996 replacement engine

[logray]

First, don't run the engine at all.

Certainly drain the oil and inspect the filter as a first step.

It might be worth opening the cam cover for more inspection, this can be done with the engine still in car.

For example if it is just a broken spring and there was not valve/piston contact, then pulling the head and replacing/inspecting hardware might be all that is needed to get you on the road, which would cost considerably less than a complete engine rebuild.

If the timing is waaaaay off, then you are looking at valve/piston contact which could spell out the need for deeper repairs, at which point you might want to look at your rebuild/replacement options. Mike has a good write up here:

https://sites.google.com/site/mikefocke2/what-can-you-do-if-your-engine-is-blown

"He indicated that the guide for the left drive train had been completely worn away, that the left tensioner was shot and when he replaced it and the cam plugs that the chain had actually jumped the timing. He said there was a significant amount of wear on the chain itself and the place where the guide used to be."

This diagnosis doesn't sound right to me.

First if you replace a tensioner for the IMS to cylinder head, you can't see the chain because there is a ramp in the way. If he was somehow able to see one of the three chains, and could see that it was worn, your engine needs to be completely torn down and rebuild. Second, if you are missing a chain ramp, as in "used to be" meaning it isn't there any longer, you're engine is toast. If one of those ramps failed and broke off they are very large components and it would almost undoubtably cause catostrophic failure. Third, if it was the main IMS to crank tensioner, you can't see the guide, you should only be able to see the paddle.

On a 2004, chain guide wear inside the head is highly unlikely, because unlike the early variocam systems, variocam plus has one large chain that goes around the variable camshaft actuators and the ims sprocket, the timing advance is accomplished inside the vane adjuster and the variable timing/lift solenoids and not by increasing/decreasing pressure on the chain like it was with the older systems where chain pad wear is common. The large long chain is tensioned and held in place by two very large ramps, which if one were to break it would certainly spell disaster.

[fpb111]

all that with only 18k miles? I would definitely get a 2nd opinion. If you are considering option #2 talk to Jake Raby at Flat 6 about one of his "better then new" rebuilds.

http://www.flat6innovations.com/engines/the-flat-6-difference

[dfinch94]

Thanks. These are helpful comments. I'm in the process of getting a second opinion. I may got the Flat 6 route if necessary.

[dfinch94]

First, don't run the engine at all.

Certainly drain the oil and inspect the filter as a first step.

It might be worth opening the cam cover for more inspection, this can be done with the engine still in car.

For example if it is just a broken spring and there was not valve/piston contact, then pulling the head and replacing/inspecting hardware might be all that is needed to get you on the road, which would cost considerably less than a complete engine rebuild.

If the timing is waaaaay off, then you are looking at valve/piston contact which could spell out the need for deeper repairs, at which point you might want to look at your rebuild/replacement options. Mike has a good write up here:

https://sites.google.com/site/mikefocke2/what-can-you-do-if-your-engine-is-blown

"He indicated that the guide for the left drive train had been completely worn away, that the left tensioner was shot and when he replaced it and the cam plugs that the chain had actually jumped the timing. He said there was a significant amount of wear on the chain itself and the place where the guide used to be."

This diagnosis doesn't sound right to me.

First if you replace a tensioner for the IMS to cylinder head, you can't see the chain because there is a ramp in the way. If he was somehow able to see one of the three chains, and could see that it was worn, your engine needs to be completely torn down and rebuild. Second, if you are missing a chain ramp, as in "used to be" meaning it isn't there any longer, you're engine is toast. If one of those ramps failed and broke off they are very large components and it would almost undoubtably cause catostrophic failure. Third, if it was the main IMS to crank tensioner, you can't see the guide, you should only be able to see the paddle.

On a 2004, chain guide wear inside the head is highly unlikely, because unlike the early variocam systems, variocam plus has one large chain that goes around the variable camshaft actuators and the ims sprocket, the timing advance is accomplished inside the vane adjuster and the variable timing/lift solenoids and not by increasing/decreasing pressure on the chain like it was with the older systems where chain pad wear is common. The large long chain is tensioned and held in place by two very large ramps, which if one were to break it would certainly spell disaster.

Thanks logray. I finally spoke to another mechanic and then looked at it myself to separate what has actually happened and what is conjecture. This is what I know for certain: (1) The left tensioner is only slightly worn at the tip (like someone scrubbed it with steel wool), (2) The "timing notch" where the tensioner was located appeared to be off by 5 degrees or so (to the right). (3) According to the mechanic, the timing jumped when he removed the tensioner. (4) I turned the car on just long enough to back it into my garage and the engine sounds horrible.

Based on what I am learning, I can't imagine that the chain guide would have come off because I would have either heard it happen (never heard anything unusual) and the car would immediately be undriveable (which was not the case until the mechanic replaced the tensioner).

For a complete car novice, how hard is it to remove the cam covers to get a better look?

[JFP in PA]

First, don't run the engine at all.

