2009 320i E90 overheating

[RayMan101]

Hi guys, so as subject says, my car is overheating, and I have no idea why.

Car just went in for a regular service, and mentioned a funny hissing sound, so with the service, my radiator needed replacing as the fins burst with water pouring out. Then on the way home after service it started overheating, took it back the next day and the mac thought it was the relay for the fan not kicking in, or its intermittent... So far the fan works fine. I pulled a code and got a P00b4 code and replaced the sensor in the radiator outlet pipe (as most forums suggested)
Well, car still overheats, the thermostat is new and works, the coolant has been bled, so no air pockets... Water pump still works (I think I have a mechanical one, cos I just can't get it kick in like all the guys say) 
The only option left that I can think of is to replace the water/oil sensor that sits on the engine itself.

If anyone has any advice, please let me know.
TIA.

 

[thefastandthecurious]

What is your coolant temperature when it overheats? How do you know that the thermostat works? I'm sitting with a similar problem :'(

 

[RayMan101]

Hey, so I have replaced the temperature switches, bought from stealers, replaced water pump (under warranty)
Replaced thermostat and housing as thermostat was not opening properly... Radiator replaced as it was pissing out coolant (after pressure test because it was leaking just a little)

So its still at the mechanic, he says that everything is working, temp is correct between 79 and 109 deg C range when running, but the engine still overheats after a short drive....

The FB BMW group suggest that o replace the fan relay as that can cause kak and have engine overheat..

Of it's not that, then it can only be a clogged CAT, clogged Heater core, temp sensor that's faulty on the engine.... Or I'll have the car stolen if it's the head gasket again....

I'll be buying a relay tomorrow morning and dropping it off, and they doing pressure test and all the other testing tomorrow again...

 

[Sheldon13]

I think 109 is high.
I have the same car and mine goes to 106 and immediately drops to 105 in traffic

 

[NtandoN]

What temp is it reading when it overheats? When the temp gets to 109 do you hear the fan running and does temp decrease?

 

[RayMan101]

Hi, yes. The fan does run.
It runs from when I start the engine. Tried replacing the fan relay and that didn't work, so I'm going to try replacing the engine oil/water temp sensor as that's literally the only thing left in the whole cooling system to replace.

They did a pressure test and it was all good. No leaks...
The CAT was ok, not clogged.
So the workshop manager his team and I are baffled... No idea why every part of cooling system works, the coolant temp is now correct, but the iDrive screen pops up with the amber or red warning saying engine has over heated...

 

[thefastandthecurious]

Have you tried running without a thermostat/drilling a hole in your old one to see if it helps? Mine reaches 108C until the fan kicks in from just idling for 45 mins. I read that the thermostat on the N46 only opens at 105C, which seems to be insanely high compared to my previous cars (non-BMW). I wonder if there's perhaps a lower temperature thermostat available lol to just preserve the engine. No wonder the rubber gaskets and seals just don't seem to last on this car. Just fixed all the usual external oil leaks now just found out when I rev the car after it has been sitting idling for 20+ min there's a light puff of smoke so I guess my valve stem seals are slowly starting to leak as well, which is going to be an expensive job... :'(

 

[RayMan101]

Lol, drilling a hole in it? No... Haven't done that... No idea how that may help...

But to date, every thing in the coolant system has been replaced and still nothing...still overheats.
Gonna try get a auto electrician in on Wednesday/Thursday to have a look and see if the wiring is somehow faulty all of a sudden..

🤦🏼‍♂️More money I don't have that needs to be spent....

 

[NtandoN]

Sounds like a water pump issue to me. On the first post you refer to it being mechanical, all e90s have electric water pumps. Check out the video below on procedure to test water pump. These pumps are known failure points on the e90.

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[thefastandthecurious]

Sounds like a water pump issue to me. On the first post you refer to it being mechanical, all e90s have electric water pumps. Check out the video below on procedure to test water pump. These pumps are known failure points on the e90.

