Overheating?

[Yeti325]

I have a 2003 325i with a hard miss on cylinder 5 with 0 compression on that cylinder, I inspected the cylinder with a borescope and everything looks good in the problem cylinder (valves appear seated no cracks or holes), just really dirty. I tried a cylinder soak last night with MMO and lots of smoke after startup, not sure yet if this helped with compression.

Anyway the car also gets really hot after running even for a short time. I have bled the radiator. I took a half mile trip in the car and the engine was almost at operating temp with the dial mid way on the gauge. The temperature gauge never reaches over dead center but I suspect the car may be overheating. If I take the car on a trip of any distance the engine will sputter and cut out.. this continues until the car has sit for a few min. Is this a sign of overheating? Anything I need to check?

[Pelican Parts]

Hello and welcome to the forum! Have you checked the thermostat? I've included a link below to the procedural guide in case it needs to be replaced.

https://www.pelicanparts.com/BMW/tec...Thermostat.htm

[MIKYZZ4]

Perform a diagnostic scan,
let's observe what the BMW codes reveal.

[Yeti325]

P0305 is the only code, sometimes EML light will come on. I'm starting to think this may be a clogged catalytic converter. I found this with a google search - "If the engine responds sluggishly or quits after running for a while, a clogged converter could be to blame. Catalytic converters can overheat because of excessive amounts of unburned gas caused by a misfiring spark plug or a leaky exhaust valve. In addition, a failed oxygen sensor can cause overheating.

[bmwdirtracer]

Wow. Okay, let's back up a while.

Welcome to the forum.

Please forget whatever that nonsense was that you read in a Google search. Someone put two and two together, and got 22 million. Sure, it's possible.... so is winning Powerball.

Let's examine the facts which you have:

First, you've got a P-code. By and large, P-codes are worse than useless. They are nothing but bureaucratic mistranslations of the information BMW wants you to know. P-codes ONLY relate to EMISSIONS ! To read the actual BMW codes, you need a BMW-specific scan tool.

Second, though, I will not discount the obvious cylinder 5 misfire code, and I won't dismiss the Zero compression on that cylinder. Furthermore, you got a borescope, and looked in that cylinder, AND did a compression test!...and I congratulate you for that acumen.

Now, I have to ask: Did you compression test all the cylinders? Did you unscrew the tester, and repeat the test on cylinder 5? We need to make sure this test is valid.

If, indeed, cylinder 5 has zero compression, and the other cylinders are fine....you need to do a leak down test, engine hot, and find out where, exactly, the compression went. (Intake, exhaust, or crankcase)

EML codes will likely not be read by an OBD2 code reader, by the way.If you want a wild-assed guess, I'll give you one a hundred times more likely than the failed O2 sensor and clogged cat: The engine overheated, warped the head, pulled the threads out of the block......

Again, though, that's just a wild assed guess, and you need further testing before condemning ANYTHING.

[ross1]

Overheating and zero compression in a cylinder is making me think about a warped valve head.
Is the exhaust valve evenly colored all around?

[Yeti325]

Okay I will look into reading the manufacturer specific codes, did not know that a regular OBDII scanner cannot read those. Compression test has been done 3 separate times to confirm results. I'm having trouble locating a leak down tester from my local auto parts stores, no one around here seems to know what that is... I will try to locate one from NAPA.


From what I could see the valves are evenly colored, and very dirty. I checked cylinder 4 for comparison and I noticed valve indentations on the piston head.

Currently I am pricing engines for this car, rather than attempting a repair because of the high miles (245k) on it.

[bmwdirtracer]

A used M54 is dirt cheap nowadays; around $500-600, with a three month warranty, sometimes six.

See:
http://car-part.com/

scroll down to page four or so, after entering your info.........

[Santi528i]

I have a 528i and just changed the radiator but the temperature is around 210,is ok?

[Yeti325]

I recently completed another piston soak which helped restore compression in cylinder 5. I used Marvel Mystery Oil and all 8oz I used drained past the piston rings in a 24hr period. I stuffed a rag in the spark plug ignition hole and turned the engine with the fuel pump relay removed and the pressure threw the rag out of the hole with some force. I tried using my compression tester and could not get a reading. I'm thinking this could be because the tester is not sealing correctly on that particular cylinder for some reason. I am still getting a misfire but it has become more intermittent rather than constant.

