Lukewarm heat from vent?

Tiny
BHAMDOC1
  • MEMBER
  • 2013 BMW 335
  • 6 CYL
  • TURBO
  • 2WD
  • AUTOMATIC
  • 118,000 MILES
Takes forever to get some lukewarm to come out. Blower works fine; these are the codes I found. When I deleted them, I got one back which is in the picture that only shows one code (AUC). Can this affect heat? Coolant is full. I thought about the heater control valve, but I have not seen it on the driver side under the hood like most BMWs. Can you ee if there is one and where it is? Hoses to the firewall I would say are warm. I also suspect the thermostat but no codes or indications.
Tuesday, January 14th, 2025 AT 10:09 AM

17 Replies

Tiny
KEN L
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Does the engine get hot? If not, I would check the thermostat, but I can tell you the auxiliary water pump for the heater goes out all the time for these cars. You can remove it and put 12 volts to it and if it doesn't work, I would replace it, also check the fuse for it as well. Check out the images (below). Please let us know what happens.
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Wednesday, January 15th, 2025 AT 11:27 AM
Tiny
BHAMDOC1
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This says bye E92, his is the F30, the newer style. And the pictures talk about the fuel lines or filter. Where is the auxiliary pump located?
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Wednesday, January 15th, 2025 AT 11:30 AM
Tiny
KEN L
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Okay, my bad, here is the auxiliary water pump which can be either one, follow the heater hoses and you should be able to find it, they don't show the location. I updated the images above.
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Thursday, January 16th, 2025 AT 8:57 AM
Tiny
BHAMDOC1
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Can you let me know if the F30 335i has an auxiliary pump and where it is? The above is for the E92
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Thursday, January 16th, 2025 AT 8:57 AM
Tiny
KEN L
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I updated the images above. Did you see them?
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Friday, January 17th, 2025 AT 11:14 AM
Tiny
BHAMDOC1
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Yes, I am able to find new and used ones online but still don't know where it is. I'll check more.
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Friday, January 17th, 2025 AT 11:59 AM
Tiny
KEN L
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Yep, I rechecked and it doesn't say where is is but it should be in the engine compartment. I would follow the heater hoses, should be connected to one of them.
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Saturday, January 18th, 2025 AT 10:17 AM
Tiny
BHAMDOC1
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  • 93 POSTS
One of the images you updated above is for a 4-cylinder, this is a 6-cylinder turbo. Heater hoses, one goes to a thermostat the other to the radiator.
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Saturday, January 18th, 2025 AT 12:18 PM
Tiny
KEN L
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Maybe some one removed it? It says it is at the rear of the engine compartment. Check out the images (below). Please let us know what happens.
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Sunday, January 19th, 2025 AT 9:58 AM
Tiny
BHAMDOC1
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That's the coolant pump. I verified with someone that only the M package has the aux pump behind the headlight. So am now just looking for where this heater control valve is. Strange hoses to connect to upper radiator and one to thermostat.
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Sunday, January 19th, 2025 AT 10:09 AM
Tiny
KEN L
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My information says it does not have a heater control valve?
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Monday, January 20th, 2025 AT 9:52 AM
Tiny
BHAMDOC1
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Weird, so what controls it? I just did a pressure test, and a common art has busted leaking, it's the use from thermostat to cylinder head, always break, and I was smelling something before, so maybe it was not holding pressure, I will replace it and see.
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Monday, January 20th, 2025 AT 9:56 AM
Tiny
KEN L
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Yep, you could also have an air bubble inside the heater core. Please go over this video, it might help:

https://www.youtube.com/watch?v=SNRb6pSwYuU

Once you get it back together, start the engine and allow it to get warm, then feel both heater hoses. Let me know what happens.
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Tuesday, January 21st, 2025 AT 10:26 AM
Tiny
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Yes, I saw this video bee, and I let the system bleed itself electronically 3 times, but I think the small leak that I didn't see may have contributed so once I put it back I will re-bleed it first. As far as I can remember the hoses were warm but not hot.
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Tuesday, January 21st, 2025 AT 10:28 AM
Tiny
KEN L
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They should be hot. Maybe the core is clogged, you might want to try to flush the core using a garden hose.
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Wednesday, January 22nd, 2025 AT 8:37 AM
Tiny
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But if both are warm doesn't that mean the water is getting in and out of the core?
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Wednesday, January 22nd, 2025 AT 9:19 AM
Tiny
KEN L
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Yes but if it is so little, it is not allowing the flow at all. I would check it if there were no heater control valve or aux water pump.
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Thursday, January 23rd, 2025 AT 9:26 AM

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