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2005 Honda Element – mystery air in engine cooling system

Home Forums Stay Dirty Lounge Service and Repair Questions Answered Here 2005 Honda Element – mystery air in engine cooling system

This topic contains 15 replies, has 2 voices, and was last updated by 2005 Element Wilf 7 months, 1 week ago.

  • Creator
    Topic
  • #895790
    2005 Element
    Wilf
    Participant

    My 2005 Honda Element has 288,000 Kilometers on it.
    It has never been in a serious accident and never over heated.

    [Well, there was one time that I was going very slow on a forest service road and discovered that it was running hot, a bit bogged down and slow, and that the fans were not working.
    I let it cool, headed back down, replaced the fan motors, and topped it up with coolant and … everything was fine. It didn’t blow steam but it did go to hot on the temp guage.]

    Step forward 1 year.

    Now that it is winter, I turn the heat to Hot, and noticed a gurgling sound.
    Gurgling only happens briefly when revving the engine.
    It sounds like air bubbles caught or trapped or passing through the heater core.

    Some people might not note it. But when revving after idling, it can be distinctly heard.
    Purging the rad of air (put a funnel on it and burped it) helped.
    I have the overflow at about 1″ to 2″ above the ‘MAX’ fill mark with no notable loss of coolant,
    But it came back in a day or so.

    So …. I took it to my usual mechanic:

    – Pressure test (4 hours) and cylinder inspection revealed no leaks into the cylinders.
    It holds pressure perfectly as can be told from the guage.

    – Vacuum test (4 hour) revealed no leaks and it held a vacuum.

    – A small leak in the lower driver side of the radiator is noted, perhaps 2 ml per hour of hard driving.

    After all the tests, drawing all the air out, it ran quiet until I stressed the engine and then it came back.
    Mechanic is at a loss to explain the cause – and he doesn’t think the small rad leak is the culprit.

    I plan to replace the radiator.

    What am I missing?
    What is the mechanic possibly missing?

Viewing 15 replies - 1 through 15 (of 15 total)
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  • #895791
    Nightflyr *
    Richard Kirshy
    Participant

    Has anyone done a combustion gas test?
    Something else..
    if there is – A small leak in the lower driver side of the radiator is noted, perhaps 2 ml per hour of hard driving.
    This doesn’t show up in a pressure or vacuum test.
    If coolant can leak out air can leak in.

    #895793
    2005 Element
    Wilf
    Participant

    [quote=”nightflyr” post=204300]Has anyone done a combustion gas test?
    Something else..
    if there is – A small leak in the lower driver side of the radiator is noted, perhaps 2 ml per hour of hard driving.
    This doesn’t show up in a pressure or vacuum test.
    If coolant can leak out air can leak in.[/quote]

    That is what I thought. Mechanic seems to think it would suck back from the reservoir before coming in through that small leak (pin hole?).

    I should add, I did replace rad cap and that also made no difference.

    #895794
    Nightflyr *
    Richard Kirshy
    Participant

    On the same school of thought …
    If it is leaking coolant out through a pin hole.
    Then why is it not pushing fluid back into the over flow?
    You can’t have half the equation work one way and the other half work in the opposite.

    #895795
    2005 Element
    Wilf
    Participant

    [quote=”nightflyr” post=204303]On the same school of thought …
    If it is leaking coolant out through a pin hole.
    Then why is it not pushing fluid back into the over flow?
    You can’t have half the equation work one way and the other half work in the opposite.[/quote]

    Reservoir hose has no leaks and is unobstructed.
    Squeezing one of the fat engine coolant hoses causes a slight volume increase in the reservoir level.
    Pinhole leak appears at very bottom of radiator, so maybe gravity + shaking + time + heat/cool cycles is why the small leak manifests there – even though the system appears to be overflowing and up-taking normally.

    #895796
    Nightflyr *
    Richard Kirshy
    Participant

    Still comes down to if the system is purged of air and completely full.
    Then after a time you have air introduced.
    You either are:
    Taking combustion gases into the cooling system.
    Or drawing air externally into the cooling system.
    Now if a combustion gas test yields a negative result your left with a external leak with in the cooling system.

