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Thread: Phantom low coolant level message + other symptoms

  1. #1
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    Phantom low coolant level message + other symptoms

    Recently my cooling system started to indicate that my coolant was low yet every time I checked it was just fine.

    I just replaced the expansion tank and sensor and there was no problem while I was bleeding the system.

    Today however I went for a 40 minute round trip and when I got to my destination in about 20 mins. it was still fine. However, as soon as I started the car it's telling me again that the coolant is low. There are no leaks that I can see and I am sure that after it cools down I'll find as before the level is just fine.

    There are some other symptoms as well which are:
    • The heater would not come on when I was driving to my destination. However, when I started the car to come back, which is when the coolant level indicator went on, the heater started working as well.
    • When I am waiting at lights (not moving) the heater seems to not work well at all. Barely blowing or maybe it seems that way because it's barely warm.
    • Yesterday, for this first time in a long time, it started to overheat which fortunately I caught in time however just before I stopped the temperature started to go down again on it's own. I let it cool for a few hours anyway and the drove home (only 0.5 miles). When I checked the level the next day while the coolant was a little low it wasn't that far off the "fill to" mark.


    I've not dealt with these types of symptoms before and if it was just the coolant level indicator I would be inclined to focus on a possibly a bad connector to the sensor but with all of the above I suspect there is a lack of coolant flow so maybe a water pump issue.

    Does anyone know the likely culprit given the symptoms above and perhaps how to test for it?

    Thanks!
    Last edited by Nybbles2Bytes; 02-18-2019 at 02:17 PM.

  2. #2
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    You still have air in the system

  3. #3
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    Quote Originally Posted by Nanniepoo View Post
    You still have air in the system
    It ran for months without this problem, that would mean air magically appeared in the system or suddenly decided to be a problem one day after all those months.

    Air in the system doesn't seem to fit that particular piece of data unless air is being injected into the system which would make it a secondary symptom and I still have to find the root cause.

  4. #4
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    Sorry you said you just replaced the expansion tank and sensor which didn't communicate months of fine performance to me

  5. #5
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    I think I found it. There's been a few replacements in the cooling system lately, new hoses, expansion tank etc. so I started looking at parts closely that have been messed with and the vent screw is missing its o-ring so perhaps air is getting into the system through that when it cools down.

    Anyway, I'll fix that and report back.

  6. #6
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    Quote Originally Posted by Nybbles2Bytes View Post
    I think I found it. There's been a few replacements in the cooling system lately, new hoses, expansion tank etc. so I started looking at parts closely that have been messed with and the vent screw is missing its o-ring so perhaps air is getting into the system through that when it cools down.

    Anyway, I'll fix that and report back.
    Nannie's point was that if you've replaced several components recently, that's multiple times you've introduced air in the system.

    What you're describing is consistent with having air in the system.

    And the vent is where air gets OUT, not into the system.

  7. #7
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    Quote Originally Posted by blckstrm View Post
    Nannie's point was that if you've replaced several components recently, that's multiple times you've introduced air in the system.

    What you're describing is consistent with having air in the system.

    And the vent is where air gets OUT, not into the system.
    If I'm not mistaken, that vent screw CAN let air in when the engine is not hot or running. Otherwise, BMW would've used a check valve there.

  8. #8
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    I replaced the o-ring on the vent screw and and I replaced a bad o-ring on the expansion tank cap and I'm not having any leaks (that I can find) which is great. However, after 2-3 of weeks of driving I'm having a consistent problem of it saying my coolant is low after it cools down but only after enough driving, perhaps 3 or 4 hours worth which means every couple of days or so.

    What happens is I take the expansion tank cap off (after it's fully cooled down) and air escapes and the coolant level comes back up to its correct level. The only conclusion I can come to is that air is being forced into the system pushing the coolant down with a few hours of driving.

    The only thing I can think of that would do this is some sort of leak between the cylinders and the cooling system which is disturbing since at the very least that would mean a fix by removing the head and replacing the head gasket and possibly something more expensive.

    Does anyone know if this can happen consistently through some way other than something expensive like a head gasket with a hole in it?

