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Air pocket in heater core???

This is a discussion on Air pocket in heater core??? within the Technical / Maintenance forums, part of the General Discussion category; My 98 that I recently flushed the cooling system on still has a gurgle coming from the heater core. It ...

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    Registered User Mr_Shamrock's Avatar
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    Air pocket in heater core???


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    My 98 that I recently flushed the cooling system on still has a gurgle coming from the heater core. It was doing it before the flush too. It only makes the sound when I accelerate and then it stops. At steady speeds it is quiet. I thought if I let it run with the heater on it would circulate all the air out. My coolant level hasn't changed. This is the truck that I just bought and the previous owner put a new engine in. I thought it had the dex-cool sludge, but it was just some remnants of what I am guessing is before the engine swap. Could the heater core be sludged up causing this sound? My heat works great so it is doing its job - I just have this stupid faint gurgle when I take off.
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    Re: Air pocket in heater core???

    Either you still have a slight leak in the cooling system somewhere that is letting air pockets form, or if you've replaced the quick connect fitting on the intake with a normal pipe fitting that may be the cause. Since I've done my intake gaskets and know I no longer have any leaks, but still have a slight heater core gurgle, I've got to believe what others are saying that it's the fitting. The quick connect acts as sort of a restrictor as the ID of that fitting is quite small compared to a normal pipe fitting. If you're not dropping coolant level, I wouldn't worry about it.

    Richard

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    Re: Air pocket in heater core???

    Would a shop with pressurized equipment be able to push an air bubble out? Just a thought.

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    Re: Air pocket in heater core???

    i have the same thing in my '98. coolant level never changes...just a gurgling sound...heat works fine...

    why the hell couldn't GM have just left well-enough alone? the pre 95 trucks never had a gurgle in the cooling system...

    2004 GMC Sierra SLE Z71 rcsb, 5.3/4L60E/3.73/G80 time bomb...3" lift, tinted 03+ Silverado tails, plasti-dipped 16" wheels (unknown brand), 285/75/16 Thunderer M/T Extremes, Thrush Welded muffler...

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    Re: Air pocket in heater core???

    Well maybe I just needed another cycle. I made this post and then ran some errands and it never made a sound. I am not sure if the fact that it was cool out so I had the heater on would have made a difference. This was actually the first time I drove it with the heat on since replacing the bypass hoses the other day, but I did run the heater when topping it off - not sure why driving it would make a difference. I even checked the level one more time before leaving this morning. Level is good in the radiator and overflow bottle. I also always pressure check my cooling system when I have had them apart. I left it at 15PSI for about 30 minutes and it stayed right there. I drove the truck for over 6 hours the other day when I picked up my trailers so I would think that would have been enough driving although I did not have the heater on during that trip.
    Last edited by Mr_Shamrock; 10-28-2011 at 06:10 PM.
    2004 Suburban 2500 Quadrasteer 4WD 6.0L
    1985 Silverado C-10 RCSB 2WD 5.7L
    1992 Sierra 1500 2WD 5.7L
    1995 Tahoe 4DR 2WD (For Sale)
    1999 Tahoe Limited
    2000 Tahoe Limited

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    Re: Air pocket in heater core???

    your killin us turn up the music.
    O2 GMC RCSB 4.8L V8 AUTO 3.73's
    rebuilt/beefed up 4L60E(at 43,000miles)
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    Re: Air pocket in heater core???

    well i'm glad yours seems to be fixed. i guess i need to tear into my cooling system and try to figure out what's wrong with mine...

    2004 GMC Sierra SLE Z71 rcsb, 5.3/4L60E/3.73/G80 time bomb...3" lift, tinted 03+ Silverado tails, plasti-dipped 16" wheels (unknown brand), 285/75/16 Thunderer M/T Extremes, Thrush Welded muffler...

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    Re: Air pocket in heater core???

    Quote Originally Posted by FordeatinZ71 View Post
    i have the same thing in my '98. coolant level never changes...just a gurgling sound...heat works fine...

    why the hell couldn't GM have just left well-enough alone? the pre 95 trucks never had a gurgle in the cooling system...
    i have owned 3 1994's, all had Gurgle :S


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    Re: Air pocket in heater core???

    Yeah, my '92 gurgles too.
    1992 K2500 LD 4x4, 5.7, 700r4, 3.73 14-bolt, G80, Cleaner than sh!t.
    2001 Tahoe LS 4x4(the wife's), 5.3, 3.73, G80, third-row seats.

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    Re: Air pocket in heater core???

    The heater control setting does not affect/change coolant flow through the heater core. Coolant flows through continously, except when you turn on MAX AC.

    For those of you that have not had the heater core out....

    The heater core is just a small radiator. At one end is a tank/header that connects all the rows together. At the other end there are two separate tanks/headers. One is the inlet, one is the outlet. The core is positioned in the heater box at about a 30 degree angle. Unfortunately, the wrong end is up. Both tubes are at the lower end. So, the coolant comes in the bottom, travels up one side of the core. Crosses over the top, and returns down the other side. It could be easy for bubbles to get trapped in there and take a while to come out. This would take even longer if you have clogged coolant passages from Death Cool or neglect. The main thing is to have an absolutely tight system. I have had cases where it would only leak slightly when cooling down, or even draw air through a leak as it cooled, but not leak out when under pressure. If the coolant level in the reservoir never moves or doesn't move much from hot to cold would be an indicator of this condition.

    As for the fitting in the intake causing/preventing the problem that doesn't make sense to me. In fact, my 97 with the factory quick connect fitting made far more noise than my 96 without it ever did. The 96 is silent now, and doesn't lose a drop of coolant. Took new intake gaskets, all new hoses, water pump, heater core, and finally radiator to fully seal it.