While driving the car does okay, but after driving a good 10-15 min and warming up, sometimes the EML light will come on, the oil pressure light will start flashing, and the battery light will come on. The engine will jolt or surge, and loose all of its power and suddenly die... Once the car sits for a few minutes (usually about 10) it will start right back up and be fully functional again. I just replaced the oil in this car and I'm not aware of any leaks so I doubt its oil related. The car also threw an interesting BMW specific code P16C3. I know this could be one of many things but if anyone has any ideas please share, thanks in advance.

[MIKYZZ4]

For upper engine cleaning:
https://www.youtube.com/watch?v=_Vo4fm0JDPY

I would attempt to obtain a different tester, for verification.
Check throttle actuator connection, but that's still a generic P-Code.

[Yeti325]

Update: when the maf sensor is disconnected the car is running much better! Drove it for 30min last night with only a few hiccups and no stalls. I’m going to check for vacuum leaks first, and then replace maf sensor if I can’t find any leaks

[bmwdirtracer]

Do NOT throw a MAF at the car until you've have had a professional smoke test of the intake system, and a crankcase vacuum test.

Disconnecting the MAF is NOT a test of the MAF ! All this does is force the engine to run in "open loop", which means that the computer GUESSES, based solely on rpm and a couple of simple parameters. You need to find the problem, not throw expensive parts !

[Yeti325]

Yes very true about the maf. Upon further investigation to vaccum leaks, I recently discovered that my DISA valve is far past repair, the o ring sealing it was completely flat and fused with the plastic grove it’s in. Not only that but it does not pass the vacuum test. When the hole is covered it still moves to open position! I replaced the o ring, I didn’t have the exact o ring on hand so I used an o ring similar and it was very tight reinstalling, I had to seat it by tightening the bolts. I’m going to replace the whole unit but I’m tight on cash at the moment. I’m considering either pulling one from a junkyard that passes the vaccum test or buying a new one on eBay. Opinions on used DISA valves?

[bmwdirtracer]

Be aware that one of the common DISA failures is the flap hinge pins breaking away from the unit. These pins are made of metal. When they get sucked into the combustion chamber, they can bounce around for a long while , beating hell out of pistons, cylinder walls, and valves....destroying the engine.

If your DISA is a genuine BMW unit, you can buy a rebuild kit from GAS:

http://www.germanautosolutions.com/b...repair_kit.php

[MIKYZZ4]

From my personal experience - once vacuum cannot be held,time for a new Disa valve;
as the diaphragm has torn, and cannot be replaced.
Look here for options:https://www.fcpeuro.com/BMW-parts/32...&keywords=DISA

[Yeti325]

I’m still having trouble after new o ring on DISA valve. The more I drive the car the more I pick up on patterns on how it breaks down. Usually it goes something like this: If the car is run after a cold start it will operate normally and will not stall or have any trouble and can drive no problem 20+ miles. If the car is started with the engine still hot or near operating temperature it will likely stall within about .5-3 miles. The oil pressure light turns on yellow and the engine rpms dip down, the oil pressure light then turns red, EML and check engine light come on. The engine rpms keep dipping and then going back up or bouncing. Sometimes this kills the engine. This only happens at less than 40 mph, it’s never stalled on the highway. Then the engine usually has to be restarted and or coast out of traffic, and off to the side of the road. Once it sits for a few minutes, even with the car still stuggling to idle, it will eventually return to a proper idle by itself and the car will be drivable. I checked the fuel rail pressure while the engine was surging and it remained at a constant 45psi so I checked that off the list. I have tried cleaning the maf, unplugging the maf, unplugging DISA valve, I’m kind of guessing at this point. I know the DISA valve is bad but could it cause this problem? Could it be the Vanos system needs the gaskets replaced ? ICV, or CCV? Possibly another vaccum leak? Camshaft position sensor? Im not getting any codes other than P0305 and P0300, and the codes that came up for unplugging the sensors. A point in the right direction would be helpful. Would love to get this car running to it’s full potential.

[MIKYZZ4]

The vacuum leak is right in front of you,
as indicated by the DISA not holding the flap,
due to diaphragm tear/crack, thereby causing -
unmetered air intrusion directly into the intake runners,
Otherwise known as an intake vacuum leak!

REPLACE THE DISA!!