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E39 (1997 - 2003)
The BMW 5-Series (E39 chassis) was introduced in the United States as a 1997 model year car and lasted until the 2004 when the E60 chassis was released. The United States saw several variations including the 525i, 528i, 530i and 540i. -- View the E39 Wiki

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  #1  
Old 05-19-2013, 11:00 AM
burbankE34 burbankE34 is offline
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Puzzling engine problem

Symptoms (1993 525i):

Rough idle when cold, smoothens out to normal idle and driving within 5 minutes.

Underpowered driving while the idle is rough. No error codes. Gaskets including TB and intake have been replaced. No vacuum leaks as far as I can tell. Disconnect test on all drivability sensors had no indications either.


================

Radiator pressure test indicated slow falling pressure. Need to top up 2 marks on coolant every 2 months. No overheating and no hint of overheating at all times. When the expansion tank is filled to the brim and engine idled from cold, almost no bubbles seen, just the odd tiny one here and there every few minutes. No bubbles seen when throttle held a 1500. Same observations about no bubbles when the engine is first brought to normal temperature, held at idle, and held at 1500rpm.

Some very light grey smoke for a few minutes when starting from cold. No black, no blue, no white. No smoke when starting from hot.

No starting trouble either when the engine is hot or cold. Fuel economy is normal for my driving style.

Fuel pump, fuel pump relay, main relay and fuel pump filter are new. Crank and cam sensors new. Plugs and coils are new. Injectors were cleaned and reinstalled with new o rings and microfilters. CCV fitting and several vacuum hoses are new or cleaned out. ICV has been cleaned more than once. No pinched wires to any sensor I can see.

======

Rough idle period seems to be slightly worse and take a little longer than 5 minutes to normalize, when the car has not been started for 2 days or more.

======

Now, my question. Could I be looking at a small crack in the cylinder head or a small tear in the head gasket? The crack seals up when the engine heats up enough to close the crack / tear. I've read this on google, but it seems too far fetched. Has anyone actually seen or heard of this happening ?

What should I do from here to confirm or deny any diagnosis ?

Thanks in advance.


Sylvester

p.s. I'm cross posting this as it is clearly a general bmw engine issue of sorts.
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  #2  
Old 05-19-2013, 01:12 PM
edjack edjack is online now
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Cold and hot cooling system pressure test. Gasket may be allowing small amounts of coolant it. Best diagnose and fix before a catastrophic failure occurs.
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  #3  
Old 05-19-2013, 05:19 PM
burbankE34 burbankE34 is offline
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Quote:
Originally Posted by edjack View Post
Cold and hot cooling system pressure test. Gasket may be allowing small amounts of coolant it. Best diagnose and fix before a catastrophic failure occurs.
Which gasket are you referring to? Head gasket ? Or the thermostat housing gasket ?

I'm not losing coolant every day and I don't get steam out of my tailpipe except on wet days. I am hopeful that the pressure test was not good because of a crack in my thermostat housing, which is made of plastic and apparently prone to such failure. Will be replacing it with aluminium very shortly.

Have been living with this engine for 1 year. No changes to its behaviour despite all that I've done.

That said, do you think the symptoms in my OP indicatea a cracked head or HG issue ? Is it possible for such issues to generate a rough idle at startup when cold, which tapers off and normalises to perfectly normal behaviour over 5 minutes? Thanks..
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  #4  
Old 05-19-2013, 08:05 PM
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dtadrian dtadrian is offline
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Puzzling engine problem

Have you tested coolant for combustibles ? Also this may be far fetched but have you looked at your throttle body to see if any coolant is leaking in there... I know that the throttle body has coolant that runs thru there. Maybe there's a crack there.
One other question... Has this engine ever overheated?


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Last edited by dtadrian; 05-19-2013 at 08:14 PM.
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  #5  
Old 05-20-2013, 02:25 AM
burbankE34 burbankE34 is offline
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Quote:
Originally Posted by dtadrian View Post
Have you tested coolant for combustibles ? Also this may be far fetched but have you looked at your throttle body to see if any coolant is leaking in there... I know that the throttle body has coolant that runs thru there. Maybe there's a crack there.
One other question... Has this engine ever overheated?


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Hi Dtadrian,

The throttle body has been checked and cleaned. No coolant, and very little dirt.

I'm losing 2 marks of coolant every 2 months. I'm driving the car virtually every day. So, for 5 minutes every day, the idle is rough. It seems to me that if I had a crack or something I should be losing coolant at a faster rate considering that I drive the car daily.

No, I have not tested the coolant for combustibles (the block testor, right?) And no I have not done a compression test on the cylinders yet.

Am I at that stage ?

