How to tell if an engine has blow by
Excessive blow-by occurs when combustion gases leak past worn piston rings down into the crankcase, which can be difficult to distinguish from normal engine vibration or running behavior without specific checks. It stops you from accurately diagnosing internal engine wear or knowing whether an older vehicle's motor requires major mechanical repair.
What people tried
Every workaround mentioned in the threads below. We haven’t tested any of them — and nobody here is claiming they worked.
- 1Running a compression test to check psi values and inspecting the EGR pipe
- 2checking if the PCV valve is working
In their words
Unedited, grouped by where they were said, most upvoted first within each place, each linked to the thread it came from.
Where this came up
People with this problem also raised
- 7Engine smoke and burnt coolant smell while driving
- 2How to know if a car has a blown head gasket
- 3Is smoke coming out of this engine part normal?
- 7Engine rattling noise and sudden coolant leak while driving
- 81How to figure out what an unfamiliar car engine noise is
- 4Can a vacuum leak cause multiple cylinder misfires and a lean code?