Hi all,
I recently acquired a low mileage s52b32. My plan is to do a top end refresh and general maintenance before swapping it into my e30.
Towards that end, I recently got a hold of a summit racing compression/leak down test kit to get some basic metrics on the engine.
The issue is that the engine has been sitting for a while, is on a stand etc. So from what I've read on the subject normal compression test procedure of disconnect fuel/spark and crank motor will not work here. Thus I chose to perform a leakdown test. I did this using the most general procedures available online: rotate cyl to TDC, inject 100psi read out leakdown listen for leakage in multiple places.
What is tripping me up is that I cannot get consistent results. below is characteristic of what I have been generally observing. (although the values have very large variances since i am not really getting consistent results from test to test.
cyl %leakdown
1 ~15
2 ~50 seems like leakage coming through intake valves
3 ~25 seems like leakage coming through intake valves
4 ~15
5 ~15
6 ~20
the thing is that sometimes I will go to a cyl and get a completely different reading than I got on the previous trials. Ok so my first conclusion was something is wrong with engine internals, pull head and take a look for valve piston contact, cyl scoring, etc. but I pulled the head and everything looks pristene. in fact there is so little carbon build up that I can wipe the pistons clean with a couple passes of a rag.
After thinking about this while I was removing the head, the intake cam seemed to be in the advanced position (~12deg) which I assume would cause overlap issues. but since the vanos system is not pressurized when I am doing this test, isn't it just free to flop around, thus giving me inconsistent readings?
I know there is a bmw specialty tool for operating the VANOS pneumatically. Is this required when doing an out of engine leak down test? I would really like to convince myself that my procedure was just borked before I reassemble my motor. Thanks!
Thomas
I recently acquired a low mileage s52b32. My plan is to do a top end refresh and general maintenance before swapping it into my e30.
Towards that end, I recently got a hold of a summit racing compression/leak down test kit to get some basic metrics on the engine.
The issue is that the engine has been sitting for a while, is on a stand etc. So from what I've read on the subject normal compression test procedure of disconnect fuel/spark and crank motor will not work here. Thus I chose to perform a leakdown test. I did this using the most general procedures available online: rotate cyl to TDC, inject 100psi read out leakdown listen for leakage in multiple places.
What is tripping me up is that I cannot get consistent results. below is characteristic of what I have been generally observing. (although the values have very large variances since i am not really getting consistent results from test to test.
cyl %leakdown
1 ~15
2 ~50 seems like leakage coming through intake valves
3 ~25 seems like leakage coming through intake valves
4 ~15
5 ~15
6 ~20
the thing is that sometimes I will go to a cyl and get a completely different reading than I got on the previous trials. Ok so my first conclusion was something is wrong with engine internals, pull head and take a look for valve piston contact, cyl scoring, etc. but I pulled the head and everything looks pristene. in fact there is so little carbon build up that I can wipe the pistons clean with a couple passes of a rag.
After thinking about this while I was removing the head, the intake cam seemed to be in the advanced position (~12deg) which I assume would cause overlap issues. but since the vanos system is not pressurized when I am doing this test, isn't it just free to flop around, thus giving me inconsistent readings?
I know there is a bmw specialty tool for operating the VANOS pneumatically. Is this required when doing an out of engine leak down test? I would really like to convince myself that my procedure was just borked before I reassemble my motor. Thanks!
Thomas
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