bradland

This falls somewhere between Highly Unlikely and Impossible. Prob closer to Impossible...
The "Reputable" repair shop is dishonest. The valve cover bolt torques spec is EXTREMELY low not to mention 98% of the 400s and 430s on the street have become even looser over time and are only finger tight

Stroock639

my bolts were literally just loosely sitting in place when i went to give them a gentle snug down... i've read here that the gasket over time shrinks away from the bolts and causes this, is that confirmed? my valve cover gaskets are definitely slowly leaking, although more like 'weeping' since there's never puddles on the ground and the oil level is always good even after 5000 miles... you can smell it though and if you hold a light at the back of the engine it looks like there's steam coming up

deanshark

Of all the vehicles I've worked on for many, many years, I've never seen a valve cover bolt that couldn't be taken off with a 1/4" ratchet. Especially the LS400 which you can take out most by hand.
Dishonest? I'd agree, and definitely not someone I'd go back to.

I never heard this but it sounds like it could be right. My theory would be more of the vibrations from bad (old) motor mounts vibrating the bolts loose over time.

bradland

I blame the rubber impregnated washer on the VC bolt. The torque spec is already negligible so when these shrink any holding strength fades away. They work great when new but 10 to 15 years later not so much...

spuds

Is there a part number for those bolts?

bradland

https://www.lexussouthatlantaparts.c...008010330.html

spuds

Bookmarked,thank you bradland.