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4.0 SOHC Timing Chains

Jimmy Hoffa

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The previous owner of my '98 Explorer had the SOHC motor replaced at 85,000 miles due to timing chain failure. I recently confirmed this with a tag on the block just above the starter that stated the motor was built in 2004. My question is; would this newer motor have updated chains and tensioners that are less likely to fail? Mileage is now 178,000 and it runs great and has no noise or rattles.
 


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drdoom

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Still a ticking time bomb.
 




J_C

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^ Sure but if you look at it that way, all vehicles this age are for some reason. With no noise or rattles it could go another 100K... from what I gather most have the chains fail closer to 200K than 85K, especially a Florida vehicle where it's not starting very cold.
 




Flash

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You would have better chain guides but the tensioners would be much the same as always.

What happens is: When you first start the engine from cold it will rev pretty high to get the oil pressure up quickly.
Until the oil pressure picks up the timing chain tensioner is operating on spring pressure only.

If the spring in the tensioner is weak the timing chain will thrash around until the oil pressure builds and tightens up the chain.
When the chain thrashes around it destroys the plastic backed timing chain guide then no amount of tensioner replacing will save it.

If you do have the better, steel backed guides; and you should, at the first sign of timing chain rattle at start up replace the tensioners and you should be good.

You can take the driver's side cam cover off and see if the timing chain guide is steel backed.
 




imp

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You would have better chain guides but the tensioners would be much the same as always.

What happens is: When you first start the engine from cold it will rev pretty high to get the oil pressure up quickly.
Until the oil pressure picks up the timing chain tensioner is operating on spring pressure only.

If the spring in the tensioner is weak the timing chain will thrash around until the oil pressure builds and tightens up the chain.
When the chain thrashes around it destroys the plastic backed timing chain guide then no amount of tensioner replacing will save it.
If you do have the better, steel backed guides; and you should, at the first sign of timing chain rattle at start up replace the tensioners and you should be good.

You can take the driver's side cam cover off and see if the timing chain guide is steel backed.

Best description I've seen of those pesky guides! Thanks for that! imp
 




Jimmy Hoffa

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Thanks for the responses. I had considered selling it because IMHO the value is not high enough to justify replacing the rear chain and tensioner. I don't have an engine hoist and time to pull the motor.

The new motor now has close to 100,000 miles and recently developed a lifter tick at idle. I decided to start using Mobile 1 to quiet it and preserve the cam chains. The lifter tick stopped in 30 seconds but after 1,000 miles the main seal has started leaking. The leak is not terrible so I will add a quart of Lucas stop leak when the oil gets low enough. My plan was to continue changing the oil and filter every 3,000 miles but with Mobile 1. All factors considered, the additional expense of full synthetic oil is cheap insurance for a 4.0 SOHC.
 




J_C

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You don't need to change oil that often with mobile 1. What would improve lifespan more is moving to 0W weight so oil pressure builds up faster, but, now we're drifting into paranoid... no matter how well you take care of her, it doesn't stop another driver from plowing into you and totaling it.
 




Jimmy Hoffa

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I heard that quite a few engine failures occurred due to lightweight oil like 5W-30, which is what's recommended. Florida never gets cold so I've gone up to 10W-40.
 




2000StreetRod

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pre-oiler

Even with new cassettes and tensioners I had cold start chain rattle for a few seconds. The springs in the new tensioners are just too weak. That's why I installed a pre-oiler. With a pre-oiler the chains are always tensioned before the engine is started. It will be interesting to see how long (miles) my cassettes last.
 




J_C

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I heard that quite a few engine failures occurred due to lightweight oil like 5W-30, which is what's recommended. Florida never gets cold so I've gone up to 10W-40.

Where did you hear this? In general you'd want lighter weight oil to flow faster, build up pressure quicker cold, even if it's not very cold outside.
 




2000StreetRod

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decades ago

Many decades ago - before multi-weight oils - people living in harsh winter climates (like North Dakota) would put 5 weight or 10 weight oil in their engines so they could start them. The problem was that once the engine warmed up to normal operating temperature the light-weight oil would break down and the bearings would wear. The invention of multi-weight oil eliminated that problem.
 




XLTrunner

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2000StreetRod...is that "preoiler" you installed like what's included in Ford's kit #YL2Z9E473AA ? My '98 has 150K miles and, although I don't yet have the feared "rattle", I was debating whether it would be wise to be proactive and replace the tensioners before symptoms developed? Seems to me from what I've been reading, that once the noise develops, you have a short window of time to replace the tensioners before costly damage occurs. My luck, I'll either be on a road trip when it happens...or, it will be in the middle of January when I'll have to work on it in sub-zero weather.

And, are you saying the new Ford tensioners have weaker springs? Or, the aftermarket ones?
 




2000StreetRod

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pre-oiler

I installed an Accusump. See: Accusump installation in Ford Explorer . But in retrospect I wish I had installed an electric oil pump instead even though it requires drilling a hole in the lower oil pan for a pickup for the pump. An electric pump makes priming the engine with oil after extensive work much easier and allows for easy complete replacement of all oil during an oil change. I'm not familiar with kit #YL2Z9E473AA but will research it later.

Yes, the springs in the new OEM tensioners and aftermarket tensioners seem weaker than the original springs. I have only used OEM timing chain components because of their superiority. See SOHC V6 Timing Chain Parts Sources
 








Jimmy Hoffa

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That's why I installed a pre-oiler. With a pre-oiler the chains are always tensioned before the engine is started. It will be interesting to see how long (miles) my cassettes last.

Please elaborate. Is it a electric pump that pressurizes the oil system?

EDIT. I just saw your previous post with the info. Wow! That's a lot of detailed info re the cam chains and tensioners. Thanks.
 








XLTrunner

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Okay.

Do you think there's any advantage to installing that kit before the chain starts to rattle...as a precautionary move to prolong the life of the cassettes/guides? Also, I'm not too thrilled to hear that the new Ford tensioner has weaker springs than the ones that came on these engines originally. If the springs are the weak link in this setup, why would they not put stiffer springs in the replacements? I don't get it...
 




Dave98XLT

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What noise would I hear if I need to replace the tensioners? Or should I replace as a precaution?

My 98 SOHC has 220k miles on the original chains and tensioners, and I have used Mobile 1 5w30 the whole way. BTW always adult driven, seldom punch it, would that make a difference in chain life?

She has a lot of new goodies, front end, bearings, tranny, tc seals, exhaust, alternator, michelins, but the rust is getting bad so I don't see her going too many more years...
 




Jimmy Hoffa

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My 98 SOHC has 220k miles on the original chains and tensioners, and I have used Mobile 1 5w30 the whole way.

Sounds like Mobile 1 is the key to longevity. Are you on the original rear main seal? I should have had mine replaced when the tranny was out last year.
 


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Dave98XLT

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I can't recall if the main seal was replaced when the tranny was out. However I am getting 4 or 5 tap-taps on startup from the right rear. Is it too late to replace the tensioner?
 




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