    #895797
    2005 Element
    Wilf
    Participant

    [quote=”nightflyr” post=204305]Still comes down to if the system is purged of air and completely full.
    Then after a time you have air introduced.
    You either are:
    Taking combustion gases into the cooling system.
    Or drawing air externally into the cooling system.
    Now if a combustion gas test yields a negative result your left with a external leak with in the cooling system.[/quote]

    I’ll throw this out — What about the thermostat?
    Is it possible for air to enter the system when the thermostat moves its valve?
    Anyone heard of that?

    #895799
    Nightflyr *
    Richard Kirshy
    Participant

    The T stat is inside a closed loop.
    Unless there is a crack in the housing that should cause an issue.
    The only other situation in which air bubbles can occur is due to cavitation.
    But if this was an issue due to design, there would be many more reports of it happening.

    #895800
    2005 Element
    Wilf
    Participant

    [quote=”nightflyr” post=204308]The T stat is inside a closed loop.
    Unless there is a crack in the housing that should cause an issue.
    The only other situation in which air bubbles can occur is due to cavitation.
    But if this was an issue due to design, there would be many more reports of it happening.[/quote]

    Cavitation – perhaps in the block heater or heater control valve?
    Or something else?

    #895803
    Nightflyr *
    Richard Kirshy
    Participant

    Not likely..
    In this situation the only possible cause would be the water pump impeller.
    But as I said, if this was a design issue more cases would have surfaced.
    May I ask..
    If you know you have a leak in the radiator why not replace it?
    And if there is a possibility of combustion gases do a gas test.

    #895836
    2005 Element
    Wilf
    Participant

    [quote=”nightflyr” post=204312]Not likely..
    In this situation the only possible cause would be the water pump impeller.
    But as I said, if this was a design issue more cases would have surfaced.
    May I ask..
    If you know you have a leak in the radiator why not replace it?
    And if there is a possibility of combustion gases do a gas test.[/quote]

    Totally. I have ordered a replacement radiator and will install that as soon as it arrives.
    That will eliminate that possibility and then we will see!

    #897232
    2005 Element
    Wilf
    Participant

    Radiator and hoses replaced. New Honda coolant. New rad cap. Inspected thermostat and all working perfectly (did hot water test). The block tubes and thermostat look pretty much new. No leaks anywhere.
    Just looking at the engine layout, there is a 1 to 2 foot climb from the block to the heater core. So maybe it is just crazy difficult to remove the air bubbles in the heater core. I don’t even see how jacking the car would make them come out. I guess I’ll just have to live with annoying gurgling sounds when the heat control is over to full-hot and the car is accelerating.

    #897242
    Nightflyr *
    Richard Kirshy
    Participant

    If the system is that difficult to bleed.
    Might try a vacuum fill.
    https://www.amazon.com/FJC-43610-Radiator-Coolant-Vacuum/dp/B00804HWOU

    #916677
    2005 Element
    Wilf
    Participant

    Update …
    I’ve done a perfect bleed, just burping it and verified that the gurgle in the heater core is 99% gone. I did this using the spill-free-funnel and the car on a incline, modulating the rpm a bit and idling. That takes a good 25 minutes to do.

    Then while mellow driving around it seems to hold the state and no new bubbles are introduced.

    To get the problem to recur, I drive up a hill nearby that has approximately a 500 feet vertical rise over 1 km. The bubbles don’t appear to manifest at the top of the hill, but in fact after I get down the hill using engine braking (1st and 2nd gear, often sustained 4000 to 4500 rpm).

    So … even after a perfect bleed. air is getting back into the system after either 1) a hard drive or 2) a hard engine brake after a hard drive.

    To check if combustion gases, I bought an OEM test kit tested twice, for even longer than required, and both tests came back negative that it is not combustion gases.

    So this really has me stumped.

    1) No loss of coolant. Either reservoir goes a little higher (from air in system displacing coolant) or it goes back to normal, after air is burped and system re-capped.

    2) No leaks. Vacuum test for 4 hours, no leaks. Pressure test 4 hours, no leaks.

    So … something is either sucking the air into the system (on cool down when engine braking at high rpm??) or under high load.

    The mystery continues.

    #916728
    Nightflyr *
    Richard Kirshy
    Participant

    What is the condition of the radiator cap?

    #916734
    2005 Element
    Wilf
    Participant

    I replaced the radiator, hoses, and radiator cap. Also inspected thermostat and looks new and works perfectly (hot water test).

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