Catastrophic timing chain failure

[damagexinc]

As most of you are aware certain SOHC 4.0L engines have that annoying rattle, on cold starts. My truck was one of those affected by that issue and today, something finally popped. Can anyone give me some good lists of parts or walk throughs on how to completely rip apart the front of my engine so i can start the long and aggravating process of getting my truck running? any help is greatly appreciated.

 

[BubbaFL]

The Haynes manual has a good teardown procedure, or if you dig around you can find ISO's for the Ford factory service manuals.

First step is damage assessment - get the valve covers off and see what broke, and check the condition of the right bank's chain and guide (the rear one). If that needs work, the engine's gotta come out.

 

[Ericmac2001]

good luck my man, i sent mine through the top of my valve cover, and it wrapped thourgh the top of the head. needless to say, i went and installed a new enginge. if thats your decision, i would recommend going 03 and newer. it doesnt have the same defect as the 99-01

 

[ERUSH97XLT]

Uh oh :thumbdwn: no good.

Your valve train is probably toast. Let's hope no cylinders were damaged by impacting the valves.

At least a rebuild, or an '03+ upgrade, as suggested by Ericmac2001, is in order.

Good luck,

ERUSH

 

[Old Hippie]

What determines possible engine damage when timing belt/chain breaks? Overhead valve engines? Ford? Buick (GM)?
My sis had a Buick. Manual said to replace timing chain or belt at such-an-such mileage. I think it was an OHV engine. I ask a GM mechanic about this and he said "haug wash, no damage will result."

 

[ERUSH97XLT]

What determines possible engine damage when timing belt/chain breaks? Overhead valve engines? Ford? Buick (GM)?
My sis had a Buick. Manual said to replace timing chain or belt at such-an-such mileage. I think it was an OHV engine. I ask a GM mechanic about this and he said "haug wash, no damage will result."

That GM tech is an idiot.

When the timing chain /belt breaks with the engine running, the valve train is no longer mechanically synchronized with the rotating assembly, regardless of the valve configuration (OHV, OHC, DOHC, etc.). Due to the rotating assembly's momentum upon failure, piston-valve impact is highly probable, causing catastrophic engine failure. Once this happens, at least the valve train needs to be replaced. If the pistons are damaged by the failure, they require replacement, too.

I've heard of people getting extremely lucky; their timing chain broke on the first crank of the starter, thereby saving the entire engine. All that's required in this case is a new timing chain and valve train resynchronization.

Just my $0.02

ERUSH

 

[BubbaFL]

What determines possible engine damage when timing belt/chain breaks?

Luck.

I ask a GM mechanic about this and he said "haug wash, no damage will result."

The government motors mechanic is wrong.

The 4.0SOHC is an interference engine - that means the valves and the pistion physically occupy the same space at different times during the cycle. It is possible for the piston to smack into a valve when a chain breaks or slips - mostly a matter of chance.

There are some threads with pictures of valve-piston collisions.

 

[ERUSH97XLT]

...The 4.0SOHC is an interference engine - that means the valves and the pistion physically occupy the same space at different times during the cycle...

+1. If your engine is an interference engine, piston-valve impact is nearly guaranteed.

 

[BubbaFL]

I've heard of people getting extremely lucky; their timing chain broke on the first crank of the starter, thereby saving the entire engine.

If that's extreme luck, I need to buy some lottery tickets. Mine blew apart while it was running (as in "chain got pi**ed off at the guide, and they both came out through the valve cover").

No valve damage!

 

[ERUSH97XLT]

If that's extreme luck, I need to buy some lottery tickets. Mine blew apart while it was running (as in "chain got pi**ed off at the guide, and they both came out through the valve cover").

No valve damage!

I guess it's possible.... people have been struck by lightning twice.

Share your lotto winnings??????

 

[damagexinc]

Thanks for the tips guys, just a quick question, if it wasnt the timing chain that popped and it was just that stupid tensioner would i have to take apart everything to put the chain back on and what not or would all that stuff still be ok,

 

[damagexinc]

interesting turn of events, i made it to my parents house to meet up with a mechanic to have him help me diagnose my problem and low and behold, THE TRUCK TURNED OVER. but only for a miniscule amount of time. any ideas what this could be?

 

[ERUSH97XLT]

Stop. Do not turn the engine with the starter. You're risking piston-valve impact!

You won't know for sure if your timing chain broke (or slipped/malfunctioned) until you remove the valve covers and slowly turn the engine by hand.

 

[BubbaFL]

interesting turn of events, i made it to my parents house to meet up with a mechanic to have him help me diagnose my problem and low and behold, THE TRUCK TURNED OVER. but only for a miniscule amount of time. any ideas what this could be?

That doesn't tell you much. Mine turned over and tried to start even with a broken chain and a giant hole in the valve cover.

If you suspect a timing problem, pull the valve covers and visually inspect the timing components (chains, guides, tensioners).

 

[damagexinc]

I have two theories as of right now one is that my engine is being starved of oil and it seized up on me, my second is that just that tensioner broke. IF it is just that tensioner, do i have to take apart my entire engine to re adjust my timing chain and make sure that all of those components are still attached?

 

[2000StreetRod]

broken tensioner?

I have two theories as of right now one is that my engine is being starved of oil and it seized up on me, my second is that just that tensioner broke. IF it is just that tensioner, do i have to take apart my entire engine to re adjust my timing chain and make sure that all of those components are still attached?

By "tensioner" are you referring to the spring/hydraulic tensioner for the left or right camshaft chain? If so, replacing the "tensioner(s)" will not solve your engine not starting. The tensioners are located on the slack side of the chains. When the starter is cranking the engine the crankshaft sprocket pulls the jackshaft sprocket via the primary chain and the jackshaft front and rear sprockets pull the camshaft sprockets via the camshaft chains. If the timing chains have not slipped the engine will start and run without functional tensioners.

If your problem is timing chain related my guess is that one or more of your timing chains has slipped. You can remove the oil filler tube cap and shine a light down the opening while slowly rotating the crankshaft by hand. If the left camshaft is rotating then you know that the primary timing chain and left camshaft chain is intact. Since you have had cold start timing chain rattle for some time there is a good chance that one of your camshaft guide assemblies has finally broken. The rear guide is a good candidate. A compression test will be very helpful. If the compression on all of the right cylinders is near zero then your right timing chain has slipped or broken. If the compression on all of the left cylinders is near zero then your left timing chain has slipped or broken. If both banks' compression is near zero then your primary chain has broken.

The following of my helpful threads may be useful to you:

SOHC V6 Camshaft Timing

Timing chain rattle resolution process - SOHC V6

SOHC V6 Timing Chain Inspection & Repair

SOHC V6 Timing Chain Parts Removal Procedure

 

[damagexinc]

well it looks like this motor is at the end of it's life, anyone know where i can get an 03+ motor for under 400?

 

[2000StreetRod]

What's bad?

well it looks like this motor is at the end of it's life, anyone know where i can get an 03+ motor for under 400?

What have you done to determine what's bad? I would not replace an engine just because it won't start.

 

[damagexinc]

i had a mechanic came and inspect the truck today and he said timing chain had tore through the first cylinder on the drivers side as i understood it and that my valves and pistons were damaged. i was quoted about 1200 to replace the motor with labor and am just wondering if thats really worth it, the car has 175000 miles on it and it's only 12 years old.

 

[2000StreetRod]

removed spark plug?

Interesting. Did your mechanic remove the front spark plug and inspect the piston, cylinder and valves with a remote camera? If not, I'd like to know how he determined the extent of the damage.