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2002 BMW 325I with 175k miles
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Discussion Starter #1
Hello, I’ve owned my E46 for awhile and my friend is now looking at them for cheap. So definitely something that needs some fixing. I found one but it has an overheating problem. They said they’ve replaced the whole cooling system, although they don’t seem positive. And the car doesn’t start because of a fuel pump, I plan on bringing one and using it to try and fix it before we buy. I was just wondering how I could tell the engine hasn’t been warped from overheating before he buys the car. I really need to make sure it’s actually fixable and the head isn’t warped from overheating. Any advice would be great, thanks!
 

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E30M3 Race F10 535 R1150Rt M Coupe
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If you could rent a cooling system gasses C.O. tester that would be awesome.
Higher level scan tool and look at the engine & rad outlet temps?
 

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Overheat? Plan on a new engine, and you won't be disappointed.

There's not a good way short of a complete teardown to evaluate a non- running engine.

btdt,
t
 
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I do a lot of this...I have several 3.0 engines and can do a head gasket if I have to. An overheated engine with a warped head IS fixable. And used, M54B30 engines are cheap and plentiful.

If the car overheated even once, there is a very good chance the head is warped. Most owners don't shut the car down quick enough and/or they try to nurse it home the last 3 miles while overheating.

When looking at overheated vehicles I do the following:

1. Assume the head is warped and factor that into the price.
2. Do a compression test
3. check for oil in coolant or vice versa. - milky oil under the cap does not mean oil mixed with coolant.
4. If the engine is cold, I might swab each cylinder before starting or doing a compression test to see if coolant is seeping into any cylinder.

IMO, the car you described - non-runner, history of an overheat should be no more than $1000 and preferably less.
 

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A leak down test would be better than a compression test. I would also fill the expansion tank to the top (yes, overfill it) when doing the leak down test. If there is any leakage from the combustion chamber into the cooling system you will see it overflow and or bubble.

Sent from my S61 using Tapatalk
 

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My wife overheated my first E46 because when the expansion tank burst and all the coolant left the system, the temperature sensor was giving a lower than actual reading on the gauge. She cooked all the rubber touching the block, but the head was totally fine. I also bought a rough one that had been overheated, couldn't bleed the cooling system properly, then let it sit and sold it cheap. That one also head was fine after replacing the cooling system properly.

But, if it were me, as above, I would compression test each cylinder and compare the spark plugs looking for one cleaner than the others. Also, I have seen a manual coolant pressure tester that attaches to the expansion tank and you can pump it up and see if it holds. Like the one pictured in here:

If you check it out. Let us know what you find out...
 

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My wife overheated my first E46 because when the expansion tank burst and all the coolant left the system, the temperature sensor was giving a lower than actual reading on the gauge. She cooked all the rubber touching the block, but the head was totally fine. I also bought a rough one that had been overheated, couldn't bleed the cooling system properly, then let it sit and sold it cheap. That one also head was fine after replacing the cooling system properly.
1)Did you actually see the gauge showing lower temperature, or just your wife's story? When the head is overheated, the sensor is hot and so the gauge should show high temp regardless with coolant or empty in the head. This same scenario happened to my wife, but the gauge needle moved pass and locked at the right side, until I turned on the key the next morning to get the needle back to normal position.

2) Why you couldn't bleed properly on the 2nd car?
 

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2002 BMW 325I with 175k miles
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Discussion Starter #10
Quick question about the car I’m looking at. Is it possible the car is overheating because the plastic intake cover at the front, under the hood is missing?
918878
 

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2002 BMW 325I with 175k miles
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Discussion Starter #11
My wife overheated my first E46 because when the expansion tank burst and all the coolant left the system, the temperature sensor was giving a lower than actual reading on the gauge. She cooked all the rubber touching the block, but the head was totally fine. I also bought a rough one that had been overheated, couldn't bleed the cooling system properly, then let it sit and sold it cheap. That one also head was fine after replacing the cooling system properly.

But, if it were me, as above, I would compression test each cylinder and compare the spark plugs looking for one cleaner than the others. Also, I have seen a manual coolant pressure tester that attaches to the expansion tank and you can pump it up and see if it holds. Like the one pictured in here:

If you check it out. Let us know what you find out...
Interesting I’ll have to check that out thanks
 

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2002 BMW 325I with 175k miles
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Discussion Starter #12
I think they won't sell it after it was fixed by you.

Pull all plugs and look at the color; the one that has coolant leaked in should have a cleaned look.
Possibly, but I’ll just take the pump out again if it works and they won’t sell it to me
 

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2002 BMW 325I with 175k miles
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Discussion Starter #13
A leak down test would be better than a compression test. I would also fill the expansion tank to the top (yes, overfill it) when doing the leak down test. If there is any leakage from the combustion chamber into the cooling system you will see it overflow and or bubble.

Sent from my S61 using Tapatalk
I’ll keep this in mind
 

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2002 BMW 325I with 175k miles
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Discussion Starter #14
I think they won't sell it after it was fixed by you.

Pull all plugs and look at the color; the one that has coolant leaked in should have a cleaned look.
What do you mean by cleaned look?
 

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2002 BMW 325I with 175k miles
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Discussion Starter #15
I do a lot of this...I have several 3.0 engines and can do a head gasket if I have to. An overheated engine with a warped head IS fixable. And used, M54B30 engines are cheap and plentiful.

If the car overheated even once, there is a very good chance the head is warped. Most owners don't shut the car down quick enough and/or they try to nurse it home the last 3 miles while overheating.

When looking at overheated vehicles I do the following:

1. Assume the head is warped and factor that into the price.
2. Do a compression test
3. check for oil in coolant or vice versa. - milky oil under the cap does not mean oil mixed with coolant.
4. If the engine is cold, I might swab each cylinder before starting or doing a compression test to see if coolant is seeping into any cylinder.

IMO, the car you described - non-runner, history of an overheat should be no more than $1000 and preferably less.
Yeah that’s the plan. Nothing over a grand.
 

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2002 BMW 325I with 175k miles
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Discussion Starter #16
Overheat? Plan on a new engine, and you won't be disappointed.

There's not a good way short of a complete teardown to evaluate a non- running engine.

btdt,
t
Good point lol
 

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2002 BMW 325I with 175k miles
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149 Posts
Discussion Starter #17
I do a lot of this...I have several 3.0 engines and can do a head gasket if I have to. An overheated engine with a warped head IS fixable. And used, M54B30 engines are cheap and plentiful.

If the car overheated even once, there is a very good chance the head is warped. Most owners don't shut the car down quick enough and/or they try to nurse it home the last 3 miles while overheating.

When looking at overheated vehicles I do the following:

1. Assume the head is warped and factor that into the price.
2. Do a compression test
3. check for oil in coolant or vice versa. - milky oil under the cap does not mean oil mixed with coolant.
4. If the engine is cold, I might swab each cylinder before starting or doing a compression test to see if coolant is seeping into any cylinder.

IMO, the car you described - non-runner, history of an overheat should be no more than $1000 and preferably less.
Quixk question, at what number does the compression test become a concern? And what numbers would indicate a warped head or bad gasket? Would they just be the same numbers as they would if they were bad?
 

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Quick question about the car I’m looking at. Is it possible the car is overheating because the plastic intake cover at the front, under the hood is missing?
No. The missing part would give better cool air and little more power.
 

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you are in good bargaining position. Not many people will take a chance on a car that doesn't run, and even if it does, may have a cooked motor. But are you equipped/skilled to change a head?
 
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