Could bad rod bearing cause DOD issues?
08-03-2017, 12:00 PM
#1
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Could bad rod bearing cause DOD issues? I bought a 5.3 Trailblazer that had a DOD issue and a noisy rod bearing when it warmed up with the intent of fixing it and ditching the DOD. I assumed someone driving it around with the miss from the DOD failure had put too much stress on the rod bearing and killed it. Upon tearing it down I found someone already had it apart and replaced some DOD lifters. I also found the Rod bearing that was bad was not in the cylinder showing the miss, and was much worse than I had thought I would find. I assumed a DOD failure had caused the rod bearing issue, but now I am wondering if the loss of oil pressure from the bad rod bearing could have caused the DOD to not function properly, and there is actually no issue with the DOD. This isnt really a performance build, or even a long term vehicle for me so I just want to get it fixed properly in the least expensive manner. Also curiosity has me wanting to know. Thoughts?
Thanks
Roy
Thanks
Roy
08-03-2017, 12:21 PM
#2
There are 3 factors that effect rod bearings on the trailblazer/envoy engine setups.
1. computer programming. The amount of fuel added and the rate at which it is added is VERY anemic causing what most tuners call "stock knock". Most run very poor quality fuel in them as well causing it to knock worse. That hammers the bearings anyway...which leads to issue 2
2. oil pan design. the front sump pans have oiling issues and cause alot of problems and lets include that those pans also have a huge gaping hole through them that somewhat decreases capacity. Most combat that by adding an extra quart which seems to help.
3. cooling/hot spot issues. The 03 and up engines have coolant caps on the back which can and do cause cooling flow issues as well as steam pockets in the back by cyls 7 and 8. That only agitates the knock issues and causes those to go bad.
Normally those onle effect 7 and 8 but can effect nearly any cyl honestly.
Add in the dod and its an even worse issue.
The ways to combat that are
Get a tune
Run good fuel
Add an extra qt to the pan
Use good bearings
Use high quality highest octane fuel
Run any number of vapor/coolant xover collection kits
That is your best bet.
Ive torn apart 4 or 5 tbss engines that #8 rod bearing was spun so bad the crank was a boat anchor after.
If the bearing were diminished to shavings those can clog the dod actuators and ruin lifters also.
1. computer programming. The amount of fuel added and the rate at which it is added is VERY anemic causing what most tuners call "stock knock". Most run very poor quality fuel in them as well causing it to knock worse. That hammers the bearings anyway...which leads to issue 2
2. oil pan design. the front sump pans have oiling issues and cause alot of problems and lets include that those pans also have a huge gaping hole through them that somewhat decreases capacity. Most combat that by adding an extra quart which seems to help.
3. cooling/hot spot issues. The 03 and up engines have coolant caps on the back which can and do cause cooling flow issues as well as steam pockets in the back by cyls 7 and 8. That only agitates the knock issues and causes those to go bad.
Normally those onle effect 7 and 8 but can effect nearly any cyl honestly.
Add in the dod and its an even worse issue.
The ways to combat that are
Get a tune
Run good fuel
Add an extra qt to the pan
Use good bearings
Use high quality highest octane fuel
Run any number of vapor/coolant xover collection kits
That is your best bet.
Ive torn apart 4 or 5 tbss engines that #8 rod bearing was spun so bad the crank was a boat anchor after.
If the bearing were diminished to shavings those can clog the dod actuators and ruin lifters also.
Last edited by tech@WS6store; 08-03-2017 at 12:27 PM.
08-03-2017, 12:55 PM
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Hey you should get a gold star for that explanation. You are spot on, it is cylinder #7 that was spun. Would it be helpful to connect those rear coolant ports upon reassembly?
Thanks
Roy
Thanks
Roy
08-03-2017, 12:58 PM
#4
You can use another coolant crossover back there...i think itll fit but dont quote me on that.
There are 5 diff styles. ls6, truck, 5thgen camaro, and a few others. or you can buy 2 billet caps with fititngs and tie it together and bring to the front. Honestly with the truck intake you can use a reg ls spider off the fbodys and vettes and early trucks also.
There are 5 diff styles. ls6, truck, 5thgen camaro, and a few others. or you can buy 2 billet caps with fititngs and tie it together and bring to the front. Honestly with the truck intake you can use a reg ls spider off the fbodys and vettes and early trucks also.