Remove plastic covers from firewall.
|
|
| Remove main relay, located on right side of firewall. |
 |
| Remove the two 10mm nuts retaining spark plug wire housing. Pull
straight up on plug wire boots. Twisting boots while pulling will ease removal. Use BMW
special tool 12 1 160 from the tool kit in the trunk to remove spark plugs. |
 |
Install a compression tester and follow
instructions provided with the tester. |
Press accelerator pedal to the floor while
cranking engine during test.
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What to look for ?
|
|
An actual number is not required, although
ideal compression will be above 175 psi, the main concern is equality between all
cylinders, no more than a 10 percent variation should be present between the highest
and lowest readings. |
| If you have a cylinder with low compression, a leak
down test should also be performed. If the results are inconclusive, you can insert a
small amount of oil in the cylinder and run a second compression test. If the compression
raises, your rings are the primary suspect. If the reading stays the same, then you
probably have leaking valves. |
