Partially Seized Motor
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Author:  StraTact [ Wed Mar 07, 2018 5:18 pm ]
Post subject:  Partially Seized Motor

I'm thinking I may have a partially seized motor.

My 1997 3800 Series II Bonneville, with only 170K miles, sat more than 2 months (since Christmas) while I took my time to install a new fuel tank, fuel pump, fuel lines and exhaust system parts.

After installing the parts, whenever I turned the key, the starter turned the motor only a bit, for about 1/2 second, then stopped. Each time I turned the key, the same happened until the starter motor died completely (but solenoid still worked). I'm sure the starter motor died because it still didn't turn after bench testing it. So I bought a re-manufactured ACDelco starter from RockAuto and installed it. Same thing happened!

So I isolated the starter by removing its 2 wires, unhooked my serpentine belt, and put +12VDC directly to the 2 starter leads, with battery negative to the starter case. Again, the solenoid works but the starter just barely turns the motor, like my first starter, for only about 1/2 second and then quits turning.

I think I have a partially seized motor from sitting only 2 months! Could this be true?

Although it only sat for 2 months, I'm guessing that it may have corrosion built up on the cylinder walls that could have caused the rings to bind up, causing the pistons to partially seize. I'm guessing it probably provided enough resistance to kill my original starter. Although I changed my Mobil1 synthetic oil only 5K miles ago, it's really black and on the low side now. I'm now worried that there might be some damage inside my motor.

Online, I found that I should change my oil again and squirt some PB Blaster into the cylinders (don't have any Marvel Mystery Oil on hand) and let it sit overnight before trying to start it.

Any other suggestions? Could it be true that sitting for only 2 months has caused this to happen?

Author:  RJolly87 [ Wed Mar 07, 2018 11:44 pm ]
Post subject:  Re: Partially Seized Motor

Pull the spark plugs, and try turning the engine over by hand.

If there is corrosion on the cylinder walls after only 2 monts, the engine is likely ingesting coolant. Hydrolock can also cause the issue you are describing, but should clear when the engine is turned over without sparkplugs.

Author:  96 SSEi [ Thu Mar 08, 2018 2:55 am ]
Post subject:  Re: Partially Seized Motor


Author:  StraTact [ Fri Mar 16, 2018 12:22 am ]
Post subject:  Re: Partially Seized Motor


Yes, I pulled the plugs, and injected a little Marvel Mystery Oil into each cylinder using a small syringe that I used to give my dog some medicine.

Then I let it sit for two days, mainly because we had a huge snowstorm here in NH.

Then I turned it by hand a few turns and then connected power again directly from a good battery and it cranked with no problem.

Finally, I re-installed the spark plugs and tried again to crank it using a good battery connected directly to the starter.

It tried to crank, but wouldn't. Each time I applied power to the starter, it only turned a little bit, then stopped.

I guess I'll add more Mystery Oil to the cylinders, and change the dirty engine oil & filter (and look to see what's in it), then let it sit overnight and try again.

Any suggestions?

Author:  StraTact [ Sat Apr 07, 2018 11:45 am ]
Post subject:  Re: Partially Seized Motor

I found out why my engine wasn't cranking much when the plugs are in, but cranking great when the plugs are all out, when my starter is connected directly to the battery of another running vehicle (Jeep Grand Cherokee).

It turns out that half of its strands of one of the 2 jumper cable wires were broken, so not enough current flowed to crank the engine (and overcome the engine compression) when all the plugs were installed. However, enough current flowed to crank the engine when all the plugs were removed.

Good thing I found out it was a bad jumper cable, because I was about to return the remanufactured ACDelco starter to RockAuto, and claim it wasn't re-manufactured correctly.

So, now my car starts properly and runs a lot better now, with no fuel line leaks.

But I think it's kinda weird that my my first Bosch battery, from PepBoys, failed after only 2 years and my second Bosch battery failed after less than just 1 year of use. Each time, it would only charge to 10.5 VDC. I returned both batteries under my 3-year free-replacement warranty, so now my car is running on my 3rd Bosch battery. Maybe it has something to do with my having to recharge my battery each time I forgot to unplug my seat's heating pad (it gets really cold here during the winters). I hope this one lasts 5 years like all my non-Bosch batteries did.

Anyways, thanks for your help and suggestions.

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