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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 03-09-2011, 12:34 PM
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bluebee bluebee is offline
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Who here has tested the E39 head gasket using an exhaust gas analyzer on the coolant?

This thread today got me thinking whether anyone here has tried testing an E39 head gasket using an exhaust gas analyzer held over the open neck of the expansion tank while the engine is running:
- How to bleed the air out of the cooling system??

This idea of using a sensitive exhaust gas analyzer (in addition to the typical recommended head gasket tests) came to me only after I researched the answer to this thread:
- My E39 overheated & I need a new head gasket (1)

Of course, the "problem" would then be to find an affordable exhaust gas analyzer tester ... and a technique that is solid enough to be useful (over the other tests, such as compression, leak-down, and pressurizing the cooling system).

If you have tried this exhaust gas analyzer test on your E39, it would be useful to know what your recommendations are.
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  #2  
Old 03-09-2011, 04:40 PM
bobdmac bobdmac is offline
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You could probably take it to any place that does a smog check. It should be less than a full-blown smog inspection. I think all they have to do is put the probe partway into the coolant reservoir (with the engine below operating temperature, obviously). I'd be surprised if there were such a thing as an "affordable" exhaust gas analyzer. By the way, I remember hearing this test described on "Car Talk," the NPR show with "Click and Clack, the Tappet Brothers."
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  #3  
Old 03-09-2011, 04:47 PM
bobdmac bobdmac is offline
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Here's what's on Ebay at the moment. Pretty sketchy, but possibly a couple of good buys.
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  #4  
Old 03-09-2011, 05:47 PM
mycul mycul is offline
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No, but on other cars yes.

Although the theory is sound, in practice its difficult to do. By the time a combustion leak into the cooling system has progressed to the point that there's an adequate quantity of combustion gas present to test, it probably means that the coolant is being forced out past the pressure relief and/or ruptured a hose or plastic neck. Because combustion pressures greatly exceed coolant system pressure, there's only a very narrow range of leakage that would allow sufficient sampling but not overwhelm the system. Remember, you're talking about inserting a probe into a small area just above hot coolant which could suddenly rise because of the suspected leak. Exhaust analyzers are pumping the sample gas through the various test precedures and coolant (or any fluid) is the last thing the machine wants to see. Yes there are water traps and filters that the gas must pass through but they are only designed to accomodate minute quantities of water and can easily be overwhelmed by large quantities of coolant. If the leak is very small you may see bubbling but that quantity of gas would be immediately diluted with the surrounding atmosphere. Something that may be more practical (and certainly cheaper) would be a block tester. I have one but I haven't seen one in retail for a long time. They're similar to an airlock used in beer or wine making. Essentially you're allowing that gas trapped above the coolant to pass through a special liquid that reacts with a color change to the presence of hydrocarbons. I've used it with some success but it too can be flooded by a sudden expansion of the hot coolant. Either way its a tricky proposition.
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  #5  
Old 03-09-2011, 10:43 PM
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Quote:
Originally Posted by bobdmac View Post
I think all they have to do is put the probe partway into the coolant reservoir
What I read is that you hold the probe 'above' the open coolant cap, i.e., it's a gas analyzer.

This presumes, of course, that hot coolant 'outgasses' whatever gasses we're looking for.

Quote:
Originally Posted by mycul View Post
Because combustion pressures greatly exceed coolant system pressure, there's only a very narrow range of leakage that would allow sufficient sampling
Interesting.

Quote:
Originally Posted by mycul View Post
Something that may be more practical (and certainly cheaper) would be a block tester.
Interesting. A 'litmus' test of the coolant, of sorts.

Quote:
Originally Posted by bobdmac View Post
Here's what's on Ebay at the moment.
Interesting. Prices all over the map.

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  #6  
Old 03-09-2011, 10:47 PM
bobdmac bobdmac is offline
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Originally Posted by bluebee View Post
What I read is that you hold the probe 'above' the open coolant cap, i.e., it's a gas analyzer.

