Honda Accord EX 1998 (Sedan) V6 - After changing radiator, car's RPM too high (2500-3000) when idle

My old radiator cracked, so I changed it myself. I put the new one in and then bought 3 1-gal of 50/50 coolant/antifreeze. I added about 3/4 of a bottle, turned on the car, and it’s rpm was about 3000
I then followed the instructions on the manual for changing the coolant (ran it idle for 30 secs, added coolant, then let it run idle until fans turned on and off twice, added coolant to reservoir and up to neck of radiator, etc.) and its rpm is still around 2700. What can I do to fix this? I cannot move the car as chrome button on the speed lever is not letting be pressed. The car does not seem to overheat as the fans come on. I’ve let the car run to the point where the fans come on once, twice, 3 times and it does not overheat, but rpm is high and cannot move vehicle due to chrome button.

Thank you.

There’s air trapped in the cooling system.

If the air comes in contact with temp sensor for the engine computer, the computer thinks the engine is very cold and the RPM’s are high. That’s because the coolant temp sensor can’t read air temperature.

I go through this every time I drain the coolant in my Honda, or any other Honda.



How do I get the air out?

I’ve tried everything in the owner’s manual, from running the engine for 30 secs, then adding more coolant to the neck, to run again the engine with the cap on the radiator halfway closed (still clamped), then adding more coolant and filling up reservoir to max, etc. I do not know how to solve this problem… please guide me in the right direction. I will greatly appreciate it.
Thank you

If I drain the coolant on the Honda (it is a V6 engine… I’ve heard the V4 engine have a bleeding thingie, but not the V6), then I will have to re-add coolant… is it not the same thing as when I installed the new radiator and added the coolant? I guess all the new coolant will go to waste after draining it?

Do you mean the gear shift lever ? Changing the radiator should not have effected that .

This is the Gear Shift Button… the car is in P (Parking) and I guess since it’s got a high rpm, the system locked the chrome-colored button on the lever so that it cannot move. I don’t know… but this was fine and in the past, it has locked once or twice in a yearly basis and it fixes itself… in any case, my main concern is getting the idling rpm to normal level (I think it’s 1500) I don’t know what to do with respect to the high rpm. Please advise. Thank you.

What year is this Honda?


1998, Honda Accord EX (4-dr Sedan)

Look below the throttle body, and you’ll see the air bleed screw for the cooling system.


I found this on another website:
Tighten the bleed bolt as soon as coolant starts to run out in a steady stream.

bleed bolt location

Well, the problem is that there is bleeding valve for the Honda Accord EX 1998 V6, only for the V4
I went through these instructions (see attachment), but the car still has high rpm!

Then there may be a problem with the Idle Air Control valve.


Make sure the heater is turned on!

@Tester Is it possible the Idel Air Control Valve would have gone bad during the radiator replacement?
Also, I must say, the car is facing down on my driveway at around a 15-25 degree angle… I hope this does not affect anything.
@Barkydog, I also read I should turn the heater on and let the car idel for about 30 mins… I did this, but for only 6 mins… the idling/high RPM is too loud of a noise… should I continue to let it idle for 30 mins with heater on?

Okay, when I was searching that came up under a V6 search. Can’t trust everything online…lol
With it running if you can safely reach the upper radiator hose, try squeezing it to help expel excess air. I would also have the heater on.
I really don’t know if any of this will help.

It could also be some electrical component got wet during the replacement that is causing the high RPMs.

That makes it very difficult to purge any air out of the cooling system.

Is there any way to jack the front of the car up so it’s somewhat level?


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@Purebred I saw a video related to what you’re mentioning (squeezing the upper radiator hose, etc.)… here is my question, do I keep the radiator cap on or off when doing this? When do I squeeze the hose, while the car is off or immediately after turning it on? I noticed that if I have the cap off the radiator and the car is running, radiator will start overflowing… when I squeeze the upper hose, some may come off, but then the coolant will go back to the neck of radiator level and it seems to get some air in the process… I’m a bit confused about this process. I didn’t try it with the heater on.

I think @Tester pointed you in the right direction, you need an uphill slope not a downhill slope to get the air out, leave the heater on.

You must have heard “wrong” because Honda doesn’t make V4 engines.