[19bmwg05]

Heads up, this is kind of lengthy.

So I picked up a 2006 325i sedan a couple weeks ago. To my bad luck, I've driven it three times in that span, all three of those times the car overheated. After it overheating on my way home from buying the car, we tried bleeding the cooling system. It looked like the previous owners had it fixed/replaced because all the hoses looked new. Second time taking it out it overheated again. We then replaced the expansion tank (sensor included), thermostat, coolant temperature sensor, and we switched the plastic bleed screw for a brass one. Third time driving the car, it overheated again. Only this time, when we started the car, there was smoke coming from the back of the engine bay and it smelled like something was burning. We decided that since we're working on it, we should at least do an oil change and change out the filters (we do this anytime we buy a car). We drain the oil and there must have been 7 or 8 quarts of oil in it. Start the car for the fourth time and theres no smoke and no burning smell.

My question for you guys is: If the previous owner overfilled the engine with oil, could that cause the engine to overheat?

Thanks in advance!

[Efthreeoh]

Any diagnosis of an N52 overheating starts with a scan of the ECU with a BMW scan tool to look for water pump trouble codes. Search E90 post for water pump. You'll find out all you need to know.

The engine oil quantity is 7 quarts.

[19bmwg05]

Originally Posted by Efthreeoh

Any diagnosis of an N52 overheating starts with a scan of the ECU with a BMW scan tool to look for water pump trouble codes. Search E90 post for water pump. You'll find out all you need to know.

The engine oil quantity is 7 quarts.

We are pretty sure the water pump is functioning properly because we heard the coolant moving around the system when we bled it. Maybe we were wrong?

[Efthreeoh]

Originally Posted by 06bmwe90

We are pretty sure the water pump is functioning properly because we heard the coolant moving around the system when we bled it. Maybe we were wrong?

I'm not going to piecemeal this diagnosis for you. Get a BMW scan tool and scan the ECU. An additional quart in the sump will not overheat the engine, you don't even know how much drained out, so you are just guessing. Stop guessing about shit and just scan the car with a BMW scan tool. The pump can be intermittent. If it stopped working or slowed down (RPM) there will be a trouble code stored.

[bushwa]

Originally Posted by Efthreeoh

Any diagnosis of an N52 overheating starts with a scan of the ECU with a BMW scan tool to look for water pump trouble codes. Search E90 post for water pump. You'll find out all you need to know.

The engine oil quantity is 7 quarts.

Like he said. Scan for codes, and not just obd2 stuff. Could be intermittent. If at any point the ecu called for he pump to run and it didn't, it'll store the event in the ecu.

[19bmwg05]

Originally Posted by bushwa

Like he said. Scan for codes, and not just obd2 stuff. Could be intermittent. If at any point the ecu called for he pump to run and it didn't, it'll store the event in the ecu.

Does the scanner have to be BMW specific, or can it be a multi-vehicle scanner like this one?

https://www.ecstuning.com/b-schwaben...599sch01a~scf/

[hassmaschine]

99.9999% you need a new waterpump.

I wont even click on links to ECS these days.

[ctuna]

It would tell you if the oil was low or high.
There would also be a light for oil pressure.
As stated water pump most likely.

Hope the last guy didn't have the belt brake and get
sucked into the engine then not drop the pan
and clean out the debris.

[nsjames]

"We then replaced the expansion tank (sensor included), thermostat, coolant temperature sensor,"


So you spent several hundred dollars on parts before you bought a diagnostic tool?

this is why people think BMWs are expensive to own.

x eleventy billion on a scan tool.
bimmergeeks now has their own protool app and adapter.
carly works.
the best is INPA/ISTA, but you'll need a laptop and some time to set it up properly.

stop throwing parts at it though. Google the things I just mentioned.

[tlow98]

Buy BMW specific scan tool. There are lots - Carly, bimmergeeks, schwaban, etc.

Anything else is a waste of time with these cars. Listen to efthreeoh - it’s literally not even worth our time replying until you have codes.

[The0pportunist]

Did the dude you bought the car of tell you about this issue?

If not, i would be seeking legal advise and getting ready to reject the car.

[MysticRob]

Originally Posted by 06bmwe90

Heads up, this is kind of lengthy.

So I picked up a 2006 325i sedan a couple weeks ago. To my bad luck, I've driven it three times in that span, all three of those times the car overheated. After it overheating on my way home from buying the car, we tried bleeding the cooling system. It looked like the previous owners had it fixed/replaced because all the hoses looked new. Second time taking it out it overheated again. We then replaced the expansion tank (sensor included), thermostat, coolant temperature sensor, and we switched the plastic bleed screw for a brass one. Third time driving the car, it overheated again. Only this time, when we started the car, there was smoke coming from the back of the engine bay and it smelled like something was burning. We decided that since we're working on it, we should at least do an oil change and change out the filters (we do this anytime we buy a car). We drain the oil and there must have been 7 or 8 quarts of oil in it. Start the car for the fourth time and theres no smoke and no burning smell.

My question for you guys is: If the previous owner overfilled the engine with oil, could that cause the engine to overheat?

Thanks in advance!

As if my own opinion will finally sway you if all these other great posts didn't (I rec'd a couple), your post reads like someone new to the world of troubleshooting BMWs. Glad you joined the forum, now read up on all the glorious problems you'll likely encounter in the future!

I highlighted a particularly concerning portion of your post above. If you don't know the smell of burning oil, coolant, or wiring/electronics, you should not just simply start throwing parts at any vehicle. Proper diagnosis of issues will go a very long way in saving you money in the future.

Changing oil may be causation (doubt it) or correlation (more likely), but whatever you do, logically think through your symptoms and go from there. As others stated, an intermittent water pump on its way out sounds much more likely than anything else. And I would guess the burning smell was more than likely oil from a leak that got hot enough to cause the smell when the vehicle overheated, as these cars are known to bleed lubricant from multiple orifices. If the car didn't overheat the 4th time you started it, then the oil likely didn't get hot enough to cook off like the prior time.

[335dlci]

I agree with codes first as stated above but also a bad waterpump can cause oil level sensor issues also.