Temp guage antics - The 1947 - Present Chevrolet & GMC Truck Message Board Network

05crewcab · 05-20-2010, 10:17 AM

Hi guys,

Lately my temp guage has been acting strange. In the morning while driving for about the first 5-10 mins the temp needle will rise consistently to HOT and stay there for about a minute, then it will fall back down to normal (vertical) and stay put. Can anyone tell me why this is occuring? It only happens in the morning...

Thanks

geezer#99 · 05-20-2010, 10:40 AM

It warms up to the hot mark because the thermostat is closed which is needed to warm up the motor. When it opens the coolant circulates freely the rad cools it and the gauge goes back to normal. Just like it's supposed to.

05crewcab · 05-20-2010, 10:49 AM

Thanks for the response.

I figured it was t-stat related, but none of my other vehicles (all makes) do this...they all just gradually warm up to operating temperature. The guage on this old truck must be pretty touchy...

Bears63 · 05-20-2010, 11:04 AM

It's also quite possible that your thermostat is sticking a little too. My '71 does the gradual warm up to operating temp, you barely notice the thermostat opening.

junkyardjohn · 05-20-2010, 02:56 PM

BELIEVE IT OR NOT.. BUT MAYBE YOU'RE 39 YEAR OLD STOCK GAGE IS FAULTY. YOU CAN BUY AN EL-CHEAPO (TEMPORARILLY INSTALL) & SENDING UNIT TO COMPARE IT TO YOUR ORIGINAL GAGE TO SET YOUR MIND AT EASE. TEMPERATURE IS YOU'RE MOTORS 2ND WORST ENEMY. (RIGHT AFTER CLEAN LUBE)

JOHN

Blazer1970 · 05-20-2010, 05:37 PM

It is because the temp sender is in the head on these trucks. The head heats up a lot faster than the intake manifold does. Since the thermostat is in the intake, the coolant in the head will get substantially above your normal operating temp before the coolant in the intake gets hot enough to open the t-stat. Most newer vehicles have the temp sender in the intake so you do not see it on the gauge, but they still work exactly the same way.

05crewcab · 05-21-2010, 12:03 AM

i'm pretty sure my temp guage is working correctly, so i am leaning towards a combination of temp differences between the sensor and the t-stat, and the t-stat sticking a little...either way, i'm not gonna worry about it anymore!

Thanks for the responses guys.

05-20-2010, 10:17 AM	#1
05crewcab Registered User Join Date: Mar 2010 Location: Minnetonka, MN Posts: 409	Temp guage antics Hi guys, Lately my temp guage has been acting strange. In the morning while driving for about the first 5-10 mins the temp needle will rise consistently to HOT and stay there for about a minute, then it will fall back down to normal (vertical) and stay put. Can anyone tell me why this is occuring? It only happens in the morning... Thanks __________________ 1971 C-20 350/350

05-20-2010, 10:40 AM	#2
geezer#99 Registered User Join Date: Aug 2009 Location: Bowser Posts: 13,731	Re: Temp guage antics It warms up to the hot mark because the thermostat is closed which is needed to warm up the motor. When it opens the coolant circulates freely the rad cools it and the gauge goes back to normal. Just like it's supposed to.

05-20-2010, 10:49 AM	#3
05crewcab Registered User Join Date: Mar 2010 Location: Minnetonka, MN Posts: 409	Re: Temp guage antics Thanks for the response. I figured it was t-stat related, but none of my other vehicles (all makes) do this...they all just gradually warm up to operating temperature. The guage on this old truck must be pretty touchy... __________________ 1971 C-20 350/350

05-20-2010, 11:04 AM	#4
Bears63 ...just another truck junkie.. Join Date: May 2009 Location: Watertown, SD Posts: 698	Re: Temp guage antics It's also quite possible that your thermostat is sticking a little too. My '71 does the gradual warm up to operating temp, you barely notice the thermostat opening. __________________ Mike "Bear" Shea

05-20-2010, 02:56 PM	#5
junkyardjohn Registered User Join Date: Aug 2001 Location: SOMERSET KY. Posts: 6,425	Re: Temp guage antics BELIEVE IT OR NOT.. BUT MAYBE YOU'RE 39 YEAR OLD STOCK GAGE IS FAULTY. YOU CAN BUY AN EL-CHEAPO (TEMPORARILLY INSTALL) & SENDING UNIT TO COMPARE IT TO YOUR ORIGINAL GAGE TO SET YOUR MIND AT EASE. TEMPERATURE IS YOU'RE MOTORS 2ND WORST ENEMY. (RIGHT AFTER CLEAN LUBE) JOHN __________________ junkyardjohn 69 1 TON TOW TRUCK // 84 4WD CUCV BLAZER// 85 1 TON 4WD STAKE TRUCK// 86 M1031 5/4 TON 4WD CUCV// ALOT OF OLD TRUCKS FOR ONE OLD MAN TO DRIVE. THERES ROOM FOR ALL OF GODS CREATURES RIGHT NEXT TO MY MASHED POTATOES// LIFE MEMBER OF P.E.T.A (PEOPLE EATING TASTY ANIMALS) DON'T RENT U-HAUL ALWAYS TELL THE TRUTH IT WILL AMAZE PART OF THE PEOPLE & ASTONISH THE REST

05-20-2010, 05:37 PM	#6
Blazer1970 Registered User Join Date: Dec 1999 Location: Old Mission, MI, USA Posts: 2,507	Re: Temp guage antics It is because the temp sender is in the head on these trucks. The head heats up a lot faster than the intake manifold does. Since the thermostat is in the intake, the coolant in the head will get substantially above your normal operating temp before the coolant in the intake gets hot enough to open the t-stat. Most newer vehicles have the temp sender in the intake so you do not see it on the gauge, but they still work exactly the same way. __________________ Tim

05-21-2010, 12:03 AM	#7
05crewcab Registered User Join Date: Mar 2010 Location: Minnetonka, MN Posts: 409	Re: Temp guage antics i'm pretty sure my temp guage is working correctly, so i am leaning towards a combination of temp differences between the sensor and the t-stat, and the t-stat sticking a little...either way, i'm not gonna worry about it anymore! Thanks for the responses guys. __________________ 1971 C-20 350/350

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