overheating prob with new engine - The 1947 - Present Chevrolet & GMC Truck Message Board Network

superchevy · 01-21-2005, 01:01 PM

I'm beginning to suspect a faulty gauge, but here's what's happenning:
Installed a new, dyno-tested 454 in my '77 Silverado. New radiator, waterpump, thermostat, hoses, temp sending unit, etc, etc. Filled with coolant. Fired up engine. While adjusting carb, setting idle, and checking for leaks, noticed temp gauge creeping toward HOT. Turned on heater to see if functioning or trapped air bubble. Heater works well, slowed temp gauge rise, but still got in the red HOT, so shut her down. Upper, lower radiator hoses hot to touch. No leaks.
Let engine cool down. Drained coolant enough to remove thermostat housing.
Removed thermostat, drilled small hole in thermostat to relieve any "air pocket" issues. Refilled radiator. Fired up engine. Took a test drive down the street and back. Pulled back in driveway, watched temp gauge go back up to red HOT.
I'm going to try to verify gauge working properly.
Any other thoughts?
Thanks, SC

CHEVYE · 01-21-2005, 01:12 PM

how hot is your gauge, or what temp? my big block is always hot and i`ve heard it`s just the norm. it sets at like 230 sometimes and my last small block ran at a constant 180, so i kind of freaked at first.

**'70_402** · 01-21-2005, 01:17 PM

i got a 180 therm in my big block and my motor usually sits at 200 or 210 even with the 180....what degree therm do you have in there??

tom hand · 01-21-2005, 02:20 PM

Get a cooking thermometer from a grocery store and remove the rad cap and put it in the coolant

jhow66 · 01-21-2005, 04:36 PM

What year 454? Might have a reverse flow pump.

superchevy · 01-21-2005, 04:54 PM

I've got a 180 therm in it.
It's a '73 454 and heads; nothing special; .030 over, 9:1 flat tops, little bit of a cam.
I'm going to put an aftermarket water temp gauge in it tonight, and see just how hot it gets.
I'll post the result.
Thanks,
SC

ebfabman · 01-21-2005, 06:57 PM

superchevy, how about the fan, clutch, and shroud? Is the setup all stock?

superchevy · 01-21-2005, 07:47 PM

Well, it must have been a faulty sending unit or gauge, as I installed a Sun temp gauge and sending unit just now, and it never got over 190. I was worried a bit, because I need to run some line pressure tests on the 700R4 to get it dialed in right, and you have to be able to idle for awhile to do that.
One step closer to getting her on the road.
Thanks for the help,
SC

Purs · 01-21-2005, 08:30 PM

glad it wasn't anything serious. I had an autometer mechanical gauge go bad. Actually the gauge was fine but the line got slightly crimped and caused the gauge to read inaccurate.

01-21-2005, 01:01 PM	#1
superchevy Got big-block? Join Date: Jul 2000 Location: Austin, Texas Posts: 2,453	overheating prob with new engine I'm beginning to suspect a faulty gauge, but here's what's happenning: Installed a new, dyno-tested 454 in my '77 Silverado. New radiator, waterpump, thermostat, hoses, temp sending unit, etc, etc. Filled with coolant. Fired up engine. While adjusting carb, setting idle, and checking for leaks, noticed temp gauge creeping toward HOT. Turned on heater to see if functioning or trapped air bubble. Heater works well, slowed temp gauge rise, but still got in the red HOT, so shut her down. Upper, lower radiator hoses hot to touch. No leaks. Let engine cool down. Drained coolant enough to remove thermostat housing. Removed thermostat, drilled small hole in thermostat to relieve any "air pocket" issues. Refilled radiator. Fired up engine. Took a test drive down the street and back. Pulled back in driveway, watched temp gauge go back up to red HOT. I'm going to try to verify gauge working properly. Any other thoughts? Thanks, SC __________________ '68 CST SWB factory 396/T400 buddy buckets, a/c, ps, pb '72 Corvette convertible 454/4spd/ac, ps, pb '73 GMC Sierra Grande short wide 454/T400 ps, pb, ac '77 K5 Blazer black on red, 350/T350/NP205 ps, pb, ac all original '78 GMC Sierra Classic short wide 454/T400 ps, pb, ac '72 GMC Sprint SP454. 1 of 38 built. '73 GMC Sprint SP454. 1 of 71 built. '75 GMC Sprint SP454. 1 of 25 built. SOLD! '72 GMC K25 4x4 468/4L80e/NP205 build thread http://67-72chevytrucks.com/vboard/s...23#post4324423 SOLD!'55 Chevy gasser 496/4spd build thread http://67-72chevytrucks.com/vboard/s...96#post4324396

