2005 LX470 with 340k: Cracked Head Gasket

[FamilyCruiser]

Recently our LX through some new codes: P0304, P0171, and P0174. We've also had the cat code P0420 in the past that went away after a new gas cap and a round of Cataclean. The cat code came back with the new codes. I had the P0304 last year and resolved with a new ignition coil and spark plug. Checked the plug and was surprised to find that the insulator was cracked. I'm seeing some evidence of leaks around the cylinder head gasket. Had our mechanic check it out and he found a crack in the head gasket, and a crack in the exhaust manifold gasket. He recommend replacing the exhaust gaskets, head gaskets, timing belt (even though we did that 40k miles ago), knock sensors, and knock sensor wires for the low price of $7300~.... I'm looking into what it would take to do some of this myself to save on cost, but wanted to get an opinion from the community on whether it makes sense to include the timing belt, knock sensors, and sensor wires. I definitely need new gaskets and plugs, but can I get away with postponing the rest? 100 series wisdom appreciated!

 

[FamilyCruiser]

Sharing some additional info just in case it helps. Last year we had to replace the radiator after it cracked and started leaking. The engine temp gauge did get near the red line while my wife was driving it, before the issue was addressed. I suspect that this may have accelerated wear on a number of parts, including the gaskets, leading to my current predicament.

 

[bruceson]

for $7300, I would have a low mileage engine put in instead. Head gaskets don't just crack. The heads will have to be machines flat. And even if you fix this, a bunch of other issues could occur from overheating the engine like bad piston rings etc. The labor to rebuild is too expensive, cheaper to just replace.

 

[jsloden]

I second the used engine route. These engines don't usually have head gasket issues. I would find one with decent mileage and get it swapped. That should save you a few grand. car-part.com is your friend.

 

[GTV]

Leak down test is needed. Head gaskets don’t “crack”.

 

[dirttrak]

The insulator on your sparkplug cracked, the ground electrode looks pretty worn out. I wonder you the truck might have overheated in the past that could have blown you head gasket