While browsing online for a replacement work car I noticed a lot of gm SUVs with the 3.6 for cheap, all claiming to have timing chain problems. A little googling tells me this was common. My question is on these engines does a failed timing chain ruin the engine? If the answer is "sometimes" is there any way to tell if the engine was destroyed without tearing it down? Can the timing chains be replaced in the chassis or does the engine need to come out?
In order.
Depends on "failed". When the chains stretch enough they will set fault codes for cam timing. If you ignore this long enough the primary chain will jump time. The only times I have seen timing chain issues lead to internal engine damage were in engines chronically run low on oil to the point where the pickup sucked air a lot. No timing chain engine enjoys running with no oil pressure, and the damage could be more attributed to being run without oil than to chain issues. (Kind of like the distinction between dying in your sleep, and falling asleep behind the wheel and having a fatal crash as a result)
If it starts and runs, it isn't destroyed. I have had very worn chains jump time while hand cranking the engine to get to the correct orientation before pulling the chains off, somehow they stay in time when running.
Solid it depends on the chassis. All longitudinal and some transverse can be done in chassis, some transverse the hood opening is physically smaller than the timing cover and you have to lift the vehicle off of the front subframe.
The vast, vast, vast majority of chains I have done - and I have done a lot of them - they were merely setting cam/crank correlation faults. Almost always bank 1 because bank 1 sees the largest amount of effect from chain stretch.
Pete. (l33t FS) said:In order.
Depends on "failed". When the chains stretch enough they will set fault codes for cam timing. If you ignore this long enough the primary chain will jump time. The only times I have seen timing chain issues lead to internal engine damage were in engines chronically run low on oil to the point where the pickup sucked air a lot. No timing chain engine enjoys running with no oil pressure, and the damage could be more attributed to being run without oil than to chain issues. (Kind of like the distinction between dying in your sleep, and falling asleep behind the wheel and having a fatal crash as a result)
If it starts and runs, it isn't destroyed. I have had very worn chains jump time while hand cranking the engine to get to the correct orientation before pulling the chains off, somehow they stay in time when running.
Solid it depends on the chassis. All longitudinal and some transverse can be done in chassis, some transverse the hood opening is physically smaller than the timing cover and you have to lift the vehicle off of the front subframe.
The vast, vast, vast majority of chains I have done - and I have done a lot of them - they were merely setting cam/crank correlation faults. Almost always bank 1 because bank 1 sees the largest amount of effect from chain stretch.
Thanks for the very good explanation, it was very helpful. As far as removing the engine, what I'm looking at is a gmc Acadia, do you know if that can be done in the car, because I dont have a lift.
In reply to gearheadmb :
You are miles ahead if you drop the subframe with engine attached. There just isn't enough room against the passenger framerail to make it all work including sight lines for proper pulley alignment.
In reply to Ranger50 :
I'd like to say that the engines that do not have a giant torque bracket in front of the front of bank 2 are the ones you can do in chassis. I honestly cannot keep the different models straight, they all blend in to "big truck" for me. So far I have only had to drop two drivetrains out.
Seeing the marks was never a concern, aside from the bank 2 secondary chain to idler sprocket mark, which I always cheat on and paint the special colored chain link with a bright yellow paint marker so I can see it through the little access hole.
Coworker just got a quote of $7000 to fix the timing chain in his 2012 CTS 3.6 AWD. I may offer to buy it from him and do it myself. These are longitudinal mounted so likely an in car job.
I may be checking back for advice if all goes well.
This is a timely bump of this post...
I have a 2007 CTS 3.6 (RWD) with only 82000 miles that I suspect has jumped timing on bank 2 ( misfires on 2,4 and 6).
I was 2.5 ish quarts low on oil.
If I remove the valve covers, will I be able to tell if it has jumped a tooth (or more)?
In reply to gsettle :
No. There are no useful timing marks.
You check if it's jumped time with a lab scope watching the cam and crank signals vs. a known good pattern, or watching the cam phasing with a scan tool.
If the cam timing is off, it WILL set codes for this, even if it's only off by a little and it drives fine. (Usually bank 1 because that sees the most effects of chain stretch) With misfires on one bank and no cam codes, I'd be looking at seeing if there's a blown fuse for the injectors/coils on that bank, or if the fuel trims are way wonky to suggest an exhaust restriction.
I'm going to offer to fix my coworkers car or buy it from him. Feel free to offer any tips on a timing/phaser/water pump service.
Our 2010 SAAB 9-5 with the 2.8T v6 has been setting the cam codes so I am going to do the chains this spring. After looking around the engine bay I am pretty sure the motor will have to come out which should be fun without a lift.
akylekoz said:I'm going to offer to fix my coworkers car or buy it from him. Feel free to offer any tips on a timing/phaser/water pump service.
I've only seen one phaser "go bad". And the solenoids are really, really easy to do in chassis.
That said, there's an all inclusive kit available now that includes everything.
Water pump doesn't have to be touched, in fact I usually leave it bolted to the timing cover when I remove it 
If it's AWD then there's a bracket that will fight you. The lower accessory bracket on the passenger side has an FU bolt that the diff gets in the way. You can tell if the timing cover has been off before because the dealership guys usually leave that bolt off, even on rear drive models.
I get my chassis confused, I don't remember if this is the one where getting to the rear intake bolts is a pain until you remove some bits of cowl or firewall, and in any case they usually stay in the manifold because they're like a foot long. But the intake comes off, then the valve covers, then the front stuff. For special tools, you'll need a harmonic damper puller (the funky squared 3 jaw type) and a power steering pump pulley puller.
The kits never come with one of the primary chain guides. It's removable but technically it's serviced with the oil pump. If it doesn't come with the kit, no harm no foul.
Before you start bolting parts up, even before you take anything apart, check the new jackshaft/idler sprockets. One of the common brands, I forget if Clevite or Melling, comes with garbage idlers that can barely turn. Don't use those The idlers are side specific because there is an oil passage that feeds them pressurized oil. It'll make sense if you pay close attention.
For gaskets, you'll need intake, valve cover, and timing cover. Timing cover set should also include the water outlet O rings, if not then you'll need those too. The water outlet bolts to the heads, with a flange O ring on one head and a spigoted O ring in the other head. Easy enough to do after the fact if it's going to hold you up otherwise.
In reply to Pete. (l33t FS) :
Good info, thanks.
Looks like this may just be a side job for me.
His $7000 quote was to replace all the while you are in there stuff except the oil pump and $3450 in labor. Cadillac dealer quoted $2900 but we don't know if that is for just chains or what.
I don't even know what to charge him for a job I have never done before. Sound like just a lot of nuts and bolts stuff.
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