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Old 02-11-2011, 09:24 AM
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Flug540 Flug540 is online now
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Location: Hayward, CA
 
Join Date: Nov 2009
Posts: 464
Mein Auto: 1998 BMW 540i 6-spd
Quote:
Originally Posted by franka View Post
Just skimming the posts above try some Techron in the gas tank. It does work and part of what it does is clean the valves o f carbon allowing them to seat properly.
Thanks for the suggestion, but I'm taking the top apart for gasket replacement already, and I think I should pull the heads too and then deal with whatever I find.

Quote:
Originally Posted by franka View Post
How many miles on the car and how many owners?
I am the third owner, bought the car almost year and a half ago with 69k miles and now it has about 80k.

Quote:
Originally Posted by bluebee View Post
Those numbers don't look too badly off. I don't know what percentage is considered abnormal - maybe someone has a spec for what the percentage off between cylinders for the BMW so you can judge against the spec?
Bentley says it should be in 174-203 range and I've seen several posts now with numbers roughly around 205, some even higher, so while my numbers may not be horrible, I think they are definitely low.

Quote:
Originally Posted by bluebee View Post
But, I would think there is a well-defined test sequence for what causes the loss of compression below spec (I don't have it though ... so if/when you find it, send it my way and I'll add it to the best links thread for others to benefit from).
It's all in Bentley. It suggests that if the wet test does not improve compression significantly, the leaky valves are the likely cause.

One last thing I want to do before I take the heads off is to verify my gauge, it's brand new, but you never know, somehow I feel suspicious of it.
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