help with coolant leak/ overheating 79' 308 | Page 3 | FerrariChat

help with coolant leak/ overheating 79' 308

Discussion in '308/328' started by jbrosseau, Aug 5, 2008.

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  1. GeoMetry

    GeoMetry Formula Junior

    Apr 14, 2008
    471
    Virginia
    Full Name:
    Richard
    I am still hoping someone can show me proof of the internal tube. I can imagine a couple of non invasive ways to retrofit something that would effectively create the internal tube.
     
  2. Spitfire

    Spitfire Formula 3

    Nov 16, 2006
    1,570
    #52 Spitfire, Mar 22, 2009
    Last edited: Mar 22, 2009
    There are several of us (myself included) who have satisfied ourselves that there was never an internal tube in our earlier style (i.e., vertical) coolant tanks. You seem to be in exactly the same position with your horizontal tank.

    Intuitively, I think we all agree that such a tube would prevent the system from sucking air back into itself. I plugged my upper hose and the problems were fixed immediately. I also purchased a check valve which I shall install next week rather than leaving the upper hose plugged.
     
  3. GeoMetry

    GeoMetry Formula Junior

    Apr 14, 2008
    471
    Virginia
    Full Name:
    Richard
    I am not convinced that the air is getting into the system via the upper tube. I have a theory that the coolant flow is in a single direction and that the air is getting sucked into the engine via the lower connection. The fact that plugging the upper hose prevents air from getting into the system is consistent with my theory because the flow is eliminated.

    I don't know how a check valve works but I imagine some sort of spring that the flow must overcome. I'm not sure the flow through the upper hose has much pressure at all because it is running in parallel to the primary flow of the system. With a cold engine, if I open the expansion tank while the engine is running there is not a lot of churning of the coolant in the expansion tank.

    I am very interested in hearing the results of installing the check valve. Is there coolant flow through the expansion tank with a check valve installed? Has the problem of air in the cooling system returned? My theory would say that you will either get no flow (same as plugging the upper hose) or you will get air in the system again. If the check valve solution works please let me know the specifics of your check valve (brand/model/specs) so I can try it on my car.

    Plugging the upper hose is a simple solution to this problem but it creates another problem. The other problem is the temperature sensor on the tank will not be exposed to warm coolant. I think the ultimate solution may be to provide an alternate method of getting warm coolant to the sensor.
     
  4. Sledge4.2

    Sledge4.2 F1 Rookie

    Oct 19, 2007
    4,779
    Marin
    Full Name:
    Geno
    This was the only thing that worked for me, and havent had a problems since. Took my car in for a major, the mechnanic unplugged it, and the overheating returned. Geno
     
  5. Spitfire

    Spitfire Formula 3

    Nov 16, 2006
    1,570
    Also, on the older cars (mine is a '77 GTB) there isn't a temperature sensor in the coolant tank. I cannot comment on the more recent model years.

    The check valve will be installed so that warm coolant can flow back into the tank, whereas nothing can be sucked in the other direction.
     
  6. GeoMetry

    GeoMetry Formula Junior

    Apr 14, 2008
    471
    Virginia
    Full Name:
    Richard
    With no temperature sensor on the tank I see no need for the second hose at all. What am I missing?
     
  7. Verell

    Verell F1 Veteran
    Consultant Owner

    May 5, 2001
    7,017
    Groton, MA
    Full Name:
    Verell Boaen
    Simon, did you ever get around to installing the check valve? If so, what did you find out?
     
  8. AZDoug

    AZDoug Formula 3

    Jun 17, 2009
    1,606
    Along the Verde , AZ
    Full Name:
    Doug
    Simple circulation to make sure everything added to the tank gets mixed in with the coolant. You don't want to top off with distilled water and not have that mix with the antifreeze, for example, and have your expansion tank burst due to freezing weather.

    My 1961 Corvette has a similar system to ensure a small amount of flow thru the expansion/fill tank. The bottom of the tank is connected to the suction side of the pump, a small 1/4" line connects the top of the tank to the top of the radiator.

