I try not to post too much on this forum now because I believe there are lots of people who need help more than I do, but I'm now clueless on what to do, so I would like some help.

Just to catch everyone up to speed on my project. I bought my LS430 in November of 2023. It has always been a project since the day I got it, having problems here and there, but nothing I couldn't fix. Enjoyed it for almost two years, putting over 10k miles on it, again with it always having some small issues. In late January of 2025, I was on my way to work when I heard the chime that I'm sure a lot of LS430 owners are familiar with. Usually, it's not a big deal, but this time the display told me that I had no oil, so I put the car in neutral, pulled over, and turned the car off immediately. Later, I was able to put oil in the car and drive just fine. I decided that I was tired of my car constantly having problems, so I decided to park it until I could solve almost all of its problems. It has been parked for over two years and was just recently moved out and back in without the engine running for unrelated reasons. So far, I have replaced the water pump, timing pulleys, cam seals, spark plug tube gaskets, and lots of other parts. Now to my current problem. I have been stuck on a confusing problem since October. A friend of mine helped install the water pump back in October, and it seems we did everything major correctly. We put the belt on, and he spun the engine over several times by hand to ensure the timing was correct. Later that month, I went to turn the engine to ensure timing again, and so I could work on replacing my cam seals, but it only took a couple of turns with a breaker bar for the engine to just stop. No weird sounds or anything, just full on stop. I have checked with a borescope and madesure that no valves are making contact with the pistons, and everything seems ok.I removed and reinstalled my camshafts since then, and the problem persists, so I'm almost certain it is NOT my camshafts or something on the top end, and I can't take off my oil pan as of right now, so I can't inspect the bottom end. Also, unless it really comes down to it, I will not take the car to a shop or sell it; I am very much determined to get this car back on the road. Thank you to everyone for your help.

I will hopefully be making more posts in the future about the work I'm doing on my car, and since I've been insanely meticulous about the process and steps I used to work on my car, I want my account to be a good spot for anyone also working on their LS430.I'm aware that there are already multiple good threads about the work that I'm going to do.Ijust would like to add to the pile of wisdom already on this forum, especially because there is a lot of conflicting knowledge out there, and I would like to steer people in the right direction.

 

Either something is locking up externally to the engine such as water pump/timing components or the engine is locking up internally. I don't see how one could watch each cylinder with a borescope to see if there was valve to piston contact. You checked every cylinder and didn't see any water that got in?

 

do the timing marks still line up ?

 

This happened to me when I did the timing belt in the LS400.

https://bobistheoilguy.com/forums/th...2#post-6048751

Unlike the Mazda guy, I bore scoped the cylinders and found nothing unusual.

Remove the plugs and give WD-40 a try.

BTW, rotating the engine backwards is a no-no. When I did it, it didn't hurt anything. Luck, I suppose.

 

When I did my timing belt as I was disassembling I had dropped a nut down into the lower cover. As I was rotating everything just to make sure it was all aligned before taking the crank off everything suddenly jammed up. It turns out the nut I dropped had worked it's way in between the crank sprocket and the belt and was jamming up. I didn't force it and it wasn't a big deal as I was taking everything apart anyway. So if it's still partially disassembled look down around the crank and the belt to make sure something isn't jamming it up.

 

Thank you, everybody for your help. To be clearer, I have checked the water pump, and everything external, and checked each combustion chamber with a borescope at the point when the engine stopped. Yes, the timing marks still line up. Paulo57509 reminded me that there was a piece of carbon that I thought was blocking the #3 piston from hitting TDC. I tried some methods to break the piece apart, but they were probably unsuccessful. I will try some WD-40 or something better at dissolving carbon tomorrow.

 

i 2nd trying to turn it with the spark plugs out. i bet theres oil or water in one of the cylinders

 

The spark plugs have been taken out, and there is no liquid in any of the combustion chambers. I tried carb cleaner to dissolve the carbon deposits, but it didn't work. I am now looking for other options.

 

As duowing mentioned... you sure something isn't wedged in the crank sprocket?

 

I have all of the timing covers off, so I can clearly see that there is nothing stuck in any of the sprockets.