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Operating temp for L98

Old Feb 20, 2009 | 07:34 PM
  #1  
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From: Dover, De
Car: 91 Formula
Engine: L98
Transmission: 700r4
Axle/Gears: stock
Operating temp for L98

I was wondering what other people with my motor usually operate at.. My l98 runs around 240, is that normal? Thank you
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Old Feb 20, 2009 | 07:48 PM
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From: 51°N 114°W, 3500'
Car: 87 IROC L98
Engine: 588 Alcohol BBC
Transmission: Powerglide
Axle/Gears: Ford 9"/31 spline spool/4.86
Re: Operating temp for L98

Water boils at 212F. A pressurized cooling system increases the boiling point depending on the pressure the cap is rated at. It's usually 15 psi. At 240, the coolant is probably right around that boiling point.

All engines operate in the 160-195F range. A cool engine makes more power but also makes a lot more emissions. EFI engines operate at 195F mainly to lower the emissions. They're usually allowed to run up to 205 before cooling fans kick in. An average, all around operating temperature for all engines is 180F. Doesn't matter if it's a tiny 4 cylinder or a monster big block.

A thermostat circulates coolant inside the engine until it reaches operating temperature. It then opens allowing the coolant to circulate through the rad where the temperature is maintained. If the thermostat doesn't open the engine will overheat. Once at operating temperature and the thermostat is open, if it still overheats there can be any number of reasons why such as;

Plugged circulation system including the rad
Electric fans not working
Fuel system running lean
Bad head gasket
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Old Feb 20, 2009 | 08:33 PM
  #3  
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From: Dover, De
Car: 91 Formula
Engine: L98
Transmission: 700r4
Axle/Gears: stock
Re: Operating temp for L98

Originally Posted by Stephen 87 IROC
Water boils at 212F. A pressurized cooling system increases the boiling point depending on the pressure the cap is rated at. It's usually 15 psi. At 240, the coolant is probably right around that boiling point.

All engines operate in the 160-195F range. A cool engine makes more power but also makes a lot more emissions. EFI engines operate at 195F mainly to lower the emissions. They're usually allowed to run up to 205 before cooling fans kick in. An average, all around operating temperature for all engines is 180F. Doesn't matter if it's a tiny 4 cylinder or a monster big block.

A thermostat circulates coolant inside the engine until it reaches operating temperature. It then opens allowing the coolant to circulate through the rad where the temperature is maintained. If the thermostat doesn't open the engine will overheat. Once at operating temperature and the thermostat is open, if it still overheats there can be any number of reasons why such as;

Plugged circulation system including the rad
Electric fans not working
Fuel system running lean
Bad head gasket
Thank you for your response.

My whole cooling system is basically new: water pump (heavy duty), hoses, radiator, rad cap, flused heater core (good flow now), fail safe thermostat (180), coolant. now one thing that may not be correct is that my left fan is always running, hot or cold, the same speed, and the right one never comes on. Any ideas if this is wrong or what else? Also its got a new fuel system: pump, strainer, filter, injectors, o rings.. so that probably isn't the issue.. also plugs wires cap rotor module coil. I get good coolant flow all the way through judging from squeezing the hoses

Last edited by krok91gta; Feb 20, 2009 at 08:43 PM.
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Old Feb 20, 2009 | 09:07 PM
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From: 51°N 114°W, 3500'
Car: 87 IROC L98
Engine: 588 Alcohol BBC
Transmission: Powerglide
Axle/Gears: Ford 9"/31 spline spool/4.86
Re: Operating temp for L98

When the engine is cold/cool, take the rad cap off and fire the engine up letting it warm up. Lots of bubbles usually indicates a bad head gasket or a cracked head feeding compression into the cooling system. Rev up the engine a couple of times, the coolant level shouldn't fluctuate very much and it shouldn't blow coolant out the rad.
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Old Feb 21, 2009 | 08:52 AM
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From: N. Illinois
Car: 92 GTA/ 00 TA
Engine: 383/350
Transmission: 700R4/T-56
Re: Operating temp for L98

The left fan shouldn't always be running.
The right fan should only come on when using the AC.
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Old Feb 21, 2009 | 09:43 AM
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From: 51°N 114°W, 3500'
Car: 87 IROC L98
Engine: 588 Alcohol BBC
Transmission: Powerglide
Axle/Gears: Ford 9"/31 spline spool/4.86
Re: Operating temp for L98

