i bought my fiero last saturday or something like that, a nice 88gt that hadnt moved for some time and was high in miles. after tuning it up and replacing the manfiolds i find that the coolant guage doesnt work, i replaced all three sensors for coolant(since theyre probably all bad) and the pigtail for the guage. for 2 days now it wouldnt go above 160 degrees f. the fan never came on either. then today it did warm up and went between 220 and just before the red pretty much at random. so im back at ground zero really with the temp issues, the car runs fine at any temp so im thinking its the guage but i dont know much about this car so that could be normal or not i dont know. if anyone can help that would be great

Welcome to the forum.
The temp gage is the sensor located in the head right by the coil.
One wire goes to the light and the other goes to the gage. You can ground them and they will peg the gage and the light. I had issues with mine when the needle fell off and never read right after that.
The temp gage in the Fiero isn’t the most accurate of gages. If you think you may be over heating you need to buy a more dependable gage and find out.
If your temp is swinging wildly it may be air in the system.
Click the link at the top of the page for the Ogre’s cave and read how to burp the system.
Good luck hope you figure it out.
Jake

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Click here to hear my cars

i just ran it for a while and watched the guage, it does kind of wobble but not to much. i made sure the coolant tank was at full and ran the car for a while, the fan cycled on at just before the red so my ghetto calculations put it at 240 the fan stayed on long enough to drop it down to 230. ill try bleeding the air out of it but if this guage really isnt to be trusted and i get another one which sensor should i use for the reading?

and is it really even good for a car to be running so hot? i read on this board how most people say its not a good idea to drop the temps down but from what i know the reason they run the cars so hot is for emmissions purposes not power output purposes, and in my case, being in the auto field means i can pass emmissions for life so thats not an issue. and ive also read that the engine bay heat is the main cause of failure in parts on this car so wouldnt dropping it down to a 160 tstat and i think the switch is set for 180 or something be good in that regard?

I have always ran a stock stat but I do like to drill a 1/32 hole in it to let the air bleed out from under it. The air can pool under the stat and cause the stat to not open untill the car has reached a temp way above what is safe for the car. I think I lost a motor due to the stat not opening when it should.
You can pick up an aftermarket temp gage and hook it up. I would retain the stock gage and sensor and just use the aftermarket to check on it. Keep in mind these cars are getting old and parts wear out. The gage could be bad, you could post in the mall and buy another one and try your luck.
You could also get a temp probe and check the temp of the motor.
This would work but it isnt cheap.
http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=91778

[This message has been edited by Jake_Dragon (edited 08-25-2006).]

The problem with dropping it down to a colder thermostat is that the computer expects then engine to run in a certain temp range. If the ecm reads the temp as too cold the car won't go into closed loop. The most basic problem there is that you'll be running rich constantly. If it wasn't for the computer, then yeah it wouldn't be a big deal to use a colder thermostat.

yeah im reading about that now in the ogres cave, im used to newer cars where the open/closed loop is regulated mainly by the o2 sensor and the newest cars that just know this stuff and i cant explain why.

this cave place says running a lower fan switch with a stock thermostat will work but if the tstat is at 195 and the fan regulates the temp at 175 would the tstat then just not open since theyre bascily in the same spot? i really am not confortable with a car running so hot when i know the 2.8 s10s dont run this hot. plus since i plan on dropping in a 3.4pushrod and a turbo i cant afford to let my car run at 235 under boost/load conditions.

quote Originally posted by megafreakindeth: o and i forgot to mention when the guage was moving between 220 and 240(regulated by fan) the coolant tank was overflowing but i know for sure it was at the full line before i did this testing

If its over flowing , you may want to do the burp proceedure in the cave, then try a new stat, check all your lines for collapsed hoses, bent tubes under the car (running from rear to front) or maybe your water pump is going out, the ones with plastic impellers will slip on you with-out notice. A real good flushing may do wonders also...

Adding to what SuperFast said. Have you tried running with the stat out. If you still overheat then you have to look for what he listed. Check the coolant tubes to see if they where crushed. Since you just got the car you have to check all the listed items out. With the stat out see if there is good flow thru the stat housing. Make sure your burped. Check for soft hoses that collapse. Check for junk between the ac coil and the radiator..

i flushed it which did wonders for cleaning the system. i looked at ogres cafe and tried to run the car without a stat cold but the coolant would just spew out sporraticly and make a mess. the hoses arent collapsed and theyre all hot. i am leaning towards airpockets still because the fan switch doesnt come on and the coolant temp sensor goes up or down at random once it hits over 200. the fan switch came on in the red once as well. what im doing now to try and bleed it is i parked the car backwards in the driveway(engine up) and ran it hot and im gonna let it cool and add water throu the tstat housing when it cools off.

the car takes forever to warm up btw, like 10-15 min, which is what happened when i wore my old cars engine out after 300,000 miles. im hoping its not that but it does have 178k on the 2.8 in it now.

If you want to run cooler all the time, you can ground the rad fan to stay on all the time. or run a toggle switch , or tap the dark-green/wht strip wire in the front trunk loom , under the hood strut, notch it right there, add the same size wire, ground it off at the 10 mm strut bolt, it will turn on with the key and off when you turn the key off..

You really can't go but the readings of the Fiero temp gauge. Both my Duke and Formula read about 150 deg by the gauge yet a scanner shows 190 (also checked with a thermometer). According to the gauge the fans come on at 260 but the scanner says 235. As long as the gauge readings stay in the same place for normal driving I wouldn't worry about it.

