So yesterday my son was changing oil on our LS400 (1990). The car has been impeccable, even now, at 260k miles. As all the oil was drained, I noticed he spilled some on the driveway and was trying to clean it up with paper towels. Seeing that it was hard to reach under the car, I decided to move the car. I started the engine, put it in reverse, and let go of the brake pedal. Trying to move the car only a few feet, I held my foot on the brake pedal, and without ever touching the gas pedal, I backed up slowly, moved by the idling engine, and then I let go, stopped, and shut off the engine. This took around 6-7 seconds. As I shut it down, I asked myself "Did I just hear the engine knock?"

And then it hit me.

(in case you haven't noticed, I ran the engine with no oil in it - no wonder it knocked)
I have not run the engine since, even though it has a new filter and oil in it now. I am afraid of what I may find out as it would be devastating to see that I ruined our favorite car that has been like a family member all these years.
Any ideas? Have I destroyed the engine? Any way to know to what extent I've damaged it? Is it at all possible that the knock was there only because of lack of oil, but that the engine is still OK???
I'd especially like to hear from those who have experience with such matters.

 

If you only ran it a very short amount of time, you may have been just lucky enough to come out of this. It helps that these engines were also very overbuilt, and can withstand a lot of abuse.

Did you change the oil while the engine was hot or cold?

From this point, it would definitely be best to put oil into the car.. You won't be able to really tell what the damage is until you open things up

But if that's the case, you're better off finishing the oil change and trying to start the car again first to see if it still runs fine

When these engines are really cold, I have heard slight pinging or knocking until they warm up a little bit, as the oil starts to circulate. What your car experienced may have been similar and caused minimal wear because it was run only a very short time.

Mistakes happen. You will probably be ok

 

Thank you CELSIOR, you've comforted me. I have finished the oil change, put in a new Toyota filter, 5.5 qt of Mobile 1 oil, and everything is ready to fire her up, but I'd probably die if I saw that I ruined the engine that has been running like new all these years.

The knock was not hard or very loud, it was more like: "Did I just hear something weird?" (after I shut it off). It sounded like a weak (metallic?) knock or something similar.

 

If it's any consolation; when I was in the dealership, I recall we had couple of Corollas come in on a flatbed because the engines had locked up. Found out that the quick service kids left the oil filters loose, and the owners kept driving with the little red light on until the engines stopped.
In both instances, an experienced tech confirmed the engines were freed up after cooling down from the tow truck drive, put some oil in it, drove it a bit to confirm it was good, then gave it back to the owner.
Did you do damage? Technically yes. Was it enough to actually make a difference? Probably not.

 

Forgot to answer this one - the engine was maybe slightly warm. I drove it that day, but hours earlier. It was a warm day, so I imagine that it was kinda room temperature maybe (I live in CA, so no real freezing temperatures here)? I usually change oil when the engine is at least warm because the oil flows better.

 

Thanks GoldStar. I am kinda hoping that with all the overengineering and shortness of my stupidity there was not much damage. We'll see, I guess.

 

oh man these are the little things that terrify me!

luckily it was just a short time, there's always still just a bit of oil remaining in the engine that doesn't drain out due to the close tolerances, and this engine is already well broken in with all the rings etc... as seated as they're gonna be

keeping my fingers crossed for you! pls post an update when there is one

 

if you use quality oil (which you do with M1), there should be enough film to protect things for the <10 seconds of run time! the sound you heard might be the oil pump starved which is expected. plus you didn't put it under load other than putting it in reverse so this is the best case scenario (if there is one) for you.

my guess is it's fine, so keep enjoying it. we all know you won't make that mistake again, and thank you for sharing so we are more cognizant as well.

 

Thank you everyone for your support! I have to admit I could barely bring myself to start the car today (didn't try it last night).
The good news - it ran like a champ. Absolutely no strange noises, no problems, nothing - just ran as always. Drove it around for about half an hour, got on the highway, pushed it a bit a few times just to test it, and it behaved the same as always. I am super sensitive to strange noises, but I heard nothing out of the ordinary.

So the car runs fine and sounds the same, like nothing ever happened.

Whew. Kids, don't try this at home!

 

To add to that: we just went on an 800-mile trip and came back and the car and the engine ran as always. Smooth, fast, and a pleasure to drive.

 

glad to hear all is well!

think about it like this; it's like you cold started your car 14 times (2 per second you ran w/o oil) in a row - where a cold start involves no oil for half a second until oil pressure is built.