98 civic overheating
 

Car is a 1998 honda civic ls swapped ex. My car will run at normal temp for a while, then will start overheating. I went to bleed my coolant system and there was a ton of air in it and the bubbles would not stop coming. There is a high picthed humming noise coming from my intake that sounds like air being sucked into a small hole. I found out its coming from my iacv on the back of my intake, because when I plug the hold on my throttle body for it, it stops making the noise. Could my coolant system be sucking in air from my iacv somehow?

Re: 98 hona civic overheating
 

Possibly a blown head gasket.

Re: 98 hona civic overheating
 

Check for white smoke coming out of your exhaust when the car is reving. If so, head gasket.

Kev

Re: 98 civic overheating
 

Also make sure your coolant lines are routed properly.

Re: 98 civic overheating
 

I just changed my headgasket last weekend. From what I can tell it's still good.

Re: 98 civic overheating
 

It also seems like my temp will jump around below normal operating temp when I hit bumps and stuff sometimes.

Re: 98 civic overheating
 

When I changed my head gasket, I noticed my intake manifold was really dirty, so I pulled it off and pulled my throttlebody and iacv off and sprayed it inside and out with brake cleaner and a pressure washer. Then after I got it reinstalled it started making that humming noise. It has never done it before then.

Re: 98 civic overheating
 

I also changed my thermostat while I had everything torn apart, because my old one was stuck closed.

Re: 98 civic overheating
 

two things, are you going off of your dash temp gauge and saying its overheating, or is the car doing something to make you believe it?
And did you try cleaning the IACV with carb cleaner, or did you pressure wash it too?

Re: 98 civic overheating
 

did you do it right?
new headbolts. (good idea)
torque it to the correct specs.
did you make the headbolts snug, then torque to 22lbs then to 53lbs doing it in a sequence?
if you don't do it right you can have a blown headgasket again.

Re: 98 civic overheating
 

Yeah I got arp's and torqued them all to spec. Usually when I've blown a head gasket my coolant gets really dirty from the oil and its really obvious but from what I can tell its still normal colored.

Re: 98 civic overheating
 

Well my dash gauge said it was overheating, so I pulled over and the engine didn't feel all that hot. So I thought my gauge was just going bad. But when I went to open the radiator cap coolant and steam went everywhere. And yeah I sprayed the inside of the iacv with carb cleaner.

Re: 98 civic overheating
 

I am not sure why someone would pressure wash the iacv and throttle body, carb or brake clean is plenty.

As for the head gasket, did you check to make sure it was not warped, did you have it machined, or straight edge and feeler gauge at least?

You might have a bad gauge, check the coolant temp sending unit.

Re: 98 civic overheating
 

I never said I pressure washed the IACV and throttle body... I said I pressure washed the intake manifold... And yes I straight edged the head and block.

Re: 98 civic overheating
 

Could it be possible that air is leaking in through my radiator cap? I have never changed it and it looks a little worn..

Re: 98 civic overheating
 

it does sound to me like you're overheating some, but i also think your temp gauge is going bad, from the fact that the needle falls when you hit a bump. (maybe losing power or signal for a second?)

did you try bleeding the cooling system? if there's air in it, you can bleed it out.

I'd say replace the cap anyway, if it looks worn enough for you to bring it up, it's a cheap enough fix to just go ahead and do.

Re: 98 civic overheating
 

Oh yeah, I'd check the hoses to the IACV too.

Re: 98 civic overheating
 

you said you have arp studs. you don't torque studs down. you tighten them til they "stretch" to the proper clearance.

Re: 98 civic overheating
 

Stupid q, how do you tighten studs? is there a place for wrench?

Re: 98 civic overheating
 

Not too sure what you mean by this. I installed them exactly as the instructions say, and I had a buddy help me that has experience rebuilding motors.

As for the overheating issue, I replaced the radiator cap and topped off the coolant, and so far so good.

I did notice that the coolant was abnormally low when I put the new cap on though. Any way I could lose coolant through a bad cap?

Re: 98 civic overheating
 

You could be losing it if it's steaming out from under the cap, yes.