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Old 11-25-2011, 11:37 AM
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bluebee bluebee is offline
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Location: San Jose, California
Join Date: Mar 2008
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Mein Auto: 02 BMW 525i M54 auto 130K
For the record, there is good advice on how to test for a blown engine due to overheating over in this E46 thread today:
- - E46 (1999 - 2006) > Lost Cause? I need blunt honesty here...
Originally Posted by moneymike View Post
Ok guys awhile ago i was having overheating was actually my the upper radiator hose over heated & he drove it for 10+ miles while stoplight car cuts off...he restarts...drives about another mile & cat cuts off again...this time wont restart...tries a few times & finally it restarts...drives another .5 miles to destination & as pulling into driveway hears a rapid knocking...once the hose was replaced & coolant returned the car has been real issues but it has started gradually running there any tests to know for sure if there is internal damage?
The good news is that a lot of good advice resulted which the OP of this E39 thread can quickly benefit from.

For example:
Originally Posted by floydarogers View Post
The chances are slim. I'm amazed that you're not losing coolant. Nevertheless, here's what you need to do:
1) Flush the coolant. Look at it; if there is oil or other contaminants, you're toast.
2) Pressure test the cooling system. If it doesn't hold pressure, there's a leak somewhere. Not losing coolant VOLUME isn't a guarantee of the engine being intact.
3) Change the oil - it was under incredible stress as it was the only thing cooling the engine. It's toast. Again, inspect the old oil, filter and drain plug. If there are metal shavings-bits-filings, you're probably toast.
4) Do a compression test. Do a leak-down test. This will show if you have bad rings/cylinders or burnt valves.
5) Have someone check the oil pressure (you need a real guage and hose to connect to the system.) If low or high, may indicate bad bearing or turned bearing (which is the likely noise heard when pulling into the drive - might also be bad kingpin.)

If all that looks "ok", you may be ok. The operative word is "may", as these engines don't like being overheated AT ALL. However, it's not unheard of to hear of abuse like this and having them last for some time. The engine's lifetime has been adversely affected at the minimum.
Originally Posted by jvr826 View Post
Contact Blackstone Labs, get an oil test kit sent to you, and collect a sample and have it analyzed. If you are in a hurry to change the oil, collect the sample prior to receiving the kit. You need a warm engine and a clean vessel with a cap, open the drain plug and let it flow for a few seconds (5-10), then duck your vessel into the stream and collect 3-4 ounces. They will let you know the percentage of coolant in the oil, if any. I suspect you'll find quite a bit.

You are in the denial phase of grief. Soon comes acceptance. You'll want to throw money at your engine, but listen to the experienced folks. It will save you time and money in the long run.
Originally Posted by SJBimmer View Post
That is great advice all around. Unfortunately for the people who don't listen, the first time they realize that they were wrong is after they have spent a lot of money having the head re-milled, buying a new head gasket and then trying to put it all together. They go to torque the new head bolts and they pull out like butter. Time serts MAY solve the problem, but if they don't, all that money, that could have been put towards a replacement engine, has been wasted. That is when extreme frustration occurs, and they sell what might have been a salvageable car, spew all sorts of obscenities about BMW's, and vow to never buy another one.
Originally Posted by Variocam View Post
Lots of great comments here, but I especially agree with jvr826's about the oil analysis. They are very cheap, and will give you a wealth of information as to whether the engine has suffered major damage. You should definitely tell them in the "comments" section of the submission form about the overheating episode, so they can pay special attention to the aspects of the analysis that might pertain to to the impact on the oil of overheating.

But to get the maximum bang for your troubleshooting buck, I would do the following:

1) Warm up the engine
2) Do a compression test. If this shows an obvious problem like, well, low compression in one or more cylinders, stop, and start searching for a replacement engine
3) If the compression looks OK (not sure what the spec is, but the readings should all be within about 5% of each other across all the cylinders), drain the oil, and fill the oil sample vessel after letting it drain for a few seconds, like jvr says (the idea is to take the sample about midway through the drain), send the sample out for analysis, and pray.
For the record, I added that useful thread as recent example #41 to the list below for others to benefit, as always, by the virtue of incrementalism:

- Summary advice to provide users who suspect a major engine repair due to overheating (1) (2) (3) (4) & how to test an engine for a blown head gasket, cracked heads, a warped block, stripped head bolt threads, cam seizures, contaminated bearings, coolant hydrolock, or piston, ring, or valve damage (1) (2) & what are the major factors in deciding whether to rebuild the engine, replace the engine, or sell the car (1) & a DIY for replacing the I6 M54 head gasket (1) (2) & replacing the V8 M62TU head gasket (1) & why these engines are so prone to heat-related damage in the first place (1) & welding the crack between cylinder #3 and the water jacket on the exhaust side (1) & what engine swaps are most recommended (1) (2) (3) & where to obtain a new or rebuilt head (1) replacement short block or long block (1) (2) & how to lift & remove the engine (1) & real-world results from people faced with similar blown engine problems from which this advice came from (1) (2) (3) (4) (5) (6) (7) (8) (9) (10) (11) (12) (13) (14) (15) (16) (17) (18) (19) (20) (21) (22) (23) (24) (25) (26) (27) (28) (29) (30) (31) (32) (33) (34) (35) (36) (37) (38) (39) (40) (41).

Last edited by bluebee; 11-25-2011 at 11:39 AM.
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