[Dirty Devil]

I've changed the thermo and flushed the radiator. My fluids are where they should be and the hoses are all new. The temp is fine for the first 20 or 30 minutes each day, but then starts climbing up and into the red. The heater blows nice and hot when the temp is normal, but blows cold when the temp starts inching upwards. Could I have a tempermental water pump? Would a clogged heater core cause this? What else affects the temperature like this? I really don't want to take it to the shop, where they usually ask for my first-born before opening the hood. Any advice is appreciated. Thanks!

 

[4Wheeldog]

Sounds like a bad head gasket. With the engine cold, take off the radiator cap and fire it up. Run it until the thermostat opens. I am afraid that you will start getting big burps of gases out of the radiator as soon as the Tstat opens. Maybe even before it warms up.
Alternatively, you can do a compression check. You will likely find 2 cylinders next to each other with low readings.
I hope I am wrong, but the heater quitting when it gets hot indicates gases in the coolant air binding the water pump. Good luck.
<IMG SRC="smilies/crybaby2.gif" border="0"> <IMG SRC="smilies/crybaby2.gif" border="0">

 

[trampas]

Man. Sorry to hear. What it might be? Well, although it might be obvious to you, the "no warm air" from heater when its in the red, means......no coolant in that core @ that time. Could be air blocking it up, or whatever the blockage is, makes it near the core when you begin to run hot. Have you disconnected the core hoses and tried to flush it out there? If you have, it must be that bigtime "air" is being introduced into the coolant system somewhere, but wouldnt count on it being a tempermental water pump, they either perform the job, or do not, eh? Hope you figure out what it is from this awesome BB, thats what its for. <IMG SRC="smilies/glasses.gif" border="0">

 

[trampas]

Yeah, im afraid Petalume might be correct, good call there. Looking forward to knowing you got it figured out, i also dd an 86runner

 

[Dirty Devil]

Thanks for the info. I had a small crack in the head that I had welded a few years ago. It may have re-cracked, which would probably act the same as a blown gasket. Sh*t!!! I was hoping it was something a little less complicated. OK, now, anyone have a used head they want to sell? <IMG SRC="smilies/smile.gif" border="0">

 

[trampas]

sorry man, dont know of any. You compression check to make sure? you should do that first. <IMG SRC="smilies/usa.gif" border="0">

 

[toyrunner]

Take it to a smog station and ask them to sniff the radiator. This will let you know real fast wether or not it is a head gasket.
Other than that, fill the radiator up and let the runner run for a bit without the rad cap on to purge any air. If all the coolant comes flowing out, might just be a bad HG.
HTH
Danny