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Thread: 01 330ci coolant circulation problem

  1. #1
    Join Date
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    01 330ci coolant circulation problem

    Hey all,

    New-to-me 01 330ci, M54B30 motor, manual trans (no mech fan). Previous owner bought the car and it randomly started overheating, so he parked it and eventually ended up selling it to me.

    Symptoms: motor starts and runs and idles like crap - has terrible low end power, plenty of power up top though
    Compression test yields 146-150 PSI on all 6 cylinders with no dropping in pressure after cranking is stopped. Values are with the engine hot, dry test - no oil
    Since the easiest way is just to pull those parts, I pulled the electric fan (which functions, turns on when needed), pulled the thermostat housing, and there was no thermostat...just the housing. Ok, so go get a new thermostat and housing. Installed, same symptoms.

    Next pulled the water pump, it looks new, no play in the bearings, metal impeller, no broken shafts.

    Heat in the cabin is occasionally hot, but sometimes it's cold, even when the engine is blazing hot (90-100 C)

    Entire radiator is occasionally blazing hot, but typically is only warm in the upper corner near the expansion tank and literally cold at the bottom. Pretty chilled near the left side. GT1 reports coolant outlet temps (aux fan activation sensor) as nearer 50-60 C, not the 90-100 C the engine temp sensor is reporting even when sitting at idle with no aux fan activation (obviously, coolant is not getting pushed through the radiator). Temps will climb as high as 105 and still rising when the motor gets shut off.

    Radiator hoses have no blockage.

    Multiple refills of the entire system have been performed following multiple different guides, making sure to bleed, on a slope, etc.

    Exhaust smells normal. No white smoke or residue. And as stated before, compression in all 6 cylinders is at spec.

    Sooo...I'm confused at this point. My gut instinct says coolant is sporadically getting circulated, but hot boiling coolant is making it all the way to expansion tank, occasionally to the heater core (but not always? it gets cold sometimes), occasionally through the radiator (but not normally).

    One last note: I replaced the original thermostat-less thermostat housing, bled the system, and it has all the same symptoms. Water starts boiling, no dice on getting the radiator hot or anything.

    Some pointers in the right direction would be most helpful or next steps would be most helpful.

    Right now the To-Do for tomorrow is to replace the water pump and rule that out.

    FYI: GT1 reports a couple other errors: Lambda sensor bank 1 heating before CAT and after CAT Lambda sensor bank 2 heating.
    Last edited by jinbtown; 05-30-2012 at 10:03 PM.

  2. #2
    hooRAH is offline Certified Ziptie Mechanic
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    I wouldn't bother replacing the water pump. The empty t-stat housing (how do you even do that? Isnt it all one part? Whatever.) tells me that someone has tinkered with this before and couldn't figure it out. If the water pump looks new, it probably is.

    The random heat and random temperature changes suggest that the coolant flow rate changes significantly for an unknown reason. I've never seen an impeller blow and suck a chunk of plastic into a cooling passage, but I wouldn't be surprised to find thats the case.

    You might want to consider pulling the Tstat (or water pump) and disconnecting the top radiator hose. Jam a garden hose in there and turn it on full blast. Does the water flow through easily, or does it back up quickly in the upper hose?
    01 330Ci 5spd / 07 Honda Pilot EX-L
    Will read/reset SRS codes in South Florida for beer money


  3. #3
    Join Date
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    Sounds like there's a blockage in the coolant passage system somewhere. Have you tried a coolant/radiator flush product? Have you tried pulling the block drain plug and different hoses that feed off from the head or block and running water through different holes to see if you can pinpoint a blockage?
    -Nick

  4. #4
    nathancarter is offline Stretch Haters Club #1 BMW CCA Member
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    Quote Originally Posted by hooRAH View Post
    You might want to consider pulling the Tstat (or water pump) and disconnecting the top radiator hose. Jam a garden hose in there and turn it on full blast. Does the water flow through easily, or does it back up quickly in the upper hose?
    This was going to be my suggestion. Test the radiator for adequate flow, or pull out the radiator and take it to a radiator shop for testing.

    Crumbling WP impellers were pretty common on earlier models, but the E46 isn't plagued with the self-destructing plastic impeller that was common on the E36. So while you can't rule out the possibility that a chunk of impeller is blocking a passage somewhere, I think that likelihood is slim.

  5. #5
    Join Date
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    Ok, here's the updates.

    Tested the thermostat in boiling pot water and it actuates correctly...the whole thing moves to block off engine flow (forcing it into the upper radiator hose) and allow lower radiator flow into the motor.

    I pulled the water pump out.
    I shoved a hose into the water pump output and turned it on. Scalding hot water came flowing freely out of the block from the thermostat output / water pump inlet and flowed for several minutes with no interruptions until the water gradually cooled the motor down and the water turned cooler.

