95 Accord runs hot on freeway

Discussion in 'Accord' started by pinkfloyd, Jan 17, 2007.

  1. pinkfloyd

    pinkfloyd Guest

    I have a 95 Accord which starts to run hot after about 15 to 20
    minutes of driving on the freeway. It runs at normal temperature on
    surface streets. I know for sure that the fans are working properly.

    I’ve taken it to 2 mechanics and one says it’s the main fan motor and
    possibly the thermostat. The other mechanic thinks the radiator needs
    to be replaced due to a clog, and if not that, then it is most likely
    the head gasket leaking. I’m really confused here. Any help would be
    greatly appreciated.
    pinkfloyd, Jan 17, 2007
  2. pinkfloyd

    jim beam Guest

    take it for a run on the freeway. when it's hot, open the hood and look
    in the coolant expansion bottle. if you see bubbles, it's head gasket.
    if not, you can get it tested to be sure. if it's not head, go for
    thermostat and radiator, in that order. but before all that, make sure
    coolant level is ok - both in the radiator and the expansion bottle.
    jim beam, Jan 17, 2007
  3. Jim beam's advice is solid. I'd add that I suspect the radiator more than
    the thermostat because the heat builds up, but that assumes it isn't the
    head gasket.

    My own head gasket test is more sensitive but has the disadvantage that the
    leak may not be as obvious when cold. I test with a cold engine by removing
    the radiator cap and starting the engine. I pinch off the overflow tube and
    put the palm of my hand over the radiator opening for a few seconds.
    Steadily rising pressure or (worse) pulsations indicate a head gasket

    If either jim's test or mine indicate trouble, shops can do chemical tests
    for hydrocarbons in the coolant to confirm the problem.

    Michael Pardee, Jan 17, 2007
  4. pinkfloyd

    Tegger Guest

    If it runs fine on city street but not on the highway, it's most likely a
    clogged rad.

    A test: Next time it starts to overheat, turn the car's interior heater on
    full-hot, along with the fan on full-blast. Does this make the needle go
    down? If so, the rad isn't cooling properly.

    One thing to check is the fins at the bottom of the rad. If they corrode
    and turn to dust, the rad will be unable to shed heat efficiently.
    Tegger, Jan 17, 2007
  5. pinkfloyd

    pinkfloyd Guest

    Thank you for the great and very helpful replies. I am going to try
    the things recommended here. Also, the mechanic that thinks it’s the
    radiator, says that since the radiator is plastic, it needs to be
    replaced. It cannot be flushed. Is this correct?

    Since I have never had to do so, what would be the best place to start
    to find a shop that can do the chemical test for hydrocarbons in the
    pinkfloyd, Jan 17, 2007
  6. pinkfloyd

    pinkfloyd Guest

    Today I checked every recommendation posted.

    First I tried the cold method to check for possibility of bad head
    gasket. I pinched the reservoir hose, and placed my palm on the
    radiator opening. I did not feel any pulsating.

    Second, after a long drive on the freeway, when I stopped, I checked
    the reservoir, and there were no bubbles.

    Third, while driving on the freeway back home, when the car started to
    heat up, I turned on the heater full blast, and the temp cooled down
    right away.
    pinkfloyd, Jan 17, 2007
  7. pinkfloyd

    Tegger Guest

    Then your rad is internally blocked (or the fins have fallen off).
    Tegger, Jan 17, 2007
  8. pinkfloyd

    Jim Yanik Guest

    First put a new Honda thermostat in it.Not some aftermarket TS,a real Honda
    Jim Yanik, Jan 18, 2007
  9. pinkfloyd

    Tegger Guest

    It's not his thermostat. I'm sure of that.
    Tegger, Jan 18, 2007
  10. pinkfloyd

    DodgeDriver Guest


    Could be it is not opening all the way causing the temp to run hot. Using
    the heater as a mini radiator helps to lower the temp. Of course that would
    also work if the radiator was partially blocked.
    DodgeDriver, Jan 18, 2007
  11. pinkfloyd

    Jim Yanik Guest

    at that age,it's certainly suspect.
    Besides,just how much heat can the heater core dissipate,if it cools down
    his motor? Maybe he's got a worn water pump too.
    Jim Yanik, Jan 18, 2007
  12. pinkfloyd

    Tegger Guest

    Heater core flow is completely independent of the thermostat.

    Inlet flow is from the head's outlet end, and outlet flow is downstream of
    the thermostat. In other words, the same circulation feeds the heater core
    that occurs in the head/block due to the thermostat bypass when the
    thermostat is closed.
    Tegger, Jan 19, 2007
  13. pinkfloyd

    Tegger Guest

    There's certainly no harm (and lots of good!) in replacing the thermostat
    while the cooling system is in dry-dock, but the thermostat is not the OP's
    particular problem here. See my other post.

    The heater core is an amazingly efficient heat-dump device. You wouldn't
    think so due to its size, but it is. It can very easily compensate for a
    rad that can't shed as much heat as it was designed to.
    Tegger, Jan 19, 2007
  14. pinkfloyd

    jim beam Guest

    Jim Yanik wrote:
    pump can't wear in a way that reduces flow - there's no parts that touch.
    jim beam, Jan 19, 2007
  15. pinkfloyd

    Tegger Guest

    But it can't compensate for a thermostat that's stuck shut!
    Tegger, Jan 19, 2007
  16. That's my view. The thermostat is a good target because it's inexpensive and
    probably due for replacement while the coolant is drained, but the symptoms
    are pretty classic for a plugged radiator. The plastic tanks in the radiator
    are also plotting to crack, I'm sure.

    Remember, 'pinkfloyd' - OEM only on the thermostat and be sure the system is
    properly purged of air when the system is refilled with Honda premix (never
    add tap water).

    When you replace the radiator and thermostat, you can Set the Controls for
    the Heart of the Sun and still stay cool. ;-)

    Michael Pardee, Jan 19, 2007
  17. pinkfloyd

    Jim Yanik Guest

    is the impeller plastic or metal?
    IMO,plastic can degrade,even immersed in the coolant.
    Jim Yanik, Jan 19, 2007
  18. pinkfloyd

    jim beam Guest

    metal. you're right, it can corrode, but rarely does. i wouldn't call
    degradation wear, but yes, that's possible.
    jim beam, Jan 20, 2007
  19. pinkfloyd

    Jim Yanik Guest

    ISTR reading somewhere about a water pump impeller that had worn away.It
    didn't say whether the impeller was plastic or metal.

    also,I believe an old thermostat could open only part way,and pass -some-
    coolant,but not enough,explaining why the heater core could dump enough
    heat to keep the motor cool. I really do not believe a heater core can dump
    enough heat -by itself- to keep a motor cool. Otherwise,there would be no
    need for such a large radiator at the front.
    Jim Yanik, Jan 20, 2007
  20. pinkfloyd

    jim beam Guest

    Jim Yanik wrote:
    it depends. it's all a matter of the energy that can be transferred per
    degree of air temp difference. if the energy coming out of the coolant
    is less than that which can be dumped through the heater matrix, then it
    definitely can. you'd need to know the numbers to be sure.
    jim beam, Jan 20, 2007
Ask a Question

Want to reply to this thread or ask your own question?

You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.