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Hey guys, I have a 1999 Honda Prelude Type SH. I recently replaced the coolant (made my own 50/50 mixture) a couple weeks ago. Haven’t really strained it since then except for yesterday. I smell a weird pungent smell so I pop the hood and there is fresh and dried coolant drops all over the bay.

I take it home, spray down with a hose (covered airbox and alternator with plastic bags) and pat dry all I can reach. Overfill reservoir is nearly empty and the coolant in the radiator is low (can’t see the level from the opening).

I start it and let it idle as I fill up the radiator. I filled up the overfill reservoir about halfway prior to this. I should probably also note that the little hose leading down into the reservoir had slid down the little nozzle a bit (this could be that this is where the coolant was escaping from) so I fixed that first as well.

While it was idling it started to (not immediately -- after a couple minutes) rev up to 2K then down to 1K and then back up again repeatedly. The engine sounded mad but she’s got 190K so I figured that was just a symptom of age. I turned it off without finishing topping off the coolant for fear of any serious or irreparable damage.

A couple things to note: when I filled up the coolant a couple weeks ago, I filled the reservoir up to the full marker I believe as well as filled the radiator up. It is not impossible that I filled past the “full” mark.
Any and all advice would be greatly appreciated. This is my first project and I am a little green behind the ears but eager to learn. Thanks in advance!

My plans are to air bleed the coolant and refill it then test the heat to see if the thermostat is okay. (temp gauge seems to be acting normally, just wanna be sure). Mainly wondering if anyone knows about the weird revving issue and if it could have anything to do with air in the system, or if it has to do with something else.
 

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okay so the idling issue is either your idle air control valve or your fast idle valve. i changed my idle air control valve and tightened my fast idle valve because i had the same problem. but both hold coolant so if your low then you more than likely just need to bleed the system to get everything filled and flowing, and of course especially getting that air out. but just keep topping it off as she idling and put heaters on full crank and it’s easy bro
 

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I just replaced a small radiator hose that was on my fast idle valve & I'll bet that either the idle air control or fast idle valve radiator hose is shot. There is one small hose for each valve

I just realized this is from half a year ago lol. Disregard! I hope you figured it out
 
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