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BMW 3-Series (E90 E92) Forum
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DIY: Flushing the E9x Heater Core (Caution Required!)
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03-31-2024, 02:31 AM | #1 |
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DIY: Flushing the E9x Heater Core (Caution Required!)
Have you found your heater growing cold, first on one side of the car and then on the other? As long as the heater core isn’t damaged or leaking, it can be flushed. BUT… BE CAREFUL! Many YouTubers recommend pressurizing the core with a garden hose or compressed-air as the first step. That could easily burst the fragile aluminum core (especially if weakened by corrosion) or blow one of the rubber o-ring seals inside the dash.
If that happens, allow me to refer you to the DIY from hell… E90 Heater Core DIY This DIY heater core replacement is incredibly well documented, but the work is difficult and takes days - or thousands of dollars to have this done by a dealer or mechanic. Last edited by GSB; 04-01-2024 at 03:49 AM.. |
03-31-2024, 02:32 AM | #2 |
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Important to Know:
For most BMW E9x models/options, the heater core circulates coolant full-time, while the blend doors/flaps inside the car direct hot or cold air into the cabin.
A gentler and more calculated approach to flushing sediment is especially important in this engine, because of the possibility of oil contamination in the coolant. The notoriously flimsy Oil Fiter Housing Gasket separates engine oil from coolant, both of which are pressurized in the engine. When that gasket fails (and it will), oil often leaks into the cooling system, perhaps very slowly at first. When oil reacts with coolant, it forms gelatinous blobs of sludge that collect everywhere in the system. That sludge may be relatively colorless at first, but it is highly corrosive to ALL of the plastic and rubber parts in the cooling system. It also blocks passages and is exceedingly difficult to remove. I discovered that radiator flush products do not budge it. The only thing that worked successfully, was filling the cooling system with a 50/50 mix of SuperClean degreaser and distilled water, then running the car up to operating temp before draining and repeating the process several times. Gobs of sludge came out each time, but the heater core did not clear, and within a year, it was totally blocked and freezing cold. The potential for oil in the coolant is highly relevant to the heater core flush procedure below. Several reputable mechanics recommend this method as the best procedure to treat any blocked heater core because it works first on oil/grease deposits (which bind the sediments in the core), then on corrosion/scale deposits. Only then, should the loose material be gently blasted out. It worked wonders for my car and saved me a fortune. Note that it is wise to replace the coolant after flushing a blocked core because the old coolant may be contaminated and circulating muck throughout the system. If sludge is found in the cooling system, it would also be wise to do a flush of the entire cooling system and replace any plastic parts, rubber seals or hoses affected by oil contamination while you're working in that area. Always monitor the health of your oil filter housing gaskets and replace them preemptively to avoid expensive repairs! Last edited by GSB; 04-01-2024 at 03:35 AM.. |
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03-31-2024, 02:33 AM | #3 |
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Accessing the Heater Core:
Last edited by GSB; 03-31-2024 at 03:55 AM.. |
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johnnyorange64.50 |
03-31-2024, 02:36 AM | #4 |
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Preparing the Flush Procedure:
Last edited by GSB; 04-16-2024 at 05:51 PM.. |
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johnnyorange64.50 |
03-31-2024, 02:38 AM | #5 |
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Flushing Steps:
Last edited by GSB; 04-16-2024 at 05:52 PM.. |
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johnnyorange64.50 |
03-31-2024, 02:41 AM | #6 |
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Replacing the Coolant and Bleeding the System:
Last edited by GSB; 04-01-2024 at 03:47 AM.. |
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johnnyorange64.50 |
04-16-2024, 05:43 PM | #8 | |
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You're welcome. I hope the flush goes well for you! |
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06-20-2024, 01:42 PM | #9 |
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This is great. I am finding a little challenge while attempting this DIY. On my 2010 320i LCI, there’s a plastic ring under the metal clamp on the upper hose on the firewall of which I am not sure on how to remove.
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06-25-2024, 01:38 AM | #10 | |
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Mr Mohlake0.00 |
08-01-2024, 04:15 AM | #11 |
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Thank you for the response. I’m not referring to this one you just shared. I’ll try get a picture of the one that I am referring to. It’s basically on the top hose which has the metal fastener. So it sits under the metal fastener and it doesn’t have any kind of screw on it or a place to loosen it.
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08-05-2024, 11:45 PM | #12 | |
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