LT1 temperature - Fourth Generation Pontiac Firebird (1993 - 2002) - Firebird Nation

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LT1 temperature


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#1 yoheer

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Posted 28 June 2020 - 12:15 PM

Hi guys. Here what I have with my LT1 and it seems strange a little

I flushed the system 2 or 3 times. 

There is hayden transmission cooler installed in front of coolant radiator in my car.

When engine oil is in workig range temp (195F) - engine is running hot

New coolant pump.

Thermostat is removed at all.

Fans kick at 200F low speed and 205F High speed

Coolant temp is 205-213F at 30-40MPH. Fans even don't shut.

190F at highway

 (outdoor temp is about 75)

 

i think its too hot

Any suggestions?


Edited by yoheer, 28 June 2020 - 12:24 PM.


#2 Injuneer

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Posted 28 June 2020 - 01:01 PM

"When engine oil is in working range temp (195F) - engine is running hot"

 

By "running hot" do you mean "Coolant temp is 205-213F at 30-40MPH (as you stated)? Fans even don't shut; 190F at highway"?  If so, that is not hot.

 

GM designed the engine to run at 210*F.  That's why that temperature is in the middle of the gauge.  Yields better fuel mileage and lower emissions.  How are you measuring oil temperature?

 

The stock t'stat is 180*F.  Why are you running without one?  Many people install a 160* t'stat, and lower the fan on/off temps in the PCM program.  Produces a small horsepower gain.  You have to use a t'stat specifically designed for the LT1's reverse flow cooling.

 

Stock fans are programmed to come on fan #1 (early 94), or both on low (late 94) at 226*F.  Fan #2 or both on high at 235*F.  Apparently your PCM has been reprogrammed for different temperatures.  Both fans running all the time can also be due to a PCM code.  Is the SES light on?  Have you scanned for codes?

 

"There is hayden transmission cooler installed in front of coolant radiator in my car."

 

Was this in addition to the trans cooler in the radiator?  Why?  It does reduce air flow through the radiator, and the air reaching the radiator can be slightly hotter.

 

Are you correctly bleeding air from the cooling system, using the two bleeder screws?


1994 FIREBIRD FORMULA
FRED

 
381ci all-forged stroker (Callies Stealth, Oliver billet rods, BME 2618-T61 nitrous pistons) - 10.8:1 - CNC LT4 heads/intake - Comp Cams solid roller - MoTeC M48 Pro engine management - 8 LS1 coils - 58mm TB - 74#/HR injectors - 300-shot dry nitrous - TH400 - Gear Vendors 0.78:1 O/D - Strange 12-bolt - 4.11 Pro-Street gears - AS&M headers - true duals - Corbeau seat - AutoMeter gauges - roll bar - Spohn suspension - QA1 shocks - a few other odds 'n ends. 800HP / 800lb-ft at the flywheel, on a 300-shot. 11.5 @ 117 MPH straight motor
 
https://www.firebird...9_698_32777.jpg

 


#3 yoheer

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Posted 28 June 2020 - 01:41 PM

I mean running hot with those temps considering removed t-stat and 200F low fan speed (I ordered 160 t-stat from rockauto and now I wait for it) I use the car only in summer. Now i've removed 180 stock t-stat just to make it run cooler.

I have an oil temp gauge installed.

I see lots of posts on the web, when guys use 160 t-stat and lower fan temp kicking. They say that they run 190 easily. With rare fans engaging.

I reprogrammed my PCM. Now it is 200/205 instead of 226/235

Hayden cooler was installed in addition to the trans cooler in the radiator, not instead of it. It was made after rebuilding my blown transmission.  It was made for longlife the tranny and heavy duty. Trans temp is 195 now.

Also I have engine oil coller installed for the same reason. And for common engine cooling. Engine oil cooler does not reduce air flow. It is installed aside.

About bleeding-I think it was correct. I used shbox manual.

Is it possible to make operating temp about 195 with rare fan engaging? Without rebuilding the whole cooling system.



