01 Suburban 5.3 Not Reaching Operating Temperature

jjtmarineb2 · April 23, 2011

hello, I have been battling and scratching my head over this problem for quite some time now and I'm at wits end! I have a 2001 Suburban 5.3 and if the temp outside is below 60-70's it will not reach operating temperature. lately it has been around 40F here and driving to work (45-50 min) the truck will not budge over 135F (confirmed with scan tool and non contact thermometer). I have replaced the thermostat twice, second time due to waterpump leakage. If I completely block off the front of the radiator with cardboard it will reach 185 (135-140 if it's really cold out) but not for a half hour or more. Heat blows marginally warm. The only modifications are a cold air intake and edelbrock shorty headers. Has anyone experienced these symptoms or have a clue as to what I should do next? Could the headers be the culprit? Any help is greatly appreciated! Thanks in advance.

8.1HD/ALLISON · April 23, 2011

Are you putting the stock thermostat back in? I wouldn't think you could get 2 bad ones. Headers should not cause issue. Has to be something thermostat related, IMO.

jjtmarineb2 · April 25, 2011

stock thermostat both times. Maybe if I get one from gm?

asc08 · April 25, 2011

http://www.gm-trucks.com/forums/index.php?...130640&st=0

Have you checked out this post? The difference is, his heat was blowing hot, but the gauge was reading low. I think in the end he determined that it was the dash gauge not reading correctly...

If the scan gauge is reading the same as your dash gauge, it could be the sending unit. In the attached topic, there was some talk of the lower portion of the radiator getting blocked, causing the fan clutch to get a 'false high' reading, causing the fan to over cool the radiator.

I would be cautious when blocking the radiator off to achieve a reading that you think is 'normal'. If the system is not properly reading the temperature, you may end up with a much bigger problem.