    Replaced the water pump with a new unit, take it out for a drive. Engine temp readings gradually climb until they reach about 100 C and this time, hardly any cabin heat (lukewarm), radiator stays cool throughout, upper radiator hose is hot and expansion tank is filling with boiling water

    Just took a look at the RealOEM diagrams. The upper radiator hose feeds both the expansion tank and the radiator correct? There's no fluid connection between the expansion tank and the radiator other than the upper radiator hose?

    If that's the case, why would I be getting hot water traveling up the upper radiator hose, dumping into the expansion tank, but not heating the radiator unless the lower radiator hose was not able to displace fluid away. Which means the thermostat is not opening. Shouldn't the motor be failsafe-ing the thermostat into the open position via the heating tube?

    What about attempting to apply +12v directly to the thermostat heating probe and manually holding the thermostat open while idling the car? then checking the radiator - any thoughts?

    apologies in advance for the double post.

    would there be any possibility that air is getting introduced into the system via the combustion chambers if the compression readings are all 147-150 and they hold compression over a period of 10 seconds (within 1 psi)?

    Is there any possibility that air is getting introduced somewhere else without a coolant leak? We're not losing fluid at all here.

    It is just confusing me how a brand new verified working thermostat refuses to open occasionally and I'm not exactly BMW-illiterate. Just never ran across a problem that seemed to elude fixing so stubbornly.
    Last edited by jinbtown; 05-31-2012 at 11:27 PM. Reason: Automerged Doublepost

  6. #6
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    i dont think air can get trapped behind the thermostat

  7. #7
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    Well, as someone had a similar idea and took out the entire thermostat, I would look elsewhere, than the therm... but it sounds to me as you might have peices of broken termostat stuck in your radiator, and / or heater core or control valve..., not to say that's the source of the problem, just a compound to it by someone's failed attempts to remedy the original one, (perhaps by gouging out the thermostat mechanism with a screwdriver)
    the thermostat is open by default, the DME applies voltage to keep it closed.

    And... as there's already been some playing around... I would look at a complete diagram (realoem) of the coolant hoses, and see if some fool didn't try to bypass the heater core or other, and ended up doing more harm than good... remember there's 2 or maybe 3 hoses under the intake, that your not seeing (hard plastic tubes actually) and if one of those was leaking, some shade tree / old school mechanic, may have tried some bypass surgery there, which may be a problem now (those tubes are not fun to replace, unless you like taking off intakes.


    Interesting problem, keep us posted.
    93 e36 vert / 95 E36 M3 Alpine / 98 M3/4 Estoril / 00 '46 Frankenbimmer CI , 68s / shark tooth injected driver bolster with slimline low gloss duct tape / angled front pass kidney grill with custom eject hood release / EE LEDs moisture sealed/ Pep Boys silicone / Google sky point OEM HIDs with glovebox leveling arm after wishbone install / custom BMW round pin diagnostic to USB cabin routed laptop with INPA for constant CE light delete / sock modded / t-shirt mod / clicking sound.

  8. #8
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    Just fyi, solved the problem this weekend thanks to my ever-knowledgeable BMW-crazy brother.

    for those on this forum (I've read 30 threads and saw this at least once in every one) that say it is impossible to have an air lock behind the thermostat by design, that is absolutely and patently false. It is indeed possible, proven by experience, and in the event of someone opening the coolant system up and blowing compressed air through it (which is what appears to have happened here), it seems even likely.

    Solved via the following method:

    Pulled the car up on ramps, opened the radiator drain plug, expansion tank drain plug, and engine block drain plug. Let everything drain overnight to get it good and dry. Loosen the bleeder screw and the expansion tank cap while you're at it.

    Come back the next day, replace the plugs and begin filling it. This 330ci does NOT have an auxiliary water pump that pumps it through the heater core, and in the event of a heater core air lock, the car will NOT ever open the heater core water valve fully, never allowing it to bleed properly.

    I followed the procedure on bmw330ci.net to a T and filled the car, began driving. Seems to now be ok, temperature cycles up to about 100, thermostat opens and in comes cool coolant from the radiator. GT1 live on INPA shows the inverse relationship between coolant temps and coolant outlet temps (radiator outlet).

    Still no heat in the car, which is THE single most telling symptom during ALL of this, according to my brother.

    I open the IHKA INPA screen and go to F6 Activate and and F4 Water Valve, open 100%, car INSTANTLY starts overheating, 105C plus. Pull off to the side of the road, wait 15 minutes (luckily we brought a gallon jug of distilled), open the ET cap and the bleeder valve, refill and rebleed. It sucks down about half a gallon.

    Rinse and repeat about 3 or 4 more times before the heat in the car is hot, and the car no longer overheats when the water valve is manually activated.

    Just for future reference, for someone that may buy or come across a car that has overheating issues, where history is unknown. Thanks for the help!! To do: vanos rebuild via Beisan Systems, 1 pre cat and 1 post cat O2 sensors, air filter and she's ready to drive!

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