellow bottle) and either Amsoil 0W-30 or German Castrol Syntec 0W-30.

I would guess that Mobil 1 5W-30 ESP if you can find it or Mobil 1 High Mileage 5W-30 would both work too as they have a nice high HTHS (esp higher). Note that ordinary Mobil 1 5W-30 is a bit lower HTHS than any of the oils above so while it might reduce the noise, perhaps not as much as the others listed above.

I am currently running German Castrol Syntec 0W-30 and the rattle is very well controlled. It is certainly worth a shot to see if motor oil selection can help with your issue, as it has mine.


Rumpledoll, oil is not rally the answer here. It may mask the noise, the the mechanical parts that have failed are still there. STP oil treatment will quite the noise for about 1500 miles. I have tried a straight 40W oil and it made no difference. I can only guess the STP has some type of tackifier in it that makes the primary chain not flop around as much. Again, I would not rely on oil as a solution, failure will be just as imminent.

Oil viscosity & chain rattle

The left and right timing chain tensioners are a spring loaded hydraulic design. Increasing the viscosity of the engine oil will increase oil pressure resulting in greater timing chain tension and reduced slop. STP oil treatment increases oil viscosity. However, the thicker the oil, the longer it will take for oil to reach the timing chain components at engine start. The chains are more likely to slip any time the oil pressure is low since the spring pressure is much weaker than the hydraulic pressure.

I agree with bluestream1 that you should not rely on oil viscosity to prevent timing chain slip and the likely resulting engine damage.

So What is the best oil and additive to use?

I have 3 Explorers with the 4.0L SOHC Engine. 100 to 120K

I have been using 10-40. I think Ford recommends 5-30.

My question is this. What is the consensus on the proper oil and additives to use?

Should I switch to Synthetic or Not?

What brand/product? ????



I would use 5-30 or 10W30. The 10W40 is a bit thick for winter use. Also 10W40 has a lot more VII that can shear down the oil over time. Synthetic is good for long drain intervals, flows better at start-up and in cold weather, and will take high heat better than conventional oil. If you do 3-5K oil changes it is not going to do anything. It won't help your chain issues. This winter I will be using 5W20 for the fist time. Keep in mind that oil does not get very hot in the winter and the 5W20 will be thicker that a 5W30 that is used in the summer.