Preparation for Azorean Bimmer project: compression test results

Hi all.

As part of preparation for a complete or partial overhaul, I performed a compression test on my pride and joy. Results on pictures. Note that on picture #1 test was performed with just the spark plug from the cylinder to be checked removed. On the other, all plugs were out, as in the bible, and the results are quite different. The test was conducted in "dry" conditions.

My initial interpretation: piston rings appears all right for the mileage (150000mi). The problem maybe resting on the valves. Note piston #5.

Curious fact. After putting everything together, I drive a little and a lot of smoke, oil burning on headers, started. I parked home and note that header between #3 and #4.

Further inputs on this are pretty much welcome.

Best regards

1 bar=14,5psi

Pretty good figures. Only way to improve them or equalise them is top overhaul. Sometimes fixing thing that are not too broken is better than waiting.

Hi all.

That's my plan of action: perform a top overhaul. My plans included short-block overhaul, but with these numbers I'll just go for a top overhaul (budget sake).

Best regards

Originally Posted by Bugsie

Hi all.

As part of preparation for a complete or partial overhaul, I performed a compression test on my pride and joy. Results on pictures. Note that on picture #1 test was performed with just the spark plug from the cylinder to be checked removed. On the other, all plugs were out, as in the bible, and the results are quite different. The test was conducted in "dry" conditions.

My initial interpretation: piston rings appears all right for the mileage (150000mi). The problem maybe resting on the valves. Note piston #5.

Curious fact. After putting everything together, I drive a little and a lot of smoke, oil burning on headers, started. I parked home and note that header between #3 and #4.

Further inputs on this are pretty much welcome.

Best regards

1 bar=14,5psi

Err....the results look the same. Could you point out the difference ?

What is the benefit in removing all of the spark plugs before testing each chamber one by one ?

Why did you not conduct a wet test ? That could have yielded interesting results and would only have taken another 20-30 minutes at the most.


rgds,
Roberto

Hi al
My understanding of the Bentley is to perform the test with all plugs ouThe main difference is on #5. Goes down to 1bar..


Quite true. But I was running late and I went only for the dry. I believe the wet is mainly to disgnose the short block but with this compression I assumed they are fine.
Thanks for the input.

Best regards.

Fernando

my interpretation of taking all the plugs out is for two reasons, 1 is that it will make the job of turning the engine over on the starter much easier for it and help you not run out of battery power. the other reason is obviously the car wont start up unexpectedly if there is no spark plugs

i may be wrong

Originally Posted by _Ethrty-Andy_

my interpretation of taking all the plugs out is for two reasons, 1 is that it will make the job of turning the engine over on the starter much easier for it and help you not run out of battery power. the other reason is obviously the car wont start up unexpectedly if there is no spark plugs

i may be wrong

Well, I believe we are supposed to either disconnect or remove all the ignition coils since we're going to test all the cylinders, and if we're going to only test one or two, we are supposed to remove the dme relay to prevent ignition.

I'm also given to understand that we should remove the fuel relay or fuse, start the car, and let the engine run for a few seconds until it dies naturally, to ensure that no fuel gets injected into the engine while turning it over for the compression test later.

Hi all.

Yes, for safety reason, I believe It's best to remove the pump fuse and the fuel pump relay and the motor die naturally from fuel starvation.

I even try to restart to double check no fuel in. After that all ignition coils out and, according to my understand on Bentley, remove all spark plugs.

In this procedure I was co-helped by and old mechanic, almost retired, and every mechanic as is own point of view. The guy insisted on removing all spark plugs. Why not do what he says, just for sympathy?? By the way, he owned a 2002 tii Schnitzer.

Best regards

Originally Posted by Bugsie

Hi all.

Yes, for safety reason, I believe It's best to remove the pump fuse and the fuel pump relay and the motor die naturally from fuel starvation.

I even try to restart to double check no fuel in. After that all ignition coils out and, according to my understand on Bentley, remove all spark plugs.

In this procedure I was co-helped by and old mechanic, almost retired, and every mechanic as is own point of view. The guy insisted on removing all spark plugs. Why not do what he says, just for sympathy?? By the way, he owned a 2002 tii Schnitzer.

Best regards

I don't think it makes a difference if the other spark plugs are there or not there. In fact, I'd be very concerned if it did. Nevertheless, since you're going to test all chambers, you might as well do so.

Hi,

I agree with you Roberto, I don't really see why, but why not. It's a old man wish!!!

Due to the extremely compression on #5, I'm going to repeat all over again and this time I'll run a "wet" procedure.

I'll post the results, but maybe only next week.

One question? Does Parts Geek suply good stuff??

Best regards

#5's compressiong (And #3's for that matter) don't seem to be too off the average. Why are you concerned ? In any case, the wet test will be interesting. However, I do believe there's a technique to interpreting dry compression tests visavis the wet test's results. Please google to confirm.

Hi,

please note the graphic not numbered. Graph #1 was with plugs and the non-numbered was without all spark plugs out and within a 10 minutes delay, # 5 from 14 to 4. I tried the test on #6 with the results on first attempt. tried several times on #5 always with that result.

To my understanding, the wet results are more likely to troubleshoot the short-block. But I will google for that.

Thanks for the input

Best regards

If I remember correctly, the wet test checks if your piston rings are ok. If the results for a particular chamber are vastly better than the dry test, then its the piston rings for that chamber which are screwed. If the results for a particular chamber are just as bad as the dry test, then one of the valves are busted.