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Compression test readings
Posted: Thu Dec 01, 2011 8:20 pm
by Reck
Hi all - Going to look at an E21 tomorrow, getting a compression test done on the engine. What sort of readings are in the 'healthy' range for an M10? Wet/dry?
Cheers
Jason
Re: Compression test readings
Posted: Thu Dec 01, 2011 9:56 pm
by mr edd
my haynes says that below 130psi is bad ....135-150psi is normal ...and above 150psi is good..I cant tell you anymore than this as i have never done a compression test...edd
Re: Compression test readings
Posted: Thu Dec 01, 2011 11:17 pm
by Reck
Cheers Edd. Does the manual mention if those figures were wet or dry? Engine hot or cold?
Re: Compression test readings
Posted: Sat Dec 03, 2011 2:29 pm
by Reck
We only ended up being able to test 3 cylinders as we couldn't shift the spark plug in cyl 3, I think there was some crap down there stopping the socket going in.
Cyl1: 95 Cyl2: 100 Cyl4: First reading 75, second reading 100?!
The values are low. I'm thinking perhaps if the valves haven;t been adjusted in a while they may not be seating properly. However, the value seemed to creep up slowly i.e. the engine would have to be turned over for about 7/8 seconds to reach those values.
There was no smoke on start/accel/decel.
Can anyone help me interpret these?
[edit] Just realised, I don't think we had the throttle wide open when we did the above. Could that have restriced airflow into the cylinders and account for lower-than-normal readings?
Re: Compression test readings
Posted: Sat Dec 03, 2011 11:49 pm
by murran
thats low dude. 50 or above on first compression, 150-160 on each cylinders after 8 comps.
i think any m10 you buy is guna need a rebuild. whats wrong with the one we fitted????
Re: Compression test readings
Posted: Sun Dec 04, 2011 1:47 pm
by drjim
That still hasn't been determined!!
Re: Compression test readings
Posted: Sun Dec 11, 2011 3:52 pm
by Reck
murran wrote:thats low dude. 50 or above on first compression, 150-160 on each cylinders after 8 comps.
i think any m10 you buy is guna need a rebuild. whats wrong with the one we fitted????
It's running, but I'm getting alot of knocking which could jsut be timing, loose downpipe etc. but the main thing that is worrying me is low oil pressure light at hot idle. Idle at cold = no oil pressure light. Idle at operating temperature = solid light.
The pump/oil pressure was fine in the old engine.. Which makes me worry is if it's something horribly worn in the bottom end.
Any ideas? Do you think switching to 15w50 from 10w40 will help?