If the temperature is too hot the one fan will stay running because it can't bring the temperature down. The second fan will also automatically kick in at a higher temperature. Somewhere in the 230-250 range.
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Old Feb 21, 2009 | 10:40 AM
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From: Austria
Car: 84 TA / 89 Formula
Engine: LS1 / L03
Transmission: T56 / 700R4
Axle/Gears: 3.73 / 3.27
Re: Operating temp for L98

if you don't have any boiling water yet it might just be your gauge that's way off?
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Old Feb 21, 2009 | 11:07 AM
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From: Philly, PA
Re: Operating temp for L98

Do you have the "chin spoiler" bolted up underneath the radiator support? It's a block plastic air dam, basically. It makes a big difference in cooling at highway speeds and even some difference in low speed light-to-light driving.
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Old Feb 21, 2009 | 02:21 PM
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From: Buffalo, NY
Car: 1988 IROC-Z
Engine: 427 SBC
Transmission: ProBuilt 700R4
Axle/Gears: Moser 12 Bolt / 3.73 TrueTrac
Re: Operating temp for L98

You can try and ground the fan switch in the passenger side head and the high speed fan should turn on.
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Old Feb 21, 2009 | 02:50 PM
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From: Austria
Car: 84 TA / 89 Formula
Engine: LS1 / L03
Transmission: T56 / 700R4
Axle/Gears: 3.73 / 3.27
Re: Operating temp for L98

i agree on the air dam, when my formula didn't have one on it it would run hot all the time. i thought i had shot my head gaskets but after i put the air damn () back on it was all fine..
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Old Feb 21, 2009 | 07:14 PM
  #11  
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From: Dover, De
Car: 91 Formula
Engine: L98
Transmission: 700r4
Axle/Gears: stock
Re: Operating temp for L98

Originally Posted by ownor
i agree on the air dam, when my formula didn't have one on it it would run hot all the time. i thought i had shot my head gaskets but after i put the air damn () back on it was all fine..

I have my air dam on, and when the gauge indicates 240 the other fan still isn't on.. so if the switch for the second fan is working perhaps the gauge is faulty.
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Old Feb 21, 2009 | 08:46 PM
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Re: Operating temp for L98

Agreed. At 240 you should be close to showing signs of actual boiling-over. Buy a new sender (the gagues is run by the sender in the cylincer head between the #1 and #3 spark plugs) and see if there is any difference.

Also, if you have access to a scan tool see what the ECM temp reading is and compare it to your dash temp gagues (they use different sensors to get theor reading).

3rd gen gagues are notiriously inaccurate.
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Old Feb 21, 2009 | 11:48 PM
  #13  
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From: Dover, De
Car: 91 Formula
Engine: L98
Transmission: 700r4
Axle/Gears: stock
Re: Operating temp for L98

Originally Posted by Damon
Agreed. At 240 you should be close to showing signs of actual boiling-over. Buy a new sender (the gagues is run by the sender in the cylincer head between the #1 and #3 spark plugs) and see if there is any difference.

Also, if you have access to a scan tool see what the ECM temp reading is and compare it to your dash temp gagues (they use different sensors to get theor reading).

3rd gen gagues are notiriously inaccurate.
The sender is already new, but i'll check into the ecm temp reading. Thank you
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Old Feb 22, 2009 | 07:17 AM
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Car: 92 GTA/ 00 TA
Engine: 383/350
Transmission: 700R4/T-56
Re: Operating temp for L98

Turn on your ac and see if the second fan comes on.
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Old Feb 22, 2009 | 09:04 AM
  #15  
krok91gta's Avatar
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From: Dover, De
Car: 91 Formula
Engine: L98
Transmission: 700r4
Axle/Gears: stock
Re: Operating temp for L98

Originally Posted by Viprklr
Turn on your ac and see if the second fan comes on.
I think i have a problem with my compressor or something, because when i turn the switch to a/c nothing happens
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Old Feb 22, 2009 | 09:08 AM
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From: N. Illinois
Car: 92 GTA/ 00 TA
Engine: 383/350
Transmission: 700R4/T-56
Re: Operating temp for L98

Barring a problem with the actual ac switch the fan should still come on. However, I don't know if it will come on with a cold engine.
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Old Feb 22, 2009 | 09:17 AM
  #17  
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From: Dover, De
Car: 91 Formula
Engine: L98
Transmission: 700r4
Axle/Gears: stock
Re: Operating temp for L98

Originally Posted by Viprklr
Barring a problem with the actual ac switch the fan should still come on. However, I don't know if it will come on with a cold engine.

oh i see.. i tried the a/c when the engine was cold. i'll try it warm today. thank you for the quick response
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