    Doug
     
  9. 78-308gt4

    78-308gt4 Formula Junior

    May 22, 2005
    735
    Memphis, TN
    I've had to bleed my system every time I drive it. The longer the previous drive, the more air bleeds out, which makes sense as it allows more time for air to be sucked in via the upper line.

    What is the best material with which to plug the line?
     
  10. Verell

    Verell F1 Veteran
    Consultant Owner

    May 5, 2001
    7,017
    Groton, MA
    Full Name:
    Verell Boaen
    #60 Verell, Dec 11, 2009
    Last edited by a moderator: Sep 7, 2017
    An often over-looked source of air getting sucked into the system is the other end of the reservoir line. The fitting (#26 colored dark red in picture) is up under the intake plenum so can't be seen or easily accessed w/o pulling the plenum.

    Often the fitting is so badly pitted by corrosion that air can get sucked in. In many cases, air can get sucked in, but it won't leak coolant. I'd suspect this fitting before I'd assume air was coming up thru the hose.

    Two other spots where corrosion pitting commonly causes leaks are where the two large hoses (#30 & #32) connect to the back of the water pump body.
    Image Unavailable, Please Login
     
  11. Spitfire

    Spitfire Formula 3

    Nov 16, 2006
    1,570
    Okay, years later, I can report that the check valve did solve my problems. In a way, I'm bumping this thread as cooling-related problems are once again being discussed in the 308 section. I believe that for EARLY CARB CARS, with vertical coolant tanks, the solution to many overheating problems is to either plug the upper coolant hose or to install a check valve. Either solution prevents air from being drawn into the system once the engine cools down.
     
  12. 308GTB1978

    308GTB1978 Karting

    Dec 21, 2013
    114
    France
    #62 308GTB1978, Dec 5, 2015
    Last edited: Dec 5, 2015
    Hello chaps,


    We are several 308 owners here in Europa to have the same problem : need to bleed the front radiator after each run ...

    Looking on 10 carbs 308 :

    - 2 have no problem and we don't know why ?
    - 2 have air in the front radiator but the level doesn't change in the cooling tank
    - 6 have air in the front radiator and the level in the cooling tank is rising up, just need 1min to bleed back to the normal situation until the next run and so on ...

    On my car I put a check valve on the upper hose of the cooling tank like this :

    [​IMG]

    I noticed that the coolant temperature was cooler but we are in winter now, nevertheless I still have to bleed the air in the front radiator after each run ...

    There is a mystery here ...
     
  13. 308GTB1978

    308GTB1978 Karting

    Dec 21, 2013
    114
    France
    No one has an idea ?

    Why the one way valve works fine for some and not for others ?
     
  14. TonyL

    TonyL F1 Rookie

    Sep 27, 2007
    3,811
    Norfolk - UK
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    Tony
    Not a good idea, in fact a very bad idea to fit a check valve on the expansion line to the tank, its there to take expanded water when it gets hot and let it back into the system when it cools down. Best to remove it.

    The smaller hose is for vacuum release when it cools back down again otherwise the water becomes vacuum locked in the expansion tank.

    If air is getting into the system it can be a few things but generally.

    1. Leaks, these can be minor that are almost undetectable as the water evaporates when hot. see 4. check all hose connections and look for corrosion on the joints
    2. Overfilled the expansion tank. (loss of water)
    3. Lack of inhibitor causing corrosion. Make sure it aluminium compatible. Hydrogen being produced.
    4. Air ingress from the water pump (positive side of pump)

    Tony
     
  15. BigTex

    BigTex Seven Time F1 World Champ
    Owner Rossa Subscribed

    Dec 6, 2002
    79,143
    Houston, Texas
    Full Name:
    Bubba
    +1.

    My car needs period bleeding, I think from air produced by water pump impeller cavitation.

    Other times the operation of the heater cores can drop water levels in the main saystem, so I avoid that, in colder climates you can't.

    the thing to do is assure the car is on an upward incline, on the systems that have only one bleed point.

    The later cars have a bleed fitting at the t stat housing, which can give you a better relust, otherwise repetitve bleeding at the front is the answer.
     
