timing chain problems

[allxlts]

so i have this 98 explorer sohc with something wrong. i have a new engine that i can put in, but if i could fix the one in there it would be awesome. so heres the deal.

i was driving home one night, and noticed the oil pressure gauge was at zero. shocked, i killed the engine and pulled over immediately. checked the dipstick, oil was full and it looked fine. started the ex up again and was listening for signs of no actual oil pressure, and nothing was wrong so i figured the sender was bad. drove it some more, and now i noticed a tap tap sound. it sounded like the timing chain was slapping around. im a diesel mechanic, so im not mechanically incompetent. ive been driving this thing for half an hour with the gauge at zero, so if i really had no oil pressure id have a serious rod knock. i also know that thats simply a dummy gauge.

now, i notice it getting louder and louder. it sounds like a diesel engine almost. i know this thing is gonna break, but its a beater and i dont have the cash for a tow. so i drive it the rest of the way home, and wouldnt ya know it about 5 miles from home it goes boom. not boom, but it just seems like i lost some cylinders rapidly. no holes in the block, no knocking from the lower end, it still turns over with the starter, it just sounds like im missing compression in some cylinders. the oil is clean and has no metal in it.

this all took place before i knew anything about explorers. i still dont actually. i know they have a timing chain problem, but i dont know what it is. nobody actually writes it out to read, its just common knowledge i guess.

so id appreciate any input at this point. im dying to drive this thing again, and i kinda need to since my subbie is about to go under the knife.

EDIT reason for title is because im assuming its timing chain related, but like i said, i dont know the first thing about the 4.0 sohc engines.

 

[my98nnj]

It's an interference engine, it's time to start your swap project.

 

[2000StreetRod]

check compression

The cassette guide assembly breaks causing the timing chain to slip. Do a compression check. Low compression on all cylinders on one bank means the chain on that guide slipped. Zero compression on all cylinders on one bank means that the timing chain broke on that bank or the chain slipped enough that pistons damaged the valves on that bank. If the compression is low on both banks then the primary (crankshaft to jackshaft) chain failed. See Timing chain rattle resolution process - SOHC V6

 

[allxlts]

the part that stumps me is, it didnt rattle or make any noise prior to this incident? it never made noise when it started.

i should add that this engine has 425k miles on it.

 

[Flash]

the part that stumps me is, it didnt rattle or make any noise prior to this incident? it never made noise when it started.

i should add that this engine has 425k miles on it.

At 425k miles you've done great.
And really, with that sort of mileage I wouldn't consider repairing it, I'd get another engine and do the preventative repairs on it before it's fitted.

Preventative repairs are replacement of the timing chains, guides and tensioners. The engine has to be out to do the rear chain and the front chain and intermediates chains are much easier to get to if out of the car.

The final prophylactic action is to fit a pre-oiler, I'm starting to think that that's the only sure way to prevent premature timing chain failure.

The cam chain tensioners operate by oil pressure over spring, the chains will often rattle about at start up until the oil pressure builds up which damages the chain guides.
The newer, steel backed chain guides are stronger than the old plastic ones.

425k, wow!

 

[allxlts]

yup, at 425k miles, and it looks factory inside and out.

but thanks alot guys. looks like shes getting a new heart!