LB7: Rotational knocking when engine is warm
- Thread starter SpotlessDemo
- Start date
Yes they do, 7.3, 6.0 and 6.4 have hydrolic lifters, idk about the 6.7 haven't been in one yet
All duramax engines have solid roller lifters. The scheduled adjustment time under (normal) conditions is 200,000 miles. It is correct that hydraulic lifters will have 0 lash as the hydraulic lifter keeps the rocker arm continuously applied to the valve. Ford powerstrokes all have hydraulic lifters up through the 6.4L and the 6.7L has a new designed hydraulic lifter with 2 lash adjusters per lifter.
I have already seen duramax engines with normal usage have lash adjustments in excess of .035 in. . The engines were very noisy and after adjustment, were quieter than I could remember them when they were new. Power levels came back up and very smooth at idle and under load. The engine only had 160,000 miles on it and was a daily driver with no aftermarket add-ons or programmers. Another was a 4500 Top Kick that was used hard with a LB7 engine. Serviced regularly, it had a complaint of low power and knocking. When we went in to change the injectors, we checked the valves. I don't know how the engine was running they were so far out of adjustment.
The engine in this post sounds like a bad injector or a FICM acting up. I'm leaning towards the injector. The only downside is not knowing more about the previous owner and what did they do to the truck. I would want to look for signs of any aftermarket items that may have been installed and then removed prior to the sale. Is the exhaust modded? Is the stock intake air filter box modded or missing? Wires or harnesses look tampered with? Did they put things back together right? bad wire crimps, ect.
As far as the injectors go, I've gotten remans from the dealer and they were bad right out of the box.
The LB7 is one tough motor. I've seem them, as I'm sure others here have, take a tremendous amount of abuse before they break. I would say that if there were power increasing addons used and they were kept under the 550 horse area, I'd say the engine is fine. The tranny, not so much.:roflmao:
I have already seen duramax engines with normal usage have lash adjustments in excess of .035 in. . The engines were very noisy and after adjustment, were quieter than I could remember them when they were new. Power levels came back up and very smooth at idle and under load. The engine only had 160,000 miles on it and was a daily driver with no aftermarket add-ons or programmers. Another was a 4500 Top Kick that was used hard with a LB7 engine. Serviced regularly, it had a complaint of low power and knocking. When we went in to change the injectors, we checked the valves. I don't know how the engine was running they were so far out of adjustment.
The engine in this post sounds like a bad injector or a FICM acting up. I'm leaning towards the injector. The only downside is not knowing more about the previous owner and what did they do to the truck. I would want to look for signs of any aftermarket items that may have been installed and then removed prior to the sale. Is the exhaust modded? Is the stock intake air filter box modded or missing? Wires or harnesses look tampered with? Did they put things back together right? bad wire crimps, ect.
As far as the injectors go, I've gotten remans from the dealer and they were bad right out of the box.
The LB7 is one tough motor. I've seem them, as I'm sure others here have, take a tremendous amount of abuse before they break. I would say that if there were power increasing addons used and they were kept under the 550 horse area, I'd say the engine is fine. The tranny, not so much.:roflmao:
And that question was asked for what? The analogy was given for peace of mind to the new owner of a LB7 Duramax. It had nothing to do with the fact that the Duramax engine has done nothing but get better with each new design. Unlike Ford, who made a new engine every few years to try to hide the flaws from the old design.and the LLY-LBZ-LMM-LML isnt?