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      01-17-2019, 03:36 PM   #23
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Originally Posted by zigsman View Post
Okay, here is a comprehensive DIY for replacing the heater core on an E90. Mine does not have the iDrive, so, if you do, there will be a few additional and different steps. Hopefully you can work around it. If you need a larger photo (better quality), PM or email me with the task number and photo description, I'll get it sent over as soon as I can. If you get stuck somewhere along the way or have a question, feel free to PM or email me. Good luck!!

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Hi Zigsman, thanks for the DIY.

My systemis blowing white dust out, which requires an evap change. Am I correct in thinking there is an Evaporator and a Heater core pretty much next to each other? Im thinking for the cost of a new one I may as well swap both out while Im there...
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      03-08-2019, 03:06 AM   #24
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Hello guys ! Is this possible without removing the R134a A/C freon ? What does change if I don't remove it ?
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      03-10-2019, 04:57 PM   #25
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Quote:
Originally Posted by fozzydj View Post
Hi Zigsman, thanks for the DIY.

My systemis blowing white dust out, which requires an evap change. Am I correct in thinking there is an Evaporator and a Heater core pretty much next to each other? Im thinking for the cost of a new one I may as well swap both out while Im there...
I did not change the evap out when I did the heater core, but normally both are located inside the A/C plenum. So, if you are going to be removing the plenum, it would not be a bad idea to change both...it'll save you from having to remove the dash again in the future to replace the other if you only replace one now.
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      03-10-2019, 04:58 PM   #26
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Originally Posted by niksss View Post
Hello guys ! Is this possible without removing the R134a A/C freon ? What does change if I don't remove it ?
No, you cannot do the job without recovering the A/C system and disconnecting the lines. The A/C lines connect directly into the A/C plenum, which has to be removed from the vehicle.
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      03-10-2019, 04:58 PM   #27
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Thanks Zig

The issue only occurs for me when the A/C is on. The heating works fine and doesn't blow any dust
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      08-14-2019, 08:33 AM   #28
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Big thanks zigsman for this extremely detailed DIY
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      08-16-2019, 11:00 AM   #29
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Wow, pretty involved DIY. Hope I never have to do this!!
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      10-31-2021, 10:46 PM   #30
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Thank you immensely Zigsman.

Could a blocked heater core be the reason for no heat coming from the driver side (UK model E92 325i)? The heat is perfect from the passenger side. Also the intensity of air blowing is less in the drivers side. I have seen something on the lines of 'blend door actuators'...I called BMW parts and mentioned this and he had no clue what it was. Is there a part number or a diagram to identify this part, if this is the reason for the problem?
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      11-01-2021, 07:02 PM   #31
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Thank you immensely Zigsman.

Could a blocked heater core be the reason for no heat coming from the driver side (UK model E92 325i)? The heat is perfect from the passenger side. Also the intensity of air blowing is less in the drivers side. I have seen something on the lines of 'blend door actuators'...I called BMW parts and mentioned this and he had no clue what it was. Is there a part number or a diagram to identify this part, if this is the reason for the problem?
Here is a link to the heater box (parts) for the E90:

https://www.realoem.com/bmw/enUS/sho...diagId=64_1454

In the diagram, you'll see the breakdown of the actuators (#4 & #5) that control the doors in the box. I believe there is only one blend door for the temperature, not two. That being the case, if the door were broken or the actuator were broken, the temperature would still be the same on both sides of the car, it would not be different. However, I could be wrong! Beings the AC unit is dual climate, meaning you can independently adjust the temperature on each side of the car, clearly there is a mechanism that allows for different temperatures on both sides at the same time. Without doing additional research on how the AC unit functions, I don't know exactly how the unit manages temperatures. Essentially, what I'm get at is this... It might be a blend door OR it might be a clogged heater core. It's important to test the blend doors BEFORE replacing the heater core. If you don't have the diagnostic software (ISTA, DIS, etc.) to independently test the blend doors, find someone that does. With ISTA, and several other software suites, you can independently activate blend doors to ensure they ware working properly. If you find that you have a bad blend door actuator, great! If, however, you find that all the actuators are functioning properly, then it is most likely a clogged heater core.

I had the same issue with my car that you are having with yours; it was warm on one side but cool on the other. My problem was a clogged heater core.