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SC3800

yes ive read about how the guage isnt accurate but i cant help but worry. alas now i am running a 174 temp switch with 160 degree stat and the hypertech chip to adjust the computer for the lower temp(also more power :-)) and the car runs much nicer now. but it says the fan comes on after four bars(160, based on the guage) and turns off at slightly below 145. i read somewhere that running a 22 ohm and 33 ohm resister (at radio shack these are 1watt resisters if anyone knows how all that works) on the sensor connector will give a reading of 160. if this information is accurate im going to do this tommrow to 'calibrate' the guage. if anyone knows if this is correct or not please let me know.

if i were to get an aftermarket guage, is it the factory guage thats inaccurate or the sensor? should i run it off one of the other sensors?

the best way to check the temp guage is with a point n shoot digital laser thermal gun. alot of auto parts chains have them and will shoot the motor for you. the base of the filler neck is a good spot.
alos an obd1 scanner or winaldl with the cable will let you see the temp the ecm is seeing, that sensor is more accurate.

Don;t waste your money on the hypertech chip. you won;t get any more power, but you will burn more gas.
run the 195 tstat, and get a fan switch from Rodney Dickman , go for the 210 one. that will give you more power than putting that bs chip in. they have been dumped, and the specs are actually worse than the stock chip.

the motor is designed to run at 195, but I agree the fan switch comes on way too late in stock form. Mine now comes on at around 215, and off at 198. very nice. 98 degree days are no problem for it.

http://www.fierosearch.com/cgi-bin/search.cgi?forum=A1&where=ALL&SearchQuery=hypertech%20chip&Action=DoSearch

quote Originally posted by 3800superfast: http://www.fierosearch.com/cgi-bin/search.cgi?forum=A1&where=ALL& SearchQuery=hypertech%20chip&Action=DoSearch

You keep this searches in a bottle somewhere?????? :roflmao:

I should say if you really want one I can sell you one for a reasonable price...... but I would rather do a remap of it if I ever get off my butt and fire up the old pc that has the burner/reader on it.

well the motor did run alot better with the chip in it but i could feel it did lower the timing a bit. i figured at least i could use a better fuel map but apparently it doesnt do that either. so meh, mabye ill try ronny dickmans 200 degree fan switch with a 180 tstat. right now my gas guage is kinda unreliable but id much rather have more gas mileage at the sacrifice of peak power.
i read the posts about how adding the lower temp sensors and tstats was bad becasue it made the computer think it was cold, but none of the posts i read mentioned using the chip, just the stock computer. i figured if the chip went so far as to recalibrate its operating temperatures it would also cover everything else but i guess i was wrong.

quote Originally posted by megafreakindeth: right now my gas guage is kinda unreliable .

http://www.fieropride.com/tech/gas_guage.htm

yes i know why the gas guage is wrong but i cant fuss with gasoline directly because i get migraines. which is funny because i work on cars but you learn to be very carefull. i plan on fixing the problem buy calculating my distances/how much gas i put in it(which works fine) till i upgrade my fuel pump/get a new sending unit which a friend can install for me.

ive ordered a 210 degree switch so i guess i have the whole collection of switches and tstats now. i just want to get this over with and move onto the suspension

so i thought i fixed all this but apparently no. after the fan cycles on and off twice, the third time it comes on, it stays on. the guage also drops from around 220(i have a 210 fan switch) to 160(which i guess its been doing this whole time, with any switch or tstat). i drive for an hour with the fan on and the service engine soon light.
while driving i turned the car off and restarted it to try and get the guage to read what it should and i think it did. it registered being slightly over 220 and, as id accelerate it would heat up slightly(60mph would be 220, 70mph would be one bar above). after about an hour of driving with the fan on it dropped slightly below 220 and the fan turned off. 15 min later it didnt turn back on and the temp went up about three bars(i reached my destination and stopped driving anywyas). the guage is probably very inacurate yes but i can watch the fan cycles and they seem to imply that im overheating just over the fan switches activation point.

im thinking minor headgasket leak? mabye its even introducing air into the system? ive burped all the air out i can by popping in the tstat, runnning it cold with the heat on, and removing it, refilling, and repeating. and after 2 hours of driving id put money on most of the bad airpockets being flushed through the system. anyone have any ideas?

megafreakindeth, Before you get into head gaskets leaks and all, whats your take on trying winald? tjm4fun brought it up above, it is more accurate--and will give you the specs you`ll need. Not sure if any one posted these links yet, may be worth a look see--we can walk you threw it, if your not familar with the program, the cables can be made for a coupe bucks, the program is free.
http://winaldl.joby.se/

ill try and put one togeather or just buy one. i wonder if the hookup for gm cars on the scan tool at work will let me just plug it into my computer since it uses the ioio port.

but, if the fan is on that means that the switch was tripped at 210or above. and if it doesnt turn off for an hour i am led to believe something is up, even wihtout the guage.

I agree wiht the taking an hour to turn back on, one of the problem we face with 20 year old cars is tracking down this stuff, they have cables allready made if that helps any ,strat110 sells them , or you can get one here;
http://www.aldlcable.com/

Did this resolve?
I vote clogged radiator. My old radiator would let me drive around for 45 minutes and suddenly failure, car puke every where.

Also wandering tempratures are known to be the plastic finned water pump and make sure that the little plastic skirt is connected under the radiator, it help the air to flow properly.