This presumes, of course, that hot coolant 'outgasses' whatever gasses we're looking for.
That's probably true. The instruments pretty sensitive.
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  #7  
Old 03-10-2011, 11:10 AM
edjack edjack is offline
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Originally Posted by bobdmac View Post
Here's what's on Ebay at the moment. Pretty sketchy, but possibly a couple of good buys.
Those are only air/fuel ratio meters; they won't work for the subject test. And they won't work on cat-equipped cars, either.
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  #8  
Old 03-10-2011, 11:34 AM
bobdmac bobdmac is offline
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Thanks. I thought they seemed cheap, except for the Bear.
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  #9  
Old 03-10-2011, 12:10 PM
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Originally Posted by edjack View Post
they won't work on cat-equipped cars, either.
But we plan on sticking them a few inches above the coolant opening.

Nowhere near the cats.

Nonetheless, I would think, if we're gonna buy an exhaust gas analyzer, we may as well get one that works both at the tailpipe and at the cooling system expansion tank opening.
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  #10  
Old 03-10-2011, 01:10 PM
bobdmac bobdmac is offline
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I think this is the price range you're looking at for a new one:

Kit, Hand Held Gas Analyzer (5 Gas)--$3,087

A discontinued model, although still listed as new, recently sold here for $800:

Mike Peterson Auctioneers Auction Catalog
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  #11  
Old 03-10-2011, 05:56 PM
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Sorry I can't be more specific, but I seem to recall seeing somewhere in the TIS that it's not reasonably accurate to use this on BMWs... for some reason. If I find it I'll post it, but there's a lot of info in there and I don't know what might have caught my eye.
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  #12  
Old 03-10-2011, 05:59 PM
bobdmac bobdmac is offline
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Thanks, I'd be curious to see what they have to say.
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  #13  
Old 03-10-2011, 06:52 PM
Jimmys 530i Jimmys 530i is offline
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Why not just put the engine in TDC, and screw in a fitting into the spark plug hole, and pressurize it to about 100 psi? That will make any leaks more obvious since you do not have the engine running and it is much quieter. You will hear or see any leaks that there are. I have done this many times and have pinpointed to where the compression is escaping.
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  #14  
Old 03-10-2011, 06:54 PM
bobdmac bobdmac is offline
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Quote:
Originally Posted by Jimmys 530i View Post
Why not just put the engine in TDC, and screw in a fitting into the spark plug hole, and pressurize it to about 100 psi? That will make any leaks more obvious since you do not have the engine running and it is much quieter. You will hear or see any leaks that there are. I have done this many times and have pinpointed to where the compression is escaping.
Sounds like a good idea to me.
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  #15  
Old 03-10-2011, 11:09 PM
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Quote:
Originally Posted by Jimmys 530i View Post
Why not just put the engine in TDC, and screw in a fitting into the spark plug hole, and pressurize it to about 100 psi?
Clearly that's 'one' of the tests one would run.
- My E39 overheated & I need a new head gasket (1)

Namely:
  • Cylinder compression tests, wet & dry (1)
  • Cylinder leak down test (1)
  • Cooling system pressure test
  • Exhaust gas analyzer over the open radiator instead of tailpipe (1)
But, this thread is about the exhaust gas analyzer method.
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  #16  
Old 03-11-2011, 05:32 PM
mycul mycul is offline
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BB, your link to the exhaust gas test method underscores my point about the difficulty in performing said test. Even though you may be holding the probe above the coolant filler, we all know that a small geyser can suddenly erupt from the cooling system (especially since there may be combustion pressures present) and immerse the probe in liquid (ask me how I know). Hold the probe too far away and you negate the efficacy of your test, too close and you suck fluid.
The shortcoming of the 100psi test is mentioned in the link also. If the head gasket will leak bubbles at 100psi, it will be BLOWING OUT at combustion pressures.
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  #17  
Old 03-11-2011, 06:25 PM
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Quote:
Originally Posted by mycul View Post
difficulty in performing said test
I don't disagree.