Certainly drain the oil and inspect the filter as a first step.

It might be worth opening the cam cover for more inspection, this can be done with the engine still in car.

For example if it is just a broken spring and there was not valve/piston contact, then pulling the head and replacing/inspecting hardware might be all that is needed to get you on the road, which would cost considerably less than a complete engine rebuild.

If the timing is waaaaay off, then you are looking at valve/piston contact which could spell out the need for deeper repairs, at which point you might want to look at your rebuild/replacement options. Mike has a good write up here:

https://sites.google.com/site/mikefocke2/what-can-you-do-if-your-engine-is-blown

"He indicated that the guide for the left drive train had been completely worn away, that the left tensioner was shot and when he replaced it and the cam plugs that the chain had actually jumped the timing. He said there was a significant amount of wear on the chain itself and the place where the guide used to be."

This diagnosis doesn't sound right to me.

First if you replace a tensioner for the IMS to cylinder head, you can't see the chain because there is a ramp in the way. If he was somehow able to see one of the three chains, and could see that it was worn, your engine needs to be completely torn down and rebuild. Second, if you are missing a chain ramp, as in "used to be" meaning it isn't there any longer, you're engine is toast. If one of those ramps failed and broke off they are very large components and it would almost undoubtably cause catostrophic failure. Third, if it was the main IMS to crank tensioner, you can't see the guide, you should only be able to see the paddle.

On a 2004, chain guide wear inside the head is highly unlikely, because unlike the early variocam systems, variocam plus has one large chain that goes around the variable camshaft actuators and the ims sprocket, the timing advance is accomplished inside the vane adjuster and the variable timing/lift solenoids and not by increasing/decreasing pressure on the chain like it was with the older systems where chain pad wear is common. The large long chain is tensioned and held in place by two very large ramps, which if one were to break it would certainly spell disaster.

Thanks logray. I finally spoke to another mechanic and then looked at it myself to separate what has actually happened and what is conjecture. This is what I know for certain: (1) The left tensioner is only slightly worn at the tip (like someone scrubbed it with steel wool), (2) The "timing notch" where the tensioner was located appeared to be off by 5 degrees or so (to the right). (3) According to the mechanic, the timing jumped when he removed the tensioner. (4) I turned the car on just long enough to back it into my garage and the engine sounds horrible.

Based on what I am learning, I can't imagine that the chain guide would have come off because I would have either heard it happen (never heard anything unusual) and the car would immediately be undriveable (which was not the case until the mechanic replaced the tensioner).

For a complete car novice, how hard is it to remove the cam covers to get a better look?

Yikes! You should not be even turning the engine over by hand if you think the timing has jumped, much less running it. And resetting the cam timing is not just a matter of pulling the cam covers to get a better look; it requires both experience and some special tooling at a minimum.

Do to the constricted engine bay on a 996, it is going to be easier to do this with the engine out of the car. At this juncture, you need to have the car flat bedded to someone that really knows what they are doing; no offense, but this is not a job for amateurs.

[dfinch94]

Good to know and no offense taken. Much rather have the experts do the tinkering and I'll just write the check . . . if and when I can afford to.

[JFP in PA]

Good to know and no offense taken. Much rather have the experts do the tinkering and I'll just write the check . . . if and when I can afford to.

These are "interference engines", meaning that if the timing jumps, pistons can start hitting valves and doing lots of damage. When the cam timing is correct, the internal components are so close that the engines should only be rotated in a clockwise manner to prevent problems; and as little as 12 degrees out of time can result in bent metal at a minimum.

[txhokie4life]

Do not start this car for any reason until you get it back in timing.

I would check timing again.

I would also boroscope those cylinders and make sure there is no valve strike.

Please find someone that knows these engines.

Mike

[987_RDC]

Resetting the timing on the 02+ engines is much more difficult that the earlier ones. Unless you want to fork out $1k just for the tools then get it towed to a mechanic. Sounds like the mechanic you used caused more harm than good. It is highly unlikely that the variocam plus mechanism wore out (guessing that's where the $7k figure came from). I am shocked that you didnt at least get error codes from the initial issue.

Edited July 24, 2013 by 987_RDC

[987_RDC]

The more I think about it, the timing should not have "jumped" unless the mechanic did NOT lock the cams which is a very simple process. Armed with the error codes it could have just been a simple replacement of the variocam plus actuators. (two on each bank ~$150)

Actually it is very likely the mechanic did lock the cams but was not familiar with the 02+ special process for replacing the tensioners and setting timing of the bank. You cannot just lock at TDC and pull + replace the tensioner and expect to have proper timing. You have to rotate to 60* prior to the TDC (OF THAT BANK!) when you are placing the tensioner. Then rotate to TDC to remove "slack" (created by the movement of the variocam plus vanes) from the chain as you are setting timing. Otherwise your variocam plus "mechanism" will not have the proper angle. (sorry if not making sense)

Again much easier on 99-01.

Edited July 24, 2013 by 987_RDC