3.8L Timing Chain question

[Sigurd Jarlson]

I bought my 88 Ciera with a 3.8L back in 2002 with 140k on it. While under the car the other day I noticed that the previous owners mechanic had painted "timing chain at 100k" on the oil pan. Based on the time frame and mileage, can I be reasonably confident that this engine got one of the "improved" timing chains, replacing the ones that are prone to fail?

Thanks,

Dan

[razoredge]

Well ? The problem was the gear teeth and it just says chain so there is no way knowing unless you can track down the mechanic. I couldnt even swear that a mechanic would replace the entire "set" but seems they should have. The nylon tooth set was still available from GM in 2000, I know this because I bought the proper OEM set for my 86 3.0 from them, before I knew about this problem.

[Sigurd Jarlson]

Thanks. Is there any way to check, short of removing the timing cover?

[CamoDeafie]

theres a sensor thats in the same general area of the plastic sproket, I can't remember which sensor it was, but if you remove it, you can see the gear....what color was the OEM replacemnt gear-to Razoredge?

[razoredge]

? steel ?

Im not sure if you can tell by pulling the cam sensor or not, David might know.

[85_Ciera_Rebuild]

Thanks. Is there any way to check

Just put a socket on Crank's Harmonic balancer bolt....and move it back/forth...it should not move much.

[85_Ciera_Rebuild]

"timing chain at 100k"


PS: Only idiots buy a timing chain...most folks buy a timing set.

[Sigurd Jarlson]

PS: Only idiots buy a timing chain...most folks buy a timing set.

Since I have no idea if the previous owners were idiots or not, I'm looking for a more definitive method.....

[85_Ciera_Rebuild]

I'm looking for a more definitive method.....

Get a socket to fit over Crankshaft's bolt that holds harmonic balancer on...and see how much timing-chain slack exists...its rather doubtful the timing chain was replaced, but most likely the timing set.

Otherwise, take off timing cover...

[Sigurd Jarlson]

Thanks.

[turbokinetic]

I'm pretty sure 99% of mechanics will say a "timing chain" when they replaced the upper and lower gears, chain, and tensioner. It's just an expression. No one replaces just the chain.

Start by disconnecting the electrical connector from the cam sensor. Remove the one bolt that holds it on the engine. The cam sensor pulls STRAIGHT out of the engine, you may need to rotate or pry gently.

Once the sensor is out, use the flashlight and mirror to look in the hole. If the cam sensor trigger- magnet is located at the hole, rotate the crankshaft to move the magnet away. This will allow you to see the camshaft drive gear.

If the gear is ALUMINUM, you have the DEFECTIVE gear and the engine needs to be updated. If the gear is STEEL you have the updated parts already in the engine.

Re-install the sensor and its bolt and the engine is ready to go.

The easiest way to determine if the gear is steel or aluminum is to scratch the gear. Once the sensor is out, after you have made sure the magnet is not directly under the hole, use a small screwdriver to score or scratch the face of the gear. If the gear is steel, yo will not make a significant mark. The screwdriver will slide easily.

If the gear is aluminum, the screwdriver will 'dig into' the gear, leaving a bright shiny score mark. This will not affect the gear because nothing touches it on the front face.

I will post some pictures shortly!

Later,
David

[Sigurd Jarlson]

Thanks David. Great info.

[turbokinetic]

Here is the entire timing gear system for an LG3 engine. This one has the update:
http://68.209.87.173/84_Century/3_8_SFI_Turbo/Rebuild/timing_gears_system.jpg

This is what you should see through the cam sensor hole:
http://68.209.87.173/Temp/Cam_gear_insp1.JPG

This is where the sensor is located:
http://68.209.87.173/Temp/Cam_gear_insp2.JPG

Here is a failed aluminum / plastic gear:
http://68.209.87.173/87_Century/Engine_repair/fail_gear2.jpg

The objective is to scratch the GEAR, not the end of the cam, because the end of the cam is steel on all engines. The gear that is aluminum will look brown becase of oil varnish so yo can not tell visually until you scratch it.

Rotating the crank back and forth to look for timing chain slack will NOT detect this problem. This is not a slack in the chain issue, it is a sudden and catastrophic failure of the bonded-on PLASTIC GEAR TEETH on the aluminum/plstic sprocket.