#4 Injuneer

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Posted 28 June 2020 - 03:21 PM

How old is radiator?  Are cooling fins clean, not blocked by leaves or debris.  Has water jacket been chemically cleaned?  Is it possible the water pump driveshaft is damaged/missing teeth?  Has the ignition timing been reprogrammed - too much advance can cause it to run hot? Is there a possibility the pump suction hose is collapsing?  Is the pressure cap the right PSI rating, and has it been tested?  Does the cooling system hold pressure in a pressure test?  What ratio water to ethylene glycol coolant?  Every component of the cooling system has to be examined.  

 

I have oil and trans temp gauges, and they run ~195°F.  So does engine.  Stock LT1 oil cooler, and since car was originally an M6, only a fan assisted trans fluid cooler, not in front of the radiator. Trans is a TH400 with very high stall, and engine is 500 HP at the flywheel (without the 300-shot of nitrous).  Only changes from stock cooling system are 160° t'stat, fans reprogrammed for on at 195°, and a Griffin aluminum radiator.  But the radiator reflects the added need for cooling from the nitrous.



#5 yoheer

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Posted 28 June 2020 - 11:48 PM

Well. The radiator is from 1994. It's original. The car is 70k miles.
Fans are okay. I didnt clean the system chemically. Just distilled water. Water pump is 10k miles. New oem delco. Dont think it is faulty. Timing is not reprogrammed.
Things that pcm been disabled:
Air pump
Egr
Cat protection
Lowered idling
Hoses seem to be okay. No leaks anyway.
Cap is 16 instead of 18. Didn,t check but it keeps pressure when hot.
The mixture is 50/50 or smth about that. Dex-cool orange.
My temps are about
195 trans oil
195 engine oil
Water temp raises to 215 with manually switched on low speed fan and deleted t-stat at 30mph

#6 yoheer

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Posted 29 June 2020 - 05:16 AM

Today is hot. 85. Coolant raised to 230

#7 Injuneer

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Posted 29 June 2020 - 06:18 AM

Setting still, at idle on an 80°F day, how high does the coolant temp get?

 

Your operating temperatures are not high.  The issue is why do you need to run the fans to keep it that low?  The problem can be restricted air flow through the radiator - blockage by the trans cooler, plugged radiator fins, missing plastic air “ducting” leading up to the radiator.  Then there the issue of reduced heat transfer due to coated/corroded surfaces exposed to coolant, or because the bottom of the radiator or th lock is filled with sludge.  Finally, restricted coolant flow.

 

How are you measuring the coolant temp - from a PCM scanner, or from the dash gauge?  Have you checked the accuracy of the two coolant temperature sensors?

 

Now you added info that you have a manual fan switch, in addition to reprogrammed fan on/off temps.  Is that wired per Shoebox, so as to avoid a code for the fans?

 

You lowered the idle RPM - why?  Auto trans stock programming is 550 RPM in gear.  How low did you reset the target idle speed?  What other programming have you changed?

 

When you switched from conventional coolant to Dex-Cool did you completely flush and drain (using block drains) the coolant system?  Is there any evidence of brown sludge at the radiator fill neck.

 

Was the question about the pump suction hose collapsing clear?  When the pump pulls a suction to make the water flow, a soft hose can collapse on itself and restrict coolant flow.  Not about leaks or appearance.

 

With regard to “chemically cleaning the water jacket”, the question wasn’t about what quality water you are using.  Have you ever used a chemical additive in water to fully clean and flush the cooling system?  That would remove scale from the cast iron parts and hopefully purge gunk from the radiator.  If not, are facilities available at auto service shops to pressure flush the complete system?  At 26+ years, things can build up the prevent heat transfer, either by coating surfaces, or even blocking critical passages.  Most people have lost a factory radiator at that many years due to sludge buildup.  If the system wasn’t cleared of conventional coolant when the Dex-Cool was installed, it will sludge up even worse.

 

Is your heater core free flowing, not plugged up?  Does the heater supply line still have the flow restrictor (part #13 in diagram)?
 

http://shbox.com/1/h...hoses_93-94.jpg



#8 yoheer

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Posted 01 July 2020 - 11:51 AM

wow. So much questions. I will figure out everything and then will give answers



#9 Injuneer

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Posted 01 July 2020 - 01:06 PM

They aren't really "questions" as much at they are suggestions on where you need to look to find your problem.



#10 yoheer

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Posted 3 days ago

a lot of rust in radiator






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