99 Explorer Sport 4.0L V6 - Timing Question

[davewilson]

Hello, I did quite a bit of searching and couldn't find an exact answer to my question...

I've got a friend with a 1999 Ford Explorer Sport with a 4.0L SOHC V6 and what I believe to be a snapped front timing chain (the one from the crank). From what I've read the engine is a non-interference engine and the chain snapped when the truck was idling at a stand still and the engine just shut off with no bad noises.. soo we're assuming there is no internal damage to the engine other than the broken chain and maybe the tensioner. Also from what I have read there are no timing marks on the cam sprockets and crank so I was wondering if there is any easy trick to go about setting the valve timing on these engines without using the Ford tool set. Otherwise, is there any shop where you can rent these tools or buy them for cheap?

Here's the story as to how this all went down for anyone who is interested: My friend was sitting at a set of lights waiting for them to go green and when they did he pressed the gas and the truck just shut off. He tried to restart it but it just cranked, but didn't make any funny noises. Luckily there was a service shop across from the lights so he just pushed it there and had them take a look. They diagnosed it as a bad fuel pump and replaced it to the tune of $1100.00(!). They then said it wouldn't start so they did a compression test and were only getting 20psi on 3 of the cylinders. The shop manager said he didn't no what the problem was and that's when my friend phoned me. I said it sounded like his valves weren't moving and that half of his valves were staying open while the other half were staying closed so we went down to the shop together to talk to the manager about what they found. The manager kept telling us that we should just cut our losses and buy a new truck and that the engine is probably toast. I suggested maybe the timing chain was broken and he said maybe, but there is no way to know for sure without at least 20 hours of labour and tearing the engine completely apart. I laughed at him and we towed the truck home with my car. I pulled off the oil filler cap and found myself staring at the left camshaft's timing chain. I had my friend crank the engine and it didn't move at all... so there is our problem. The left timing chain still seems tight on the cam sprocket, but it just won't turn, so that leads me to believe that the front timing chain that is driven by the crank is broken, and now I'm looking for any hints or tricks to set the valve timing once we get a new chain, and if there are any other things we should look out for when doing this job.

Thanks for reading and thanks for any advice in advance!!
Dave.

 

[Carguy3J]

First, your friend should go straight back to that shop and tell the manager that he and/or his mechanics are a bunch of incompetent crooks, and demand a refund on the fuel pump "repair". Obviously it wasn't needed, and even if it was, it shouldn't cost $1100, even at the dealer.

Second, use the site's search feature, and search for "SOHC timing chain". You'll find numerous helpful, and "how-to" threads. With the amount of damage you describe, however, I would suggest you plan on pulling the motor, in order to change ALL the timing components, as well as pulling the oil pan, to clear out any debris. While you are in there, you should also replace the oil pump, in case it swallowed something.

 

[2000StreetRod]

left, not primary chain

The primary chain allows the crankshaft to rotate the jackshaft. If the primary chain was broken then the compression would be almost zero on all cylinders, not just cylinders 4,5 & 6 (left side). The broken chain is the one that connects the jackshaft to left camshaft.

The SOHC V6 is an interference engine and if one valve is fully extended it will be struck by the piston in that cylinder. However, when the chain breaks the camshaft usually rotates to a position that equalizes two of the valve spring pressures. That often means that no valve is fully extended. The left cassette (timing chain, guide assembly and sprockets) can be replaced without pulling the engine. See the following link for related information: SOHC V6 Timing Chain Inspection & Repair