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
Compression test readings
Re: Compression test readings
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
e21 320 (12/1975) 320i/4 (3/77)running gear.
e21 316 (1981) TRE702X.
e21 316 (1981) TRE702X.
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Reck
- E21 Pro
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- My E21(s): 83 316, 1.8 M10, RHD
- Location: Manchester, UK
Re: Compression test readings
Cheers Edd. Does the manual mention if those figures were wet or dry? Engine hot or cold?
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Reck
- E21 Pro
- Posts: 823
- Joined: Mon Mar 29, 2010 12:26 am
- My E21(s): 83 316, 1.8 M10, RHD
- Location: Manchester, UK
Re: Compression test readings
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?
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
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????
i think any m10 you buy is guna need a rebuild. whats wrong with the one we fitted????
Jeroen wrote:Bmwe21.net, for all your insurance solutions
Re: Compression test readings
That still hasn't been determined!!
1983 316 Pustergrun - track sluG!
1982 Saphirblau Baur 325i
Cars all gone!
1982 Saphirblau Baur 325i
Cars all gone!
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Reck
- E21 Pro
- Posts: 823
- Joined: Mon Mar 29, 2010 12:26 am
- My E21(s): 83 316, 1.8 M10, RHD
- Location: Manchester, UK
Re: Compression test readings
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.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????
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?