I hope this helps!
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      01-16-2024, 05:44 AM   #32
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Is it easier to change the heater core on a right-hand-drive? Just remove lower dash and get the core out?
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      03-31-2024, 04:35 AM   #33
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Just WOW. What an amazing DIY, but what an awful job. I hope I never have to do this!
If anyone has a heater core that has blocked and gone cold, but is NOT leaking, try a heater core flush before attempting this job...
DIY: Flushing the E9x Heater Core (Caution Required!)
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      03-31-2024, 09:36 AM   #34
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Originally Posted by tino_tino View Post
Is it easier to change the heater core on a right-hand-drive? Just remove lower dash and get the core out?
That's a question I cannot answer. I have never worked on a right-hand drive.
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      03-31-2024, 09:37 AM   #35
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Originally Posted by GSB View Post
Just WOW. What an amazing DIY, but what an awful job. I hope I never have to do this!
If anyone has a heater core that has blocked and gone cold, but is NOT leaking, try a heater core flush before attempting this job...
DIY: Flushing the E9x Heater Core (Caution Required!)
Thanks! It was not a fun job and I knew it was a semi-common problem and figured a DIY could be helpful for many others.
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      03-31-2024, 09:14 PM   #36
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Absolutely. Doing a DIY with your level of detail is extremely hard work, time consuming, and often goes unappreciated. So, thank you!
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      01-05-2025, 04:07 PM   #37
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Thanks for posting this. I’m regrettably at the point where I think I might be doing this job…

Any idea if it might be possible to snake a borescope into one of the vents to get a look at the core?

I’m losing a small amount of coolant and I cannot pinpoint the leak. Not only that, but some passenger vents (but not all… ????) are cooler than driver side.

I confirmed in INPA and by listening that all flaps are operating, but I will visually inspect right blend flap before going with the nuclear option. I also replaced inlet/return hoses to core (18 years old and quite swollen) and flushed the core. This seemed to improve but not solve the issue. Maybe I didn’t run enough water through; maybe it’s beyond just flushing to unclog; maybe it’s not even clogged; I dunno.

Anyway,, I’d feel a lot better about going this road if I can first confirm w/ borescope that my core is leaking. Any tips on getting a look at it would be appreciated!
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      01-06-2025, 02:08 AM   #38
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Originally Posted by e90yyc View Post
Thanks for posting this. I’m regrettably at the point where I think I might be doing this job…

Any idea if it might be possible to snake a borescope into one of the vents to get a look at the core?
MAYBE you'd be able to get a borescope down to the fine tubes in the core, but certainly not through them. And I don't know that you'd be able to see far enough into the tubes either. I'd say it's a waste of time. You'd have to remove those hoses anyway, so just do the core flush properly. It's not difficult once you've removed those hoses.

Quote:
Originally Posted by e90yyc View Post
I’m losing a small amount of coolant and I cannot pinpoint the leak. Not only that, but some passenger vents (but not all… ????) are cooler than driver side.

I confirmed in INPA and by listening that all flaps are operating, but I will visually inspect right blend flap before going with the nuclear option. I also replaced inlet/return hoses to core (18 years old and quite swollen) and flushed the core. This seemed to improve but not solve the issue. Maybe I didn’t run enough water through; maybe it’s beyond just flushing to unclog; maybe it’s not even clogged; I dunno.
Loss of coolant obviously means you have a leak somewhere, but if the core was leaking, you'd find your carpets wet and you'd smell coolant in the cabin. I doubt the core is the cause of the leak. Once the car has fully heated up and has been idling for a while, you may notice a whisp of steam coming from the location of the leak.

Swollen hoses mean one thing... at some point, oil got onto the hoses from outside, or more likely, oil got into the coolant, probably through the oil filter housing gasket. Make sure you have replaced that gasket before spending any more money on rubber or plastic parts in the cooling system! Oil destroys them.

If oil has made its way into your coolant, at ANY time, you can bet your bottom dollar that it has reacted with the coolant, forming gelatinous muck that coagulates in the heater core and everywhere else. A classic radiator flush product is USELESS at dissolving that muck. You'll need to use dishwasher detergent pods or SuperClean degreaser in your cooling system over and over to get rid of every trace before starting your core flush.

My core flush procedure is specific to dissolving any kind of muck that binds your sediment BEFORE proceeding any further. Once the alkali and acid flush has completed, you will still find loose, heavy, sand-like scale in the bottom half of the core, and that needs to be blasted out with higher pressure and flow from a garden hose, applied in a controlled fashion, as described in the instructions.

