87 Fiero 2.5L Iron Duke Overheating (Page 1/1)
Chic_in_a_mask APR 13, 02:18 AM
I will try and make this as short as possible, but with all the details. My fiero has been overheating since I purchased it. Starting to get her on the road again after she sat for 3yrs, but surprisingly she runs fine. Taking care of all the minor things but right now I am on the cooling system. So, I have changed the serpentine belt, water pump, cooling sensor, temperature switch, and fan relay. Pipes, radiator and thermostat are all good. Of course I flushed and bled the system. The previous owner told me that the fan isn’t turning on so I have to turn on the A/C B/L button when she starts to get to hot. It would only overheat at a stand still, but now she is slowly overheating while I am driving as well. I am aware that the temp gauge on the dash isn’t accurate, but am positive it isn’t right because as soon as I start her up the needle is right under 220 every time. And even after changing everything I stated, she is still running the same as I described. I also ran the heater and no hot air was blowing out. Also both caps are fine, but mostly everything on this fiero is original. Aside for bleeding her again and double checking wiring and grounds I am at a loss. I could really use anyone’s help and advice on this issue. I would really appreciate it, thank you!

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“Wherever you go, there you are.”

Patrick APR 13, 02:26 AM

quote
Originally posted by Chic_in_a_mask:

My fiero has been overheating since I purchased it.



We get "overheating" posts like this about once a month.

What is indicating to you that the engine is "overheating"? You cannot go by the dash temperature gauge. You need to get a scanner (or WinALDL) connected and see what temperature info the ECU is being fed.
Chic_in_a_mask APR 13, 04:23 AM
Thank you for responding Patrick! Yes, I am sure this topic is redundant at this point but I want to make sure there isn’t something I am missing in the posts and info I have been reading. I will check the ECU next, thanks! Do you recommend a reader for my type and year of car? And do you have anymore info of what may be going on with certain temperatures the reader will give me? As in if certain temps mean this or that?

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“Wherever you go, there you are.”

Patrick APR 13, 11:36 AM
So, I take it then that your engine is showing no actual signs of overheating?


quote
Originally posted by Chic_in_a_mask:

Do you recommend a reader for my type and year of car? And do you have anymore info of what may be going on with certain temperatures the reader will give me?



I use a laptop and a cable and run WinALDL. It displays information from all sensors, including the temp sensor which connects to the ECU (not the temp sensor that controls the often incorrect dash gauge).

I might mention that my setup cannot read the info from an '87 duke. It's kind of an oddball engine, and if the truth be known, the '87 and '88 4-bangers are my least favorite Fiero engines.

Have a look in This thread for one option. And contact phonedawgz in that thread for further options.

[This message has been edited by Patrick (edited 04-13-2019).]

Chic_in_a_mask APR 13, 06:10 PM

quote
Originally posted by Patrick:

So, I take it then that your engine is showing no actual signs of overheating?

I use a laptop and a cable and run WinALDL. It displays information from all sensors, including the temp sensor which connects to the ECU (not the temp sensor that controls the often incorrect dash gauge).

I might mention that my setup cannot read the info from an '87 duke. It's kind of an oddball engine, and if the truth be known, the '87 and '88 4-bangers are my least favorite Fiero engines.

Have a look in This thread for one option. And contact phonedawgz in that thread for further options.





Thankfully the engine does not show signs of overheating! Just the fan not turning on and coolant steaming from radiator cap. On the note of the PHONEDAWGZ post I have to thank you so much for that info. I found him on eBay and ironically right before I read your post I was looking at his scan tools he has there. I ordered the one that will work on my 87’!!! Super stoked and will post my find on my Scan tool post. All thanks to you!! You are the MAN Patrick! I literally can’t thank you enough.

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“Wherever you go, there you are.”

Patrick APR 13, 06:44 PM

quote
Originally posted by Chic_in_a_mask:

Just the fan not turning on and coolant steaming from radiator cap.



Keep in mind the rad fan will not turn on with the factory fan switch until the coolant reaches 235°. (If so equipped, turning on the A/C will also turn on the fan.) A lot of us have swapped out the fan switch to one that instead turns on at 210°... but I just remembered the oddball '87-'88 duke doesn't use a fan switch, the ECM controls the fan.

If steam is coming from your rad cap, sounds to me like the wrong rad cap has been installed. You need a non-vented one. Many of the parts catalogs list the incorrect style/part number for the Fiero rad cap. Information at Ogre's Cave under Radiator Caps Here.

[This message has been edited by Patrick (edited 04-13-2019).]

theogre APR 14, 11:33 AM
Again? 235° fan on is Wrong for 87 duke.
Then add 220°F IS NOT "overheating" by any measure and Is Not overheating at 235° either but fools everyplace think they know better the GM Ford and other Real Engineers.

87/88 L4 is ECM control rad fan and turns on at 221°F
Simply read engine temp and fan1 in data from the scanner.

See my Cave, Rad Fan and rest of section because likely has heater plumbing problems too. Standard Tstat can make the engine temp rise and fall quickly but is normal for them. More so w/ cold weather days.
Get the "quick connect" heater fitting BEFORE you try to disconnect the old one.

About the only data correct is never trust dash gauges and lights trying to "Fix" a problem. Always check them by whatever needed it the time. Example: No Low or High Oil Pressure First check oil level then use a "shop" gauge to test pressure because dash gauge can lie for several reasons. Even the sender and gauge are brand new, the wiring can still make them lie.

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Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should.
(Jurassic Park)


The Ogre's Fiero Cave

[This message has been edited by theogre (edited 04-14-2019).]

Patrick APR 14, 02:34 PM

quote
Originally posted by theogre:

About the only data correct is...



You're such an... Ogre. lol

Falstaff APR 18, 02:06 PM
It's important to know if your caps are holding pressure and the coolant is in good shape. Water boils at 212 F, but a 50/50 coolant mix boils at 223 F. With 15psi in the system (being held in by the cap) the boiling point raises to 257 F. Those numbers reflect a coolant that is mixed properly and in good condition.

Overheating is only possible once the coolant boils. At boil the coolant (or any liquid) can't absorb anymore heat and that is when overheating happens. I used to work in shop in St. Louis and in the summers we sold a LOT of radiator caps. Many times someone's overheat problem was caused by a cap that held no pressure.