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How to do a Compression Test on an E46 BMW 3-Series

364 ratings | 32512 views
OTC Deluxe Compression Tester Kit: https://www.amazon.com/dp/B004K2FSXI This video is for entertainment purposes only. 50sKid assumes no liability for any repairs or modifications performed by the viewer as a result of the information contained in this video.
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Text Comments (84)
erickrayos (1 month ago)
instead of the DME relay, wouldn't it be better to pull the fuel pump fuse, crank it a few times before removing the spark plugs and whatnot to clear the remaining fuel in the system and then do the rest?
stewart (5 days ago)
I agree im trying to diagnose a problem not create a new one
T k (2 months ago)
Are you repeatedly turning the key, or does the engine crank like that by itself? How long do you crank for?
CDMusicGroup (3 months ago)
THumbs up
773steve (6 months ago)
so u take out all spark plugs at once not one at a time and floor the gas as you turn the key?
Da Maestro (9 months ago)
is it that neccessary to pull out the fuse ?
James Excell (8 months ago)
Da Maestro yeah. You need a magnet to get the spark plugs. They are quite cheap too. So worth.
Qing Yang (9 months ago)
Hi 50sKid, I got a wired situation that might need suggestion. I recently purchase an e46 2 330xi, and found out the CEL light oil light and abs light won't show up when ken in position 2. Of course till now I haven't seen any CEL once even unplug the MAF. While if use OBDII you could find the MAF code if unplug. So, what should I do? It has 3 monitors not ready right now, seems generic OBDII scanner can't do anything to reset them all into not ready for starting over. Car runs and drives.
CompoundBMX (1 year ago)
Did you need the OTC Deluxe compression kit or just the normal kit? thanks I subscribed a couple weeks ago as I have quite a few jobs to tackle on my 330Ci Deluxe kit: https://www.amazon.ca/OTC-5605-Deluxe-Compression-Tester/dp/B004K2FSXI/ref=sr_1_4?ie=UTF8&qid=1523996023&sr=8-4&keywords=otc+compression+tester Normal kit: https://www.amazon.ca/OTC-5606-Compression-Tester-Kit/dp/B000R5CPAQ/ref=sr_1_3?ie=UTF8&qid=1523996202&sr=8-3&keywords=otc+compression+tester
CompoundBMX (1 year ago)
Perfect thanks a lot, ordered! Love your channel man.
50sKid (1 year ago)
just the normal kit is good enough
deuce2ii (1 year ago)
OK, thanks for explaining compression tests on BMWs. I have a 2001 M Z3 Roadster. My mechanic replaced the oil filter housing gasket. When are returned it to me, my wife started to drive it home, but noticed that the oil light was on. Long story! - SHORT.... They forgot to put the oil back in the engine. As far as I know, the car has been driven about .2 miles without oil. I've always used synthetic. The mechanic believes that the synthetic should hold up for what happened to the BMW. He has agreed to to a compression test to see if there is any leakage. Can you give me any advice before we do the compression check?
50sKid (1 year ago)
A compression check won't tell you if there was damage to the bearings. I'm not worried about the compression rings in the pistons or anything like that. What gets damaged the most by oil starvation is engine bearings. There are main bearings, rod bearings, and cam bearings. Unfortunately there's no real way to know if they're damaged without disassembling the engine. Maybe you can put oil back in it, run it for a bit, then look in the filter for shiny bits of metal, signifying bearing damage. Good luck.
Mario del Campo (1 year ago)
Can't wait to see a video on putting fuel injector cleaner into the cylinders and compare those numbers. I'm gonna grab some pop corn...
Shahzeboy 1 (1 year ago)
what can i do if my car does not turn over? it just makes that clicking sound? since nothing happens i cant even diagnose it, any idea before i go and buy tools and things i may not need? (the battery is not the issue iv taken care of that variable)
jonathan zuniga (1 year ago)
Shahzeboy 1 that sounds like a bad starter. Start there and check your battery and alternator
ParanoiaGentlman (1 year ago)
6:50 Lol that’s the one Scotty Kilmer has 😂
50sKid (1 year ago)
Ohhhhh hahaahaha
ParanoiaGentlman (1 year ago)
50sKid opps meant the other one 😂
ParanoiaGentlman (1 year ago)
50sKid oh sooner 6:50
50sKid (1 year ago)
Aww, man, he's got a blue OTC gauge? Well that just poops all over my day.
