Sick motor in '96 LX450

[TexasDoug]

The noise frequency is an important clue. It sounds like about 5 ticks per second or 300 RPM, when it is idling at 600 RPM. The cam runs at half the speed of the crank, so it seems more likely cam / valve related than crank / piston.

Wow, great point. I won't have any meaningful updates until the weekend when we can spend a bit more time with it. We'll pull spark from each plug just to be sure and see if that has any impact. It appears the previous owner had about as much auto knowledge as me (enough to be dangerous) but a lot less fear. We're finding all sorts of sloppy DIY weirdness in this truck (e.g. belts wrong / loose, etc), but for how little we paid for it I suppose that's to be expected.

 

[Pin_Head]

Piston slap, rod knock etc can make more noise on the power stroke making noise at half the RPM of the crank,but it will also quiet when you pull the spark plug.

 

[NCFJ]

Hard to tell with just video sound. I can tell you that I bought my wife's 95 80 with a "blown" motor. Drove it on the trailer puking water out of a huge crack in the radiator lower tank. New radiator and a fresh round of fluids all around, she has been driving it for two years. It is our wheeling truck, never let us down. Best I can tell is it has a wrist pin knock.

Drive on! Unless you fear deeper damage.

 

[TexasDoug]

Final verdict (for now - I'll update down the road if/when the engine finally gives out for a post mortem) from one of the best Toyota shops in town is that they think it's a slightly bent rod and we might as well just drive it til it grenades. The top end has been rebuilt recently, so it's likely the HG blew and it overheated which led to the rebuild, which of course would't solve the bent rod problem though.

So basically no shocking conclusions to share here. BIL is gonna keep the truck and just drive it. If the engine goes tomorrow, we'll start engine hunting. If it goes 5 years from now, awesome.

Now to sort out the disaster that is the hoses in this thing ...

 

[TexasDoug]

For posterity, I should point out for anyone reading this thread in the future that this video only shows the truck idling which makes it pretty hard to distinguish knock from other misc noise and what I think is also noisy valves. There is a subtle knock that can be heard at 2.5K RPM or so upward that isn't demonstrated well (if at all) by the video. I'm guessing the first shop we took it too encountered this sound before we did, hence the confusion on our part and the genesis of the original post. But now we hear it too.

My BIL are both scratching our heads about how we missed that when driving the truck before purchase. Maybe additives quieted it down some? Regardless we're gonna stop worrying about it and just carry on rehabilitating the truck.

 

[AmabilisCruiser]

I'm having this exact same sound coming from my engine - figure it out yet? My shop is stumped and my journey is just beginning. Good tips in here so far.

 

[TexasDoug]

I'm having this exact same sound coming from my engine - figure it out yet? My shop is stumped and my journey is just beginning. Good tips in here so far.

Never figured it out but the truck is still running strong and it’s been my brother in law’s daily driver for the last 3 years. The noise is still there and it’s no worse or better. But we definitely aren’t worried about it anymore