Temperature problem! Need help... - The 1947 - Present Chevrolet & GMC Truck Message Board Network

jeff1vol · 02-13-2007, 01:21 PM

My temp. gauge keeps fluxuating to hot and back down to normal, but the engine does not seem to actually be running hot (no steam, etc.)!? As long as the truck is moving the temp will hold steady, but if I stop for a period of time with the engine idling, the temp. will start going up and down again.

Is this a bad thermo? Is there a sending unit that may be bad? Have any of you guys had similar trouble. The engine is a GM 350.
Thanks,
Jeff

bobthecop · 02-13-2007, 01:37 PM

sounds like the thermostat is closing early and opening late. That would be my guess, or a flow restriction.

1971LT1SWBPOSI373 · 02-13-2007, 02:05 PM

Could be a partially plugged radiator (flow restriction) or even low on coolant. Is the radiator actually full????

sb69chevy · 02-13-2007, 03:18 PM

A radiator hose isn't bad is it? That was my problem once. Thought it was the thermostat, changed it but neglected the hoses. Ran well for a day, then blew the lower rad hose off.

Just a thought.

Longhorn Man · 02-13-2007, 03:21 PM

that sounds like classic sticking t-stat, or low coolant level.

Rick Mills · 02-13-2007, 04:12 PM

Quote:

Originally Posted by Longhorn Man

that sounds like classic sticking t-stat, or low coolant level.

cooters · 02-13-2007, 08:12 PM

is your sender on top of the thermostat housing? This would happen in that case. Otherwise it seems to be a thermostat problem

GREASEMONKEY72 · 02-14-2007, 04:00 AM

whens the last time you changed the t-stat? because just like everyone has said thats most likely what it is

jeff1vol · 02-14-2007, 03:56 PM

sure its not a bad hose. I just replaced both about 3 months ago. If the coolant level is appropriate, I'll just get a new thermo and try that out.
Thanks again for your responses.

hvychve · 02-15-2007, 03:43 AM

what about the wire from the sender to the gauge, is it intermittantly shorting out ?

02-13-2007, 01:21 PM	#1
jeff1vol Registered User Join Date: Dec 2006 Location: Fredericksburg, VA Posts: 71	Temperature problem! Need help... My temp. gauge keeps fluxuating to hot and back down to normal, but the engine does not seem to actually be running hot (no steam, etc.)!? As long as the truck is moving the temp will hold steady, but if I stop for a period of time with the engine idling, the temp. will start going up and down again. Is this a bad thermo? Is there a sending unit that may be bad? Have any of you guys had similar trouble. The engine is a GM 350. Thanks, Jeff

02-13-2007, 01:37 PM	#2
bobthecop Senior Member Join Date: Nov 2006 Location: Yukon Oklahoma Posts: 2,647	Re: Temperature problem! Need help... sounds like the thermostat is closing early and opening late. That would be my guess, or a flow restriction. __________________ Happiness is towing your "new" truck home. 1972 C-10 1982 GMC (parts truck??) 1969 c10 parts truck 1969 C-10 ( my sons) 1992 Silverado 4X4 (now the boys truck)(now mine again) 2002 Tarus (my wife loves that car)

02-13-2007, 02:05 PM	#3
1971LT1SWBPOSI373 Registered User Join Date: Mar 2002 Location: Springfield, VA Posts: 460	Re: Temperature problem! Need help... Could be a partially plugged radiator (flow restriction) or even low on coolant. Is the radiator actually full???? __________________ 1971 Shortbed 350/350 w/ Posi-traction 3:73's 1996 Chevy Silverado TJ in Springfield, Virginia Likes old Chevy trucks Drinks Miller MGD

02-13-2007, 03:18 PM	#4
sb69chevy Registered User Join Date: Oct 2006 Location: Springfield, MO Posts: 375	Re: Temperature problem! Need help... A radiator hose isn't bad is it? That was my problem once. Thought it was the thermostat, changed it but neglected the hoses. Ran well for a day, then blew the lower rad hose off. Just a thought. __________________ 1969 C/10 swb, 350, powerglide (daily driver) 2005 CRV (wife's ride)

02-13-2007, 03:21 PM	#5
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,693	Re: Temperature problem! Need help... that sounds like classic sticking t-stat, or low coolant level.

02-13-2007, 08:12 PM	#7
cooters Senior Member Join Date: Oct 2006 Location: Edmonton Alberta Posts: 458	Re: Temperature problem! Need help... is your sender on top of the thermostat housing? This would happen in that case. Otherwise it seems to be a thermostat problem

02-14-2007, 04:00 AM	#8
GREASEMONKEY72 Registered User Join Date: Aug 2006 Location: Bakersfield,CA Posts: 7,893	Re: Temperature problem! Need help... whens the last time you changed the t-stat? because just like everyone has said thats most likely what it is __________________ -steven Alte Seele S.S. "Allison" '72 C/10 LWB 350SB/TH350 - DD PITBULL IS NOT A CRIME

02-14-2007, 03:56 PM	#9
jeff1vol Registered User Join Date: Dec 2006 Location: Fredericksburg, VA Posts: 71	Thanks ya'll! I'll check the levels soon. I know for sure its not a bad hose. I just replaced both about 3 months ago. If the coolant level is appropriate, I'll just get a new thermo and try that out. Thanks again for your responses.

02-15-2007, 03:43 AM	#10
hvychve To The Levy Join Date: Jan 2007 Location: california Posts: 391	Re: Temperature problem! Need help... what about the wire from the sender to the gauge, is it intermittantly shorting out ?



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