  9. #9
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    I would use another radiator/expansion tank cap, maybe that is defective.
    As the engine’s coolant heats, it expands, increasing pressure inside the closed coolant system. The radiator cap controls this expansion and provides a constant pressure on the system. The caps pressure rating varies by engine application anywhere from 13 – 16 psi. High performance caps range from 19 – 32 psi. Water boils at 212° F, increasing the pressure in a closed system increases the boiling point. This allows manufacturers to manufacture engines with higher operating temperatures. The radiator cap also allows the engine’s coolant to expand and contract without all allowing air to enter the cooling system. The upper seal seals and protects the system at all times. After the engine warms and system pressure reaches the caps rated pressure, the pressure spring compresses and pressurized coolant flows into the reservoir or coolant overflow tank. This allows for expansion of the heated fluid. The cap also allows the coolant to flow back into the radiator as the engine cools. The radiator cap also contains a vacuum valve. As temperatures drop and the coolant contracts a vacuum is created in the engine’s cooling system. The vacuum valve opens and allows coolant to flow from the overflow tank back into the radiator. This allows for contraction as the fluid cools.
    https://www.freeasestudyguides.com/e...iator-cap.html
    Shogun tricks and tips for the E32 series are HERE!

  10. #10
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    Quote Originally Posted by shogun View Post
    I would use another radiator/expansion tank cap
    LOL, I thought they were doing something different. What I mean is that I am familiar with the old metal radiator cap where you see the springs but this thing just looks like a black piece of plastic with some o-rings. It never occurred to me that there would be valves hidden up inside the plastic molding.

    Yeah, a bad valve in the cap fits the symptoms perfectly, especially since I just did a chemical test today looking for exhaust (CO2) coming out of the expansion tank and the test came up negative and I didn't see any sign of air being forced into the system.

    Basically, that's got to be it.

    Thanks!!

  11. #11
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    I think I'm still going to have to do a compression and/or leak down test because the cap has some white on it as if there was oil getting into the cooling system and maybe it was motor oil in the cooling system that caused the cap to fail.

    I find this strange given that I don't have any other signs of a problem, that is: I don't see any bubbling into the cooling system; I don't see the oil looking funny, it seems to idle just fine and there's not white nor blue out the exhaust nor anything else that I can see that indicates a problem.

    Just a little white on that expansion tank cap and that's it. Maybe I've a very tiny leak that could be fixed with a head gasket stop leak product although I've never used those and really don't want to but if it proves to be something very tiny maybe it's worth a try.

    Anyway, I'll give the results once I've done the tests.

  12. #12
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    So a basic compression test, with the numbering starting from the cabin and working towards the front of the car, yielded (PSI):
    1 155
    2 140
    3 140
    4 145
    5 145
    6 152
    which seems okay to me although #5 took a few extra cranks compared to the others to get to that pressure perhaps it could be worth a leak down test on it but I suspect I should be looking elsewhere for where the oil could be getting into the coolant.

  13. #13
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    Those compression numbers look good. Watching your thread as I have developed similar coolant issues.

  14. #14
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    I love diagnostics and research before replacing parts... it can save so much unnecessary cost and time... so I've been doing quite a bit of reading and I think I can relax a bit.

    First, the compression probably would have been higher over all if I had thought to keep the throttle fully open when testing and the engine had already cooled down a bit by the time I did the tests and Arizona's quite a bit above sea level so I'm not going to concern myself with the numbers seeming a little low, as so many had said, it's that the numbers are about the same that matters.

    After hours of reading two things jumped out at me, first, if anyone else has touched the cooling system there's a chance that they messed up and got some oil in with the coolant, which in my case there is some chance of that. Second, if the coolant looks brown it's more likely rust and other particles than oil leaking into the cooling system and that's backed up by many saying that an oil/coolant leak is rare compared to an exhaust/coolant leak in E36's especially since they have no inter-cooler like some later models.

    Finally, particles are far more likely to foul up a valve in the cap than oil IMHO.