Gibran Carrillo (1 year ago)
Thanks really good video
Vic Ayuro (1 year ago)
Hi whats next after detecting a low or high compression test what part should be change? Thank you.
CDMusicGroup (3 months ago)
+50sKid is high compression always good?
50sKid (1 year ago)
Your next step is to do a leak down test and figure out where the air is escaping
sal dI (1 year ago)
Hi , my 2011 BMW 328i (N52N engine )has a problem and i Don’t know what that is , i changes ignition coils and sparks and even water pump and thermostat but still i have the check engine light and engine is rattlig, i have done the compression test two of the cylinders are 120 , two of em 150 and two 180 , i don’t know what should i do ? can you give me a mind with that ?
CDMusicGroup (3 months ago)
+50sKid maybe it's a head gasket issue if the places where the compression is similar are cylinders right next to each other? or is it still too soon or not making enough sense to use that idea and move forward w/ it?
sal dI (1 year ago)
50sKid thank you
50sKid (1 year ago)
Your compression sounds very unbalanced. Those two low cylinders are a problem. If you have a check engine light, check your codes and diagnose things from there. You will need to do a leak down test next to figure out where the compression loss is occurring.
Don G (1 year ago)
50sKid, what is the scanner you are using? Im looking your videos but i can't find it. btw Thanks for very informative videos. Keep up the great work!!
Cody Koala (1 year ago)
never buy a bmw
Ojileb M (6 months ago)
Cody Koala lmao keep driving ur awesome toyota corolla bud
Peter Gizmos (1 year ago)
followed your instructions and did a compression test today. all cylinders in in the 170 to 175 psi range except for #2 which is at 160 (i'm 90% sure bad head gasket, there are other indications that i'm not mentioning). great tip on pulling out the blue plastic cube, way better than the people that pull the fuel pump fuse. per instructions of the tester when the engine is hot it said to wait 10 minutes with aluminum heads before pulling spark plugs for good measure. thanks! btw. i'm curious what your compression was after you rebuilt the engine. like you said who knows how accurate my gauge is...
Peter Gizmos (1 year ago)
none of the usual head gasket symptoms. cylinder pressure leaking into the coolant pushing steam out of the over-pressure relief in the cap on the expansion tank and after 20 to 30 minutes the low-coolant light comes on. i was 90% sure what it was and now i'm even more sure because the block tester turned yellow. here is a link with the details of everything that was happening: http://forum.e46fanatics.com/showpost.php?p=17256442&postcount=22
50sKid (1 year ago)
About 180 in all cylinders. What are the other indications? Do a leakdown test to see where the air is leaking out of
Peter Gizmos (1 year ago)
also did not push down the throttle at all, i don't think it matters. pressure was maxing out by the 3rd or 4th crank and i did 7 for each for good measure.
Brendan OConnell (1 year ago)
great video - thanks!
What happend if you not pull down de acelerator pedal ? the compression down in the readings? how much ?
CDMusicGroup (3 months ago)
keeping the pedal down helps disengage fuel injectors, you can reference this statement by watching EricTheCarGuy's video on compression tests from 2010
50sKid (1 year ago)
I honestly have never seen it have very much effect because the idle air control valve is always open and allows air to be drawn into the cylinders. Maybe the compression will reach it's maximum level quicker if you open the throttle plate.
010FSL101 (2 years ago)
Damn i bought that HF compression test kit a long time ago when i found some silver metallic particles in my coolant and i was also losing coolant so i suspected a head gasket leak but its been like 10 months now, after replacing the major cooling components i'm not loosing coolant but even after flushing 10 times i still have silver particles in my coolant. I suspect the previous owner put some sort of leak stop in the coolant to stop a leak. Anyways i can't return that HF tool back even tho i haven't even opened it, maybe i'll test it one day just for fun.
Peter Gizmos (1 year ago)
if your car just keeps producing them i would start collecting them, melt them down into silver bullions, then sell
Miguel Contreras (2 years ago)
savage! I'm doing mine right now....E46, 83K, 03'
Ari Lin (2 years ago)
Was your compression readings withing specification? My 330ci with 110k miles tested 175-180psi across all cylinders.
