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Thread: Throttle body heater

  1. #1
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    Question Throttle body heater

    My 87 325i convertible came with the Throttle body heater bypassed. Since i had the intake and tb off the car i thought i would look at it closer. Some id10T buggered up one of the screw holes with what looks like a sheet metal screw. Needless to say, I cannot reconnect the TB heater. I have read a ton the last few days trying to decide if I am fine keeping it bypassed. I am putting all new hoses in as you may have guess with my other post. Just for giggles i priced a new tb... yikes. The TB works great otherwise. (at least it did when i took it off ). I ordered new tbh and gasket before i noticed the issue. I have new tbh hoses coming, but now seems to be a waste. Is either hose long enough to go to the port and thermostat housing? Also, what is the current opinion on the bypass? Most threads i read were 2015 and earlier (2004ish i think).

    I think i am ok, just would like the warm and fuzzy from the group.
    1987 BMW 325i Convertible


    “Speed has never killed anyone, suddenly becoming stationary… that’s what gets you.”
    Jeremy Clarkson


  2. #2
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    No e30s, again :(
    it gets cold where you live so I would hook those up. not that carb'd cars had them a lot back in the day but might as well be as efficient as possible. if you lived where I lived, I would say you can leave them off but carb icing happens so I imagine tb icing happens, too.
    No e30s again.

  3. #3
    richardodn's Avatar
    richardodn is offline Old Guy BMW CCA Member
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    Everyone should have them hooked up. As you are in Indiana, I'd get it done before next winter. Don't worry about getting a new one. Just get a good used one. In the short term, just get a fitting that will connect the two TB hoses together. While you have it off, make sure all the hose nipples on the TB are still tight. They have been known to come loose. If any are, epoxy them back in.
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  4. #4
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    No e30s, again :(
    I don't know if you have ever had a carb ice up while driving but its surprising sometimes. it happened to me during the summer months in Georgia. my little karman ghia would do it regularly because of the humidity. you let off the gas and rpms jump up into redline so you have to flip the ignition off quick
    No e30s again.

  5. #5
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    That little heater cap is a big pain. I don't think it is unusual to have one bolt hole messed up. I just retapped mine to a slightly larger size for different size bolt. Worked ok and nobody knows.

  6. #6
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    ok... the existing one is held in with screw and 2 bolts. I guess i will have to wait until the gasket comes in to see how thick it is. Looks like it was leaking badly from the attempted repair and it was bypassed.
    1987 BMW 325i Convertible


    “Speed has never killed anyone, suddenly becoming stationary… that’s what gets you.”
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  7. #7
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    No e30s, again :(
    well, that's a bummer but if it doesn't hold you can always get one off ebay or the junkyard
    No e30s again.

  8. #8
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    i have one and gasket showing up today.
    1987 BMW 325i Convertible


    “Speed has never killed anyone, suddenly becoming stationary… that’s what gets you.”
    Jeremy Clarkson


  9. #9
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    I have installed it but cannot test because i am still waiting on lower rad hose. I think it is sealed. i think....
    1987 BMW 325i Convertible


    “Speed has never killed anyone, suddenly becoming stationary… that’s what gets you.”
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  10. #10
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    It’s wise to pressure test it with air anyways before you fill up the system,

  11. #11
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    what psi? I have a small "hotdog" compressor i can use. I can do that tonight.
    1987 BMW 325i Convertible


    “Speed has never killed anyone, suddenly becoming stationary… that’s what gets you.”
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  12. #12
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    Based on what I’m reading online radiator cap pressures are around 15 psi so I would charge the system to at least 20 psi just to be on the safe side. I believe that if all the parts are in good condition it would hold much more than that without an issue, but since we are talking about 30-year-old cars here, I would not encourage someone to test the limits of the cooling system too much unless they’ve all been replaced in their entirety. Filling the system with 20 pounds of air sounds good but understand that the coolant is under almost just as much pressure but it’s extremely hot, so depending on what you used to repair the parts that temperature could still be a factor still once you start driving it

  13. #13
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    all new hoses.. new thermostat, water pump, gaskets, heater core and heater valve, new throttle heater gasket now. 30 year old plastics make me nervous. Bought a Harbor Freight cooling system pressure test kit i was going to try tonight. It has decent reviews... and if it doesnt work, i can return it.
    1987 BMW 325i Convertible


    “Speed has never killed anyone, suddenly becoming stationary… that’s what gets you.”
    Jeremy Clarkson


  14. #14
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    Sounds like a good investment. Let us know how it works!

  15. #15
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    worked like a charm. found out everything held at 11 psi but could not get thermostat housing to seal no matter what i did. I had to resort to permatex thermostat housing/water pump sealant. I was already torquing the bolts way too much. But after letting it set up for 24 hours, it did the trick. I got the pressure up to 11 psi and no leaks. I got it mostly bled, but not much heat out of heater core. So still more work to do. But no leaking at the throttle body! yay!
    1987 BMW 325i Convertible


    “Speed has never killed anyone, suddenly becoming stationary… that’s what gets you.”
    Jeremy Clarkson


  16. #16
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    Good to hear! It’s so much I easier the fix a leak when there is no liquid in a plumbing system. Was the O ring on the thermostat?

  17. #17
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    yes it was... i tried a couple of different ones. I gently sanded and scraped the surfaces.. just could not get it to seal... but it is now. Temp stays at middle, but i guess i need to drive it to force the remainder of the air out. Tomorrow i will put the interior back together (apart for heater core replacement.)
    Last edited by doctorx69; 04-22-2019 at 12:04 AM.
    1987 BMW 325i Convertible


    “Speed has never killed anyone, suddenly becoming stationary… that’s what gets you.”
    Jeremy Clarkson


  18. #18
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    I usually leave mine on ramps or with the front elevated while filling it and running it, and don’t forget to open the bleeder screw on the t stat housing

  19. #19
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    i did that... Ran it for 30 mins revving the engine at times to 2000-2500. no more air is coming out but warmish heat coming out. No air bubbles coming out of bleeder screw anymore. Not overly worried since temps never got past middle. I think it is ready for test drive. I still need to bed in the new brakes and after that, it should be ok. At least the throttle body heater is working.
    1987 BMW 325i Convertible


    “Speed has never killed anyone, suddenly becoming stationary… that’s what gets you.”
    Jeremy Clarkson


  20. #20
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    after the test drive yesterday... now have hot air coming out. Patience... not a quality i have a lot of... lol.
    1987 BMW 325i Convertible


    “Speed has never killed anyone, suddenly becoming stationary… that’s what gets you.”
    Jeremy Clarkson


  21. #21
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    No e30s, again :(
    Good deal
    No e30s again.

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