I have a Y8 in my 1990 Si. This is the problem. A couple of days ago, at idle, my temp guage started rising, but when driving it would go back down. I opened my hood and noticed my overflow bottle was filling up and overflowing like mad. My fan was working though. The next day I drained my coolant (just the radiator) and filled it with new coolant. My car stopped overheating at idle, but my overflow bottle keeps filling up to the top and almost spewing out! I know it's not the head gasket because I have no oil in my coolant and vice versa. I'm thinking it's the thermostat...I don't know exactly though.

BTW: I changed my radiator cap and my lower radiator hose stays cold.

 

Could also be your friendly radiator cap.

 

Anybody else have any input on my problem?

 

one of 2 things...... water pump! or the thermostat...... the easist way to tell is to just take the thermostat out and see if this fixes the prob..... if it does then replace it...... if not then the pump.......

 

Hmmm could be the water pump starting to fail, cuz the car drives fine now, only sometimes the overflow bottle fills to the top, and sometimes the level goes back to normal. It's weird. Can anybody else help diagnose my problem? Much appreciated.

 

mine did that for awhile, then i just started to not care anymore, and the prob went away,lol

 

ttt

 

if the lower hose stays cold its your thermostat. pull the thermostat out and throw it in some boiling water and watch to see if it opens. If it doesn't you've found your problem.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by vitrox &raquo;</TD></TR><TR><TD CLASS="quote">if the lower hose stays cold its your thermostat. </TD></TR></TABLE>

.. or something else is plugging up the system.

 

could be just junk clogging it.. or an air bubble.. but the air bubble isn't likely since it worked before.. you can always open the bleeder valve and see if fluid come out.

 

ttt

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by jc836 &raquo;</TD></TR><TR><TD CLASS="quote">Could also be your friendly radiator cap.</TD></TR></TABLE>

I agree.

Don't think it's the water pump, so check the easy stuff first. Radiator Cap and the Thermostat.