50sKid (2 years ago)
Interesting, I would like to know what your leak down results are!
Shayne McGuire (2 years ago)
I'm confused as to why you did a compression test to diagnose a random misfire prior to replacing the coil (or moving the coil) when you knew you had a bad coil.
Shayne McGuire (2 years ago)
I get it. I too can't sit around with an issue when diagnosing can be being done .
50sKid (2 years ago)
Because I did not know for certain that the coil was bad. The problem was only happening when the car was cold and I had already warmed the car up on this particular day so my diagnosing had to be stopped until the next day. I decided to do the compression test so as not to waste time.
Adrian Labrie (2 years ago)
I've played with BMW motors for a while now so I can say I've experience with them starting from m50's to m70's. They are actually very nice and fairly easy to extract power out of. The idle air control valve is also powered from the same relay if I'm not mistaken.
Adrian Labrie (2 years ago)
I'll msg u in fb where to get it cheaper, I just bought another set this week. Great guy to deal with and very prompt.
50sKid (2 years ago)
Yeah I already expect that some of the threads have pulled out and that I'll have to sort the whole timesert issue out. Problem is the $450 kit they want to sell you to do the job right. I'm investigating other ways to get the dual drill bit so that I can keep the 6mm inset in each bolt hole. I'm sure that it overheated. But it's only $45 to get a head decked.
Adrian Labrie (2 years ago)
The rings I used on the last build are Hastings however the factory 52tu oil are also a good choice and u will need to use the m54 top ring as it's 1.2mm. Interesting results in ur leakage test. I hope u don't have an overheated engine as the machining cost will dramatically increase. If it's got the mls gasket then u unfortunately have a high probability for a warped head/pulled threads. I recently had an engine come in that was cooked and the diagnosis was a cracked water pump impeller and thermostat was corroded. The dme controlled heater element almost always corrodes behind the plug on the thermostat side not such a big issue but when the load changes the dme can't keep it open in the 80 odd deg's and it will fall back to the mechanical 97deg C. Time-serts are the way to go for thread repair.
50sKid (2 years ago)
The idle air control valve is a stepper motor that, when powered, will close a flap over an orifice a little or open it up a little, but never closing it all the way. When not under power, the flap is "loose". When you pull one out and shake it, it rattles. So whether it's under power and in the default position or completely powered down because the DME relay is pulled, either way air still gets in. So which aftermarket brand of M52TU piston rings (those are the ones with the 3 piece oil control rings) have you tried to install in the M54 to solve the oil consumption problem?
Adrian Labrie (2 years ago)
M54 engines have an electronic throttle body, wouldn't pulling the dme relay disable it so you would not be testing compression with a WOT. Also if u add oil to the cylinder it helps the rings to seal better and increase compression reading however if ur valves are leaky you won't see much change. The purpose is so u can diagnose if it's a worn ring problem or a valve leak issue. M54's are famous for carbon deposits around the ring lands and also the oil control ring is one piece which wears faster than the common 3 piece. If ur going to pull the engine and replace the rings use aftermarket 3pc oil or m52tu oil rings.( not the top compression as it's different) Ccv is also another common issue on these motors.
CDMusicGroup (3 months ago)
please respond to 50sKid's question
010FSL101 (2 years ago)
i think i read somewhere that pressing the throttle all the way disables the fuel injectors so that way you don't have to take the relay out it's a built in feature.
50sKid (2 years ago)
Interesting point about the throttle body! I'm actually unsure about that. In any case, it won't really make a noticeable difference whether it's open or closed on most cars. Enough air gets past the idle air control valve during a cranking test. I put it in there for the sake of completeness. Regarding oil control rings (I knew all this info, but thank you for posting it), are you sharing what you've learned from msg boards or are you a machinist and/or have experience rebuilding these engines? I've been wanting to get the opinion of a machinist on this.
repcsi (2 years ago)
I had 225K miles (360thousand km) in my M54B30 (e46) and it still felt like a freight train, no hesitation, liked to rev, only some strange noises in the cold mornings. I also used a trailer to get my e30 to the race track with it. Had no real signs of fatigue... For me what was telling is oil consumption, still it could also be the valve seals, but I did not disassemble that engine to be sure, maybe sometime in the near future! :)
repcsi (2 years ago)
yeah I tried to write that probably the valve seals are also done, but the piston rings are bust too :)  I'm looking forward to that video! :)
50sKid (2 years ago)
Oil consumption is due to the oil rings on the piston. Gonna do a video about it soon.
cheepGeek (2 years ago)
Where did you get your good compression tester? Can you supply a link?
