Expansion Tank Overflow w/ White Smoke From Tailpipe & Hood

mellyloumellylou Band Wagon
in Engine & Drivetrain
The symptoms: While my boyfriend drove home from work, in my 1990 Honda Civic wagon (base model, 5spd), the tempurature gauge went from cold to hot within seconds. He pulled over, checked coolant and it wasn't leaking, or empty and radiator was cold. Previous owner also mentioned that temp gauge wasn't always accurate. When he drove up our driveway, white smoke started to spew from under hood and there was some smoke from tailpipe. What we believe to be coolant, had also leaked out into driveway.

Checked head gasket and no leakage, no coolant mixed with oil. I just bought this car about two weeks ago and a mechanical friend had mentioned that expansion tank has a metal straw piece that apparently has fallen into tank and the cap is not properly sealed either (the hose nipple connection can be lifted out of cap). Coolant on two occasions has filled expansion tank and leaked from unsealed tank cap. Currently, with the mishaps yesterday, the expansion tank is filled 3/4 with coolant, which usually it is empty.

We're going to check radiators hoses and see if they need to be replaced and try to do this ourselves, due to a tight budget. Also, going to replace expansion tank hose and attempt to fix expansion tank cap--at least buy a gasket that will seal cap and try to troubleshoot detached metal piece.

Any suggestions? I'm going to wait to do maintenance for a few hours and see if anyone has some good ideas?!

Thanks so much!
Mel

Comments

  • NZ-DB8RNZ-DB8R Moderator
    The "nozzle" on the overflow bottle should be able to lift out. Im betting that the hose that is meant to be attached on the inside of the bottle has fallen off so that it cannot suck the water back.

    If smoke came out your exhaust that means it went through the engine which really only points to headgasket.

    The reason for the gauge not working is probably that there was an air bubble around the temp sensor due to having low coolant levels or having been re filled incorrectly without bleeding the coolant through
  • SiWagonSiWagon Council Member
    Expansion tank should NOT be empty.THere's a hi & low mark on the tank.

    As far as the metal straw( :?: ).Unscrew the exp. tnk cap.You can now lift out the tank.Shake out the straw.Clean tank if you'd like.Show us a pic of the gasket & metal straw(shouldn't be there),but I don't think that's the prob.Replace the tube with a tighter fitting tube.The tube and gasket can be had off any 88-91 Civic and probably most Hondas.

    With the engine fully warmed.Squeeze the upper radiator hose.It should have pressure(a good sign) vs. how it feels when the engine is cold.


    On another matter that might be related,but of a small concern:
    viewtopic.php?f=7&t=102&hilit=back+box
  • mellyloumellylou Band Wagon
    I am certainly a newbie (I'm sure very obviously) to DIY car maintenance, but the head gasket does not appear to be leaking and there is no coolant in oil. There is a pic of it below.

    I do think it must be an issue of pressure at this point and we're going to trouble shoot the cap and add a gasket underneath the cap to reservoir, as there is no gasket, which is my first guess as to why the tank is not holding pressure. After this, we can test the hose, which you suggested to see what the difference between hot and cold. Also, I think there must be a straw type piece that is definitely missing on the cap (cap is pictured below), as I can't understand how coolant in reservoir, would be able to go anywhere from there (but onto the ground of course).

    I'll see what this metal straw business is about--my friend saw it in there when reservoir was empty and now it is full and coolant probably needs to be bled.

    Thanks so much again!
  • mellyloumellylou Band Wagon
    Also, thermostat and water pump were just changed, which should help to isolate issues...
  • NZ-DB8RNZ-DB8R Moderator
    The headgasket wont be leaking on the outside if it is blown. It blows between the cylinders so you wont be able to see anything from the outside other than your coolant will look like a chocolate milkshake.

    The overflow bottle looks fine other than once you put the plastic nozzle into the lid there should be a rubber hose attached to the inside which should be submerged in the coolant/water inside the bottle.
    It doesnt need a gasket as it doesnt need to be sealed. With the hose inside the bottle being always submerged it means that the changing pressure inside the radiator can be move freely between the overflow and radiator. Without the hose the water will flow from the radiator into the overflow and then be unable to get back.
  • mellyloumellylou Band Wagon
    Problem fixed! Added an o-ring to the plastic nozzle, fished the rubber hose out from the bottom of the reservoir and put it back where it belongs. I was referred to an amazing mechanic who came to me and repaired a hose that was behind the engine block, which had sprung a pretty horrible leak. Radiator was pretty much empty and not able to intake from reservoir, due to the fallen hose. He fixed it for $40 and between you helpful guys and him, I learned a lot today!

    Feelin' accomplished and so glad it was not head gasket!
  • JakerJaker familEE
    Just to add a bit more info to this thread. The overflow bottle is never pressurized. It is usually vented to atmosphere. It does not require an airtight seal to function normally. This is how it works:

    When the engine operates normally (normal hot/cold temperatures), the overflow bottle does absolutely nothing. It merely sits there with a reserve of coolant (that occasionally evaporates). However, if the motor runs too hot (overheats) the excess coolant will flow into the overflow bottle. There is a bypass system built into the rad cap/radiator fill neck, and this is where the port for the hose to the overflow bottle is attached (as can be seen in the pics). Now your engine is shut off and cooling, but your overflow bottle is full. The bypass in the rad cap seals back up or closes, and as the engine cools this creates a vacuum in the cooling system from the missing coolant. That vacuum will open the bypass in the rad cap/radiator neck, and suck the coolant back out of the overflow bottle into the radiator. However, in your case, the "straw" for the bottle was detached, so the vacuum was sucking air, not coolant.

    This system will also work well if you have a very minor coolant leak. As the coolant leaks out of the motor, or is burned off by a minor head gakset leak, when your motor cools fully, the vacuum will once again suck coolant out of the overflow bottle into the motor's cooling system. Keep your overflow bottle topped up at all times, and you'll be golden for as long as the coolant leak is not serious. You should still fix it, but at least this buys you some time. However if you ever go to fill the overflow bottle, and it is totally empty, you'd better pop the rad cap and make sure to top up the radiator too, as there's a good chance there wasn't enough coolant in the overflow bottle to re-fill the rad completely.
  • mellyloumellylou Band Wagon
    Mechanic said head gasket was perfect and that it was a combination of reservoir issues, as well as the hose behind the engine block--we could visibly see a spray of coolant.

    Thanks for the extra advice, very informative and I will definitely make sure to regulate my overflow tank, to make sure there is no other leakage.
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