When to Change the Timing Chain? | Ford Explorer Forums - Serious Explorations

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When to Change the Timing Chain?

SR77

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I am just about to hit 100,000 miles on my 96 Explorer 5.0L AWD and was wondering if I should be thinking of changing the timing chain soon. Is this something that should be done at a certain mileage(What Mileage?) or as preventative maintainace or wait to change it when it fails? Also if it does break, is the 5.0L V8 designed to not bend or break anything internally or is the engine done if the timing chain breaks?
 



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The timing chains on 302 will go 150,000 if not even 200,000 miles if the oil was changed at the proper intervals. It's kind of unusual to hear of the timing chains breaking on the 302's. However they will stretch over time. If you're in there doing other work, such as replacing the front oil seal, then replace it. If not, then I wouldn't worry about it yet.
 






mvoeller said:
The timing chains on 302 will go 150,000 if not even 200,000 miles if the oil was changed at the proper intervals. It's kind of unusual to hear of the timing chains breaking on the 302's. However they will stretch over time. If you're in there doing other work, such as replacing the front oil seal, then replace it. If not, then I wouldn't worry about it yet.
what about on the 4.0L ohv? I got 194k and I have had it since 154k I don't believe anyone would have changed it before I bought it...
 






Probably the same reliability as a 302. Older Ford engines had nylon/plastic sprocket gears. They usally wouldn't last 100k. I think Ford learned from that cutting corners poor decision. Any abnormal signs after 75k or so should prompt replacement. Good luck,
Don
 






kinda what i was thinking...so i should prolly change it soon eh?
 






Thanks for the replys. I guess I will just leave it be then. Are there certains signs to look for when the timing chain is too stretched out? Whats happens if the chain is too stretched out. Also in the freak occurance that the chain did break, will the Ford 5.0L be toast or is it designed not to bend or break anthing internally.
 






as far as I am aware... the 4.0L OHV and the 5.0L OHV are NON INTERFERENCE engines, which means if the valves stop moving (broken chain) the pistons will not hit them.

the 4.0L OHC explorer engine is an INTERFERENCE engine, which means if the valves
stop moving the pistons will slam the crap out of them which is why it is so imperitive to replace the timing belts on those engines at the proper time.

I have 137000 on my 1994... when I get closer to 200k (if I still own it) i will consider launching the task of replacing it.

So if the timing chains go your engine will simply stop running, and you may wonder why. My dad had an old ford escort and the timing belt snapped... it just went "plump" and was dead until it was replaced.

you should be good though, only 100k on it isn't too bad. Just broken in! :)
 






me on the other hand...194k on the 4.0L OHV yeah prolly needs changing eh? ;)
 






monkeydude3 said:
as far as I am aware... the 4.0L OHV and the 5.0L OHV are NON INTERFERENCE engines, which means if the valves stop moving (broken chain) the pistons will not hit them.

the 4.0L OHC explorer engine is an INTERFERENCE engine, which means if the valves
stop moving the pistons will slam the crap out of them which is why it is so imperitive to replace the timing belts on those engines at the proper time.

The SOHC engine doesn't have a belt, it has chains (three on a 4x4, to be exact). To my knowledge there is no scheduled service interval as it's not considered a wearable part.

-Joe
 






one sysmptom of a stretched t-chain is that the power band moves up, so if you used to have plenty of power at 2000rpm, and notice that you have power at 2500 or 3000 instead, it's a good bet that the chain is stretched.

on a distributor motor, having to bump timing was a good sign, with computer control, the computer does it automatically.

on the old ford 302's the nylon gears were for noise control, and with the normal heat/cool cycles of the engine, and the hot oil constantly washing over them, the nylon would chip off. most replacement gears were solid unless you got them from ford. old chains were good for roughly 70k-80k

a test, is also to pull a valve cover (unless you can see a rocker without pulling it) and slowly rotate the engine forward untill you see the rockr move, then stop and slowly rotate the engine backwards untill you see the rocker move again, the amount of rotation will give you the slop in the chain, tensioners reduce the apparent play slightly, but not a great deal.

The BEST way with the older 50 motors was to pull the fuel pump blockoff, and feel the chain.

an odd developement I've noticed is that older cars, if you had the chain out for some reason, you could tell if it was bad if you could lay it on the table so it was a loop sticking up, and touch the center together, modern chains come curled up in a small box, so it's no longer a good check.

ken.
 






What are the signs of a timing chain that is going out? I currently have 125k on my 2000 ex 5.0 awd.
 






The 302 timing chains can go a long time, often 150-200k. If you have odd symptoms that pointed to internal engine issues, then it might be time. Don't mess with it if the engine is running fine. If the timing chain goes, the engine will stop running immediately. It is very rare for a chain to skip just one tooth and still keep running. They typically will break or jump lots of teeth and often. The engine will not run if the chain fails, and yes parts will bend, badly.
 






The 302 timing chains can go a long time, often 150-200k. If you have odd symptoms that pointed to internal engine issues, then it might be time. Don't mess with it if the engine is running fine. If the timing chain goes, the engine will stop running immediately. It is very rare for a chain to skip just one tooth and still keep running. They typically will break or jump lots of teeth and often. The engine will not run if the chain fails, and yes parts will bend, badly.
So the 302 is has an interference valve train?
 






The 302 timing chains can go a long time, often 150-200k. If you have odd symptoms that pointed to internal engine issues, then it might be time. Don't mess with it if the engine is running fine. If the timing chain goes, the engine will stop running immediately. It is very rare for a chain to skip just one tooth and still keep running. They typically will break or jump lots of teeth and often. The engine will not run if the chain fails, and yes parts will bend, badly.

my engine runs fine but ive had something similar to a knock and ive only felt it once but it was consistent and got stronger and lasted about 10 seconds. any ideas?
 






Check for low oil. It could also be leaky lifters or weak oil pressure.
 






Concentrate on the oiling, and the lifters commonly will make some noise before things like the timing chain.
 






So the 302 is has an interference valve train?

No, any engine will fail dramatically if the valvetrain isn't kept in time. If the valves of any engine are open at the same time the pistons are moving up and down out of time with the cam, valves will hit pistons. All timing chains or belts are thus critical. If you have an idea that one is failing or has, fix it immediately.
 






No, any engine will fail dramatically if the valvetrain isn't kept in time. If the valves of any engine are open at the same time the pistons are moving up and down out of time with the cam, valves will hit pistons. All timing chains or belts are thus critical. If you have an idea that one is failing or has, fix it immediately.
I was asking because there are a few engines out there that have a "non-interfering" valve train in that if one or more valves are left open at maximum lift (i.e. the timing chain broke) the piston will never hit them.

http://en.wikipedia.org/wiki/Interference_Engines

This references the Mazda B engine as a non-interfering one which would not suffer a fatal death if the timing belt/chain broke.

Its pretty rare to find a non-interfering engine, I just never had confirmation about the 302.
 






Ah, well yes the non interference engines will be the rear type. I never heard the term interference engine before about 15 years ago, I had thought it was something special like certain parts had to be pressed together because they had dimensions which interfered. I'll bet those non interference engines were made because the timing belts(or chains) were common to fail. LOL,
 



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Interference engines are usually the ones with high compression. Then the valves drop more than height of the chamber. I have the timing fail in a 1.9L Ford 4cyl, in a 2.5L Hyunday V6 and nothing bad happend. 302 has lousy compression, it is not interference engine. Mostly smaller engines fall into this category... and any high-performance ones.
Here is a list of interference engines: http://www.aa1car.com/library/timing_belts_interference_engines.htm
 






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