  16. ME308

    ME308 Formula 3

    Nov 5, 2003
    1,542
    Munich, Germany
    Full Name:
    Michael
    if all components of the cooling system are in good working order and the cooling system is properly filled from the start,
    there is no need to touch the system until the next change of the fluid ;)
     
  17. TonyL

    TonyL F1 Rookie

    Sep 27, 2007
    3,811
    Norfolk - UK
    Full Name:
    Tony
    Sorry meant to say negative side of pump.
     
  18. Steve King

    Steve King F1 Rookie

    Feb 15, 2001
    4,367
    NY
    I did the method on post 57 in the attached thread. It worked like a charm on my 77. I never had to bleed the system again after installing the valve on the radiator.
     
  19. rkljr

    rkljr Formula Junior

    May 16, 2011
    723
    South of Boston, MA
    Full Name:
    Richard
    Not sure why you would want a check valve and IMHO it is not a good idea. As noted, fluid needs to flow both ways.

    I also have a '79 and it is entirely stock with a couple minor and unrelated parts. As others have noted, if you have bled it multiple times from the radiator and the thermostat housing and you are continually getting air in the system, there is a leak somewhere.

    If it is bled properly, it should not over heat even on 95F plus days in traffic. Others have talked about leaks and I can imagine they are difficult to find. I know when I had all the hoses replaced five years ago, the amount of corrosion was scary. If they are original like mine where, you likely have the same issues. For a good reliable ride, I would replace them all.
     
  20. 308GTB1978

    308GTB1978 Karting

    Dec 21, 2013
    114
    France
    #70 308GTB1978, Dec 30, 2015
    Last edited: Dec 30, 2015
    Thanks for your answers.

    In fact I did a test with the check valve as some owners have good result with it.

    It is important to say that the bleed valve is in respect of the original way of circulation of the fluid (permit to go back to the expansion tank).
    I've done the test : when cold, as soon as the engine is started, the fluid starts to travel the check valve back to the expansion tank.

    Other important point, everything is new : fluid, hoses, radiator, water pump etc etc ... Bleeded several times !!

    The coolant circuit have been pressurized when cold with 1 bar : no problem, no leak !

    I have three ideas :

    - air entry by the water pump
    - cavitation from the water pump
    - air from the cooling tank 'aspirated' by the pump and then send to the front radiator : the air is trapped in the front radiator

    The last one seems to be the most likely but the question is : why so many cars are concerned but some never ??
     
  21. kerrari

    kerrari Two Time F1 World Champ
    Silver Subscribed

    Oct 22, 2004
    23,482
    Coolum Beach AUSTRALIA
    Full Name:
    Karen H.
    79 car and only time in over 13 years I've ever had an overheating problem was a failed thermostat. Temperature range where I drive would never be under 10deg C and not often over 35.
     
  22. 308GTB1978

    308GTB1978 Karting

    Dec 21, 2013
    114
    France
    I have no overheating problem ;-)
     
  23. TonyL

    TonyL F1 Rookie

    Sep 27, 2007
    3,811
    Norfolk - UK
    Full Name:
    Tony
    Do you have water loss?

    Do you have to top up the system after bleeding the air? Remember its a sealed system so anything additional can only be pulled in under suction

    Inhibitor correct?

    The check valve is not the answer
     
  24. 308GTB1978

    308GTB1978 Karting

    Dec 21, 2013
    114
    France
    #74 308GTB1978, Dec 31, 2015
    Last edited: Dec 31, 2015
    No water loss as far as I can see, never need to add water, the pressure test when cold is ok (see : http://nsa34.casimages.com/img/2014/07/06/140706075715439155.jpg) !

    The coolant liquid is the good one for aluminum gasoline engines !

    The fact is always : one run means : air from the tank is in the front radiator, the level in the tank is near the maximum, just need to open the bleed from the radiator : air is forced out then level in the tank goes back to its normal position !

    All owners that have the problem have ALL the same symptoms.

    Crazy yes ;-)
     
  25. Brian A

    Brian A F1 Rookie

    Dec 21, 2012
    3,079
    SanFrancisco BayArea
    Full Name:
    1983 US 308 GTS QV
    Cavitation is nasty stuff for pumps, but does not cause permanent air bubbles.
     

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