honda accord overheat

[LHoang]

i have a 1997 honda accord lx 4 cyl. I have an “overheat” on the interstate but not while im driving around town. It doesn’t overheat to the point to where i have to pull over but the temperature gauge goes above what it normally sits at. It will sit usually about the half way mark for awhile and occasionally it will just drop. I have noticed that i can switch on the heat for a just one second and it will drop immediatly. I’ve been driving this car for awhile and i know this isnt normal. In the past ive replaced the radiator, both cooling fans, timing belt and water pump. I went out and bought a new thermostat for it thinking that is the problem. Any insight on my problem given the symptoms?

Topic

[college man]

sounds like air in the cooling system.
is the cooling system full? are the cooling fans
coming on? here are some videos to help.

[LHoang]

coolant is all the way full. the fans are working fine as well. even driving down the interstate at 80mph it still does it. so thats why i dont think it is a cooling fan issue.

[college man]

Then follow the bleeding procedure video.

[dreamer2355]

+1.

Those spill free funnels work great.

[LHoang]

alright. i bled the cooling system and their were a fair amount of air bubbles that came up. Im going to test drive it today and see if that did the trick. also i bought a block tester just to expand my tool collection and noticed that when i pour in the fluid to the tester, it leaks fluid from the tip. not alot but it drips out. is this normal or is this tool broke?

[EricTheCarGuy]

What you describe are the classic symptoms of air in the cooling system. ANYTIME you open the cooling system for service you must bleed the air from the system and by the sound of it you’ve done a fair amount of work to the cooling system recently. Keep us posted.

[LHoang]

ok. ive bled all the air out of the cooling system and it still does the same thing. I was sitting at idle after a long drive and i noticed it started to do the same thing. I put it in neutral and revved the engine to 2 grand and i noticed it started to go down. what could that be

[dreamer2355]

You probably still have an air pocket.

I would invest in one of those spill free funnels.

[Levin]

Have you confirmed that both fans do come on when the car reaches about 96C? I know you said you’ve replaced them but replaced doesn’t always mean much. With the car running turn on the A/C and turn the fan dial to on. Both fans should be spinning…if theyre not the fans are faulty.

Have you checked the radiator pressure cap? Does it still function and has all of its sealing o-rings inside. If you squeeze it with your thumb does the valve move in/out?

Park the car on an incline with the front somewhat higher than the rear. Once cold open the radiator cap and add coolant until you see a steady stream coming out of the bleeder screw. Once this happens close the bleeder screw. With the radiator cap off and now radiator fully topped up, turn the car on and run it at a fast idle(1500-2000rpm) with the temp gauge all the way to hot and fan off. If you start seeing the fluid level go down as some small bubbles appear top it up. Make sure you always keep it topped up to the max. This is where a spill free funnel helps as you can easily overfill the funnel and let it take in what it needs. As the car is running give squeezes to both upper/lower rad hoses. When you squeeze you’ll either see bubbles or fluid level will just increase. Don’t worry if some spills over the radiator and overflows…you can easily clean it with some water. Let the car run with the radiator cap off and by topping up the radiator continuously until both fans turn on (should take about 10 minutes). Once both fans turn on and no more bubbles appear place the radiator cap on the radiator and make sure your overflow bottle is filled up to the correct level/line.

If the fans do not come on, you’ve got an issue with the fan switch possibly.

[college man]

do you have good heat in the car or does it come and go?
if the heat comes and goes hot then cold then you need to
repeat the bleeding procedure.did you replace the rad cap?

[LHoang]

Alright. Ill bleed the system again. Ill have to get one of those spill free funnels and do it to make it easier. I have great heat. Its always hot.

[twiggy]

Is it possible that you are getting a false indication of overheat?

[Pat]

i guess i will throw my 2 cents in here as well. Make sure your AC/Heater is OFF when you are watching for your fans to function, as mentioned before after 10ish mins or so they should both come on. That being said. If both do not come on you may have a bad temp relay to your fan. if you turn on the AC/HEAT on a lot of autos it will switch another relay that is a direct one that instantly turns the fan on and cools down your ride. I hope this helped out some. “oh just cause im curious, does it seem like it is taking longer than normal to warm up around town” if so it could be the thermostat stuck open. But from the sounds of it “the heater turning on cooling it instantly” could just be the bad relay connected to the thermal portion.

Hope this helps out. Let us know 🙂

[LHoang]

Both cooling fans are working as they should. I’m pretty sure its not a false indication of overheat.

[LHoang]

im going to bleed the cooling system again, but could it be a possibility that i have blocked passages in my cooling system. im guilty of not using distilled water when i mix my coolant. i used plain tap water. also could it also be the water pump not working right? hence when i rev my engine it cools it down?

[Author]

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