Cylinder # 1-175 psi
Cylinder #2-175 psi
Cylinder # 3-50 psi
Cylinder #4-150 psi
Cylinder #5 and #6-200 psi
Is this acceptable engine?
Absolutely not, the difference between all the cylinders should ideally be 10% or less. 200 psi to 180 psi would be fine, but the 150 psi and 50 psi cylinders mean this engine is BAD.
No.
All cylinders should be within a few percent of each other in a good engine.
#3 has a severe problem (or the test equipment does).
I'd re-test immediately with results like that in case the cylinders were initially dry and turning the engine over for testing gradually distributed oil up the cylinder walls and wetted the rings, giving the higher results later on.
The full set of results should be consistent from test to test to be trustworthy.
jon is correct. average compression for a petrol engine ought to be in range of 150 -190 psi but the important part is balance between cylinders ought not to exceed 10%. anything under 100 psi for example would indicate a major issue on that cylinder. bad valves? rings shot? it will need rebuilding and reworking. better off getting a different engine or at least one with no issues needing looking at. bet the low pressure cyl is burning oil.
If'n it was a 5 cylinder or you only expect to get power from 5 cylinders it is very good. For a 6 banger, number 3 cylinder is almost dead. You have bad rings, bad valves, leaking head gasket, or a cracked head. Look at $1000 and up for a shop to fix it.
That's a BMW, you have alot of work ahead of you.
Get the thing looked at by a BMW tech before you start playing around.
Leakdown tests and engine bulletins for correct repair should be consulted.
There can be ways to fix things like this in chassis.
Until testing is complete, no repair is recommended.
No. Cylinder #3. has big-time cylinder wall, piston ring or valve problems. A dry and wet compression test will tell you which the motor has.
#3 is a problem for me. Others are OK. Retest #3 after adding about one tsp of engine oil thru the spark plug hole. If the compression increases a significant amount you have worn rings. No improvement signals a valve not seating.
if you didnt typo #3 its junk
Looks acceptable to me
BMW 520i compression:
Cylinder # 1-175 psi
Cylinder #2-175 psi
Cylinder # 3-50 psi
Cylinder #4-150 psi
Cylinder #5 and #6-200 psi
Is this acceptable engine?
