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

OTC Deluxe Compression Tester Kit: 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.

[@pawekarski]

Thanks a lot! Keep up doing great job! Your videos helped me a lot maintaining my E46

[@kellyanderson7115]

I just did a boroscope/compression test of my 2001 330xi with 132K miles. The cylinders look awesome using the boroscope - nice crosshatch all the way up and down the cylinders. The compression check had four cylinders at 185PSI and two at 187PSI. It doesn't get much better than that! BTW, I bought the compression tester based on your suggestion and it is a very nice tool.

[@Ken-we9jc]

looking forward to the leak down test brother!!! keep up the great work!!

[@dironizareyes596]

Should u disconnect the fuel pump for this compression test

[@HamidRHariri]

Very informative. Bookmarked it. Thanks J.

[@5riverz456]

Cant wait for these videos. My e46 has been parked since march because it has a misfire also.

[@grullon120]

Thanks for the video mate, really appreciate that!

[@dokgodie]

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

[@tonycopelyn8730]

This is my 2nd rebuild on this enginr....1st rebuild I increased piston ring gap...compression test was 90is on all cyl after rebuild.. 2nd go round 120is on all cyl...both values using the dreaded harbor freight tool... You got a 30psi differential...using a diffetent tester...so Im in range and no matter what I will not do this again...I wont complain...donor block no boring no oversized piston just straight swaped out innerards...I can live with this before was horrible using 1L of oil/500miles

[@tahirrana6875]

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...

[@dong8069]

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!!

[@bocon007]

great video - thanks!

[@Steve060590]

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

[@50sKid]

Nice, thanks for contributing that information. I will look into it in the future.

[@Jet3ch]

Where exactly do you run that line from Ccv to manifold?

[@Wormarder]

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

[@Jet3ch]

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

[@michaltimko]

@@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.

[@fablabengineering2015]

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.

[@50sKid]

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?

[@fablabengineering2015]

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]

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.

[@fablabengineering2015]

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.

[@PedroPerez-hg1zh]

Estoy empezando en la mechanica y tus videos me han sido muy instructivos y motovacionales gracias y sigue haciendo tus videos son de los mejores que he visto...

[@fredericlinden]

Hope you are well ! One question : I experienced a loss of power on the highway... Diagnostic from two shops : no compression at all on Cylinder nr.3, 160 on all the others. Essentially, one team, after changing the spark plugs (that revived Nr.5) thinks sending the head to a machine shop, changing the valves and rings (most likely nothing wrong with the pistons), and maybe a few other minor things, shall suffice. Shop Nr.2 also diagnosed no compression in Nr. 3. Either also rebuilt the engine head, replace head gasket, air intake boot, one ignition coil and 6 new spark plugs. Or engine replacement. What do you think ?! Thanks in advance for your consideration.

[@MrGibratan]

Thanks really good video

[@repcsi]

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! :)

[@50sKid]

Oil consumption is due to the oil rings on the piston. Gonna do a video about it soon.

[@repcsi]

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! :)

[@carlodonnell146]

what about the wet compression test with a little oil in the cylider to see if it is the rings that's causing the loss? ok you answered my question at the end there. Good videos!!!!!

[@nonagreeable]

Are you repeatedly turning the key, or does the engine crank like that by itself? How long do you crank for?

[@th1alb]

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...

[@th1alb]

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.

[@50sKid]

About 180 in all cylinders. What are the other indications? Do a leakdown test to see where the air is leaking out of

[@th1alb]

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: forum.e46fanatics.com/showpost.php?p=17256442&postcount=22

[@mariodelcampo8164]

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...

[@contrerasmcr100]

savage! I'm doing mine right now....E46, 83K, 03'

[@georgec7402]

Could you do a video on instrument cluster repair?

[@javid515]

If I did a wet test, how long should I wait before doing a leak down test so I don't affect results?

[@pjwoo276]

1) Would it be better to do the cyl leak down 1st, for just in case you might need to do a wet compression test ? 2) If you did need to add oil into a cylinder for a wet test, how long, how many miles, street traffic or freeway driving would it take to, what ?, burn off that oil in order to get an accurate reading on the leak down test ? 3) Do you think it would be better to do the leak down test first for just in case you might need to do a wet compression test on any cylinders ? 4) I wonder what other things made you conclude that the HF gauge was not good. I hear that different gauges read differently, which SUCKS. How do you know which brand was more accurate ? I really enjoy your vids. I hope you don't mind answering all my questions.

[@vsboss155]

For N42 engine, take out fuel pump fuse and remove throttle body.

[@erickrayos]

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?

[@spilmer1]

I agree im trying to diagnose a problem not create a new one

[@qingyang9808]

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.

[@kennaysmith9850]

You always do a compression test when the engine is cold and then add a small amount of oil in the cylinder and repeat the test hold the throttle blade wide open and crank the engine until it builds the maximum amount of compression possible with oil and without.

[@rampage3337]

you don't put oil in the cylinders.... that will fuck upp your reading. you only put oil in if the comp has a high diffarance betwen cylinders just to check if it's a piston ring problem.

[@matmanpromotions6457]

@@rampage3337 thats what he said.. do test clean. repeat test with oil to ascertain if rings or valves are the issue

[@mono1i]

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]

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.

[@jaygovinda723]

Thanks a lot

[@773steve]

so u take out all spark plugs at once not one at a time and floor the gas as you turn the key?

[@010FSL101]

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.

[@th1alb]

if your car just keeps producing them i would start collecting them, melt them down into silver bullions, then sell

[@JAydUBr6]

I'm having trouble finding a fitting that will screw inside the cylinder, can you tell me what size it is I just need an adapter I have the hoses and gauge but my fittings are too big.