01-21-2005, 01:12 PM	#2
CHEVYE my gas saver Join Date: Sep 2003 Location: Clarksville, TN Posts: 2,046	how hot is your gauge, or what temp? my big block is always hot and i`ve heard it`s just the norm. it sets at like 230 sometimes and my last small block ran at a constant 180, so i kind of freaked at first. __________________ 85' SWB, 4.3/TH350, getting ready for paint 84`SWB, 462ci./TH400, cowl hood, 15" billet spec., flows, blazer buckets/console, flat black 71`SWB, project ebay feedback

01-21-2005, 01:17 PM	#3
'70_402 Senior Member Join Date: Dec 2003 Location: Pampa, Texas Posts: 1,554	i got a 180 therm in my big block and my motor usually sits at 200 or 210 even with the 180....what degree therm do you have in there?? __________________ https://www.ebay.com/itm/29620574751...mis&media=COPY

01-21-2005, 02:20 PM	#4
tom hand CCRider Join Date: Feb 2000 Location: Olive Branch,MS,USA Posts: 2,232	Get a cooking thermometer from a grocery store and remove the rad cap and put it in the coolant __________________ 72 GMC Sierra SWB almost finished---- 84 Softail Olive Branch MS

01-21-2005, 04:36 PM	#5
jhow66 Registered User Join Date: Jun 2002 Location: Knoxville Tenn. Posts: 3,058	What year 454? Might have a reverse flow pump. __________________ 56 Chevy Bel-Air 2dr. HT (purchased new) 71 Chevy Cheyenne SWB PU (502HO) 65 GMC short bed step--work in progress and my gofer

01-21-2005, 04:54 PM	#6
superchevy Got big-block? Join Date: Jul 2000 Location: Austin, Texas Posts: 2,453	I've got a 180 therm in it. It's a '73 454 and heads; nothing special; .030 over, 9:1 flat tops, little bit of a cam. I'm going to put an aftermarket water temp gauge in it tonight, and see just how hot it gets. I'll post the result. Thanks, SC __________________ '68 CST SWB factory 396/T400 buddy buckets, a/c, ps, pb '72 Corvette convertible 454/4spd/ac, ps, pb '73 GMC Sierra Grande short wide 454/T400 ps, pb, ac '77 K5 Blazer black on red, 350/T350/NP205 ps, pb, ac all original '78 GMC Sierra Classic short wide 454/T400 ps, pb, ac '72 GMC Sprint SP454. 1 of 38 built. '73 GMC Sprint SP454. 1 of 71 built. '75 GMC Sprint SP454. 1 of 25 built. SOLD! '72 GMC K25 4x4 468/4L80e/NP205 build thread http://67-72chevytrucks.com/vboard/s...23#post4324423 SOLD!'55 Chevy gasser 496/4spd build thread http://67-72chevytrucks.com/vboard/s...96#post4324396

01-21-2005, 06:57 PM	#7
ebfabman Registered User Join Date: Nov 2001 Location: Concord, NC Posts: 2,489	superchevy, how about the fan, clutch, and shroud? Is the setup all stock?

01-21-2005, 07:47 PM	#8
superchevy Got big-block? Join Date: Jul 2000 Location: Austin, Texas Posts: 2,453	Well, it must have been a faulty sending unit or gauge, as I installed a Sun temp gauge and sending unit just now, and it never got over 190. I was worried a bit, because I need to run some line pressure tests on the 700R4 to get it dialed in right, and you have to be able to idle for awhile to do that. One step closer to getting her on the road. Thanks for the help, SC __________________ '68 CST SWB factory 396/T400 buddy buckets, a/c, ps, pb '72 Corvette convertible 454/4spd/ac, ps, pb '73 GMC Sierra Grande short wide 454/T400 ps, pb, ac '77 K5 Blazer black on red, 350/T350/NP205 ps, pb, ac all original '78 GMC Sierra Classic short wide 454/T400 ps, pb, ac '72 GMC Sprint SP454. 1 of 38 built. '73 GMC Sprint SP454. 1 of 71 built. '75 GMC Sprint SP454. 1 of 25 built. SOLD! '72 GMC K25 4x4 468/4L80e/NP205 build thread http://67-72chevytrucks.com/vboard/s...23#post4324423 SOLD!'55 Chevy gasser 496/4spd build thread http://67-72chevytrucks.com/vboard/s...96#post4324396

01-21-2005, 08:30 PM	#9
Purs Got Big Block? Join Date: Apr 2000 Location: West Texas Posts: 1,510	glad it wasn't anything serious. I had an autometer mechanical gauge go bad. Actually the gauge was fine but the line got slightly crimped and caused the gauge to read inaccurate. __________________ "Experience is what you get when you didn't get what you wanted."



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