Quick Timing Chain Question

[jonboyb]

I know there's a million posts and I've read them...but never found one quite like mine. I have a 2003 Mountaineer 4.0 2wd I picked up from my FIL about a year ago as a beat around vehicle...only has 135k miles. Been driving it for maybe 6-8 months now daily to keep commute miles off my truck. A few weeks ago, I had the passenger door open when I cranked it, and at startup heard a distinct rattle...for just a millisecond at startup. It's silent at all rpm's...none of the horror stories on the 2500-3000 rpm rattle. It will not make the noise again unless the vehicle sits for an extended period...like 3-4 days or more, and you'd never notice unless the doors are open or standing outside the vehicle when cranked.

I'm certain it's timing related, I can let it sit a few days then do the full-throttle oil priming procedure before start-up and it's silent. Seems like the tensioner(s) just bleeding down after extended sitting. I'm an avid mechanic and normally I'd just tear in and replace the entire timing component suite, but we all know this engine is a bear to get to the rear components, and trying to diagnose WHERE the rattle is when it only does it for a split second on start-up after sitting for days is near impossible. Buying factory parts not exactly cheap either.

Am I overthinking this....considering its just a beat around car and only doing this after long term sitting? Had I never cranked it with the passenger door open....I wouldn't even be posting this....LOL. Thanks.

The only other thing I might add is my FIL's dealership had been using 5w-20 in it for as long as his records show (he bought new) but he had it changed religiously at 3000 miles. I did put it back on a diet of 5w-30 Motorcraft when I bought it from him at about 125k miles.

 

[Tech By Trade]

Sounds normal. you could try swapping the tensioners but it probably wont get any better. The spring in the tensioner is supposed to hold it tight until the pressure builds but they wear out over time. OEM is the best replacement quality. The only problem with replacement is the risk of shattering the plastic guides due age and the increased pressure of the new tensioners. Other option is a preoil system or like you have been doing, prime it when it sits for a while. I run 5w20 synth. The thinner oil should be able to get pressure up quicker, only problem is it will drain quicker. If someone built a steel backed guide for these things they would be a bullet proof engine.

 

[Number4]

You can try just swapping the tensioners. Just make sure you prime them. The 4.0 is known to just grenade when it comes to timing.

 

[Drewmcg]

I'm not sure why the two tensioners are not identical, but they're not. I'd recommend you buy an OEM bank 1 tensioner and a replacement OEM gasket (washer). Actually, get two washers, since they're super thin and easy to bend/break. Be prepared for some leakage/tweaking after you replace until you get that washer centered and the new tensioner torqued right. Be sure you've got the new tensioner primed in a large container of oil so its rock hard before you thread it in.

And for gosh sake stick with 5w-30 oil as recommended by Ford. It should give better protection to the chain/cassette, and should be less likely to bleed down out of the tensioner (your apparent problem).

I suspect you know this already, but Motorcraft filter is probably your best bet for anti-drainback performance (though Wix gets rave reviews, too).

You're not overthinking this. If that passenger side cassette goes, it can cost you a whole engine, or a re-manufactured head, and you need to pull the engine for repair. Its a big deal.

 

[boominXplorer]

Wix (napa gold) version of oil filters have the anti drain back valve with a better filter material than the Motorcraft 820s. It does come at the 2x the price.