It appears the tools are also somewhat prohibitively expensive, at least if you want to have dual-use tools that can also be stuck in the exhaust pipe.
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  #18  
Old 03-11-2011, 07:33 PM
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Here is a much cheaper tool.
http://www.napaonline.com/Search/Det...006_0282440235
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  #19  
Old 03-12-2011, 05:12 AM
Jimmys 530i Jimmys 530i is offline
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Quote:
Originally Posted by mycul View Post
BB, your link to the exhaust gas test method underscores my point about the difficulty in performing said test. Even though you may be holding the probe above the coolant filler, we all know that a small geyser can suddenly erupt from the cooling system (especially since there may be combustion pressures present) and immerse the probe in liquid (ask me how I know). Hold the probe too far away and you negate the efficacy of your test, too close and you suck fluid.
The shortcoming of the 100psi test is mentioned in the link also. If the head gasket will leak bubbles at 100psi, it will be BLOWING OUT at combustion pressures.
Whenever I am replacing an engine due to overheating, I always make sure it is blown. The first step I take is fill it up with water, leave the cap off, and spin it over. 99% of the time I have a geyser of water shooting out. That always confirms that the engine is blown. I am pretty sure that you have a hard time keeping the probe dry while there is water shooting out.
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  #20  
Old 03-12-2011, 06:14 AM
pshovest pshovest is offline
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Very true, but if there is water shooting out of expansion tank there's not much value in sniffing for HC's since engine clearly has a problem. Not all head gasket leaks are as obvious as water shooting out. I used an exhaust gas analyzer at expansion tank to convice myself I had a GOOD head gasket. I bought a '00 528iM w/78k last summer. I drove it home 120 miles and found it was 8 ounces low on coolant. I was NOT in a good mood! Cooling system clearly wasn't holding pressure for more then a few minutes, based on squeezing upper radiator hose and amount of vapor released when opening radiator cap. A pressure test of cooling system showed it was holding pressure. Exhaust gas analyzer at expansion tank was only showing 3-4 ppm HC. Problem was a bad radiator cap that could be heard very faintly hissing immediately after shutdown after a good run thru the gears to get coolant nice and warm.

Paul S
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Quote:
Originally Posted by Jimmys 530i View Post
Whenever I am replacing an engine due to overheating, I always make sure it is blown. The first step I take is fill it up with water, leave the cap off, and spin it over. 99% of the time I have a geyser of water shooting out. That always confirms that the engine is blown. I am pretty sure that you have a hard time keeping the probe dry while there is water shooting out.
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  #21  
Old 03-12-2011, 01:36 PM
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bluebee bluebee is offline
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Originally Posted by gtxragtop View Post
Must have been a temporal URL as it doesn't work for me:
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  #22  
Old 03-12-2011, 01:42 PM
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Originally Posted by Jimmys 530i View Post
fill it up with water, leave the cap off, and spin it over.... a geyser of water shooting out...confirms that the engine is blown
I love the simplicity of this test!

I'm shocked, though, that I had not seen this test when I did the cursory research into what people on Bimmerfest recommended when someone asked if their head gasket is blown.

Results here:
My E39 overheated & I need a new head gasket (1)

In fact, I probably read about fifty threads (hundreds of posts) and nobody had (to my recollection) suggested this simple test.

Let's see how it works.
  • You fill the cooling system with fluid & leave the expansion tank cap off
    • Presumably you bleed the cooling system also (using the aux pump method presumably)
  • Then you start the engine
  • The cooling system PSI is 14.7 (because the cap is off) but the engine pressure is well over a hundred psi
  • If the head gasket is leaking, exhaust gases leak into the cooling system
    • Presumably these leaks are explosive
    • Is that what causes the fluid to shoot upward?
One question (since I'm trying to get to the bottom of this to help others):
  • How "dramatic" (i.e., obvious) is the shooting of the fluid upward?
  • Does it simply well outward, or is it a two-foot geyser?
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  #23  
Old 03-12-2011, 01:46 PM
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Originally Posted by pshovest View Post
I used an exhaust gas analyzer at expansion tank to convince myself I had a GOOD head gasket.... Exhaust gas analyzer at expansion tank was only showing 3-4 ppm HC.
Interesting. Very interesting.
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  #24  
Old 03-12-2011, 01:46 PM
bobdmac bobdmac is offline
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Quote:
Originally Posted by pshovest View Post
I used an exhaust gas analyzer at expansion tank to convice myself I had a GOOD head gasket...Exhaust gas analyzer at expansion tank was only showing 3-4 ppm HC. Problem was a bad radiator cap that could be heard very faintly hissing immediately after shutdown after a good run thru the gears to get coolant nice and warm.

Paul S
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So what analyzer did you use? Mind telling us how much it cost and how you used it? Is it within reach, economically speaking, of the home DIY'er? Is this a rare diagnostic scenario?
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  #25  
Old 03-12-2011, 03:15 PM
JCasper JCasper is offline
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I did just today, it didn't pass. It's a pretty simple way of diagnosing a head gasket problem.
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