BMW How To Perform A Compression Test, What Is A Compression Test, Test Your Engine Health BMW Z3

I need to find out the health of my BMW engine as a diagnosis step. I am going to show you with full DIY steps on how to perform a compression test on your engine. The vehicle being used is my BMW Z3 with the M54 6 Cylinder engine that has a failed head gasket.
There are specific steps to successfully perform a compression test. I will make it easy for you to be able to test your engine by following my method as shown in my video. I will also include descriptions of specifications for a compression test and general guidelines you can follow.
Compression testing can help you identify a specific cylinder or cylinders to focus on during your engine diagnosis.
I also include ways to help determine the reason why your compression test may be low and how to test your engine piston rings with a simple method.
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An engine makes power by compressing vaporized fuel and igniting it in a compressed state. The engine's compression can be measured using a compression gauge installed in the spark plug hole.
When piston rings wear out the compression required to efficiently burn the air to fuel mixture is reduced. After performing basic diagnosis it is important to perform a compression test. A compression test is designed to check the condition of the valve train and piston rings. Valves need to seal and close properly and the piston rings need to seal the bottom crankcase.
When would you need to perform a compression test:
Smoke from exhaust
Poor acceleration / vehicle sluggish
Misfire issues
Poor fuel economy
Adding more oil than normal Oil consumption
Or to get the general health of your engine
How to correctly perform a compression test:
If possible warm up your engine. Disable fuel and ignition. Remove and inspect spark plugs. Install compression gauge. Crank the engine over 3-5 times or seconds. Be consistent for each cylinder. Record your readings. Add oil to cylinder to check sealing of rings or for washed out cylinder walls.
Chapters:
00:00 Intro What Is A Compression Test
00:54 Ignition Coil Removal Plus Pro Tip
02:11 Disable Fuel System Steps
03:24 Spark Plug Removal Plus Pro Tip
04:49 Recommend Using a Battery Charger And Cover Any Possible Power Sources
05:06 Compression Testing Specifications Explained
05:39 Matching Up The Correct Compression Tester Fitting And Installing In Cyl. 1
06:46 Compression Testing Cylinders 1 through 6 With Pro Tips
09:49 REASONS TO PERFORM A COMPRESSION TEST
10:24 Evaluating The Compression Test Results
11:01 How To Test The Piston Rings Or Cylinder Wash Out
12:46 What Other Test Should You Perform -- Cylinder Leakage Test
14:33 Conclusion and Time To Walk Zion

[@micdev42]

This is a great video: thanks for recording all the steps. I'm just about to do a compression test on my 2007 325i E93 with N53 engine. This video has given me the confidence to have a go. Cheers from the UK.

[@micdev42]

Just did the test yesterday using a cheapo £20 compression tester from ebay. Success! I did the test cold, pulled the relevant fuses, removed all spark plugs, then tested each cylinder. The results were unexpectedly good: PSI from cylinder 1 to 6: 225, 220, 225, 235, 225, 235. I did 7 or 8 cranks of the starter. I say unexpectedly because I recently had a compression test done at a local garage and his results were really low and he told me the engine was no good so best to sell. I'm glad I did it myself as I was suspicious of his results. Anyway I can now go on to tackle the real issues - the dreaded N53 misfires... To that end I'm replacing all spark plgs and coils with new OEM parts in the next few days. Cheers

[@MarioDallaRiva]

Thanks Roger for the info! Carumba is exactly what I said too 🙀 Great to see big Z. Man, that’s a clean engine bay. The way it should be 👌🏼

[@AskTheCarExperts]

Hi Mario, Zion is the best Dog! Super friendly but scary looking when someone comes knocking. The engine is worse than I expected. I think I am going to out together a video on odd issues and problems I have seen at work and make it a members only thing 😀

[@devinsmith4151]

There is always ways to do things multiple ways. We were always taught to press the accelerator to the floor on cranking. At the dealer, 9 out of 10 the guys will never disable the fuel system. A strong battery is good, with the maintainer connected. Some say coat the threads of the tester and hand screw it in. We always do it on a stone cold engine. Personally for diagnosis, I always get the best gauges I can afford. Snap-On's stuff is good in a sense since spare parts are easy to get a hold of. Fuel pressure is a different story, back in the day a bad gauge would jump if you tapped on the glass. Never cut corners on diagnosis equipment whenever possible. Southmainauto had a nifty trick of using a transducer on the radiator cap with each cylinder test, people will always find new ways to know more of the engine's status without even opening up the bugger. Always give cred to the guys that help us to improve our diagnosis skills.

[@garyvanremortel5218]

I've heard of doing starter tests to see if the current peaks for each cylinder during the compression stroke are the same.

[@devinsmith4151]

@@garyvanremortel5218 Possibly, still any test will only give you an idea of vaguely what's going on. As Mercedes Source used to say, its never just a headgasket. I was brought to the understanding that once an engine has been cooked, everything goes out of spec. Fixing a overheated engine is a hit and a miss, usually just not worth it depending on severity.

[@garyvanremortel5218]

@@devinsmith4151 Yeah, the starter current test was just a quick and dirty clip-on probe way to see if they were all the same.

[@powermegab]

Hi. I was wondering if there is a cylinder leakage test anywhere on your channel, because I can't find it... ? Thanks

[@AskTheCarExperts]

Hello, Yup I have that :) kzbin.info/www/bejne/r5mrp2B3rMd5n7s

[@bobbyz23]

What's normal compression for a 2009 BMW 535i? Or BMW in general? Some people say 120 is low i don't think so.

[@AskTheCarExperts]

Hello Bobby, I would like to see at least 150 to 180. Best action is to compare to the other cylinders.

[@Thomas-fc6gf]

Did this engine run with those numbers

[@AskTheCarExperts]

LOL Great question Thomas! It DID run. I was able to pull it in and out of my garage multiple times. It did not run very well however. Putting the timing together now and hope to be driving it this spring. More videos to come!

[@Thomas-fc6gf]

@@AskTheCarExperts thanks for your reply. I just recently got an m54 from the junkyard, it has 180psi on 4 cylinders, 158psi on the 5th and one with 130psi That’s with the engine on a pallet, not warm or anything. I’ve heard that compression will improve with the engine warm. So what do you think? I’m hoping I’ll be able to use this engine for my swap, even though 2 of the cylinders are a bit lower

[@garyvanremortel5218]

210psi on my Jaguar.

[@AskTheCarExperts]

Hi Gary, I was hoping for at least a few of the cylinder on the Z3 M54 engine to come close to that. Going to do a cylinder leak down next before starting the head removal.

[@garyvanremortel5218]

@@AskTheCarExperts Yeah, that's the kind of test we do on Continental and Lycoming aircraft engines.

[@AskTheCarExperts]

@@garyvanremortel5218 That's cool! Never worked on an airplane yet 😀

[@garyvanremortel5218]

@@AskTheCarExperts asktheplaneexpert...

[@AskTheCarExperts]

@@garyvanremortel5218 😆