new cooling- temp is oscillating - The 1947 - Present Chevrolet & GMC Truck Message Board Network

vtwinsport · 12-02-2009, 07:53 PM

New rad, high flow edlbrock water pump, 180 thermostat (yes its in properly), fan clutch, hoses, belt.
So here it is; Periodically, my temp gage runs up to 210/215/ 220 from 190/195 then comes back down to normal rather quickly (within minutes).
Any suggestions? All I can think of is a slipping belt but I should hear that right? Sticky thermostat?
Thanks in advance

cableguy0 · 12-02-2009, 07:55 PM

thermostat sticking.

spaseghost · 12-02-2009, 08:10 PM

a pain in the ass air bubble?

donut · 12-02-2009, 10:24 PM

Is the truck fully warmed up? My temps fluctuate quickly when the thermostat is opening and closing.

STOCKISH · 12-02-2009, 11:17 PM

Sounds like air in the system. Check it first thing in the morning and run the heat while you top it off. Have seen people have to raise the front of the truck with a jack to get the radiator cap higher than the heater core during filling.

vtwinsport · 12-03-2009, 10:57 AM

Hey thanks guys,
spaseghost; 1972super- never thought of an air bubble. thx
Will try that then the thermostat again

**Boog** · 12-03-2009, 01:41 PM

Some guys drill an 1/8" hole in the thermostat to help eleviate the air bubbles and swear by it. I've not tried it myself however.

vtwinsport · 09-04-2010, 08:58 PM

Didn't have to drill the water neck outlet at the intake. Seems when I upgraded to Auto meter guages, my local speed shop never mentioned the need for a new temp sending unit. My current sheep shop gave me one rated with the right ohms resistance for the autometer gauage and all is well. Runs steady at 180.
Thanks for all comments.

gchemist · 09-04-2010, 10:24 PM

Stop and go traffic? If so, then it's normal.

vtwinsport · 09-04-2010, 11:06 PM

yes, stop and go and on hwy.
Seems to have fixed all the concerns. The shop put a laser temp reader on water outlet and hoses and they confirmed the thermostat was working (oscillating) and true temp was 120-170 at the water neck when opened and closed.

12-02-2009, 07:53 PM	#1
vtwinsport Registered User Join Date: Nov 2008 Location: edmonton, alberta Posts: 293	new cooling- temp is oscillating New rad, high flow edlbrock water pump, 180 thermostat (yes its in properly), fan clutch, hoses, belt. So here it is; Periodically, my temp gage runs up to 210/215/ 220 from 190/195 then comes back down to normal rather quickly (within minutes). Any suggestions? All I can think of is a slipping belt but I should hear that right? Sticky thermostat? Thanks in advance __________________ 76 Silverado, 2wd, long box, 350/th350, 3.42 posi, edelbrock performer 64cc heads, edelbrock 1405, 2101 intake, Hedman Headers, Comp Cam XE262 http://beerbreadbike.wordpress.com/

12-02-2009, 07:55 PM	#2
cableguy0 Senior Member Join Date: Apr 2000 Location: Delta,Pa Posts: 14,948	Re: new cooling- temp is oscillating thermostat sticking. __________________ Owner of North Point Car Care in Dundalk Md. We specialize in custom exhaust on both modern and classic vehicles. We are a full service auto shop from classics to modern vehicles. Feel free to contact me with questions. I will give a 10% discount to any board member.

12-02-2009, 08:10 PM	#3
spaseghost certified tard Join Date: Jun 2009 Location: grand junction, colorado Posts: 182	Re: new cooling- temp is oscillating a pain in the ass air bubble? __________________ 85 swb bbc 5% tint 16.356 @ 84.81 8/07/09 4800 Ft., bad timing, carb tune, and traction, fugg it. 16.169 @ 84.29 8/28/09 good timing, no carb tune, some traction... 06 Equinox LT AWD, wife's and family ride 03 Mustang V6, CAI, Duals, Pullies, Programmer, Short Throw, wife's dream car?! 90 Eagle Talon, other project / space taker, GOT head!! 08 Silverado 2500 HD, the bad ass work truck

12-02-2009, 10:24 PM	#4
donut Registered User Join Date: Aug 2009 Location: S.C. Posts: 1,593	Re: new cooling- temp is oscillating Is the truck fully warmed up? My temps fluctuate quickly when the thermostat is opening and closing. __________________ '86 C-30 dually, 454/tbh400 '73 K-20 350/350/205 (sold ) I'm kinda like duct tape- no real purpose, but handy to have around.

