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Running hot - bad temp sensor maybe? by Corvus
Started on: 09-04-2013 11:21 AM
Replies: 7 (208 views)
Last post by: EvilSqueezles on 09-04-2013 03:48 PM
Corvus
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Report this Post09-04-2013 11:21 AM Click Here to See the Profile for CorvusClick Here to Email CorvusSend a Private Message to CorvusEdit/Delete MessageReply w/QuoteDirect Link to This Post
I noticed that the engine in my stock '88 Formula has been feeling VERY warm after I drive it for half an hour or so. I open the trunk and heat just pours off of the engine. The coolant was replaced maybe 2000 miles ago and the temperature gauge on the dash always seems to read very cool. I'm guessing that this isn't normal.

Could it be a bad temp sensor? What else could it be?

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[This message has been edited by Corvus (edited 09-04-2013).]

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Gall757
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Report this Post09-04-2013 11:44 AM Click Here to See the Profile for Gall757Send a Private Message to Gall757Edit/Delete MessageReply w/QuoteDirect Link to This Post
Could be normal. There should be a drop in coolant temperature when the thermostat opens. Some open a little late: maybe yours is getting tired.
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EvilSqueezles
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Report this Post09-04-2013 11:45 AM Click Here to See the Profile for EvilSqueezlesClick Here to Email EvilSqueezlesSend a Private Message to EvilSqueezlesEdit/Delete MessageReply w/QuoteDirect Link to This Post
Possibility of a bad sensor. They work off of resistance, the more you heat it up, the less resistance it has, and the gauge rises.

Another thought, if you're not having any overheating issues. Do you have all the factory heat shields still on the car? If not it will heat the engine bay up in a hurry, even though your motor may not be running all that warm. Should be a shield on both manifolds and the crossover pipe if its a v6. If its a 4 than I'm not sure how many shields it should have or where they are all located. One way to check your sensor is to hook a meter up to it, switch it to Ohms and ground the negative meter lead, and placed the positive lead to the wire off the sender that goes to the temp gauge. Start your car, you should begin to see the resistance drop the longer the car is running. There is a post somewhere on here that tells the heat to resistance ratios to compare with what your gauge is showing.

BTW, you live 45 minutes from me
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Corvus
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Report this Post09-04-2013 12:21 PM Click Here to See the Profile for CorvusClick Here to Email CorvusSend a Private Message to CorvusEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by EvilSqueezles:

One way to check your sensor is to hook a meter up to it...



I'll try that. Where is that sensor actually located?
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Corvus
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Report this Post09-04-2013 12:23 PM Click Here to See the Profile for CorvusClick Here to Email CorvusSend a Private Message to CorvusEdit/Delete MessageReply w/QuoteDirect Link to This Post

Corvus

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quote
Originally posted by EvilSqueezles:

BTW, you live 45 minutes from me


Nice! I see the turn-off for Altona every time I drive past Galesburg.
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fierofool
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Report this Post09-04-2013 02:04 PM Click Here to See the Profile for fierofoolClick Here to visit fierofool's HomePageClick Here to Email fierofoolSend a Private Message to fierofoolEdit/Delete MessageReply w/QuoteDirect Link to This Post
The gauge unit is in the corner of the head, just left of the # 3 exhaust port. It has a 2 wire connector. You can check your gauge by letting the car sit at idle without the AC running. Watch the gauge to see at what point the cooling fan kicks on. It should be somewhere close to the straight down position. Normal operating position is just left of straight down. If you want to check it against the GM resistance chart, let the engine cool down. Lay a thermometer in the engine bay so you have an accurate temperature reference, then use this chart. Put the negative probe on the base of the sensor and the positive on the terminal. One of them will give no reading since it's for the light. The other is for your gauge and resistance reading.

http://gafiero.org/bbs/index.php?topic=641.0

[This message has been edited by fierofool (edited 09-04-2013).]

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Marvin McInnis
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Report this Post09-04-2013 02:20 PM Click Here to See the Profile for Marvin McInnisClick Here to visit Marvin McInnis's HomePageSend a Private Message to Marvin McInnisEdit/Delete MessageReply w/QuoteDirect Link to This Post
What you're experiencing is probably normal if you don't have any other signs of cooling system overheating. By far the primary source of heat in the engine compartment is the exhaust system. The exhaust systems heats the air by convection/conduction, and it heats nearby parts by infrared radiation. As already stated, you need all the OEM heat shields in place to minimize radiational heating from the exhaust system.

The Fiero V6 has two independent temperature senders ... one connected to the gauge and one connected to the ECM. Borrow an OBD scanner from your local auto parts store and compare the temperature reported by the ECM sensor with the temperature reported on the gauge; even better, measure the resistance of the gauge sender with a good quality ohmmeter and look up the corresponding temperature. The ECM and gauge temperatures should be fairly close to each other ... certainly within 10 or 15 degrees F ... and should track each other.

[This message has been edited by Marvin McInnis (edited 09-04-2013).]

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EvilSqueezles
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Report this Post09-04-2013 03:48 PM Click Here to See the Profile for EvilSqueezlesClick Here to Email EvilSqueezlesSend a Private Message to EvilSqueezlesEdit/Delete MessageReply w/QuoteDirect Link to This Post
Yep, easy way to spot the sensor is look at the ignition coil and then look down. It'll be right at the end of the head kinds tucked right under where the trunk fan tube comes in (if you have it). 2 green wires.

Yea. Galesburg is a common place for me unfortunately.

edit to add : http://www.fierosails.com/tempgage.html

[This message has been edited by EvilSqueezles (edited 09-04-2013).]

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