Replaced tensioners - still have slight rattle

[dreiwhit]

All,

My wife's 2002 Explorer (4.0 V6) developed the rattle on cold start. I replaced both the left and right tensioners, but the rattle continues for about 3-5 seconds on a cold start and then goes away. The rattle does not happen on a warm or hot start. The only thing I have yet to do is an oil change.

I thought that if it was a timing chain or cassette, the rattle would continue and go away? Am I wrong? Could this be the timing chain or cassettes?

Thanks,

Whit

 

[WaterBrat]

I have not yet replaced by timing tensioners, but a couple of ideas from reading other posts. When you start the Ex hold the pedal to the floor while cranking for a few seconds. This keeps the car from starting as it thinks it is a stuck throttle. It will allow some oil pressure to build up before the engine starts. Also did you prime the tensioners before installation? I read they should be rock hard. Let us know what you find.

 

[dreiwhit]

I have not yet replaced by timing tensioners, but a couple of ideas from reading other posts. When you start the Ex hold the pedal to the floor while cranking for a few seconds. This keeps the car from starting as it thinks it is a stuck throttle. It will allow some oil pressure to build up before the engine starts. Also did you prime the tensioners before installation? I read they should be rock hard. Let us know what you find.

I did prime both of them before I put them in, and they were rock hard when I put them in.

I'll try holding down the accelerator pedal when I start it up.

Update: I held down the accelerator pedal for a few seconds while cranking it. I then cranked it up and had the rattling noise. I timed it rattling for about 85 seconds before I shut the engine off. This time it did not start.

Its due for an oil change, so i'm going to try that on Monday morning to see if that makes a difference. I'm just trying to rule everything out.....

 

[08EddieCA]

I have a new reman motor with almost 700 miles. My (Motorcraft) tensioners were pretty loud in the beginning at start up. Dealer suggested I use a 10/30 weight oil for the first 3k miles to allow the tensioners time to settle/ratchet to the appropriate tension. The change in oil weight did make a big difference with start up chain sounds, FWIW.

Next oil change will be back to 5/30 weight.

 

[dreiwhit]

I have a new reman motor with almost 700 miles. My (Motorcraft) tensioners were pretty loud in the beginning at start up. Dealer suggested I use a 10/30 weight oil for the first 3k miles to allow the tensioners time to settle/ratchet to the appropriate tension. The change in oil weight did make a big difference with start up chain sounds, FWIW.

Next oil change will be back to 5/30 weight.

Thanks Eddie. I'll give it a try.

The only other thing that I can think of is that when I primed them, I used the only oil I had available - SAE 30 weight. After I put each tensioner in, there was a rattle for maybe 5-10 seconds and then the rattle went away. This was on a cold start. Leaving it sit for a while, then the rattle came back.

That's what has me perplexed. If it was a timing chain/cassette, the rattle should have never went away.

 

[08EddieCA]

I understand being perplexed, lol!! The first replacement engine I installed also made the same chain rattle on cold starts.

When I replaced the replacement motor (the first new motor had some issues) with the new motor I have installed now, it also makes the same chain rattle at cold start up. Still does but not as loud.

I'm starting to believe these 4.0 SOHC motors are just loud until proper oil pressure is reached and the motor is warmed up close to operating tempature.

 

[Drewmcg]

How many miles on her truck?

I've done the timing chain repair twice on these engines (not like others here, who've done 40 or so). In my limited experience, its not the tensioners that fail nearly as much as the guides/cassettes. Once they're fully lubricated the noise dies down, but this, to me, is an early sign that you need to r&r one or more timing chains/guides.

I don't see using anything but 5w-30 weight oil ever on this engine. Thicker is not necessarily better. I'm particularly wary of the 10w-30 dealer recommendation on the reman. Anything to make a noise go away makes his life better, but not necessarily the engine.

Slightly lighter weight (and cold) oil should lubricate the chain & cassettes quicker. Some like synthetic more for quicker flow rates at low temp (even for same rated viscosity). Note: If you pull a tensioner (not that difficult, especially the driver side) on a cold engine and it feels "rock hard"--then the noise has nothing to do with your tensioner. If its spongy/springy, you can prime it and reinstall it and see if you get the noise on cold start. If you do, then you know that cassette is the issue--but not necessarily that the tensioner is bad. New cassettes don't make that noise (in my experience) on cold start--or many of the hundreds of thousands of people who bought these 4.0 SOHC's would have been complaining from the get-go.

If the tensioner is okay, the only other option is guide is worn or chain is loose. And chains don't really stretch that much.