Having a little trouble diagnosing a heating problem in my 4th gen H23a.
Here's a quick rundown:
*Temp gauge shows that car starts to overheat when it sits stationary for more than say 20 secs (traffic lights etc) but goes back to normal once the car gets moving at a decent pace. (ie when enough air starts blowing through the engine bay)
*Radiator fans are not coming on at all.
*BOTH fans come on when A/C is turned on.
*Even with the AC on (ie both fans running) car will still overheat at stationary.
*Car has just had a major rebuild- although the problem was present BEFORE the rebuild. (and probably caused the problem that lead me to have to fix the car)
*Rad has been crack and pressure tested, cleaned, flushed and bled.
*Thermostat has been replaced with a new one. (mechanic was dodgy though, so can't rule out that its not thermostat.)

Allright thats about all I can think of.
My thoughts are that it is the thermostat. It seems to me that, regardless of wether the fan is coming on or not, if the AC turns both fans on and the engine STILL isn't getting cooled, then the cooled water musn't be getting into the engine =themostat.

I really need some ideas here- I don't know the heating system well at all...

 

does any coolant leak off the backside of the engine or anything?
if so it could also be the waterpump//

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by "Arch-Angel" &raquo;</TD></TR><TR><TD CLASS="quote">Temp gauge shows that car starts to overheat when it sits stationary for more than say 20 secs (traffic lights etc) but goes back to normal once the car gets moving at a decent pace. (ie when enough air starts blowing through the engine bay)</TD></TR></TABLE>
I had a similar problem one year ago... All I had to do was to replace a nipple on the radiator...

Greetings! Dayne

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Chase &raquo;</TD></TR><TR><TD CLASS="quote">After you know the car is warmed up, grab onto the upper rad hose. It should be hot (not just warm or cool). If its not hot then your thermostat is stuck closed and likely is your problem. </TD></TR></TABLE>

Hose is pretty damn hot...

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Chase &raquo;</TD></TR><TR><TD CLASS="quote">All I had to do was to replace a nipple on the radiator... </TD></TR></TABLE>

Nipple? What part do you mean? Where abouts is it?

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by specialedition &raquo;</TD></TR><TR><TD CLASS="quote">does any coolant leak off the backside of the engine or anything?
if so it could also be the waterpump//</TD></TR></TABLE>

No visible coolant leak, and no white smoke.

What about the radiator fans? Any ideas on them?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Arch-Angel &raquo;</TD></TR><TR><TD CLASS="quote">Nipple? What part do you mean? Where abouts is it?</TD></TR></TABLE>
I mean a plug at the top of the radiator

 

Thermostat.

 

I agree with the waterpump, although I'd certainly try to rule everything else out first due to it's location. I'm thinking your flow may be low. If it was the thermostat, it wouldn't cool down when you are moving because it wouldn't allow anything into the radiator.

You can try taking out your thermostat temporarily. That done, fill it up and back your top hose off the radiator. Start the car and see how much water flows out of that hose. If it looks good, put it back on, refill, and take a test drive with no thermostat. If it's all good then, then the problem is the thermostat. If not, it's something else.

Also, make sure you bleed out the air from the system at the top of the thermostat housing. That pocket of air can cause pure ******* havoc. I found that out the hard way when I had my CBR600 and didn't take care to get out all the air.

 

OK, thanks for all the help guys, but it seems as if the mystery of the overheating prelude has taken another twist...
I've now worked out that the car mainly overheats when the A/C is on! No kidding, when I tested it, I was cruising along the freeway, car was normal temp (by the gauge anyway) and I flicked the A/C on. Within 20 secs, the temp gauge read 2 bars above halfway. Then pretty much as soon as I turned the A/C off, it started to drop back to normal. Funny think is that the A/C doesn't actually work- fans come on, but it doesn't get very cold.
So now I'm starting to think that it is the gauge that playing up. And to further confirm my suspicions- After i arrived home from this freeway drive (about an hour of steady driving), I'm parking my car, and within about a min of idling, the gauge creeps up again... this time all the way to the red bar! I immediately turn off the engine (don't wanna cook the thing), thinking that my best option is just to lift the hood and let the heat dissapate that way. I turn the key back to the accessories position and the gauge has dropped back to half way again!!!?!?

So, yes, i'm thinking the gauge has issues... problem is that if i'm wrong then i am going to be doing some serious harm to the car. I was thinking of buying some aftermarket gauges (like oil and water temp) just to compare the reading they give me to the car's gauge.

Once again, I'm looking for suggestions.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by BrokeLude &raquo;</TD></TR><TR><TD CLASS="quote">If it was the thermostat, it wouldn't cool down when you are moving because it wouldn't allow anything into the radiator.</TD></TR></TABLE>
yeah but I think the car was cooling down just by the amount of air flowing in under the hood.

 

mine was doing that, i replaced the thermostat.....i think its to high tho because it still goes up 1 bar sometimes even 2 then drops. Also my temp gauge reads hot faster when my headlights are on.......wtf?

 

try another sensor to see if it works, its only a couple of bucks

 

i read in a post not long ago that someone had problems with the temp gauge and overheating and it ended up being the engine ground wires. May wanna make sure they are all good and not corroded too

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by PrettyLude &raquo;</TD></TR><TR><TD CLASS="quote">try another sensor to see if it works, its only a couple of bucks</TD></TR></TABLE>
you mean like an aftermarket gauge? would oil temp or water temp be best?

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Sabbotage &raquo;</TD></TR><TR><TD CLASS="quote">i read in a post not long ago that someone had problems with the temp gauge and overheating and it ended up being the engine ground wires. May wanna make sure they are all good and not corroded too </TD></TR></TABLE>
good point, I'll check it out

 

i had the same problem. Then i flushed and refilled my rad all the way and bled everything and that was that. Did you replace the waterpump with your fresh rebuild? I hate mechanics. I do everything on my car now.