2000 BMW 323i Cylinder compression

How did you measure it? Was the throttle wide open and did you let it go through several compression cycles? Were they all pretty even?

If they're all the same, I'd say your measurement is faulty. The engine should be hot, all the plugs removed, and cranked over several revolutions with the throttle wide open.

[Thinks] Does vanos effect the compression reading while just cranking? Because different camshafts with unchanged compression do.

They don't?

Kyle.

98 740iL 97 M3

Yep, what Kyle said.

If you are going to be doing a job as involved as pulling a head off, you will need a manual to get the all the minutia anyway, such as torque specs, etc.

Bentley manuals are pretty expensive manuals, but well worth it IMO.

-Fred W

the compression was fairly even but each was different all pretty close to

90-100 psi. I did this on a cold engine and throttle closed. I did one complete test of the cylinders for about 20 seconds each and got the compression up to 130 but that was it. Thats why i was wondering what the compression should be. i had a friend thats a mechanic also do a compression check and he came up with the lower numbers. Thats great that there is finally a manual unfortunatly its not available for another few months but yes definetly worth the money. I talked to someone in service at BMW and they told me you could access a website that BMW has that is an online manual but its 25 bucks a day or a couple hundred for a week.

If they're within that tolerance regardless of how you measure them, then they're ok. But the accepted way is with the throttle wide open on a hot engine - the instructions for the compression tester should tell you this.

Do it in the accepted way and report back.

Change your friend to a mechanic who knows his job. ;-)

You can buy pirate copies of the TIS (repair) and ETK (parts) CDs on Ebay for a few dollars.

FWIW, low compressions due to valve problems are really a thing of the past. And certainly not on all cylinders. Head gaskets can fail, or heads crack, but this would not effect all compressions. Similarly things like broken rings or damaged pistons.

If all the compressions are within about 20% at cranking, it's likely they are fine at running speeds.

I believe compression should be at least 150 PSI with the throttle wide open. You can get the manual online through Bentley Publishing

. It looks to be available right now. Having the print version would be preferable, but having access online is better than nothing and is cheaper than paying BMW for access to the TIS. Actually, I find the TIS to be a good supplement to the Bentley for my 97 M3, but not really as a stand alone manual. It assumes in many tests that you have access to all of the special tools and a GT1 or MoDic computer that the BMW dealers use. There are usually several people selling copies to the TIS on eBay for around $25 if you want one for yourself.

Kyle.

98 740iL 97 M3

The good news is, you screwed up the same on all 6 cylinders.

Your compression should be closer to 150 psi. The important thing is that all are within about 10% ...

I would retest it warm with the throttle wide open through several cycles. The fact that they were all close says it's probably OK to me.

-jim

Kyle and Lori Greene wrote:

Me too.

While the numbers are low, they are relatively uniform, so the compression should work out to be OK. It shows that the same mistake was followed all of the way through the test, and this should level the results.