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BMW 3-Series (E90 E92) Forum
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E90 Heater Core DIY
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01-17-2019, 03:36 PM | #23 | |
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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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03-10-2019, 04:57 PM | #25 | |
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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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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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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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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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03-31-2024, 09:37 AM | #35 | |
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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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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.
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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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Last edited by e90yyc; 01-06-2025 at 12:07 PM.. |
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01-06-2025, 01:49 PM | #41 | |
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![]() 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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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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![]() That dye looks SERIOUSLY, ominously, green!! ![]() |
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