95 Accord runs hot on freeway

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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.
Ive taken it to 2 mechanics and one says its 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. Im really confused here. Any help would be greatly appreciated.
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pinkfloyd wrote:

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.
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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 failure.
If either jim's test or mine indicate trouble, shops can do chemical tests for hydrocarbons in the coolant to confirm the problem.
Mike
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Thank you for the great and very helpful replies. I am going to try the things recommended here. Also, the mechanic that thinks its 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 coolant?
"Michael Pardee" wrote:
> > >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. > > > > > 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 > failure. > > If either jim's test or mine indicate trouble, shops can do > chemical tests > for hydrocarbons in the coolant to confirm the problem. > > Mike
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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" wrote: > 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 coolant?
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Then your rad is internally blocked (or the fins have fallen off).
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First put a new Honda thermostat in it.Not some aftermarket TS,a real Honda TS.
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It's not his thermostat. I'm sure of that.
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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.
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wrote in message

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.
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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.
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wrote in

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.
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But it can't compensate for a thermostat that's stuck shut!
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wrote in

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. ;-)
Mike
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"Michael Pardee" wrote:

I apologize, but I dont understand about setting the controls for the Heart of the Sun and still stay cool.
Thanks for all your help. It is greatly appreciated.
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"Set the Controls for the Heart of the Sun" is from 'Umma Gumma' - my fave Pink Floyd album ;-)
Mike
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Jim Yanik wrote: <snip>

pump can't wear in a way that reduces flow - there's no parts that touch.
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is the impeller plastic or metal? IMO,plastic can degrade,even immersed in the coolant.
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Jim Yanik wrote:

degradation wear, but yes, that's possible.
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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.
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