12-02-2009, 11:17 PM	#5
STOCKISH Formerly- 1972SuperCheyenne Join Date: Oct 2008 Location: Wake Forest NC Posts: 5,782	Re: new cooling- temp is oscillating Sounds like air in the system. Check it first thing in the morning and run the heat while you top it off. Have seen people have to raise the front of the truck with a jack to get the radiator cap higher than the heater core during filling. __________________ --Josh My Build Thread:http://67-72chevytrucks.com/vboard/s...d.php?t=799218 A good crossthread is better than Loctite any day. Life is not about what you have, but who you have to share it with.

12-03-2009, 10:57 AM	#6
vtwinsport Registered User Join Date: Nov 2008 Location: edmonton, alberta Posts: 293	Re: new cooling- temp is oscillating Hey thanks guys, spaseghost; 1972super- never thought of an air bubble. thx Will try that then the thermostat again __________________ 76 Silverado, 2wd, long box, 350/th350, 3.42 posi, edelbrock performer 64cc heads, edelbrock 1405, 2101 intake, Hedman Headers, Comp Cam XE262 http://beerbreadbike.wordpress.com/

12-03-2009, 01:41 PM	#7
Boog laying low Join Date: Mar 2001 Location: Searcy, Ark. USA Posts: 13,524	Re: new cooling- temp is oscillating Some guys drill an 1/8" hole in the thermostat to help eleviate the air bubbles and swear by it. I've not tried it myself however. __________________ Boog 69 Chevy stepside, 358/T350, 4.11 posi, 4.5/4 drop, rallys, poboy driver primer is finer 91 Chevy sportside, Tahoe, Yukon & GMC Crewcab All GM..'nuff said. I stand for the flag and kneel at the cross

09-04-2010, 08:58 PM	#8
vtwinsport Registered User Join Date: Nov 2008 Location: edmonton, alberta Posts: 293	Re: new cooling- temp is oscillating Didn't have to drill the water neck outlet at the intake. Seems when I upgraded to Auto meter guages, my local speed shop never mentioned the need for a new temp sending unit. My current sheep shop gave me one rated with the right ohms resistance for the autometer gauage and all is well. Runs steady at 180. Thanks for all comments. __________________ 76 Silverado, 2wd, long box, 350/th350, 3.42 posi, edelbrock performer 64cc heads, edelbrock 1405, 2101 intake, Hedman Headers, Comp Cam XE262 http://beerbreadbike.wordpress.com/ Last edited by vtwinsport; 09-04-2010 at 11:07 PM.

09-04-2010, 10:24 PM	#9
gchemist BAD BOW-Silverado XST Join Date: May 2000 Location: Senior Member from Austin, TX Posts: 6,431	Re: new cooling- temp is oscillating Stop and go traffic? If so, then it's normal. __________________ Gerardo a.k.a. Mad Chemist Silverado XST videos

09-04-2010, 11:06 PM	#10
vtwinsport Registered User Join Date: Nov 2008 Location: edmonton, alberta Posts: 293	Re: new cooling- temp is oscillating yes, stop and go and on hwy. Seems to have fixed all the concerns. The shop put a laser temp reader on water outlet and hoses and they confirmed the thermostat was working (oscillating) and true temp was 120-170 at the water neck when opened and closed. __________________ 76 Silverado, 2wd, long box, 350/th350, 3.42 posi, edelbrock performer 64cc heads, edelbrock 1405, 2101 intake, Hedman Headers, Comp Cam XE262 http://beerbreadbike.wordpress.com/



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