5.3 running warm

[wishiniwasfishin]

The truck is an 06 with about 110k on it. 5.3. About a year ago, on a road trip it overheated. I took the thermostat out on the side of the road and refilled with bottled water and that did nothing. Limped to an autozone and put a new water pump and new thermostat in the truck in the parking lot and got no changes. Eventually made it to a shop where they traced the issue to the sensor that turns the fan on, and also I had new hoses put on. Now, when I'm running the truck at any speed below about 60, the temp is getting up to but not hitting the 260 area on the dash. It's boiling coolant over and you can hear and smell it's hot. When I get up over 60 or so, the needle drops back quick to about 210. There is no blockage and everything is clean in the bay. I'm stumped because the whole system is new and it's only doing it at slower speeds. Looking for any suggestions. The one thing I've heard and read is to try to change the rad cap, but my 06 doesn't have one. Looking for help before the Xmas holiday road trip!! Thanks

[rjgti]

you have one. it is on the expansion tank

[rjgti]

a blocked or dirty rad will cause issues. take ran shroud of and back flush rad with hot water

[wishiniwasfishin]

So should I idle it til the theromostat opens and leave the cap off? The rad is clean as it can be.

[kstruckcountry]

I'd make sure it's good and burped for starters.

 

Sent from my SM-G920V using Tapatalk

[wishiniwasfishin]

Just drove home from work, sideroads it stayed at 210 and then jumped to 230 ish and back down. Then on the interstate the same thing. It jumped up to 240 or so and the dash said hot coolant. Then it just fell back down to 210. I'm parked at the house now and it's bubbling over.

[dkjbama]

If the pressure cap on your coolant reservoir isn't functioning properly, the system will not hold the increased pressure of the coolant as it is heated. The increased pressure increases the boiling point of the coolant. If the cap fails, the system is at atmospheric pressure instead of 12psi. The coolant will boil in the block and heads inhibiting its ability to remove heat from the engine. A new cap is about $10 at any parts store and it goes on top of the expansion tank. For $10, it's worth a try before you tear anything else apart.

 

 

EDIT TO ADD VIDEO. Different truck, same principle.

 

[muddkatt]

If you have or had air in the system AND use Dexcool anti-freeze then there is a very high chance that the radiator and heater core water passages are clogged up. Pull a hose off and see if the there is a red mud layer inside the hoses. I never did find a way to really clean that crud out of a radiator. Ended up replacing it on a Grand Prix. Like mentioned above, not burping the system will cause it to run hot, and then cause the clogging I am referring to.

[Nanotech Environmental]

Early Dexcool had issues. That isn't likely to be a problem in the Op's 06.

 

To the OP - I'd check the lower rad hose clamp on the right side. They can rust over time and can break, such that they still look fine, but can't clamp properly. Ask me why I know this?

I went thru a similar issue as described & it was frustrating trying to solve it.

I'd check all the clamps as well while you're at it.

[muddkatt]

Early Dexcool had issues. That isn't likely to be a problem in the Op's 06.

 

To the OP - I'd check the lower rad hose clamp on the right side. They can rust over time and can break, such that they still look fine, but can't clamp properly. Ask me why I know this?

I went thru a similar issue as described & it was frustrating trying to solve it.

I'd check all the clamps as well while you're at it.

It was a 2005 Grand Prix that I had issues with. Don't know if they changed the formula for 2006, but its not going to hurt the OP to check it out.

[wishiniwasfishin]

Drove it to the store and put a new cap on and another gallon of coolant in it and it overheated worse than it has before. New thing today though, I put the heat on full blast and it was cold. So I'm thinking Heater core, but before that I'm tempted to Change the thermostat (again) just to be sure. Opinions?

[diyer2]

I would check the thermostat new and old if you put another one in. Put in boiling water with meat thermometer and see what temp they open.

[rjgti]

any bubbles in the expansion tank. is the oil clean

[muddkatt]

I re-read the entire thread to date and here is what I would do:

 

1. Pull heater core hoses and flush the heater core. If the flow is good and no sludge/crap shows in the discharge, move to next step.

 

2. Remove thermostat, replace water neck without t-stat in place. Remove top radiator hose and start vehicle. You are looking for a a GOOD flow of water. (Note, I have seen water pumps that had damaged vanes that would not move water, that is what you are looking for.) If water pump is not moving ample water, replace it with a Delco pump, not Autozone junk.

 

3. Once pump is known to be good, replace t-stat with NEW one. Fill and burp system. Does heater now work? Still running hot? Check radiator for internal blockage.

[wishiniwasfishin]

Alright here's an update. Took tstat out had no water pushing. Got a new water pump and tstat and still was having issues with moving water. What I did was take top rad hose off and fill that and the rad (it took a lot) and also used water hose to blast out whatever might be in the heater core and also filled those hoses. Truck did fine with heater working and not getting over 210 and this was all with 90% water. I took the hose off the water pump and drained the water and refilled with appropriate coolant and then did the same filling the rad hose and heater core and hoses and still was having the same issues as before. Also to add, I was doing all of this with the motor running and hot. After a few hose refills I think I have it fixed. Drove all over and idled etc and I have heat and it's staying cool. I'll watch it the next few days. Thanks for the help guys merry Xmas. I will repost in a few days good or bad.