mysterious intermittent coolant leak on a QV | FerrariChat
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mysterious intermittent coolant leak on a QV

Discussion in 'Technical Q&A' started by alfa-guy, May 31, 2005.

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  1. alfa-guy

    alfa-guy Rookie

    Jan 27, 2004
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    #1 alfa-guy, May 31, 2005
    This has got me puzzled.

    A couple of weeks ago, parked the car ('85 308QV) in the garage after a short drive. Noticed a little while later a large puddle of coolant under the engine, towards the passenger side of the car. So, this did not appear to be from the overflow.

    Checked the level, seemed ok, pressure tested the system and coould not find any leaks.

    Since then I've driven the car several hundred miles both around town and on a few trips ranging from 50 to 150 miles without a relapse and no further problems until today.

    Drove the car a short distance this morning (far enough to get everything up to temperature) and made a few stops. When I was walking back to the car at the last stop I noticed some smoke from the rear of the car. Coolant was dripping from somewhere near the front (passenger side) of the engine, but could not really tell where it was coming from.

    Drove the remaining 2 miles or so home, parked the car in the driveway, no leaks, and no puddles. Pressure tested the system again shortly thereafter, and again no leaks found.

    This is really disconcerting and does not make any sense. If it were a hose, or a connection it would do it all the time. Car does not run hot or overheat at all.

    Jacked the car up and got underneath it. Cannot find any evidence of a leak. Weep holes in the water pump do not look like anything has been coming out of them. I rebuilt the water pump about 5 years and 22,000 miles ago.

    I've never known a water pump to leak occasionally either.

    Any ideas?

    TIA,

    Jeff
     
  2. f355spider

    f355spider F1 World Champ
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    #2 f355spider, May 31, 2005
    Check the hoses around the vertical aluminum pipe to the right front of the engine, near the fire wall (make be cracked or lose hose clamp). On the 328, there is a known interference (1986 to mid 1988 models) where the air cleaner will rub against the pipe, wearing a pin hole in it, causing minor leaks. Check that too. May require removal of the air box to get a good look...or if up on stands, look up from below.
     
  3. alfa-guy

    alfa-guy Rookie

    Jan 27, 2004
    42
    #3 alfa-guy, May 31, 2005
    it does not appear to be anything that simple. On the 308 it is easy to install the coolant pipe too close to the alternator pulley which would be similar to what you are referring to.

    Unfortunately, anything like that ... a loose hose clamp, small pinhole in a hose, or tube etc would appear as a leak during a pressure test.

    Both times that I've pressure tested it after this has happened reveal no leaks and it holds pressure. Don't see how a leaking hose, clamp, or connection could be intermittent?

    Thanks,

    Jeff
     
  4. f355spider

    f355spider F1 World Champ
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    #4 f355spider, May 31, 2005
    Of course they can be intermittent...don't ignore the obvious. ;)
     
  5. Dr Tommy Cosgrove

    Dr Tommy Cosgrove Three Time F1 World Champ
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    #5 Dr Tommy Cosgrove, May 31, 2005
    I blew out that little 3 inch hose that is under the intake manifold on that side once before. Easy to fix AFTER the intake is off.
     
  6. GrigioGuy

    GrigioGuy Splenda Daddy
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    #6 GrigioGuy, May 31, 2005
  7. Ken

    Ken F1 World Champ

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    #7 Ken, May 31, 2005
    A dumb question or two:

    When you pressure tested it, does the pressure go throughout the entire cooling system? In my lotus, it doesn't due to the swirl pot. (I don't know how a Mondial cooling system works).

    Did you have the heater on when you tested it? Was it on when it leaked?

    Ken
     
  8. robert_c

    robert_c F1 Rookie

    May 12, 2005
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    #8 robert_c, May 31, 2005
    im talking out of my ass so be forewarned.

    Could it be the coolant overflow tank has a leak. when the car is hot the overflow gets full and leaks, as it cools off, the overflow gets sucked back into the radiator?

    again, im talking out of my ass.

    My friend had a mysterious leak once, by his feet, and after the dealer replaced the heater plumbing he discovered a leaking bottle of coolant under his seat.
    DOH!!
     
