Coolant reservoir steams

[accordlove]

Just changed the thermostat and heater control valve that was leaking. I flushed the cooling system and refilled with fresh coolant. When my car gets up to temp (needle about half way) and only when the climate control knob is on cool, the coolant in the reservoir starts to steam and get hot. Anything i can check before i rule it out as a bad head gasket?

[Fleetw00d]

I'm assuming you see no oil in the coolant and no coolant in the oil? Had you been losing coolant prior to the flush and refill?

Put proper mix of coolant in? Did you bleed the system (bleeder screw at the top of the thermostat housing)? I've found that raising the front of the car (12 inches or more if you can) allows you to get the system pretty full without having to run the engine. Fill the radiator, squeeze the upper hose to help push any air in it to the radiator. Once you have the radiator good and full, crack the bleeder until you get a solid stream of coolant trickling out. Close the bleeder, refill the radiator to the top, then install the cap.

If it was the head gasket leaking, it would leak all the time regardless of the position of the climate control. With the temperature on high (assuming the fan is on), the heater is removing heat from the coolant, but the thermostat should compensate by allowing a little less coolant to go to the radiator to maintain the system temperature.

If you didn't bleed the coolant, you may just be experiencing whatever air is in the system expanding as the system heats up and being pushed into the overflow tank.

[accordlove]

ok my rad is full of new 50/50 coolant, i made sure all old coolant and water was out of the system and had it raised like you said. so basically all i need to do is go raise the car back up and open that bleeder valve?

edit: coolant in oil.... No the oil is fine, under the cap and the dipstick is fresh, i changed the oil about a month ago, it was black but not milky. the steaming reservoir just started happening after the heater control valve started leaking.

[Bunta]

How old is your radiator cap? If it is pushing hot coolant into the reservoir it may be due that. You have your cap tested to make sure it hold pressure.

[accordlove]

How old is your radiator cap? If it is pushing hot coolant into the reservoir it may be due that. You have your cap tested to make sure it hold pressure.

do i boil it in a pot like the thermostat test?

it probably old af, i just bought this car for $350 it didnt even start lol has over 300k miles

[accordlove]

If it weren't for this site, my car would've been in the junk yard, previous owner was about to scrap it.

thanks guys

[Bunta]

do i boil it in a pot like the thermostat test?

it probably old af, i just bought this car for $350 it didnt even start lol has over 300k miles

no, there is a pump that you can screw the cap to the end of that you would push the handle down to develop pressure against the cap. It has a gauge on it that shows the pressure developed and you can tell if it holds pressure or bleeds it off. I'm sure Honda could check it for cheap enough or possibly one of the car part stores may be able to check. I'd hate for you to spend money needlessly though so test everything before spending money.

[Fleetw00d]

do i boil it in a pot like the thermostat test?

it probably old af, i just bought this car for $350 it didnt even start lol has over 300k miles

Good catch Bunta. The cap works on pressure, not temperature. I think most local auto shops (maybe even auto part stores) will have a cap pressure checker; they would probably do it free. The cap is supposed to keep about 15 psi pressure in the cooling system; this helps raise the boiling temperature of the coolant.

[Bunta]

something like this....

[accordlove]

oreillys has a rad cap with a temp gauge on it, i think i might get it tomorrow. if i need one.