[E90convert]

Hello!

I recently purchased a 2012 F30 335i 8AT. Car has 94k miles on it. After purchasing, I noticed the passenger side heat does not blow hot. It will blow very cold and mild (~70-80F) when turned to the hottest setting. I do notice that when the car is static and the fan speed is very low that the air is warmer.

I did some searching on forums and found that vacuum bleeding has shown to be successful for some. So I bought a Schawben bleeder off ECS tuning, and performed the vacuum bleed, which I added maybe 1/2qt of coolant. I continued to do the 12 minute electronic bleed and drove the car. No dice. Still blows cold, no improvement.

So what shall I try next?

[BashShah]

I think your vent value is not working properly on the passenger side, I don't think it is a coolant issue at all.

[E90convert]

Originally Posted by BashShah

I think your vent value is not working properly on the passenger side, I don't think it is a coolant issue at all.

Thanks for the response. Have you experienced or heard of this problem before? Is there a way to check if the value displayed matches the value commended to the HVAC controller?

[BashShah]

I have heard of this on my e90.
ok if you have ISTA programming tool, I think.....and I am not 100% sure, ....
there is a way to test or move the valves through ISTA.

This link might be a good start:
https://f30.bimmerpost.com/forums/sh...d.php?t=696777

[E90convert]

Can anyone comment on the heater core design for these? And if you can flush them?

[E90convert]

Did some diagnostic work today playing around with the climate control to understand more how it works and what could be wrong.

1. Do the blend doors work? I went to manual climate mode, front vents only, minimum fan speed. Turned each knob max hot to max cold a few times and listened/timed the blend doors. All the blend doors seems to be working correctly. On the passenger side, cold air turns to warm air (not hot).

2. Is the cabin temp sensor working correctly? I turned both knobs to max cold, then turned knobs to 61F (one click up) and each blend door actuated the same. Thought there is that 60F is max cold (no heat), and 61F is now the target cabin temperature, so the blend doors go to heat (its like 15F outside). Verified that both sides went from ice cold to heat (hot on driver side, luke warm on passenger side).

So I have two thoughts on what is going on.

1. The passenger side blend door is working, but maybe not reaching full stroke. I am skeptical this is the case since both actuators are actuating for the same times and there is heat.

2. The heater core is clogged and is somehow bias to one side. Judging by F30 heater core pictures, it looks pretty simple. But I haven't seen a picture of how the air flows over it. Maybe the passenger side flows over the right side of the core which is clogged and limited/no flow. I think this is the most plausible and my next step will likely be to flush the core. Further, it seems at low fan speed the passenger side is gets warmer. I suspect the heater core is able to build more heat over the whole core, not just one side.

[E90convert]

http://www.agcoauto.com/content/news/p2_articleid/121

Some good diagrams here on why my passenger side may be blowing cold if the heater core is clogged on one side.

[BashShah]

Good Diagnostic,
read this thread if you have not read it already?

https://f30.bimmerpost.com/forums/sh....php?t=1460558

Possible heater core or air in the the coolant.

[AngelFarelli]

I have the same issue on my 2012 335i n55 f30! Have done little research and nothing to fix it but I've heard that flushing the heater core works for most people. Definitely subscribed to this thread

[E90convert]

Just an update. I ordered equipment from Amazon, just need the time to actually perform the work. If this works, I'll post a list of the equipment I purchased for future people with this problem. Maybe this weekend since the weather is above freezing.

[vanko25]

Hey did you manage to fix this.

I have the same issue with my 335i.

It just only started to get colder at night and felt that passenger side doesn't blow air at all in automatic.

When in fan in manual it blows cold air.

[E90convert]

Originally Posted by vanko25

Hey did you manage to fix this.

I have the same issue with my 335i.

It just only started to get colder at night and felt that passenger side doesn't blow air at all in automatic.

When in fan in manual it blows cold air.

