So I did some searching, and came up with about 150 posts\threads regarding bleeding the coolant system, all with slightly different or incomplete instructions. I have a 91 Si with a DOHC ZC swap. I had to replace my thermostat, and I believe there is some air in the system. I've read to run the car with the radiator cap off until it stops burping air, and I've read to loosen the bleeder screw with the car cold and off, then fill the radiator until it comes out the bleeder steadily, but it seems to me you'd need the water pump engaged to circulate it from the radiator to the bleeder... Can someone let me know the correct way to accomplish this! If someone has a decent answer I also suggest we put this thread in the Civic\CRX FAQ for future reference

 

Need an answer quick

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Doh! &raquo;</TD></TR><TR><TD CLASS="quote">loosen the bleeder screw with the car cold and off, then fill the radiator until it comes out the bleeder steadily</TD></TR></TABLE>exactly how i do it and have NEVER had a problem

 

huh? i would never bleed it that way^^^
heres a good way of doing it .
run the car without the rad cap on. your gonna have to wait a wile because you have to make sure your fans come on so you know for sure your Tstat is open. then you wait till it stops burping.
now, the bleeder is the highest part of the cooling system and you should really finish bleeding from there to get the last bit of air out. crack it and then turn it till coolant will start slowly coming out. keep it open wile the car is running and is hot. then close it when bubbles stop coming out.

make sure car is cold when you start it with no rad cap. and turn the temp in the car to hot.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by janz3n &raquo;</TD></TR><TR><TD CLASS="quote">huh? i would never bleed it that way^^^
heres a good way of doing it .
run the car without the rad cap on. your gonna have to wait a wile because you have to make sure your fans come on so you know for sure your Tstat is open. then you wait till it stops burping.
now, the bleeder is the highest part of the cooling system and you should really finish bleeding from there to get the last bit of air out. crack it and then turn it till coolant will start slowly coming out. keep it open wile the car is running and is hot. then close it when bubbles stop coming out.

make sure car is cold when you start it with no rad cap. and turn the temp in the car to hot.
</TD></TR></TABLE>

This is the best way. As stated, make sure to turn the heater all the way hot in the car (doesn't have to be blowing BTW) to make sure the coolant in the heater core is flowing as well.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by janz3n &raquo;</TD></TR><TR><TD CLASS="quote">
heres a good way of doing it .

now, the bleeder is the highest part of the cooling system and you should really finish bleeding from there to get the last bit of air out
</TD></TR></TABLE>

I just park on a slight hill or jack the front of the car up so the rad cap is the highest part in the cooling system. never had a problem that way

 

i guess you could do it that way.. but some people dont have a jack. im kinda suprised no one said i was wrong about the bleeding process. that i left something out. but thats the way i did it when i did my mpfi swap and iv had no problems .

 

ive heard from pros a good way to keep that air bubble out is to drill a
little tiny hole like 1/16 or even smaller. And that will prevent it.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by russianswty &raquo;</TD></TR><TR><TD CLASS="quote">ive heard from pros a good way to keep that air bubble out is to drill a
little tiny hole like 1/16 or even smaller. And that will prevent it.
</TD></TR></TABLE>

[/sarcasm] I hope.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by BlueCrxNC &raquo;</TD></TR><TR><TD CLASS="quote">

[/sarcasm] I hope. </TD></TR></TABLE>

He is probably speaking of drilling a tiny hole in the thermostat. I have heard this with other vehicles but not on a Honda.

 

make sure u have the t-stat on the right way....u'd be surprised how many people put it in wrong.

 

you cant put in in the wrong way. the housing wont fit around it

 

Just open the radiator cap, and leave it off. Air will rise to the highest point in the system.

 

i didnt think the rad was the highest point. wouldnt the iacv be the highest point? i could jack it up i guess. im having some nasty issues. i ran a hose small hose from the bleed valve on a b16 head which is right behind the dizzy. the hose went to a small can that the coolant went to. when the can got a bit of coolant in it i put the hose to the bottom. when i did that is was like a motor boat. there were so many bubbles coming out of it. i did this for like 15 minutes and the bubbles never stopped. whats going on?

 

Ok, it might not be highest point but the bubbles will work there way out of the cap. Or you can use the bleeder, I rarely ever have to.

 

ok when i use the bleeder valve should i have the rad cap on or off? i had it on and it was a nice steady flow but then about 2 minutes later a bunch of air came out and bubbled like crazy. im still trying to understand how this whole cooling system works. does the rad actually suck out some of the coolant fromthe overflow or what? because sometimes its empty

 

leave the rad cap off and while the motor is running keep adding water till its full.

 

i think im just going to start from scratch again and drain all my coolant out. what would happen if i left the rad cap on and bled that valve?

 

at the honda dealer i worked at, if the car has a bleeder valve use the bleeder valve. no problems. if there is no bleeder valve, we use a no spill funnel. take off the radiator cap with the car cold, drain coolant, fill car with coolant, installed no spill funnel, let car run to operating temp. fans should cycle twice, then remove funnel, and poor extra coolant into overfloow bottle. no spill funnels are like 35 bucks from matco, snapon, and cornwell sell them aswell. worth the money.

 

ok well i have been bleeding the system for the last hour and there were alot of air bubbles. all i did is jack up the front of the car so i made sure the rad cap was at the highest point and then drained all my coolant and then poured it back in with the car running. i watched it for about 15 minutes with no air bubbles so i put the cap on and then within 1 minute the car overheats. it got about 3/4 of the way up. both of my fans were running and it couldnt even cool it down. so, im thinking its a rad cap now. could this be?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by the.hamburglar &raquo;</TD></TR><TR><TD CLASS="quote">ok well i have been bleeding the system for the last hour and there were alot of air bubbles. all i did is jack up the front of the car so i made sure the rad cap was at the highest point and then drained all my coolant and then poured it back in with the car running. i watched it for about 15 minutes with no air bubbles so i put the cap on and then within 1 minute the car overheats. it got about 3/4 of the way up. both of my fans were running and it couldnt even cool it down. so, im thinking its a rad cap now. could this be?</TD></TR></TABLE>

I don't think its the rad cap, if its not overheating with it off, then it should not be the cap. The radiator cap keeps pressure in the system, when pressure is applied to the coolant system the boiling point goes up.

When you did the swap did you replace the water pump, or the thermostat ?

 

might need to replace t-stat

 

t stat is brand new, water pump is newer. there is a sound coming from the timing belt area. a new rad cap is my first option and then a new water pump is the second. the pump is not leaking anything but could air be getting in through the seals or something?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by the.hamburglar &raquo;</TD></TR><TR><TD CLASS="quote">t stat is brand new, water pump is newer. there is a sound coming from the timing belt area. a new rad cap is my first option and then a new water pump is the second. the pump is not leaking anything but could air be getting in through the seals or something? </TD></TR></TABLE>

Whats the sound, is the water pump leaking ? When the bearing fails, its design so you start leaking antifreeze

 

what are the things that couild be wrong with the water pump? im guessing the seals might be gone but then it would be leaking coolant right? other than that the last thing would be the impellers. there are only two things right? well im prettyu sure the impellers are good because the water pump is almost new.

other than that one more thing i should add is that with the rad cap off and the car is idleing i can definatly see flow which is good. however when i rev it to about 2000 or so the flow gets faster, as it should. but then when i let it back down to 750 idle, it will surge between 1000 and 1200 for about 3 minutes and then it will steady itself out. about 30 seconds after it surges i can see air bubbles coming out the top of the rad so maybe its not the cap. maybe i do have an air leak somewhere else. the only places i can think of is the water pump, iacv, fitv. would this be possible?