Cold air on one side of the car (passenger side in the US) is a CLASSIC sign that the lower half of the heater core is clogging up. Before long, the driver's side will also grow cold as the clogging worsens to restrict the top half of the core as well. Oil leaks into coolant MUST be fixed before you start, and all traces of that muck must be thoroughly flushed out, otherwise your core will start clogging up all over again.

Last edited by GSB; 01-06-2025 at 02:14 AM..
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      01-06-2025, 03:30 AM   #39
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Snaking a scope down a vent will not give you an inside look of the core to see if it's clogged, if that is your concern. Based on what you've described, it sounds likely that the core is getting clogged. If flushing does not help, then you might just need to bite the bullet and swap it out. If you are concerned that it is leaking, it would most likely be leaking at the connection point, which is on the driver side. The core sits under your stereo and the coolant lines feed in from the left side of the center hump. You can pull the carpet back a bit and check for water marks, dampness, and molding. Those would be the tell tale signs of a leaking core. Whether it's leaking or clogged, it would probably need to be replaced. There's no sure test that I'm aware of to prove it's clogged...so you just gotta go by symptoms.

Mike

Quote:
Originally Posted by e90yyc View Post
Thanks for posting this. I’m regrettably at the point where I think I might be doing this job…

Any idea if it might be possible to snake a borescope into one of the vents to get a look at the core?

I’m losing a small amount of coolant and I cannot pinpoint the leak. Not only that, but some passenger vents (but not all… ????) are cooler than driver side.

I confirmed in INPA and by listening that all flaps are operating, but I will visually inspect right blend flap before going with the nuclear option. I also replaced inlet/return hoses to core (18 years old and quite swollen) and flushed the core. This seemed to improve but not solve the issue. Maybe I didn’t run enough water through; maybe it’s beyond just flushing to unclog; maybe it’s not even clogged; I dunno.

Anyway,, I’d feel a lot better about going this road if I can first confirm w/ borescope that my core is leaking. Any tips on getting a look at it would be appreciated!
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      01-06-2025, 11:58 AM   #40
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GSB and zigsman: Thank you both so much for the detailed responses!

GSB: I should have chosen my words more carefully, haha, my apologies! I was referring to getting to the point where I will likely be replacing the core. I’ve already done the flush and have run the gamut of tests. Looking like a clogged and leaking core at this point, sadly.

There’s a thread in the General forum on my adventures, but for ease I’ll re-post a couple pics here. By removing the blower, I was able to view the front side of the core. It definitely appears to be leaking, but I’m not 100% certain.

I’ve owned the car for about eight years and practically every wearable part on it has been replaced under my ownership (OFHG included). Was well cared for by its one PO, which was nice. Possible there’s some sludge in the coolant system but it’s been changed multiple times and I’ve never noticed any indication of oil, but the suggestion to do a full flush using a detergent of some kind is a good one.

I do regret not using a fluid transfer pump to flush the core thoroughly—I used a garden hose (I know…) and only flushed for maybe a min and a half total. In any case, it was more to see if it helped (it did, but didn’t completely solve the heat problem).

I’m going to add UV dye tonight, give it a few days, and then check to see if she glows. Pics included show core (as viewed through duct immediately downstream of blower), both in natural light and under UV light (no dye in system at time of photo, but there does appear to be dried coolant on the core; it glows greenish).

Think I mentioned this but I am losing a very small amount of coolant—very small—and cannot locate a leak in the engine bay. Many new components in cooling system including radiator (genuine… went through three of the Mahle Behr ones and every single one leaked!) and other hoses, as I manual-swapped my car and ended up converting cooling system over to MT spec by removing AT cooler and replacing a few other bits.

I have noticed a light film on my windshield, too. Nothing crazy but to a degree that I’d think might be consistent with the coolant loss I’m experiencing.

Hoping the UV dye gives me the certainty I’d like.

I’ve also read conflicting reports on whether it’s strictly necessary to pull the dash to do just the core.

Anyway, sorry for derailing your excellent DIY thread!!!
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      01-06-2025, 01:49 PM   #41
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Quote:
Originally Posted by e90yyc View Post
GSB and zigsman: Thank you both so much for the detailed responses!

GSB: I should have chosen my words more carefully, haha, my apologies! I was referring to getting to the point where I will likely be replacing the core. I’ve already done the flush and have run the gamut of tests. Looking like a clogged and leaking core at this point, sadly.

