concerned about the broken valve issue

luk · **Joined:** Fri Oct 26, 2018 2:45 am **Posts:** 26

Hey all, after reading about so many issues with broken valves here I am getting paranoid about this happening to me. It seams to happen quite often after guys replace the rockers as I have just done. I am wondering why this is the case. Bad replacement rockers?, coincidence?, what about the new rockers could cause the old about to break valves to go... and fairly soon after installation.... any thoughts?

flash7210 · **Posted:** Sat Apr 13, 2019 6:37 pm

I’ve got over 220,000 miles and have never broken a valve.

However, I did have to replace a cracked head at 160,000 miles.
I’d much rather deal with a cracked head than a broken valve. Much less damage.

IMO, cracked heads and broken valves are related to heat.
Either high exhaust temperatures or poor coolant flow.
So...

Delete the egr.
Open up the exhaust flow.
Make sure the turbo functions properly.
Make sure the intake flows well with no holes in the hoses.
Install a Provent to keep oil out of the intake path.
Keep your cooling system flowing well and healthy.

geordi · **Posted:** Sat Apr 13, 2019 7:52 pm

That a valve would fail soon after replacing the rockers... Seems to me like an awful coincidence. The valves fail after about 300 billion cycles which roughly translates to 200k miles.
The rockers are just levers, and the lifters (hydraulic lash adjusters) press upward on the rocker and provide the anchor point to counter the valve on the opposite end. The rockers are designed to fail if the timing is botched and the valves contact the pistons. I do not see a reason for the valve to fail just by replacing the rockers, UNLESS something else was done wrong, perhaps the timing is off just enough to allow the pistons to "kiss" the valves but not hard enough to break the rockers?

WWDiesel · **Posted:** Sat Apr 13, 2019 11:27 pm

High heat is the exhaust valves no. 1 enemy, keeping EGT under control below ~1300 deg.s F at all times on a diesel engine is a major factor along with having proper boost, proper fueling, and adequate coolant flow.
Valve guide wear has been ruled out as a contributing factor and metallurgy failure most likely due to overheating so far has been suspected as the major contributing failure factor to exhaust valve failure.
We have also ascertained by inputs from many on this forum that proper coolant flow through the head during the very critical engine warmup period is an absolute necessity to prevent any hot spots in the head that can lead to blown head gaskets and / or overheating in the exhaust side area of the head. That is why in-hose thermostats are no longer recommended to be ever used on this engine due to its unique coolant flow design and requirements.

concerned about the broken valve issue

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