Hey there - no I have not fixed this yet. It is getting colder and it is on my list of things to do here in the September/October timframe. SilkSmoooth another member messaged me his proceedure I am trying.

Drain coolant from the lower water pump hose. (ALL coolant will evacuate from the system.

Remove both heater core lines(they are on drivers side).

Get two long heater hoses to fit over the two heater core outlets or clear pvc (3/4 inch fits perfectly). Both hoses need to be long enough to get outside of the front bumper so you can flush in to a bucket with both hoses.

Flush water through both ends. I purchased a lisle heater core back flush tool to attach to my garden hose.

Spray the garden hose with tool through both ends, for long periods, switching back and forth after a minute or so and alternating pressure through the hose( this will help create turbulence inside the heater core to stir up the crap) I did this for at least 20 minutes, back and forth through each hose.

After this, I purchased some prestone heater core flush and poured it in the heater core through the hose and let it sit. Tie or tape each hose up to the hood latches to make sure the prestone doesnt come out and stays in the heater core. I left my car for about 24 hours like this.

Then proceed to rinse back and forth with the garden hose, again! Same way as above!

Then once done. I filled the radiator up with 50/50 Zerex coolant specfic for BMW ( got it autozone).

Then reattach the heater hoses.

Secure the lower hose on the water pump.

You then have to vacuum fill the system. THIS HAS TO BE DONE and Done PROPERLY!

You then have to bleed the cars system once vacuum filled.

Turn ignition on.
Connect a battery charger to 10AMPS(CRUCIAL)
Turn on low beam headlights (CRUCIAL)
Set heater to MAX Heat 84 degrees on both sides and the lowest fan speed.

Hold accelerator to floor for 12 seconds, then release.

Within a couple of seconds you should begin to hear the water pump cycle.

[SilkySmoooth]

Hello everyone! If you have any questions about my procedure above that E90 convert posted, please let me know.

A couple tips I can add:

Fill 3 gallons of Zerex 50/50 coolant for BMW in a clean 5 gallon bucket when refilling the system using the vacuum filler tool.(schwaben or OEM tools (OEM tools same, but cheaper)
you have to overfill the bucket when vacuum filling to assure you have plenty of coolant to pull from so you don't suck up air. ISTA says this. Use Newtis.info - If you don't have ISTA for reference on how to perform this filling procedure.

I would say the lisle heater core backflush tool is required because it seals perfectly at the end of the hoses you attached to the heater core. This perfect seal allows for optimal water pressure from your water hose to force crud from the system.

Also when topping off the coolant reservoir after vacuum filling, remove the bleed screw on top completely while you topoff the coolant reservoir, then replace the bleed screw AND cap before performing the auto bleed procedure.

[E90convert]

So I did as described above, with a few deviations. I was not able to get the lower hose off the the heater core, it was seized on and I did not think it would be good to get aggressive and break the fitting. So I disconnected the lower heater core hose at the upper radiator pipe and was able to flush that way. Unfortunately I could only apply pressure to the upper fitting of the heater core. Not sure which direction it flows in vehicle.

Vacuum filled and then did the bleed procedure. After a few days of driving, I can say it helped with heat overall and a LITTLE bit on the left and right side. It is still noticeable to me that the passenger side is weaker heat than the driver side. Tolerable yes, annoying yes. Maybe next year I'll get ambitious again attempt to fix it.

[335ioncrack]

Hey, I’m having the exact same issue. I have a 2015 335i. Please update if you’ve fixed it and how.
Thanks.

[Aaroona]

Was this issue ever resolved?

Theres about a 10-15c difference between my left and right vents, measured via ISTA, and certainly noticeable by the amount of head (or lack there of) being produced.

Ideally would like to find a way to resolve. Did a heater core flush at the workshop, but while that improved the situation, it didn't resolve it.

[oranga]

SilkySmoooth Thanks for your rundown of the heater flush procedure. You mentioned 3/4" tubing, is that the inner or outer diameter of the tubing?