  9. tuttebenne

    tuttebenne F1 Rookie

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    #9 tuttebenne, May 31, 2005
    What pressure were you testing at?
     
  10. alfa-guy

    alfa-guy Rookie

    Jan 27, 2004
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    #10 alfa-guy, May 31, 2005
    For all the suggestions. This is really unnerving.

    The first time this happened I chalked it up to the alignment of the planets or some other such sillieness. After it happened today for the second time, I'm a little more worried that something will let go at the most inconvenient time and place :)

    Drove the car a little bit this afternoon. No leaks.

    When it does leak, this is not a small or occasional drip, there is a pretty good size (alarming) puddle unerneath it.

    The weep holes in the water pump look clean as there does not appear to be any evidence of leaks from them. The leak does seem to be somewhere in the vicnity of the water pump or up higher under the intake.

    I know all my hoses are on borrowed time, but am (was?) hoping that they would last through this season as I'm planning to replace them over the winter.

    Anyone have any idea as to how long water pumps usually last in these cars? I know that the bearings tend to seize when the cars are not used regularly. This happened shortly after I bought mine, but since then the car has seen pretty regular use.

    Wondering if it is time to rebuild the water pump again after five years and 22,000 or so miles?

    Thanks,

    Jeff
     
  11. f355spider

    f355spider F1 World Champ
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    #11 f355spider, May 31, 2005
    Quick diagnosis. Next time you see the puddle...immediately shut down, and stick your fingers under the weep holes of the water pump, to see if it recently leaked (likely). Also, immediately put your hand under the intake manifold housing and feel around the hoses on top...feel where the hose joins, around the seams...I traced a leak or two there after new hoses were installed...just a matter of tightening the clamps. If your hoses are older than 10 years, plan on changing them all out...you are on borrowed time.


    Dave
     
  12. Gary48

    Gary48 Guest

    Dec 30, 2003
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    #12 Gary48, May 31, 2005
    Everybody pretty much covered everything but one problem to consider especially on a short drive Would be a balky or intermittently stuck thermostat which could cause a coolant pressure spike and actually spike higher on shutting off the motor (still absorbing heat from the hot motor) I have seen this happen once and then not do it again. It doesn't loose a lot but will make a puddle of about a foot and a half in diameter. Worth a check.

    Gary
     
  13. tuttebenne

    tuttebenne F1 Rookie

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    #13 tuttebenne, May 31, 2005
    Water pumps should last ten years if the car is used occasionally. Mine is going on 18 years.
     
  14. PhilB

    PhilB Formula 3
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    #14 PhilB, May 31, 2005
    It would seem to me that the leak is in the heater hose. In front of the passenger seat, underneath the car, is a sheet metal pan that when removed, will reveal the area underneath the battery. This is typically where I drain coolant from. The pipes in this area transition from the ones molded into the bottom of the car from the negine compartment, the the rigid pipes leading upto the raditator. The transition is done with regular (soft) coolant hose connections like those that connect the radiator to the rigid pipes. The rigid pipes in this are have a "T" fitting to enable coolant to flow to the passenger compartment heater when the heater is turned on.

    As your problem happens only occasionally, it could be a heater hose that is failing.

    My $.02.

    Good luck,
    Phil
     
  15. Dr Tommy Cosgrove

    Dr Tommy Cosgrove Three Time F1 World Champ
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    #15 Dr Tommy Cosgrove, May 31, 2005
    I really want to say it's the water pump
     
  16. geekstreet

    geekstreet Karting

    Feb 7, 2005
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    #16 geekstreet, May 31, 2005
    Some thoughts

    Up the testing pressure & hold longer. Old caps were rated at 0.9bar, newer replacements are 1.1bar. Test while still hot if possible, so that hoses are softer & weaker. As mentioned, max pressure is often after shutdown. Make sure you've got no air when testing, otherwise you may not see the leak.

    Some hoses go "internally", allowing leakage into the lining between core & outer skin. Feel/squeeze them along length (esp near ends) to see if spongy. Possibly one is leaking into the lining where you can't see it until it is "full".
     

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