E280 Engine knock (M272 3.0L)
05-13-2020, 03:02 PM
#1
Junior Member
Thread Starter
E280 Engine knock (M272 3.0L)
Hello all,
My son has a 2007 E280 4matic that he bought super cheap. We know that the car has had a hard life... Since we got it, we have done some work to get it to an OK daily driver condition (I'm teaching him as we go, and that's sort of the idea anyway). There has always been a bit of an engine knock, so I bought lifters (a mechanic friend said that it was definitely lifters - or cam followers if you want to get technical...) and I did that job at the beginning of COVID lockdown. Well, the knock is still there.
So I still have a knock and I'm stubborn. Plus I have time...
I'm guessing at this point that it's the big ends of the con rods that are the problem. Is there a way to determine if I need to have the crank machined before I pull the motor? I don't rally want to wait a month after opening up the engine to get new bearings either. I've been down the road where I have to wait then come back to a project and ask, "Where does this go?"
Just to be clear for my American friends, the E280 wasn't available in the US, but is basically a lower spec E350 with the 3.0L M272 instead of the 3.5L. Available in Canada and Europe as I understand it. This particular engine was made after the balance shaft fix.
Thoughts on this? Pull the engine then order parts? Bank on being able to use std bearings and assume that the journals are OK or pull the engine first and be sure? Talk to wreckers and get a good core (I've thought about getting a 3.5L long block and go with that - the 3.0 is a bit underpowered for the size of the W211)? Throw it all away?
FWIW, I also see this as an opportunity to buy tools...
Here's a video moving around the engine. The knock seems slightly more pronounced on the driver's side near the firewall, but the difference is pretty subtle (might be sound bouncing off the engine compartment).
Thanks,
Miles
My son has a 2007 E280 4matic that he bought super cheap. We know that the car has had a hard life... Since we got it, we have done some work to get it to an OK daily driver condition (I'm teaching him as we go, and that's sort of the idea anyway). There has always been a bit of an engine knock, so I bought lifters (a mechanic friend said that it was definitely lifters - or cam followers if you want to get technical...) and I did that job at the beginning of COVID lockdown. Well, the knock is still there.
So I still have a knock and I'm stubborn. Plus I have time...
I'm guessing at this point that it's the big ends of the con rods that are the problem. Is there a way to determine if I need to have the crank machined before I pull the motor? I don't rally want to wait a month after opening up the engine to get new bearings either. I've been down the road where I have to wait then come back to a project and ask, "Where does this go?"
Just to be clear for my American friends, the E280 wasn't available in the US, but is basically a lower spec E350 with the 3.0L M272 instead of the 3.5L. Available in Canada and Europe as I understand it. This particular engine was made after the balance shaft fix.
Thoughts on this? Pull the engine then order parts? Bank on being able to use std bearings and assume that the journals are OK or pull the engine first and be sure? Talk to wreckers and get a good core (I've thought about getting a 3.5L long block and go with that - the 3.0 is a bit underpowered for the size of the W211)? Throw it all away?
FWIW, I also see this as an opportunity to buy tools...
Here's a video moving around the engine. The knock seems slightly more pronounced on the driver's side near the firewall, but the difference is pretty subtle (might be sound bouncing off the engine compartment).
Thanks,
Miles