Hope this helps!
Later,
David

[Sigurd Jarlson]

Great Pics!

[turbokinetic]

Great Pics!

Thanks! They are "recycled" pictures from my 84 Century Olympia'a 3.8 Turbo build, and my 87 Century's timing chain repair!

David

[85_Ciera_Rebuild]

Rotating the crank back and forth to look for timing chain slack...

Should confirm if new chain was installed...recently...nothing more, which was his original question.

[Sigurd Jarlson]

My bad. I thought it was the chain that was problematic, not the timing gear. Getting all mixed up with my 2002 Ecotec that, according to the internet, has timing chain issues that are concerning me.....

[turbokinetic]

My bad. I thought it was the chain that was problematic, not the timing gear. Getting all mixed up with my 2002 Ecotec that, according to the internet, has timing chain issues that are concerning me.....

Yep, it's just the upper gear that fails on these. BUT you should always replace the chain, both gears, and the tensioner as a set.

[Ray_McAvoy]

While we're on the subject of 3.8L timing chains, I just thought I'd share this pic of the one I pulled out of my 88 this past winter:

http://i175.photobucket.com/albums/w131/ray_mcavoy/88CutlassCiera_TimingChain.jpg

I got really lucky and caught it just in time!

[CamoDeafie]

Holy!

[Sigurd Jarlson]

While we're on the subject of 3.8L timing chains, I just thought I'd share this pic of the one I pulled out of my 88 this past winter:

http://i175.photobucket.com/albums/w131/ray_mcavoy/88CutlassCiera_TimingChain.jpg

I got really lucky and caught it just in time!

Original timing set? How many miles?

[turbokinetic]

While we're on the subject of 3.8L timing chains, I just thought I'd share this pic of the one I pulled out of my 88 this past winter:

http://i175.photobucket.com/albums/w131/ray_mcavoy/88CutlassCiera_TimingChain.jpg

I got really lucky and caught it just in time!

WOW you were indeed VERY lucky!!!! I don't see how that was still running! :(

David

[Doug B.]

Yep, thats chewed up, and to the OP, I would agree with 99.9% of mechanics would replace the entire set, not just a chain. Common wording is Timing chain replacement.. I would say you haven't got any reason to worry.. Im sure the stock aluminum gear failed at 100K and you have a steel gear now.

[85_Ciera_Rebuild]

I don't see how that was still running! :(



On a Wing and a Prayer....

[bodieman]

Another suggestion is, instead of trying to scratch the face of the cam sprocket, try inserting a small telescoping magnet into the cam sensor hole, and touch the face of the sprocket with it. If the magnet sticks, the sprocket is steel. If not, then it's aluminum. Hope this helps.

[ciera187]

is this the same for a 90 and 92 3.3l

[turbokinetic]

is this the same for a 90 and 92 3.3l

No, the 3800 (1989 and newer) and all 3300's have an all-steel timing gear system. There is no periodic maintenance of the timing chain or gears on these engines.

Virtually all the pre-1989 Buick engines had the plastic gear. All the FWD 3.0 and 3.8 had plastic. Not sure how far back it went with the RWD stuff.


Another suggestion is, instead of trying to scratch the face of the cam sprocket, try inserting a small telescoping magnet into the cam sensor hole, and touch the face of the sprocket with it. If the magnet sticks, the sprocket is steel. If not, then it's aluminum. Hope this helps.

That is what I tried first but I couldn't tell if the gear was steel, or if it was attracting to the camshaft or chain links. There is so little room to work in the cam sensor hole! On an engine stand the magnet is easy but I was unsure when checking in-car.

If the gear is aluminum, it is junk anyway and getting replaced. If it is steel, you aren't going to successfully scratch it anyway. :)

David

[Ray_McAvoy]

Original timing set? How many miles?

Yup, original timing set as far as I know. Just a little over 180,000 miles.


WOW you were indeed VERY lucky!!!! I don't see how that was still running!

Yeah, when I pulled the cover off and got a look at that sprocket, I was amazed that the few remaining teeth had been enough to keep the thing running.

I think it was a lucky coincidence that the tensioner happened to fall apart before the chain slipped on what was left of that sprocket. The failed tensioner allowed the chain to rattle against the timing cover ... that's what tipped me off to the problem