50sKid (2 years ago)
I put it in the description for ya.
5Riverz (2 years ago)
Cant wait for these videos. My e46 has been parked since march because it has a misfire also.
AndersDog94 (2 years ago)
You could try and put some engine cleaner like that you can put in the oil before a change, down the cylinders, like 30ml and let it sit the night over, then blow it out the next day by cranking the engine and then start the engine and drive it. Then test the compression again. Could be fun to see if that made a change.
CDMusicGroup (3 months ago)
+50sKid , @andersDog94 do you guys think this is unsafe for a direct injection n54 335i?
Wildart2 (4 months ago)
I would like to see that too, Fifty
50sKid (2 years ago)
Yeah I've seen that video and I plan to do that soon in my own video, but for a different reason than trying to help gain compression.
Hamid Hariri (2 years ago)
Very informative. Bookmarked it. Thanks J.
Steve 060590 (2 years ago)
Great Video as always :) I had some issues with the compression on my 2005 330ci, too. I work at the BMW Plant in Germany and I asked one of the Engine Developers about it.They gave me the tip to increase the Vacuum in the Crankcase. It helps the low Tension Piston Rings to seel better. You do that, by running a vacuum line from the ccv to the intake manifold. At my Engine it doesnt Change the compression (No Vacuum at a compression test) but the Engine is more powerful again. On the Dyno now it has 225HP instead of 210HP.Maybe you ll give that a try :)Greetings from Germany
Mike (29 days ago)
+wormarder Isnt that hose from CCV going to fuel pressure regulator on m52 ? Thats why its blinded on m54 because m54 has fuel pressure regulator built in fuel filter.
M.I. A. (5 months ago)
wormarder oh ok I see. The ccv has an extra rubber plug I can remove and i see the back of the intake manifold next to secondary air valve hose connection also has a place. I will try this! I have an M54B30
wormarder (6 months ago)
M.I. A.  M52TU engine is using that 'fix' straight from the factory... In M54 in the ccv this output is blinded with piece of rubber
M.I. A. (9 months ago)
Where exactly do you run that line from Ccv to manifold?
50sKid (2 years ago)
Nice, thanks for contributing that information. I will look into it in the future.
Jerzy Kiler (2 years ago)
Thanks a lot! Keep up doing great job! Your videos helped me a lot maintaining my E46
joerg bauer (2 years ago)
Thanks for sharing this video. As always, very educational! Same issues and same compression values with my m54 200.000km. Looking forward for your leakdown results. Btw. whats your opinion about "solutions" like https://www.youtube.com/watch?v=_Vo4fm0JDPY ? Greetings from Germany Jay
50sKid (2 years ago)
Totally valid repair method in that video for fixing a situation where you have a stuck compression ring due to oil varnish deposits. The solvent gets things loose just like WD-40 would a bolt. However, if you do have actual compression, tired compression, it's not going to give you any more compression because a stuck ring is not the cause. We'll find out the cause when I post the leak down test results!
Jesse Lyons (2 years ago)
Hey I been using a harbor frieght gauge since 2005. The same one. Not the one you have in the video. But a hf one. It was my first engine tester.
50sKid (2 years ago)
Pretty surprising how inaccurate they are (I've tried two just to make sure)
Kyu Kim (2 years ago)
great video. Regarding on misfire, check disa valve. I had cylinder 6 misfire and after all the diagnosis it turned out disa valve flap getting stuck due to oil residues. Hope you find the problem
Ken (2 years ago)
looking forward to the leak down test brother!!! keep up the great work!!
Tahir Rana (2 years ago)
Hi Bud, I had the same issue on my 2003 330xi on cold start with cylinder #6 will miss fire... I changed fuel injector #6 and problem was fixed...
Jay Govinda (2 years ago)
Thanks a lot
George C (2 years ago)
Could you do a video on instrument cluster repair?

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