Today is the day that I was hoping i could finally have my ‘85 GT back on the road. But for some reason, it is overheating. Or atleast my gauge says so. I’ve been replacing the engine over the past couple weeks and now it’s about ready to go, except for this problem. I have filled up on coolant, burped the system, and replaced the water pump. After around 5 minutes or so of running, the temp will be at or above the halfway mark, 220°. But the temp light doesn’t turn on until the temp has been up a few notches past 220° for a while. In addition, it fluctuates. It’ll hover around the 3rd or 4th notch past 220° on the temp gauge, and will sometimes just trend down a notch or two and sometimes it will trend up. The metal coolant pipes and hoses that connect them to the engine don’t seem to be getting very warm when the car is running.
In addition (this might be important), the radiator fan only seems to come on when I turn the A/C on.
Either your temp gauge or the sender is probably faulty.
Connect a scanner to see what coolant temperature is actually being reported to the ECU.
Sorry i’m a bit of a noob here, but how will i connect a scanner if our cars are OBD1? I thought you read codes and such by jumping two pins underneath the center console and watching the check engine light blink?
There's a ton of information posted here and elsewhere about how to access real time information from the Fiero's ECU.
A little update: Coolant started pouring out of the overflow reservoir. Quite a bit of it ended up on the ground. Even with the heater on full blast, the coolant system filled, and all else is said and done with a new t-stat and all the radiator and tstat housing caps back on, it is still overheating.
Any chance you installed a water pump with a plastic impeller? I've heard they sometimes become loose on the shaft.
I am just about 100% positive it had a metal impeller. And i forgot to add (my apologies), the metal coolant tubes that run from the front of the car to the back are now getting extremely hot, so atleast i know that there’s not a problem with the tubes. I also just burped the coolant system by jacking the back of the car up to where the t-stat housing was above the radiator, ran it for a while, and let all the bubbles and air pockets out. I took it for a 5 minute drive, the gauge got up to 260°+, but nothing seems to have gone wrong
I've used the following procedure with half a dozen different Fieros (running a Stant SuperStat 195° thermostat and a 210° on and 200° off fan switch) and never had an overheating issue...
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Originally posted by Patrick:
* Make sure rad cap is the proper one for Fiero use. The catalogs are wrong! You want a non-vented cap. * Check that the overflow tank and the small hose to the rad are both in good shape. Otherwise air gets sucked in. * Ensure that coolant level in overflow tank is at the "Cold" level. * Position rear end of Fiero higher than the front. * Remove thermostat housing cap and thermostat... and then add coolant to thermostat housing with rad cap also removed until coolant runs out the top of the radiator. * Re-install rad cap.
* Continue to add coolant until you see the level come up to where the thermostat normally sits. * Put thermostat cap on and turn just barely enough to hold cap on. * Start engine and run for about 30 seconds. * Remove thermostat cap and check coolant level. * Repeat last four steps until coolant level no longer drops.
* Re-install thermostat and thermostat housing cap.
As long as there are no blockages anywhere in the cooling system and the water pump is circulating coolant, you should be good to go.
[This message has been edited by Patrick (edited 08-22-2020).]
I've used the following procedure with half a dozen different Fieros (running a Stant SuperStat 195° thermostat and a 210° on and 200° off fan switch) and never had an overheating issue...
I do have the 195° thermostat and the fan switch is whatever came stock. I did the exact procedure you sent in your last quote except i had the thermostat housing cap completely removed. It has the stock radiator and thermostat housing caps.
Even when I used to drive the car with my old 2.8 V6 (before it threw a rod), there’d be a noticeable drop in power when the car would run too hot. It is important to note that 100°F days here in Tucson, Arizona are pretty normal during the summer months. Last summer, the car would get up to a temp of 220° maximum on the gauge and maybe a notch above if I was traveling on the interstate on a hot day.
At what temp does the temperature light on the dash come on? Like I said, I know it works but it just won’t come on unless the gauge is reading 260°+ for more than a couple minutes.
It has the stock radiator and thermostat housing caps.
Rad caps probably wear out eventually. Do you know for a fact that yours isn't releasing pressure when it shouldn't be?
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Originally posted by jaredaltizer:
I did the exact procedure you sent in your last quote except i had the thermostat housing cap completely removed.
I'm not sure what you mean by that. The thermostat housing cap obviously needs to be "completely removed" in order to add coolant.
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Originally posted by jaredaltizer:
I do have the 195° thermostat and the fan switch is whatever came stock.
At what temp does the temperature light on the dash come on? Like I said, I know it works but it just won’t come on unless the gauge is reading 260°+ for more than a couple minutes.
I don't know about the dash light, but the factory fan switch doesn't turn the rad fan on until the coolant reaches 235°F. I'm a firm believer in swapping the factory fan switch to a 210° on and 200° off one.
[This message has been edited by Patrick (edited 06-24-2019).]
