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  1. #1
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    Question Coolant Loss with No Leaks

    My 350 used to have a coolant leak near the thermostat hosing, so I fixed that and now my engine has no visible signs of coolant leaks, but yet it still loses coolant and I have to fill up the side tank every few weeks. My oil is not milky. What could be causing this?

    Thanks

  2. #2
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    Default Re: Coolant Loss with No Leaks

    Could be a slow head gasket leak meaning you're losing the coolant in the cylinder. Bad leaks usually show up as white vapor from the tailpipe(s). Wouldn't hurt to pull the plugs and see if one or two look worse than the others...might help you chase it down.

    Devon
    Fuel & Brake Systems Engineer
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  3. #3
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    Default Re: Coolant Loss with No Leaks

    Quote Originally Posted by DaWildcat View Post
    Could be a slow head gasket leak meaning you're losing the coolant in the cylinder. Bad leaks usually show up as white vapor from the tailpipe(s). Wouldn't hurt to pull the plugs and see if one or two look worse than the others...might help you chase it down.

    Devon
    I have no vapor coming from the tail pipes all my plugs are clean as a whistle, thanks to my MSD 6A, and no coolant smell from the exhaust. Could it still be a slow head gasket leak?

    Thanks

  4. #4
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    Default Re: Coolant Loss with No Leaks

    Have you looked at the fan side of the radiator? may have a pinhole leak there and the fan is pulling the vapor toward the engine not allowing you to see it from the front. just an idea.
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  5. #5
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    Thumbs up Re: Coolant Loss with No Leaks

    i pulled my valve covers to paint them,and saw green stuff,aka coolant bad head gasket the radiator is a good call also,i wouldnt run it too long till you figure it out
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  6. #6
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    Default Re: Coolant Loss with No Leaks

    Quote Originally Posted by 65specialconver View Post
    i pulled my valve covers to paint them,and saw green stuff,aka coolant bad head gasket the radiator is a good call also,i wouldnt run it too long till you figure it out
    How could it be a head gasket if my oil is clean and my exhaust is clear and coolant smell free? Where else can it go? Is there a test to find a leak this small? To remind everyone the leak is extremely slow it takes 4-5 weeks to empty the side tank and this is with me driving ~25 miles a day. Should I pull the fan and shroud and look for a leak on the engine side of the rad?

  7. #7
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    Default Re: Coolant Loss with No Leaks

    heater core leaking possibly ...check for dampness under passenger side carpet

    bottom line ...go to a shop and get the radiator and system pressure tested ..
    * 1972 350 GS....started frame off resto...08-2005
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  8. #8
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    Default Re: Coolant Loss with No Leaks

    i would find a shop in your area that has a four gas and have them hang the probe over the radiator neck (do not submerge the probe in the coolant!!!) covering the probe with a rag and see if you get any hydrocarbon readings anything over 10hc is a leaking head gasket. you only get milky oil or steam out the tail pipe if its leaking reallly bad or if somthing cracked.
    rick w.

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  9. #9
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    Default Re: Coolant Loss with No Leaks

    Have you pressure checked the radiator ?...could just be a faulty cap for that matter and you wouldn't even be able to see tthe little bit of steam ( water ) escaping.

    Mark

  10. #10
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    Default Re: Coolant Loss with No Leaks

    btw ....are you running only water ...???
    * 1972 350 GS....started frame off resto...08-2005
    2 late now-its finish or BUST...-39.8 % almost done -

    *2010 Ford Fusion Hybrid...this is where I will
    make all my Buick parts money back...ahahahaha

    Frank Rex

  11. #11
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    Default Re: Coolant Loss with No Leaks

    About 2 years ago, I had a similar "vanishing coolant" situation with my turbo Regal and added a couple GM stop leak pills. It worked and I haven't had any problems since then. Maybe that's worth a try.
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  12. #12
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    Default Re: Coolant Loss with No Leaks

    Quote Originally Posted by rex362 View Post
    heater core leaking possibly ...check for dampness under passenger side carpet

    bottom line ...go to a shop and get the radiator and system pressure tested ..
    I agree with this advise.

    It is possible that you had air pockets in your system and they are working out as you run the motor?
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  13. #13
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    Exclamation Re: Coolant Loss with No Leaks

    yes been there,done that
    Jamie McClintonPride and joy '65 Special convertible w/340-4
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  14. #14
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    Default Re: Coolant Loss with No Leaks

    Quote Originally Posted by sean Buick 76 View Post
    I agree with this advise.