There’s a thread in the General forum on my adventures, but for ease I’ll re-post a couple pics here. By removing the blower, I was able to view the front side of the core. It definitely appears to be leaking, but I’m not 100% certain.

I’ve owned the car for about eight years and practically every wearable part on it has been replaced under my ownership (OFHG included). Was well cared for by its one PO, which was nice. Possible there’s some sludge in the coolant system but it’s been changed multiple times and I’ve never noticed any indication of oil, but the suggestion to do a full flush using a detergent of some kind is a good one.

I do regret not using a fluid transfer pump to flush the core thoroughly—I used a garden hose (I know…) and only flushed for maybe a min and a half total. In any case, it was more to see if it helped (it did, but didn’t completely solve the heat problem).

I’m going to add UV dye tonight, give it a few days, and then check to see if she glows. Pics included show core (as viewed through duct immediately downstream of blower), both in natural light and under UV light (no dye in system at time of photo, but there does appear to be dried coolant on the core; it glows greenish).

Think I mentioned this but I am losing a very small amount of coolant—very small—and cannot locate a leak in the engine bay. Many new components in cooling system including radiator (genuine… went through three of the Mahle Behr ones and every single one leaked!) and other hoses, as I manual-swapped my car and ended up converting cooling system over to MT spec by removing AT cooler and replacing a few other bits.

I have noticed a light film on my windshield, too. Nothing crazy but to a degree that I’d think might be consistent with the coolant loss I’m experiencing.

Hoping the UV dye gives me the certainty I’d like.

I’ve also read conflicting reports on whether it’s strictly necessary to pull the dash to do just the core.

Anyway, sorry for derailing your excellent DIY thread!!!
Wow, that does seem suspicious. I fear the day that my heater core starts leaking!! If I recall correctly, there are O-rings where the aluminum coolant pipes meet the core. I have no idea whether it would be possible to separate the core and replace those O-rings without removing the dash.

I've also had to replace my original radiator, and 3 years later, the new one is leaking too. I can't believe the plastic trash that they build into this car! My Hondas have never had issues like this, and they're much older!

Last edited by GSB; 01-06-2025 at 01:55 PM..
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      01-11-2025, 12:10 AM   #42
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Quote:
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Wow, that does seem suspicious. I fear the day that my heater core starts leaking!! If I recall correctly, there are O-rings where the aluminum coolant pipes meet the core. I have no idea whether it would be possible to separate the core and replace those O-rings without removing the dash.

I've also had to replace my original radiator, and 3 years later, the new one is leaking too. I can't believe the plastic trash that they build into this car! My Hondas have never had issues like this, and they're much older!
Going to check tomorrow to see if the UV dye I added to the cooling system is visible on the core. Almost hoping it is, because that’ll settle things, ha…

What radiator did you go with? If Mahle Behr, not surprised… I had three leak on me when new. FCP sells as OE but they are not. (I’ve brought this to their attention as have others, but I think the part still shows as OE…) Ended up getting the genuine part in the end.

Actual OE is Modine (Germany), but AFAIK it is available only as a genuine BMW part. Pricey, yes, but the quality difference is beyond comparison. If I knew what I know now, I’d have just bought genuine from the get go.

Pic of coolant reservoir with dye under UV light. Thinking the leak will be easy to spot if it’s there .
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      01-11-2025, 11:37 PM   #43
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Originally Posted by e90yyc View Post
Going to check tomorrow to see if the UV dye I added to the cooling system is visible on the core. Almost hoping it is, because that’ll settle things, ha…

What radiator did you go with? If Mahle Behr, not surprised… I had three leak on me when new. FCP sells as OE but they are not. (I’ve brought this to their attention as have others, but I think the part still shows as OE…) Ended up getting the genuine part in the end.

Actual OE is Modine (Germany), but AFAIK it is available only as a genuine BMW part. Pricey, yes, but the quality difference is beyond comparison. If I knew what I know now, I’d have just bought genuine from the get go.

Pic of coolant reservoir with dye under UV light. Thinking the leak will be easy to spot if it’s there .
I went with Pacific Best, non-OEM, because they had a very pro-looking website bragging about their incredible manufacturing processes and certifications. It fit perfectly, looks like OE, but isn't. Obviously the same cheap crap as all the others with no identifying marks. I don't like OE either. You spend a fortune, only to find that it's made of the same cheap and nasty materials as the others with a BMW logo on it. And then it leaks, just like all the others.

That dye looks SERIOUSLY, ominously, green!!
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