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post #1 of (permalink) Old 07-01-2001, 02:20 PM
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454 runs too hot

Recently acquired a '89 GMC 4x4 with 454. Was running hot so I replaced cracked heads, water pump, fan clutch, thermostat and upgraded to 4 core radiator. Runs at 230 with A/C on in traffic- 220 w/o A/C. Any ideas

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post #2 of (permalink) Old 07-01-2001, 02:39 PM
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Re: 454 runs too hot

how about a radiator flush.... or better yet, a new 3 core radiator with trany cooler.

post #3 of (permalink) Old 07-01-2001, 02:44 PM
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Re: 454 runs too hot

<font face="Comic Sans MS">He upgraded to a 4 core radiator already... I'm going to stick with what I told him in the Q&A forum that the reason it is heating up is the huge condensor for the A/C is in front of the radiator and in a warmer climate with the A/C on it's going to be pulling lots of heat out and dumping it directly into the radiator. Meaning that you have much hotter air flowing through the radiator and it won't cool as effectively. Heat transfers better as the temperature differential goes up. The cooler the air you can get flowing through the radiator the better. Just shut off the A/C in heavy traffic when you're at slower speeds (higher speeds = more airflow through your radiator and better cooling). More airflow works because you have two possible ways to improve your cooling in a radiator. Increase the temperature differential (cooler air), and increase the volume of air flowing through the radiator. Technically the condenser causes problems also because it disrupts the airflow through the radiator. [img]/wwwthreads_images/icons/crazy.gif[/img] Just my thoughts. Especially since it's assumed that it's operating fine when the a/c isn't on and in lighter traffic (assuming higher speeds)... [img]/wwwthreads_images/icons/crazy.gif[/img]

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Do you have a clutch fan? Is it properly working? Do you have a fan shroud? You need one. If you don't have one procure one. It'll make a huge difference. </font>

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post #4 of (permalink) Old 07-01-2001, 02:50 PM
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Re: 454 runs too hot

Hey there
I have a 73 C20 with a 454. It used to run at 195* no matter how the driving conditions are.
Last week I took it out and it was running at 240* and when I shut it down it would shoot to 280*.
I verified that the gage was correct with my infra red temp gun. And it was on the money.
It has been several years since I replaced the stat so I am going to try that first. I Have been running a 195 stat in it and when the weather is realy hot the engine runs about 210*
When I first got the truck it was summer and I was hauling wood and stuff and the temp would get real hot.
I installed a tranny cooler and ran the ATF through it first then routed it through the radiator.
That dropped the engine temp way down.

post #5 of (permalink) Old 07-01-2001, 03:05 PM
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Re: 454 runs too hot

I think Sandman is probably on target. Something else to check. I had a bad stat in my '96 Blazer. Popped in AutoZone and picked up a new one. Still overheated, just not as quickly. Removed the new stat and compared the size of the orrifice with the old one. It was quite a bit smaller restricting water flow. Also, new doesn't always mean good.

Good luck,


post #6 of (permalink) Old 07-01-2001, 05:12 PM
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Re: 454 runs too hot

got an 88 with a 454 and put in a 180 stat since I live in the desert and it dropped quite a bit. Went from 210 to about 190.

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post #7 of (permalink) Old 07-01-2001, 05:20 PM
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Re: 454 runs too hot

hmm... still running hot with a 4 core, huh? I think you should look for lower temp stats like desertrat suggested. Maybe even go as low as 160* - I doubt your engine will run that cold, but it just means the cooling system will open up that much earlier, and stay open that much longer.

post #8 of (permalink) Old 07-01-2001, 06:03 PM
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Re: 454 runs too hot

I'm running a 180 stat in the K5 and it never goes above 170.
it was 90 the other day and running in traffic it stayed at 160.
A bit to cool for me.
Another thing to consider is that the cap plays an important role in cooling.
The higher the pressure the cooler the plant will run.
I have Stant 13lb caps on all of my rigs.
The 81 Burb that I have has a 454 as well and A/C it stays within the normal range but it also has an oil cooler as well as a tranny cooler.
But it also rarely gets above 90* here.

post #9 of (permalink) Old 07-03-2001, 11:38 AM
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Re: 454 runs too hot

A friend of mine had the same problem with his truck!
he and I have almost identical trucks 1ton Chevy's with 454's mine is a 1990 his is an 1989
Mine stays right at about 190-200 with the AC on. His was running like 260 without the ac on.
He changed everything out (like you did), it still ran the same [img]/wwwthreads_images/icons/mad.gif[/img]
Then we adjusted his timing! That was it! the temp dropped right down to the same as mine! His timing was a little too advanced, yours might be too!
It would be worth a try[img]/wwwthreads_images/icons/smile.gif[/img]

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post #10 of (permalink) Old 07-03-2001, 12:13 PM
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Re: 454 runs too hot

I've also got a 454 C2500 that I'm fighting the same problem with.New radiator helped some but it still wants to run 210 driving around on hot days.I've been doing some research and you should read the post at www.enginecooling.com,go to the link for 34 inch rad. cores.Seems that GM is having a lot of problems with this powertrain in trucks.I'm going to try and find a lower temp 42 mm t/stat ,I'll be checking the mairine shops soon as the regular parts places don't have anything lower than 195,then if thats comes up empty I'll cut the center out of the old one and reinstall just the disk.I've also been sizing up electric fans everytime I go into a junk yard.I've also noticed that the calibration of the clutch fan is "hi" and I might see if a 6.5 diesel cluth fan fits the front of the water pump as they seem to come on lower around 190 or even less as the C2500 suburban the wife pulls her horse's with never runs much over 180 as the fan "locks" up and pull LOTS of air through the radiator.I've also noticed that 6.5 diesels have extra hole's and duct work in the front bumper to let in more air.I've also noticed that the grills are more "open" by having smaller grating starting in 94 than the earlier trucks.Maybe to let more air into the rad????

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