[@nestop.9892]

Good day sir... My e46 sounds just like that, i have replaced the coils and spark plugs, fuel pump, crankshaft sensor today, and now im trying to figure out what is going on. Any advise is highly appreciated. Thank you and have a great day

[@paulloper8333]

Did you find out what it was?

[@nestop.9892]

@@paulloper8333 yes sir, it was the Camshaft, and Crankshaft Sensor.

[@iLike2Think3606]

Do you remember what the code was on the check engine light?

[@drentide]

What’s your opinion about using sea foam???

[@luisorosguerrero3014]

Im doing this test on my mine i overhead it one time to 3/4 to the pressure doesnt stay on 180 in each one and it goes down slowly what could it be?

[@romeoholder4453]

Hey 50skid, i have a 2005 bmw e53, It has a misfire and the code is P0302. we did a compression test when the engine was cold and there are the results, cyl 1- 230psi, cyl 2- 180psi, cyl 3-230, cyl 4-230, cyl 5-230psi and cyl 6-230psi. Now we did another test after running the engine and these are the results cyl 1-200psi, cyl 2-140psi, cyl 3-200psi, cyl 4-200psi, cyl 5-200psi and cyl 6-200psi. The cylinder head we bought from ebay had a warpage, and when i took it to a machine shop, they advised not to cut it. we are now thinking of pulling of the head to take it to another shop. Are these heads known to carry a warpage and do you advised cutting them?

[@elijahhall4879]

have a 2009 bmw 328i replace pump car start and run fine . about 15 mins then stop.will'nt crank for about 15-20 min then run fine then stop running again...help

[@anders949494]

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.

[@50sKid]

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.

[@Wildart2]

I would like to see that too, Fifty

[@Cdswjp]

@@50sKid , @andersDog94 do you guys think this is unsafe for a direct injection n54 335i?

[@cheepGeek]

Where did you get your good compression tester? Can you supply a link?

[@50sKid]

I put it in the description for ya.

[@jesselyons2002]

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]

Pretty surprising how inaccurate they are (I've tried two just to make sure)

[@luke_barrientos]

Aye but green it’s in the good so I can just add like 30 psi to the freight gauge

[@fablabengineering2015]

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.

[@50sKid]

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.

[@010FSL101]

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.

[@Cdswjp]

please respond to 50sKid's question

[@ettienneVNZL]

If my 330i is cold, how much bar should i get to insure my engine is good?

[@Cdswjp]

THumbs up

[@williamh6591]

Wish I could have this guy come look at my 330ci

[@ParanoiaGentlman]

6:50 Lol that’s the one Scotty Kilmer has 😂

[@50sKid]

Aww, man, he's got a blue OTC gauge? Well that just poops all over my day.

[@ParanoiaGentlman]

50sKid oh sooner 6:50

[@ParanoiaGentlman]

50sKid opps meant the other one 😂

[@50sKid]

Ohhhhh hahaahaha

[@injustice4566]

what is the compression for m47 ?

[@shahzeboy1609]

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)

[@SPARTANxB312]

Shahzeboy 1 that sounds like a bad starter. Start there and check your battery and alternator

[@lelekkozje3049]

How to test compression on vvt engine?. N42 od n46

[@vicayuro2643]

Hi whats next after detecting a low or high compression test what part should be change? Thank you.

[@50sKid]

Your next step is to do a leak down test and figure out where the air is escaping

[@Cdswjp]

@@50sKid is high compression always good?

[@steveallam]

Use marval mystery oil 200-300km before your next oil change.

[@christianv.r.8205]

Alguien sabe si ocupa anillada con los valores que arroja??

[@PedroPerez-hg1zh]

Me gustaria hacer una consultant sobre un bmw x3 2007 3.0 claro te pagaria tus honorarios por tu tiempo donde te puedo coctactar si se puede claro. Gracias de ante mano y que tengas en maravilloso dia

[@Tucimori]

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.

[@50sKid]

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.

[@Tucimori]

I get it. I too can't sit around with an issue when diagnosing can be being done .

[@saldi3543]

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 ?

[@50sKid]

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.

[@saldi3543]

50sKid thank you

[@Cdswjp]

@@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?

[@jprosalz]

What happend if you not pull down de acelerator pedal ? the compression down in the readings? how much ?

[@50sKid]

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.

[@Cdswjp]

keeping the pedal down helps disengage fuel injectors, you can reference this statement by watching EricTheCarGuy's video on compression tests from 2010

[@damaestro5667]

is it that neccessary to pull out the fuse ?

[@JamesExcell-InterJex]

Da Maestro yeah. You need a magnet to get the spark plugs. They are quite cheap too. So worth.

[@apinanseehanam239]

150psi

[@apoloteam79]

330ci fabricado en 10 del 2000, 325.000km valores de 190 en los 6 cilindros

[@rampage3337]

it's not important to do it consistantly. ones it reaches the max pressure it will stay there

[@ricky9720]

Min spec is 174 psi /12 bar

[@andyridley2236]

Actually, you should turn the engine 8 times on each cylinder 6 is not enough your needle was still moving.

[@luke_barrientos]

Lol a bad compression gauge, the one that I have :(

[@jjb8181]

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 kzbin.info/www/bejne/lYfSZZmjZa93hrs ? Greetings from Germany Jay

[@50sKid]

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!

[@TheJosephayal]

never buy a bmw

[@georgesmbyd6603]

Cody Koala lmao keep driving ur awesome toyota corolla bud