4800 vortec engine temp

andy.morris79 · December 12, 2014

When the outside temps are below freezing, my truck will not come up to normal temp (195-205). It will stay at about 185. New thermostat, waterpump, radiator, and cap. Its not holding pressure like it should but no sign of leak. When outside temps are above 35, the temp comes up fine within a few miles, when below freezing, i can drive 30+ miles and still only around 185. Any info?

fondupot · December 12, 2014

is the thermostat a 185 degree thermostat?

andy.morris79 · December 12, 2014

186 degree. Also new fan clutch.

00Silverado4x4 · December 12, 2014

Not sure what you mean by not holding pressure?? If the pressure is low then you need to replace the cap.

andy.morris79 · December 12, 2014

I have already replaced the cap. New radiator, new water pump, new thermostat, new cap, new fan clutch. It will not come up to normal temp when the outside temp is below freezing. Like when i leave for work in the morning it may me 28 deg outside and i could drive 30 miles and it would not get above 185. Then in the afternoon when the outside temp is 50, and the truck has been sitting for 8 hrs, i drive back home and it does just fine. But then other mornings when the outside temp is 40, it does fine too so im at a point where i dont understand it. Now with the pressure, the radiator hoses dont hold pressure at all. None of the time. Like there is a leak, but im not loosing any coolant nor is there any sign of a leak.

andy.morris79 · December 13, 2014

Anybody? Anything?

Crf450r420 · December 13, 2014

Must be a leak to not hold pressure. Have it pressure tested. They pump up the system by replacing the radiator cap with a pump. Have them put a lot pressure if it holds at say 12 psi and go to 25 psi. If it holds at both then it must be the cap which they can test also. Small chance the seal area for the cap on the radiator is messed up. The thermostat maintains the minimum temp of the motor, so that is the highest it will get when it is cold out. The top temp in hot temps is regulated by the thermal efficiency of the system or the fan on temp if all is working well.

andy.morris79 · December 15, 2014

Correct me if im wrong but the purpose of the thermostat is for it to stay closed until the engine gets up to the operating temp of the particular thermostat, in this case being 186 deg, then it opens up. Then allowing coolant from the radiator to flow into the engine. Then, the radiator and fan clutch maintain the "normal" operating temp of the vehicle. The thermostat does not maintain the "normal" operating temp of a vehicle. It is there just to get the engine up to that operating temp of that particular thermostat. Correct?

andy.morris79 · December 23, 2014

So much for this!

00Silverado4x4 · December 23, 2014

New thermostat stuck partially open??

Crf450r420 · December 23, 2014

Correct me if im wrong but the purpose of the thermostat is for it to stay closed until the engine gets up to the operating temp of the particular thermostat, in this case being 186 deg, then it opens up. Then allowing coolant from the radiator to flow into the engine. Then, the radiator and fan clutch maintain the "normal" operating temp of the vehicle. The thermostat does not maintain the "normal" operating temp of a vehicle. It is there just to get the engine up to that operating temp of that particular thermostat. Correct?

Right. Thermostat maintains the minimum operating temperature of the motor. It does not have just an open and closed positions, so as it gets close to the right temperature it will start to open and to allow more coolant to flow (there is a bleed hole so it never stops all flow). It will be fully open a little after it reaches the setup temperature and after that it is the air over the radiator maintaining the temp (if it's not moving or not moving fast enough the fan will come on moving the air). If the thermostat is stuck open it will take a very long time to heat up all of the water in the system to get the motor up to temperature and even more so in cold weather. If you are in very hot weather with it stuck (or without one) and you run it long enough it is possible for it to get heat soaked to the point that the motor over heats.

If the water doesn't move slow enough it won't pick up the heat from the motor or loose the heat at the radiator, so everything can get to hot. That is why all heat gaskets block off most of the coolant passages between the heads and block. If the large passages were allowed to flow as much as could fit through the cast passages it wouldn't pick up the heat from the motor. The radiator slows the water down by sheer volume. The amount of area of the radiator is way more than the hose to and from it, so once the water enters the radiator it slows down and then once it's back in the hose and volume goes back down it speeds up again.