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General E46 Forum
This is the place to get answers, opinions and everything you need related to your E46 (sedan, coupe, convertible and wagon) BMW!

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Old 04-18-2013, 11:38 AM   #41
Jakall
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Quote:
Originally Posted by Kubica View Post
I would try a slightly thicker oil and overfill it slightly before junking the motor.
I've tried that many a time to no avail. Given the variety of sounds being made, the oil it's burning through, and the amount of diagnostic work that has already gone into the engine, I think there are bigger problems than oil viscosity.

Last edited by Jakall; 04-18-2013 at 11:39 AM.
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Old 04-18-2013, 11:46 AM   #42
jdstrickland
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You said you used a used block. If therer was a piston bore that was out of round, then the piston would slap against the block as it moved. This would cause a knocking sound that increased with speed.

The pistons are connected to rods that are connected to the crank. There are pins and bearings in different places that if not tight would make a knocking sound as the piston moved. The sound would change with speed and load. Heavy load would make the sound more pronounced or happen earlier and last longer through any given sound-event.

You said the engine made no noise until it was rebuilt, this tells me that the rebuild is high on the list of usual suspects.

I see two options, rebuild again, or live with the noise and hope the engine does not fall out.
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Old 04-18-2013, 12:30 PM   #43
cposk
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You mention that only quality techs/shops have worked on the car. Does this include the engine build? Everything should have been measured/checked/documented in the process. If they just bolted everything together, then piston slap is my guess. It would also explain the oil loss.
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Old 04-18-2013, 01:04 PM   #44
Jakall
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You're right... the engine rebuild seems to have been half-assed, and subsequent mechanics showed me evidence of this (the transmission wasn't bolted to the engine correctly, for instance). Excessive oil loss (which was exactly the reason I got the engine rebuilt in the first place) only just abruptly started recently, whereas it gradually got worse leading up to the initial rebuild.

One way or the other, I suspect one or more pistons, cylinders, and/or wrist pins are shot. Unless the thread makes a strong recommendation to the contrary, like I said, my plan is to get a warrantied longblock. I'm not sure what I want to do with the current bad engine, but an open to suggestions. Before pulling it, my plan was to have a compression test and leakdown test performed, as I trust this will confirm one or more cylinders are hosed.
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Old 04-18-2013, 02:10 PM   #45
jdstrickland
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Quote:
Originally Posted by Jakall View Post
You're right... the engine rebuild seems to have been half-assed, and subsequent mechanics showed me evidence of this (the transmission wasn't bolted to the engine correctly, for instance). Excessive oil loss (which was exactly the reason I got the engine rebuilt in the first place) only just abruptly started recently, whereas it gradually got worse leading up to the initial rebuild.

One way or the other, I suspect one or more pistons, cylinders, and/or wrist pins are shot. Unless the thread makes a strong recommendation to the contrary, like I said, my plan is to get a warrantied longblock. I'm not sure what I want to do with the current bad engine, but an open to suggestions. Before pulling it, my plan was to have a compression test and leakdown test performed, as I trust this will confirm one or more cylinders are hosed.
Once emptied, the current engine will make a very nice anchor for your mechanic's yacht.
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Old 04-18-2013, 02:13 PM   #46
jdstrickland
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Compression and leak down tests may not expose oblong cylinders. The rings can easily fill the oblong sides of the cylinders, but the pistons can still slap and bang around.

I hate to diss Turner, but it seems that the used motor was a bad thing to buy.
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Old 04-19-2013, 10:23 AM   #47
Jakall
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Misshapen cylinders seems probable, though I'm not convinced it's the cause of the tapping. We disabled the cylinders one by one, and I listened to it myself... there was no change in the tapping. Given, we didn't drive the car like that, but the tap is still clearly audible (though soft) at idle.
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Old 04-25-2013, 05:18 PM   #48
thekrauthouse
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Originally Posted by jdstrickland View Post
Once emptied, the current engine will make a very nice anchor for your mechanic's yacht.
No yachts for this mechanic, wife nor I like water that much. Maybe a nice table though.

Did a compression test on it today, wet and dry. Here are the numbers

Dry
Cyl1 #180
Cyl2 #175
Cyl3 #200
Cyl4 #200
Cyl5 #170
Cyl6 #205

Wet
Cyl1 #200
Cyl2 #215
Cyl3 #225
Cyl4 #230
Cyl5 #210
Cyl6 #235

I will be doing a leak down test tomorrow, just didn't have time today from working on another e46.
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