    It is possible that you had air pockets in your system and they are working out as you run the motor?
    This may be possible since I swapped an intake a few weeks ago, but it had the same condition before the swap. I am going to get everything tested tomorrow.

    Thanks

  15. #15
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    Default Re: Coolant Loss with No Leaks

    Quote Originally Posted by rex362 View Post
    btw ....are you running only water ...???

    No I am running probably around 60/40. I have no idea what it is since I've added 50/50 and I think the previous owner added something stronger.

  16. #16
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    Default Re: Coolant Loss with No Leaks

    just asking just in case.... bcs if you run only water ...it will eventualy slowly evaporate ....

    hit a shop with a pressure gauge or maybe some auto parts place might loan em out ....make sure you dont have a small leak that you cant detect with the eyball before you start pulling heads off the motor...
    * 1972 350 GS....started frame off resto...08-2005
    2 late now-its finish or BUST...-39.8 % almost done -

    *2010 Ford Fusion Hybrid...this is where I will
    make all my Buick parts money back...ahahahaha

    Frank Rex

  17. #17
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    Default Re: Coolant Loss with No Leaks

    btw also look from underneath ....at that relief hole thingy on the bottom side of the water pump ...see if you have signs of leakage \
    .....might be blowing in spurts out of there while driving .....it will look smeared like dry trailing stuff powder like from drying off


    the weep hole the weep hole .....





    have you been beating on that car ..???
    * 1972 350 GS....started frame off resto...08-2005
    2 late now-its finish or BUST...-39.8 % almost done -

    *2010 Ford Fusion Hybrid...this is where I will
    make all my Buick parts money back...ahahahaha

    Frank Rex

  18. #18
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    Default Re: Coolant Loss with No Leaks

    I had this problem and it was actually the over flow tank cover leaking when it would slosh around a corner. Not saying this is your problem but I went threw all that I just had to seal up the cover.

  19. #19
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    Default Re: Coolant Loss with No Leaks

    I had a water pump that would ONLY leak after it was warmed up and under full throttle, and by the time you stopped & looked, it was dry. I found it because I knew it was leaking somewhere (and not in a cylinder or oil), so I had the engine up to temp,front end up on jack stands, then raced the engine. And ther she blows, backed off the throttle and it would completely stop.
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  20. #20
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    Default Re: Coolant Loss with No Leaks

    Quote Originally Posted by 71Custom View Post
    I had this problem and it was actually the over flow tank cover leaking when it would slosh around a corner. Not saying this is your problem but I went threw all that I just had to seal up the cover.
    Yea I plugged the overflow hose. The level never rises much between cold and hot and every time I would go up and down a hill some would dump out, and being in Alabama that is quite often.

  21. #21
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    Default Re: Coolant Loss with No Leaks

    I really appreciate all the responses. I am gonna go check out the water pump right now.

    Thanks

  22. #22
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    Default Re: Coolant Loss with No Leaks

    I just checked the water pump and it seems dry and residue free , however it's hard to see with the balancer and pulleys in the way.

  23. #23
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    Default Re: Coolant Loss with No Leaks

    I just threw on a borrowed pressure tester and once I got up to 15 psi the needle very very slowly crept down. I also threw my cap on the tester but it didn't really tell me much. I now have a new problem, I idled the motor to get it warmed up and the system never pressurized. It seems my cap is still letting water pass into the overflow tank, but why? The coolant and engine were hot.


    I'm so frustrated.

  24. #24
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    Default Re: Coolant Loss with No Leaks

    Quote Originally Posted by GSX-PKV View Post
    About 2 years ago, I had a similar "vanishing coolant" situation with my turbo Regal and added a couple GM stop leak pills. It worked and I haven't had any problems since then. Maybe that's worth a try.
    Tell me more about these pills

  25. #25
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    Default Re: Coolant Loss with No Leaks

    Quote Originally Posted by 71skylark3504v View Post
    I just threw on a borrowed pressure tester and once I got up to 15 psi the needle very very slowly crept down. I also threw my cap on the tester but it didn't really tell me much. I now have a new problem, I idled the motor to get it warmed up and the system never pressurized. It seems my cap is still letting water pass into the overflow tank, but why? The coolant and engine were hot.


    I'm so frustrated.
    My system pressurizes now, not sure what happened last night.

 

 
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