    So with all that, and that it passed a chemical test for CO2 in the cooling system, and that the oil doesn't seem to be contaminated, I think I'll just flush the cooling system completely and see if the problem goes away rather than fret over what further tests I could do to find something internally wrong in the engine. Then if it comes back, I'll start fretting again.
    Last edited by Nybbles2Bytes; 03-22-2019 at 05:23 AM.

  15. #15
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    I have a small leak in the heater core or the lines getting to it. Had it for a few years. Worse in winter with heater use. Just the slightest smell of coolant on occasion. No visual signs of the leak. Check coolant comes on. Tank looks full until you burp the system. Less of a problem during the summer. Probably fix it this summer.

  16. #16
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    Quote Originally Posted by doclees View Post
    I have a small leak in the heater core or the lines getting to it. Had it for a few years. Worse in winter with heater use. Just the slightest smell of coolant on occasion. No visual signs of the leak. Check coolant comes on. Tank looks full until you burp the system. Less of a problem during the summer. Probably fix it this summer.
    Now there is a harrowing thought. My heater fan went out as well... Man I don't want to take my dash out, what a pain in the ass.

  17. #17
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    It's a car. Embrace the suck!
    Working on the 325 reminds me how much I LOVED my old Jeep Wrangler. A bus ate it.

  18. #18
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    Did you have the system pressure tested yet?
    Working on the 325 reminds me how much I LOVED my old Jeep Wrangler. A bus ate it.

  19. #19
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    Well, the diagnostics continues. With the new cap I still had a pressure issue so I performed a leak down test and got the following results. The engine wasn't as warm as I would have liked by the time I got to doing the testing but there's not much I could have done about that. In any case here are the results using 90 PSI:
    1 4%
    2 3%
    3 4%
    4 13%
    5 22%
    6 4%

    Also when testing cyl. 5 some air was coming out of cyl. 3 spark plug hole which is kind of strange and when testing cyl. 4 a tiny bit of air was coming out of cyl. 5. The compressing test did not given any indication of this at all, in fact, I would have bet on cyl. 2 from the compression test results.

    I'm betting I've got minor head gasket problem. I think before looking at a removing the head it's worth trying some gasket stop leak. According to Scotty Kilmer on youtube his choice was Steel Seal but it doesn't work with modern coolants so now he uses Bars Head Seal. Obviously I'm going to have to pull the head off one day and do a proper fix but I think this is a good short term choice since it seems like such a small leak (judging by how well the car runs) that this stuff might have a chance.

    I kind of feel like asking if anyone has any experience with particular head gasket sealers, other than just telling me to "get a proper fix" which I will do eventually but then again I don't know how you could possibly gather the data to determine that one is better than the other so I don't know if it's worth asking. It seems to me you just have to pick one with what little info. you can find and just go for it not really knowing how good one will be compared to another.

  20. #20
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    I can't remember the product for the life of me but it was a 2 part product that a friend used on his van. Had to flush out the coolant and fill with water and the 2 parts. Run it and it sealed it for at least 50k miles. He sold it after that. Somewhere in the $50 range.

  21. #21
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    Duraseal I'm pretty sure. $50 is more like $150 now.

    - - - Updated - - -

    Thermaweld looks like it. Not Dura-seal.

  22. #22
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    Quote Originally Posted by Nybbles2Bytes View Post
    Recently my cooling system started to indicate that my coolant was low yet every time I checked it was just fine.

    I just replaced the expansion tank and sensor and there was no problem while I was bleeding the system.

    Today however I went for a 40 minute round trip and when I got to my destination in about 20 mins. it was still fine. However, as soon as I started the car it's telling me again that the coolant is low. There are no leaks that I can see and I am sure that after it cools down I'll find as before the level is just fine.
    Check the connector that goes into the coolant level sensor. I had same issues you described on my '96 328i. For short drives the coolant level indicator never came on; drive about 15-20 minutes and allow engine coolant warm up and I would get the check coolant message when turning off the car. Car was not overheating. Took the car to my mechanic last week; one of the harness-side connectors to the coolant level sensor wasn't making a good connection, which resulted in arcing which resulted in a connector that was failing/melting. Your issue may be different; but at least check on this to see if that is the culprit or if you can validate the connector is good.

    Hope that helps!

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