Ok, here is my story. Car specs in sig w/ ~55K in milage.. I have never had any problems with my car prior to this year and we have not even hit the "real heat" of the summer (I live in AZ).
So, Friday my g/f and I head out for lunch and to run some errands. All is fine for about the first hour or so out on the road. I get back to the office to drop her off and this is when i first notice the engine temp (well, the thermo) is sitting right around 240ish. As I mentioned earlier, it has never done this and usually runs right around the 220 mark even during long trips. Anyways, I continue on to finish my errands while keeping a close watch on the temp. About 10 minutes later while sitting at a red light the temp jumps into the red and the check gauges light comes on. I immediately shut off the A/C and pull over. I wait about 10 minutes and start it back up. Thermo jumps right back to to the 240ish range. I leave the A/C off and head for some open road (heading home) and the thermo slowly makes it way back to the 220/230 range. I get home and park it for the day.
This morning I get up and decide to drain and refill the fluid. All goes fine and the old fluid even looks good. I also checked all the hoses and all seem to be stiff and I don't think any could/are collapsing on me. I finish up around noon and head out for a 15-20min ride. All is good and it never gets above 220 mark even with A/C on high.
About 2:00pm I head to a birthday party and all is good for the first 15min or so and then bam it jumps back up to the 240ish range and I have to kill the A/C.
Anyways, I am at the party the rest of the evening and then just left to come home. The thermo never gets above 220 on the trip home, but when I pull into the garage and get out I can hear the fluid boiling from inside the radiator and hoses. After a few minutes it stops, but WTF???

Any idea, help, thoughts??? I am stuck here.

Thanks for your support in advance and sorry this was so long...

 

Hmm did you try checking to see if your thermostat is bad/stuck??

 

Are the fans comming on? You should get one fan when it reaches full temp and the other should come on with the A/C.

 

I did check the thermostat and it seems fine. Not real sure how to tell if it is bad or not though. Also, the fans are coming on when they are supposed to.

Does anyone think it might be the water pump? I am really not looking forward to replacing it..

 

"Supposed to" as in what GM said, or "supposed to"
like make the thermostat have some authority? If
I take my fans back to stock it coughs and drools
after a good run in the Florida heat too. Stock fan
settings don't even start trying, until 224F. Bogus.

 

Yes, supposed to as in GM dictated.. How can I change mine? I do not have access to LS1edit and have not been able to find anyone around here that could do this. All the shops I go to are **** and will not modify cars or setting for me. This is why I do 99% of my own work now...

 

Changing the waterpump is super easy, don't sweat it.

 

Seems to me the cheap, hardware way out is to do
the fan switch mod, only use a thermostat. There are
kits you can get to do it w/ variable turnon temp.
Rig it so you keep the radiator temp at 180F, and
end of worries. I had bought one of these for like
$29.95 at Pep Boys but returned it after I got the
Predator. I think it was by Hayden, it was right there
with the tranny coolers.

Also a chance there's someone in the little corner of
cactus hell you call home, who's got an '01 F-body
HPTuners copy by now and could help you out.
Might give a shout in your "local" forum and see...

 

Thanks again for all the great advice. You all never let me down... I will check around.

 

my did the same thing but only one day

 

Mine over heated only to find out the freakin nut came off of the drivers side fan!

 

I vote for the the thermo. Has the thermo ever been replaced?
And if your fans are cutting on, I would think it might be your thermo. I would change the thermo out since it's not as pricey as the water pump.
But usually if the water pump isn't working. The car would immediately get hot, not wait awhile to overheat.

 

Great to know. It is still the stock thermo and the fans are coming on. I think I will try replacing it. Seems pretty straight forward. Thanks again.

 

If you hear coolant boiling in the radiator you have air in the system or something is leaking. If something is leaking then the pressure in the system is leaking as well. Either way, if the pressure drops, the coolant will boil. Remember that pressurizing fluid raises it's boiling point. So if a superheated fluid (pressurized coolant) is suddenly de-pressurized, it boils violently.

Also, air in the system will make your temp gauge act spastic since it can't read air temperature, only fluid temperature.

 

I would replace both the radiator cap, the thermostat, and the coolant first, as they are the cheapest. Boiling indicats that proper cooling system pressure is not being maintained, which is either a leak in the system or a faulty radiator cap. You have not mentioned any obvious leaks, so you should replace the cap...they are about $7 from GM.
If replacing those doesn't stop the problem, then your water pump is going. Start inexpensive and work your way up!

 

I just got back from work and it drove normal again today. I only work 5 miles from home so I was not on the road for more then 20 mins, (air was cranked on hight the whole time) but everything seemed normal again. I am gonna go get a cap and replace it for ***** and giggles. I am gonna go check the levels again and inspect hard core for any leaks.

Thanks again everyone.. Working on my car would suck without all the different support offered here.. Without all of you, my mechanic would be fat and happy!!

 

Replace the thermo with a 160. The water pump is fine. It sounds normal to me. My family lives over there and my car always ran hot there in the summer. You may look into an lt1 radiator for better cooling. It fits in perfectly and you just need to cap off the heater inlet/outlet. Same thing that slp sells except the lt1 radiator will run much less cash. It holds double the volume. You could also wire in a switch to ground to the fan relays to be able to turn those on early. It will set the ses light though unless you program out the codes in ls1edit. 160 thermo and lt1 radiator would be my advice for AZ summers. Cost would be about 230 for both and an hour and a half for the install. Good luck

 

I also live in Chandler and drive a 2001 Z28. The first mods I did when I bought the car was a 160F Thermostat ($45 off of Ebay) and a manual fan switch ($35 from Speed Specialties). Worked great, I did it to eliminate high rpm pinging more than to keep it from overheating. Since the manual switch, I've reprogrammed the PCM to turn the fans on at 180 & 195. My car has not gotten hot yet, but we are still having pretty cool temps out here for June (only 99F right now!).

Thanks,
Glenn