loud engine knock after replacing motor mount (video) (1 Viewer)

[wpns4l]

Vehicle: 1992 FJ80. 3FE and 208k miles. Never has had a knock and has 150-156 compression across all cylinders.

Today i replaced my broken driver side motor mount. To do this i removed the nuts on the driver side mount and loosened the top nut on the passenger side mount. Then using my floor jack and two pieces of 2x4 wood i jacked the engine up at the front of the oil pan. I was able to remove the driver side mount and slide the new one in pretty easily. Tightened everything down, started the motor and immediately heard a extremely loud knocking sound.

I immediately turned the engine off cause i thought maybe my fan was hitting the shroud. It was not. The fan moves freely, all belts are less than 10k old. Oil change in the last week. My vehicle has never had a knock before. The sound starts as soon as the engine starts and does not fluctuate in loudness. I was afrai to rev it but i hit the gas a little and did not notice a increase in knocking speed.

I noticed i put a small dent in the oil pan. If i had to guess its maybe 1/4'' deep and 3-4 inches long. I've included a picture and outlined in red where i placed the wood and you can kinda see the dent.

Any ideas? I am assuming i've jacked something up inside the oil pan or engine.

 

[ton504]

Check your radiator fan and shroud. Looks like the shroud is falling apart and possibly hitting the fan.

Edit - Never mind, I didn't fully read your post. Maybe its worth checking again.

 

[wpns4l]

Check your radiator fan and shroud. Looks like the shroud is falling apart and possibly hitting the fan.

Edit - Never mind, I didn't fully read your post. Maybe its worth checking again.

The fan doesn't hit the shroud. It's broke as a result of the broken motor mount. It freely spins without hitting the shroud and before replacing the mount the vehicle did not have this noise

 

[flintknapper]

That 'hollow' knocking sound sure sounds like something contacting the oil pan.

Can you place your hand on the pan with the engine running and 'feel' for contact?

 

[wpns4l]

That 'hollow' knocking sound sure sounds like something contacting the oil pan.

Can you place your hand on the pan with the engine running and 'feel' for contact?

I will check tomorrow. I found this thread. damaged oil pan while changing motor mount and it sounds exactly like my problem. Looks like i'll be dropping the pan and either getting a new one or hammering mine flat again. I would think the crankshaft wouldnt sit so close to the bottom of the pan that such a shallow dent would hit it.

 

[wpns4l]

UPDATE:

So it was the dent in my oil pan hitting the crank that was making the noise.

Over the past two weekends I've been working on it. First weekend i got the pan off and flattened out the dent. Today i cleaned it all up and put it back together. I originally tried to use RTV on the gasket and pan to get it to stay in place while i put the oil pan back on but it didn't want to stay put. So then i used some RTV and small zip ties and attached the gasket to the engine block then put the pan on. Worked like a charm and wished i did it the first time.

Now my only fear is i might have over tightened the oil pan bolts. I turned them till tight and then a 1/4 past that but after some reading it sounds like that might be to much? Hopefully not. Will find out either tomorrow or next weekend when i put oil in it.

 

[flintknapper]

Thanks for the 'follow up'. So many times we never hear back from the person who posts about a problem.

By taking this issue to its conclusion and sharing it with us, it serves to give someone else a little 'direction' in the future, should they experience the same problem.