5.3 fluctuating coolant temps/heat problem
10-20-2014, 06:46 PM
#1
5.3 fluctuating coolant temps/heat problem I have a 2004 Silverado with 130k miles, and it has developed an issue where the coolant temps go up to about 244* and then back down to ~204*, verified with the Torque app. The high temps only last for maybe 203 mins, and then go right back down. This happens at any time, whether it be sitting in traffic, city driving, or on the highway.
Now the very weird part (and problem since it's now cold where I live) is that when the temps go up, the air blowing out of the vents is COLD no matter what I have the HVAC set to. When the temps stabilize back to the normal 204* range, the air blows hot as it should. Today I played with the HVAC and no matter what I did, setting it to hot or cold, or having it on or off, had no effect on the temps, so the HVAC doesn't seem to have any part in these fluctuations. I don't smell coolant at any point in my drive or afterwards if that helps any.
Does anyone have any idea what the culprit here is? Right now I'm thinking there's a large air bubble in the coolant system that when it reaches the heater core causes the core to lose heat and the system to blow cold air. But at the same time I don't know why/how an air bubble would cause the coolant temp sensor to read high at the very same time I'm losing heat. Would the thermostat possibly be sticking? I'm not real familiar with the LSx cooling system as I've never had to deal with it, and I have yet to see how everything is routed under the hood.
Also, since I only drive this thing to work and back, I never have the chance to check the coolant level (always have my son with me when I get home so I'm always too busy to remember to check the coolant) so I don't know if it's low. I'll try and remember to check that tomorrow when I get home.
Thanks in advance, it sucks not having heat when it's 40 degrees out
Now the very weird part (and problem since it's now cold where I live) is that when the temps go up, the air blowing out of the vents is COLD no matter what I have the HVAC set to. When the temps stabilize back to the normal 204* range, the air blows hot as it should. Today I played with the HVAC and no matter what I did, setting it to hot or cold, or having it on or off, had no effect on the temps, so the HVAC doesn't seem to have any part in these fluctuations. I don't smell coolant at any point in my drive or afterwards if that helps any.
Does anyone have any idea what the culprit here is? Right now I'm thinking there's a large air bubble in the coolant system that when it reaches the heater core causes the core to lose heat and the system to blow cold air. But at the same time I don't know why/how an air bubble would cause the coolant temp sensor to read high at the very same time I'm losing heat. Would the thermostat possibly be sticking? I'm not real familiar with the LSx cooling system as I've never had to deal with it, and I have yet to see how everything is routed under the hood.
Also, since I only drive this thing to work and back, I never have the chance to check the coolant level (always have my son with me when I get home so I'm always too busy to remember to check the coolant) so I don't know if it's low. I'll try and remember to check that tomorrow when I get home.
Thanks in advance, it sucks not having heat when it's 40 degrees out
Last edited by LS1again; 10-21-2014 at 06:14 AM.
10-21-2014, 06:09 AM
#2
So this morning on the way in to work, an 8 mile/15 minute drive of mixed city and highway, the temp stayed right up between 239-244 and never went down lower than I think 230, which was for less than a minute. Luckily it was a "mild" 50 degrees so I didn't need the heat too bad lol.