Temperature spiking - The 1947 - Present Chevrolet & GMC Truck Message Board Network

FMJ_Blazer · 09-04-2011, 08:07 PM

Hope someone can help me. Have a 71 blazer with 355 blueprint engine with electric fan and stewart warner gauges and matching sending unit. Temperature was solid at 195, but the other day on my way home from work, the gauge spiked at 240. I slowed down and it dropped to 200 or so. It will spike up and then settle down again. Engine has 300 miles on it. It will do this under a varying of situations - subdivision to highway, makes no difference.

I searched and could not find similar problem.

rsavage · 09-05-2011, 01:53 PM

There are a lot of variables. Is the radiator clean and of ample size to cool the new engine - i.e. Do you have a 4 core or 2 core (if stock copper/brass radiator)?. Are you sure that you have no air pockets in the coolant or did you push some out over the first few days of running so that now it is low? Do you have a stat in it? You could try a 165 or 180. If it got that hot, I'd replace the stat. My experience is that once they've been overheated they don't work properly. Don't have a lot of experience with electric fans so couldn't venture an opinion other than what temp do you have it set for turning on? Is it moving air the right way? Shroud on it? Timing not too far advanced? Radiator hoses not collapsing when running? These are some of the things I'd look at in trying to diagnose the problem. Good Luck - keep us posted.

FMJ_Blazer · 09-10-2011, 11:43 AM

sorry for the delay in replying...had to travel this past week. I appreciate the response and questions to spur some thinking Yukon. Electric fan is on inside and pulling air through so no shroud. Hoses are not collapsing. I just bought a new 180 thermostat and will install today. 180 is where the fan is set to come on. I guess I could lower that. The advance is a little high at 14 based on recommendation from blueprint engines. The radiator is a brand new unit and it has been a year since i bought it. Believe it is a stock 3 row from LMC. You mentioned air pockets. How do i know if I have or how to get rid of?

What is weird is that my left bank is running hotter than my right. Not sure why.

BobbyK · 09-11-2011, 05:03 PM

Did you let the system "burp" itself after filling the rad the 1st time?

09-04-2011, 08:07 PM	#1
FMJ_Blazer Registered User Join Date: Nov 2010 Location: Cumming, GA Posts: 26	Temperature spiking Hope someone can help me. Have a 71 blazer with 355 blueprint engine with electric fan and stewart warner gauges and matching sending unit. Temperature was solid at 195, but the other day on my way home from work, the gauge spiked at 240. I slowed down and it dropped to 200 or so. It will spike up and then settle down again. Engine has 300 miles on it. It will do this under a varying of situations - subdivision to highway, makes no difference. I searched and could not find similar problem.

09-05-2011, 01:53 PM	#2
rsavage Registered User Join Date: Aug 2009 Location: Alden NY Posts: 2,705	Re: Temperature spiking There are a lot of variables. Is the radiator clean and of ample size to cool the new engine - i.e. Do you have a 4 core or 2 core (if stock copper/brass radiator)?. Are you sure that you have no air pockets in the coolant or did you push some out over the first few days of running so that now it is low? Do you have a stat in it? You could try a 165 or 180. If it got that hot, I'd replace the stat. My experience is that once they've been overheated they don't work properly. Don't have a lot of experience with electric fans so couldn't venture an opinion other than what temp do you have it set for turning on? Is it moving air the right way? Shroud on it? Timing not too far advanced? Radiator hoses not collapsing when running? These are some of the things I'd look at in trying to diagnose the problem. Good Luck - keep us posted. __________________ 1961 C1 Corvette 1959 El Camino 350 TPI, 9" 4 w disc 69 Blazer K5 - sold July '20 2021 Durango RT 5.7

09-10-2011, 11:43 AM	#3
FMJ_Blazer Registered User Join Date: Nov 2010 Location: Cumming, GA Posts: 26	Re: Temperature spiking sorry for the delay in replying...had to travel this past week. I appreciate the response and questions to spur some thinking Yukon. Electric fan is on inside and pulling air through so no shroud. Hoses are not collapsing. I just bought a new 180 thermostat and will install today. 180 is where the fan is set to come on. I guess I could lower that. The advance is a little high at 14 based on recommendation from blueprint engines. The radiator is a brand new unit and it has been a year since i bought it. Believe it is a stock 3 row from LMC. You mentioned air pockets. How do i know if I have or how to get rid of? What is weird is that my left bank is running hotter than my right. Not sure why. Last edited by FMJ_Blazer; 09-10-2011 at 11:49 AM.

09-11-2011, 05:03 PM	#4
BobbyK Registered User Join Date: May 2000 Location: Petrolia,Ontario,Canada but working in Port Huron,Mi. Posts: 1,771	Re: Temperature spiking Did you let the system "burp" itself after filling the rad the 1st time? __________________ 71 blazer,350SBC,approx.375HP,700R4,factory GM TPI.Dual electric fans,33x12.5x15 ATR on stock suspension. Petrolia,Ontario,Canada but working in Port Huron,MI. See ALL my Blazer pic's HERE



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