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    Re: Air pocket in heater core???

    In the somewhat recent past I argued that it couldn't be the fitting, either. I did have a very small intake gasket leak, which I fixed. Cooling system is tight - 1994 5.7 - and it gurgles, sometimes.

    Richard

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    Re: Air pocket in heater core???

    I had the waterfall in my dash before I replaced everything and sealed the system up. I haven't had the stupid quick mis-connect on my heater hose for years.

    How about the radiator cap? If the system isn't holding pressure you're more likely to get steam/air pockets, and push coolant into the overflow.
    Last edited by 454cid; 10-28-2011 at 06:15 PM.
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    Re: Air pocket in heater core???

    Quote Originally Posted by 454cid View Post
    I had the waterfall in my dash before I replaced everything and sealed the system up. I haven't had the stupid quick mis-connect on my heater hose for years.

    How about the radiator cap? If the system isn't holding pressure you're more likely to get steam/air pockets, and push coolant into the overflow.
    You might be on to something with the cap. It appears to be the same cap that was on the truck when the PO had the dex-cool issue and it was caked pretty good with that crap. I cleaned it all out, but maybe it is time to just replace it. It looks old and is quite possibly the original from 1998. That is the only thing that isn't included in the pressure check that I did - I will have to look in my kit to see if it has the adapter to test the caps. I think I am going to grab one tomorrow just for the hell of it anyway.
    2004 Suburban 2500 Quadrasteer 4WD 6.0L
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    Re: Air pocket in heater core???

    ok well i stand corrected. i've had an '89 K1500, '90 C1500 and a '91 K1500 and none of them ever gurgled...figured it was a '95-up problem...sorry!

    2004 GMC Sierra SLE Z71 rcsb, 5.3/4L60E/3.73/G80 time bomb...3" lift, tinted 03+ Silverado tails, plasti-dipped 16" wheels (unknown brand), 285/75/16 Thunderer M/T Extremes, Thrush Welded muffler...

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    Registered User Mr_Shamrock's Avatar
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    Re: Air pocket in heater core???

    Just an update - new cap installed a few days ago and it is still gurgling. I thought it went away, but it just doesn't do it all the time. I had the radio off the entire ride today and I would say every 3rd or 4th take off it would do it. I tried taking off hard and slow and it seems the hard take offs make it louder (I guess spinning the water pump faster so it makes sense) Coolant level hasn't changed either. I think I am going to remove the heater lines and back flush the core.
    2004 Suburban 2500 Quadrasteer 4WD 6.0L
    1985 Silverado C-10 RCSB 2WD 5.7L
    1992 Sierra 1500 2WD 5.7L
    1995 Tahoe 4DR 2WD (For Sale)
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    2000 Tahoe Limited

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    Re: Air pocket in heater core???

    well i'll keep following this...i'd like to fix mine but for now i just use the radio knob adjustment method...

    2004 GMC Sierra SLE Z71 rcsb, 5.3/4L60E/3.73/G80 time bomb...3" lift, tinted 03+ Silverado tails, plasti-dipped 16" wheels (unknown brand), 285/75/16 Thunderer M/T Extremes, Thrush Welded muffler...

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    Re: Air pocket in heater core???

    Quote Originally Posted by Mr_Shamrock View Post
    Just an update - new cap installed a few days ago and it is still gurgling. I thought it went away, but it just doesn't do it all the time. I had the radio off the entire ride today and I would say every 3rd or 4th take off it would do it. I tried taking off hard and slow and it seems the hard take offs make it louder (I guess spinning the water pump faster so it makes sense) Coolant level hasn't changed either. I think I am going to remove the heater lines and back flush the core.
    The core in mine is brand new (well, a few thousand miles on it now) as I'd replaced it not long ago. Not to deter you from flushing it out but I don't think it's gonna help.

    Richard

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    Registered User 454cid's Avatar
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    Re: Air pocket in heater core???

    Quote Originally Posted by Mr_Shamrock View Post
    Just an update - new cap installed a few days ago and it is still gurgling. I thought it went away, but it just doesn't do it all the time. I had the radio off the entire ride today and I would say every 3rd or 4th take off it would do it. I tried taking off hard and slow and it seems the hard take offs make it louder (I guess spinning the water pump faster so it makes sense) Coolant level hasn't changed either. I think I am going to remove the heater lines and back flush the core.
    You've got to be getting air in it somehow. When was the last time you had the heater hoses off? Maybe you've got a small leak in one/both. Maybe a small leak in the core itself? Given that the level rises and falls with temperature it would be easy to miss small amounts and not know it.
    454cid
    1999 K3500 RCLB

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    Registered User Mr_Shamrock's Avatar
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    Re: Air pocket in heater core???

    I had one side disconnected last week because I was replacing the short rubber hose that goes to the water pump. I haven't had the one that goes to the intake off at all. I don't smell coolant at all.
    2004 Suburban 2500 Quadrasteer 4WD 6.0L
    1985 Silverado C-10 RCSB 2WD 5.7L
    1992 Sierra 1500 2WD 5.7L
    1995 Tahoe 4DR 2WD (For Sale)
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    2000 Tahoe Limited

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    Registered User 454cid's Avatar
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    Re: Air pocket in heater core???

    Quote Originally Posted by Mr_Shamrock View Post
    I had one side disconnected last week because I was replacing the short rubber hose that goes to the water pump. I haven't had the one that goes to the intake off at all. I don't smell coolant at all.
    You may not smell coolant in small amounts. Depending on where a leak is, it could actually dry from the engine heat. You're hearing air in the system, so it has to be coming from some place.
    454cid
    1999 K3500 RCLB

 

 
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