2010–2023 GX460 (4.6L V8) · Last verified
My GX460's coolant level keeps dropping with no puddle. Is it the valley plate?
The short version
- Slow drop
- You can ride it out for a while. Top off and watch the level.
- Stop driving if
- The reservoir runs very low or the temperature gauge climbs. Overheating can blow a head gasket, which turns this into a far more expensive repair.
- Expect it
- It's a known weak spot on the GX460's V8, and it usually shows up after 100k miles. Mine had it.
- Rule out first
- A worn radiator cap or loose coolant fittings can also cause slow loss. Both are cheap to check.
- Confirm it
- A shop can look into the engine valley with a borescope. Coolant pools there and runs down the back of the engine, which is why there's no puddle.
- The fix
- Replace the valley plate gasket. The intake has to come off, so most of the bill is labor. Get two quotes. $1,400–$2,000 is fair; around $4,000 is too high.