No, this engine has never overheated while I owned it for over a year now. It has not even hinted at overheating. That adds to my puzzlement.
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  #6  
Old 05-20-2013, 01:02 PM
dvdlkd dvdlkd is offline
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I had a 2000 528 that had a blown head gasket when I got it. Very small at first, but car would car would periodically overheat (at first every few months to the point I couldn't drive 5 miles without it overheating). As bad as that leak got, the engine never ran bad and was very smoot even at first start. I finally figured this out with a block tester I purchased on-line. But the block tester gave me negative results when I opened the expansion tank and pulled the test with a cold engine. The test didn't show positive until I tried it after an overheat situation (coolant blew out expansion tank cap) and I did the test after letting car cooldown an hour. You do need to figure out where your coolant is going. If you have access to the cooling system pressure test rig, hold the pressure and look at all the hose connections while engine is cold. I hate to say this because of the work involved but could the leak be in your heater core? Do you smell coolant when you turn the heat on?
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  #7  
Old 05-20-2013, 09:19 PM
burbankE34 burbankE34 is offline
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Quote:
Originally Posted by dvdlkd View Post
I had a 2000 528 that had a blown head gasket when I got it. Very small at first, but car would car would periodically overheat (at first every few months to the point I couldn't drive 5 miles without it overheating). As bad as that leak got, the engine never ran bad and was very smoot even at first start. I finally figured this out with a block tester I purchased on-line. But the block tester gave me negative results when I opened the expansion tank and pulled the test with a cold engine. The test didn't show positive until I tried it after an overheat situation (coolant blew out expansion tank cap) and I did the test after letting car cooldown an hour. You do need to figure out where your coolant is going. If you have access to the cooling system pressure test rig, hold the pressure and look at all the hose connections while engine is cold. I hate to say this because of the work involved but could the leak be in your heater core? Do you smell coolant when you turn the heat on?

Thanks dvdlkd. Thankfully, I don't smell coolant in the cabin when the heat or a/c is turned on. However, it does look like I'll have to get a block testor at least to check on combustion gases in the radiator. I'll be sure to do the test when the engine is hot, like maybe 30 minutes after shutdown. The engine has never overheated, and never run hot either, at least while I owned it.
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  #8  
Old 05-21-2013, 09:34 AM
burbankE34 burbankE34 is offline
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Hi Everyone,

Thank you for your thoughts on this issue. I would like to post an important update.

I let my car sit overnight, removed the spark plugs in the morning, and took a good sniff out from each chamber.

Petrol in all chambers. Coolant and petrol in cylinder 3. No other smells in any chamber.

Spinning the engine with the plugs out threw out practically nothing. I put some white paper across the spark plug holes to see if anything hit it while the engine was cranked.

This was yesterday. Just did the test again this morning. Same thing.

Before the car was shut down for the night, and after a drive, I removed the plugs and sniffed the chambers. I smelled nothing but a hot engine, a faint whiff of exhaust, hot air. Seemed perfectly normal to me. However, letting the engine sit overnight produces a petrol smell in all chambers and coolant smell as well in cylinder 3 alone.

==========

It looks like :

1. A HG or cracked head issue, affecting cylinder 3. Likely to be HG as a cracked head tends to throw coolant into to adjacent chambers, if I remember what I read correctly.

2. Leaking fuel injectors across all chambers. This is despite having change the o rings, pintles, and microfilters, inside each of the injectors, just 2 months ago. Did not backflush though. Can that can save leaky injectors?

============

Am redoing this test again as we speak. Just came back from a hard drive, unhooked my battery terminal, and am giving the car a few hours to cool down, before I remove the plugs for a final sniff. This is to eliminate any wiring problems that may be keeping the injectors open even when the car is shut down.

I've sprayed contact cleaner into my engine through the brake booster fitting when the car was running rough. I expected the idle to improve assuming there was a vacuum leak at play. The idle remained rough, but differently so. When the idle normalised 5 minutes later, I hit the manifold with another very short burst of contact cleaner. The engine died immediately. Upon restarting, the engine was rough for a full minute, before becoming normal. I had ensured that the brake booster fitting was not a vacuum leak during this time.

My engine clearly reacts poorly to rich mixtures.
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  #9  
Old 05-21-2013, 09:35 AM
burbankE34 burbankE34 is offline
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I think what's happening is that I've got leaky injectors which stay leaky. While open loop operation is going on (when the engine is cold) the idle is rough. However, as closed loop operation comes online progressively, the DME compensates for the rich mixture by cutting down injector times. I guess my injectors don't leak so bad that the dme cannot fully compensate for it.

If I can confirm that this problem is caused by the injectors and not by faulty wiring, a faulty dme, or a bad fuel pressure regulator, then the rough idle is almost fully caused by the leaky injectors. I'm probably going to send for a set of 6 rebuilt and flow matched injectors. They're pretty cheap at $120 shipped and I was tempted to do this last christmas anyway.

This will not fix the coolant leak issue, but considering that :

-nothing flies out when I spin the engine after leaving a hot engine to cool down overnight,
- that there's no persistent white smoke out the tailpipe or even the hint of it, after the first 5-10 minutes of driving (does not apply on wet days),
- that I'm only losing 1 mark of coolant every month,
- my engine does not overheat under any circumstances, it does not even run hot, and I do drive her hard from time to time,

I think the coolant leak is not much of a problem for now. The rough idle is probably caused by the leaking fuel. Good injectors should cure it by 90% I hope and I can live with the rest by just topping up coolant every now and then. A new HG, cylinder head, or engine, is a very expensive affair.

What do you guys think ? Am i reading this situation correctly ? Thanks..
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  #10  
Old 05-21-2013, 03:25 PM
poolman poolman is offline
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Might try some kind of head gasket repair in a bottle--from what I hear,, the Blue Devil stuff works pretty good on cars that aren't too far gone
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  #11  
Old 05-21-2013, 09:07 PM
burbankE34 burbankE34 is offline
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Originally Posted by poolman View Post
Might try some kind of head gasket repair in a bottle--from what I hear,, the Blue Devil stuff works pretty good on cars that aren't too far gone
That's a good idea. Unfortunately, I've already tried K seal last December. No improvement, and clearly there is coolant leaking into chamber 2 today. I didn't check my chambers then, so it may have fixed other problems, or reduced this one by a little, for all I know.

I might try another one or two bottles for the heck of it, or maybe steel seal, after I get my injectors sorted out. That should fix the rough idle almost completely.
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