Rattle in Head

[ncgoblin]

Well I did some more research and this is similar to the sound I am hearing very close. Another guy came across the video and actually pulled his oil pan and inspected faulty bearings this could be unfortunate. I am going to try a few more things before inspecting the bearings but if this is the case what are my options?

 

[DCMoney]

Well I did some more research and this is similar to the sound I am hearing very close. Another guy came across the video and actually pulled his oil pan and inspected faulty bearings this could be unfortunate. I am going to try a few more things before inspecting the bearings but if this is the case what are my options?

Rebuild the bottom end, crank, bearings, etc. you still have the bad top end motor laying around?

I had a main bear come apart in one of my older car years ago. Rebuilt the bottom end drove it for another 50K miles before selling it. Crank bearing surface was toast, a reman crank was only $180, bearings wernt. Good learning experience as well, biggest take way, no more Chrysler products...

Knew where the pic of the bearing was, 9mm for reference...

 

[ncgoblin]

Rebuild the bottom end, crank, bearings, etc. you still have the bad top end motor laying around?

I had a main bear come apart in one of my older car years ago. Rebuilt the bottom end drove it for another 50K miles before selling it. Crank bearing surface was toast, a reman crank was only $180, bearings wernt. Good learning experience as well, biggest take way, no more Chrysler products...

Knew where the pic of the bearing was, 9mm for reference...

I have not tore down the other engine I may do that first to see what this issue was with it. I do know it has low compression in I believe #3 and #4 cylinder.

 

[Karter2026]

Rebuild the bottom end, crank, bearings, etc. you still have the bad top end motor laying around?

It is about $300 for a complete crank kit with bearings. at Autozone

 

[DCMoney]

It is about $300 for a complete crank kit with bearings. at Autozone

That sucks.

NCGoblin have you drained the oil and checked the filer yet? Any metal shavings in it?

 

[ncgoblin]

That sucks.

NCGoblin have you drained the oil and checked the filer yet? Any metal shavings in it?

I did drain the oil and ran a magnet throughout the oil nothing came back.

 

[ncgoblin]

Today I had someone that could rev the engine while I walked around with a stethoscope. Before attempting this I removed the header and noticed the gasket covers partially the opening I thought this was a ZZP header but I believe it’s a eBay one so I went ahead and ordered a ZZP for peace of mind (see photo). So I cut a gasket and Noise is still noticeable. When the engine is cold there is no rattling when revving to 4K RPM. But right at about 170 the engine starts to rattle at 2.5k RPM maybe oil is thinning or heat is expanding a part? I also noticed a rattle sound coming from the water pump but louder near the top of the chain upper guide. I did replace the water pump when originally installing timing chain this was never swapped out and both engines had the rattle noise I am wondering if this could be the cause but why only when warm?

The engine seems to run fine other then the rattling noise I brought up around the neighborhood obviously cautiously.

Supercharger is quiet no rattle this was brought up as possibly a bad coupler.

 

[ncgoblin]

Well guys I have figured out the issue bad rod bearings as shown in the Photos. #2 rod I could move with my fingers. The sound is only obvious at operating temperature 170ish and at 2-3000k RPM. There was not a single article I could find on the cobalt forums or YouTube giving an example of the sound.

To replace:

1. Remove AC pulley
2. Remove intercooler pump
3. Remove oil pan
4. Remove rod cap a little tap with a brass tap helps
5. Install OEM bearings
6. Use old bolts and check clearance with plastigauge
7. Remove cap
8. Install back with new torque to yield bolts
9. Clean oil pan and pickup I like Berkebile 2+2 very strong but a bit $$
10. Install gasket sealer around oil pan
11. Put all exterior parts back on

Now the only problem I can see with this method is there is no way to verify the crank main bearings which may have some wear. I was desperate to get one engine running while I do a complete rebuild of my spare engine this is the only reason I went this route.

The rattle noise is gone.

One concern I have which may not be a big deal is while troubleshooting I swapped timing covers which has an embedded oil pump and also went with castrol 5w30 conventional my oil pressure after warmed up is about 23-25 psi and cruising 40-50 anyone see concerns?

 

[Ross]

25psi sounds low to me. I am installing a oil pressure gauge in my engine now, but haven't started it yet.
Your bearings look like low oil pressure!

from: https://www.cobaltss.com/forums/2-general-discussion/8306-proper-oil-pressure.html
According to the factory service manual the only info is "minimum oil pressure at 1000 RPM should be between 50 and 80 psi".
The GM Ecotech build book recommends installing a 30 Lb oil pressure cutoff switch.

 

[DCMoney]

Glad you found the issue, sucks, but at least you know.

Was the engine ran low on oil? Its weird to have all the bearings end up like that if everything was working the way it should.

EDIT:
I agree with Ross.

 

[ncgoblin]

Glad you found the issue, sucks, but at least you know.

Was the engine ran low on oil? Its weird to have all the bearings end up like that if everything was working the way it should.

EDIT:
I agree with Ross.

I always check the oil and its on the level but this is a used cobalt so who knows when I got it how it was maintained. Honestly if I were to build another goblin I would either buy a new engine or rebuild before installing. It is worth any headache that could come up with a used engine.