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" frameborder="0" allow="accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture" allowfullscreen></iframe>

The water pump for the 4cyl 2.0 N46 in the 320i is mechanical as far as I know. The engine was carried over from the E46 generation. Only the petrol 6cyl e90s had electric water pumps I think.

 

[thefastandthecurious]

Lol, drilling a hole in it? No... Haven't done that... No idea how that may help...

But to date, every thing in the coolant system has been replaced and still nothing...still overheats.
Gonna try get a auto electrician in on Wednesday/Thursday to have a look and see if the wiring is somehow faulty all of a sudden..

🤦🏼‍♂️More money I don't have that needs to be spent....

It will allow the coolant to circulate through the entire cooling system and radiator the moment the car is switched on with the mechanical water pump running, rather than at a specific temperature when the thermostat opens. Basically manually making the cooling system run at full capacity. Usually doing this will make the car underheat so a good way to check if your issue is electrical or not I suppose. Was it still doing the same thing even with a new temperature sensor?

 

[NtandoN]

The water pump for the 4cyl 2.0 N46 in the 320i is mechanical as far as I know. The engine was carried over from the E46 generation. Only the petrol 6cyl e90s had electric water pumps I think.

My bad, you're right.

 

[RayMan101]

Sounds like a water pump issue to me. On the first post you refer to it being mechanical, all e90s have electric water pumps. Check out the video below on procedure to test water pump. These pumps are known failure points on the e90.

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" frameborder="0" allow="accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture" allowfullscreen></iframe>

Hey bud, thanks for you post. But my water pump is brand new, and mechanical, the "old" unit is in my boot and definitely mechanical, the newer models after mine are electric as you say..

 

[RayMan101]

Anyway.... After some more money spent, the issue lies with my ecu/computer (whatever you want to call it)

The auto electrician confirms that all the items are new and working, but the ecu doesn't send the signals to the thermostat to open, and (if I understood correctly) doesn't get the temp readings from the radiator temp sensor...

So, now I have to go sell my body in CT somewhere so I can have my ecu tested and repaired/reprogrammed/whatever....
Definitely don't have the cash for a full swop of the keys, ecu, EBM and all that....

FML.... Hahaha!

 

[RedlineRacer]

Not sure if the 320i's thermostat works the same as the other e90s, but if it does then the thermostat should open regardless of the ECU signal once the coolant reaches the temperature at which the mechanical part of the thermostat is rated to open at (105C), according to someone who did a teardown of his thermostat in this thread:

Possible thermostat failure

Possible thermostat failure

www.e90post.com

 

[RayMan101]

That's quite interesting.. thanks.

 

[RayMan101]

Hi guys....
So a update:
No more overheating (so far and fingers crossed)

The ecu had water damage and the part that controlled the thermostat to open and close wasn't getting enough constant voltage... Had a guy here in Brackenfell repair and so far all good. (With all the replacement parts.
Currently were still checking and have a test oil level/temp sensor thing on loan and all's good.
So it was definitely ecu damage and repair was cheaper than replacing with a 2md hand reprogrammed unit, and also Mayne a intermittently faulty sensor that was in the sump?
Who knows.... But it works....
So far.

 

[Loy187]

Hi guys, so as subject says, my car is overheating, and I have no idea why.

Car just went in for a regular service, and mentioned a funny hissing sound, so with the service, my radiator needed replacing as the fins burst with water pouring out. Then on the way home after service it started overheating, took it back the next day and the mac thought it was the relay for the fan not kicking in, or its intermittent... So far the fan works fine. I pulled a code and got a P00b4 code and replaced the sensor in the radiator outlet pipe (as most forums suggested)
Well, car still overheats, the thermostat is new and works, the coolant has been bled, so no air pockets... Water pump still works (I think I have a mechanical one, cos I just can't get it kick in like all the guys say)
The only option left that I can think of is to replace the water/oil sensor that sits on the engine itself.

If anyone has any advice, please let me know.
TIA.

Hey bud, thanks for you post. But my water pump is brand new, and mechanical, the "old" unit is in my boot and definitely mechanical, the newer models after mine are electric as you say..

Raymann101 how do you bleed mechanical water pump