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2004 325i automagic
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Discussion Starter #1 (Edited)
I am looking at a friend's 2003 325i (Oct 2002 build date) with 170k miles that has been losing coolant without any external leak and also suffering from intermittent cold start misfires (INPA codes 239, 240, 241, 242, 243; and P1347/P1349 type codes on obdfusion). This car was overheated after busting a radiator end cap on the highway. Unfortunately, it was driven to a gas station and then towed to a shop where the radiator and some other cooling system parts were replaced, but within about 6 months it began consuming coolant.

The car actually runs very strong but it runs low on coolant once or twice a week on only a 15 mile or so daily roundtrip commute. (EDIT: I spoke further with the owner, and it actually needed coolant once every 10 days or so, maybe every 150 miles.) There are definitely no external coolant leaks to be found, and I pressureized the coolant system and it held 21psi for hours. Fwiw, LT fuel trims are about 7 to 8%, and the DME #3 connector was covered in oil from a leak out of the exhaust cam position sensor.

I did a leakdown test and confirmed leakage into the expansion tank on cylinders 2 through 6, but the actual leakdown numbers on all cylinders are only about 5.5% or so (90psi vs 85psi at cylinder, approximately). Does this make sense? Has anyone seen small leakdown numbers with pressure loss into coolant system?

I'm confident this is a bad headgasket or cracked head, but the low/good leak down numbers surprised me. Never done a leak down test before, either, so can't compare it to anything else, but I did make sure to keep each cylinder at TDC using a breaker bar as best I could.

Fwiw, compression test & leakdown numbers posted below as a case study / data point for anyone esle going through this, and also a video on youtube of a leakdown test on #5 cylinder showing bubbles at ET. Btw, this video was an afterthought after I tested all the cylinders; on the first run coolant was pushed up and out of the tank along with bubbling.

Cold compression test results (1 thru 6):
195psi, 195psi, 207psi, 197psi, 187psi, 192.5psi

Warm compression test results (1 thru 6):
195psi, 180psi, 185psi, 182.5psi, 175psi, 182.5psi

Leak down test results (1 thru 6):
  • 1: 95psi input vs 90psi @ cyl; leakage into valve cover (?)
  • 2: 90psi input vs 85psi @ cyl; leakage into coolant ET & into #1 (?)
  • 3: 90psi input vs 85psi @ cyl; leakage into coolant ET, into #4 & intake
  • 4: 90psi input vs 85psi @ cyl; leakage into coolant ET (slightly, less than others) & into #3
  • 5: 90psi input vs 85psi @ cyl; leakage into coolant ET
  • 6: 90psi input vs 85psi @ cyl; leakage into coolant ET (big), no other leakage

Leakdown test video on cylinder 5:
https://www.youtube.com/watch?v=cWGfozFO8xM
 

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2016 340i xD 6-spd
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Makes sense to me. I drove my e36 for about 10 miles after losing a belt. I didn't know anything about cars at the time.

My cracked head led to coolant loss which began as a rough stumbling in the a.m. and progressed to a much longer stuttering...until it burned off the coolant and ran perfectly fine-ish.

This was literally a 5 mm long crack maybe 0.5 mm wide. No external leaking...progressively greater coolant loss. There are apparently many ways for the head to crack resulting in oil in coolant, coolant in oil, either or both...so I'm lead to believe.

Good luck. I can't say your head is cracked, but it certainly could be.
 

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2004 325i automagic
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Discussion Starter #3 (Edited)
Makes sense to me. I drove my e36 for about 10 miles after losing a belt. I didn't know anything about cars at the time.

My cracked head led to coolant loss which began as a rough stumbling in the a.m. and progressed to a much longer stuttering...until it burned off the coolant and ran perfectly fine-ish.

This was literally a 5 mm long crack maybe 0.5 mm wide. No external leaking...progressively greater coolant loss. There are apparently many ways for the head to crack resulting in oil in coolant, coolant in oil, either or both...so I'm lead to believe.

Good luck. I can't say your head is cracked, but it certainly could be.
Yikes, 10 miles ... I think thats what happened here or something close to that. The owner doesn't know much about cars, but at least two shops have recommended replacing the engine due to bad headgasket, which it turns out was correct advice.

I should have also mentioned that there is no indication of oil in coolant or vice versa, no mayo under fill cap, but definitely from what I've read there is no one failure mode here but a range of possibilities.
 

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I had similar experience: https://forum.e46fanatics.com/showthread.php?t=1127986
It's a long thread because there was a lot of skepticism about my initial diagnosis.

In brief, my previous engine developed an internal coolant leak without being overheated, at least not during the last 40K miles since I bought the car. Cylinder leakdown test didn't detect anything alarming. The internal leak was ultimately confirmed by UOA detecting very high sodium, potassium, and over 2% antifreeze content in the oil in less than 1,500 miles. The car made a last 20 mile trip to a shop I know, where we found the situation had worsened (there was oil in the coolant, not just coolant in the oil). All this without overheating, no codes, nothing except rare hiccups at idle, and probably some loss of power, which is difficult to judge since I went easy on the gas pedal anyway.

We did engine swap at this shop since I was able to find locally a good ZHP engine with low miles. When I removed the head of the old engine, there was evidence of a head gasket failure at cylinders 4-6. Didn't have much time to do further examination since I was about to overstay my welcome at this shop.
 

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Discussion Starter #5
Hey Megalocnus,

It looks like your old engine also had decent leak down numbers but with bad HG and cracked head issues. Thanks for reference your thread, I was hoping to find a similar instance.

I had read the latter part of that thread already about the check valve O2 pilot mod and also about the elevated copper levels you found in the uoas. On my car I actually had slightly elevated copper levels (16ppm) on my previous oil change and last week i sent in another sample after another oil change. Curious what the copper levels are doing this time around.

Hope things are still going well with the 'new' engine.
 

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Discussion Starter #6
Update:

I spoke further with the cars owner and it turns out the rate of coolant loss was much less than I originally understood. It was going from full to coolant light on in about 10 days or so, or approximately 150 miles. Still not a good thing, of course, but it buys them some time to save up for an engine swap or otherwise make a decision about this car. Given the small leak down numbers and slower coolant loss, this engine might last a little while longer.

In meantime, I put in the AC Delco type radiator stop leak pellets (ginger root, turmeric, almond shell, sodium carbonate & polyethylene glycol). Not much to lose at this point, and if it can slow the coolant loss down a bit it will make life easier for the owner.

Also, after properly bleeding cooling system , the heat and A/C started working again, and fwiw there have not been any misfires in the last few days since I cleaned all the oil out of the DME connector. At least no misfires yet, that symptom had been intermittent and correlated with cold mornings (for California at least).
 

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OP, overheated leads to leaking head gasket and possible cracked head. This happened to my wife's 323i twice, and I just bought good used complete heads on eBay for less than $300 each, replaced and car has been running excellent -- zero engine oil top off in 10K miles. Replace the head is cheaper and easier than replacing the whole engine with a used one, which is a can of worms by itself. Your friend engine was good except the cracked head or blow gasket.
 

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Discussion Starter #8
OP, overheated leads to leaking head gasket and possible cracked head. This happened to my wife's 323i twice, and I just bought good used complete heads on eBay for less than $300 each, replaced and car has been running excellent -- zero engine oil top off in 10K miles. Replace the head is cheaper and easier than replacing the whole engine with a used one, which is a can of worms by itself. Your friend engine was good except the cracked head or blow gasket.
I've been thinking about that option as well, but kind of dismissed it out of hand due to alot of issues I've read about. There are plenty of e46s in the local bone yards everytime I visit where I could probably find a good head.

A few questions/comments for you:

  • Did you ever have issues with the block being warped?
  • I'm worried the threads might pull out of the block and that that would lead to having to pull the whole block in order to install timeserts properly.
  • Did the used replacement heads require a machine shop visit for any reason? Like for valve work or testing of any kind?

I need to get a handle on the pros, cons and costs of each alternative. Perhaps if I'm prepared to handle any contingincies replacing the head might be a viable & cost effective option. Need to research a bit more.
 

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Discussion Starter #9 (Edited)
Sapote, nevermind the questions ... I found your post over at bimmerforums detailing the issues you had on the second go around and the solutions. I guess it's kind of a crap shoot, especially with the block threads pulling out. That didn't sound like fun. Need to research more.
 

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I don't think your friend block has pulled threads yet, as it is running ok. You can do time-sert with block in situ, but careful and not tap threads crooked as I did one. You can check the head condition by carefully examine the color/condition of the 6 chambers. Both my ebay heads had no valve/seat issue, but I had to clean the debris trapped on the valve seats before they sealed good.
 
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