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goodwrench9124
goodwrench9124, ASE Certified Technician
Category: GM
Satisfied Customers: 3432
Experience:  37 years of dealership exp. Ase Master Certified, GM Master Certified Tech. Awarded GM Top performer
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Coolant is boiling in reserve tank.

Resolved Question:

Coolant is boiling in reserve tank.
Submitted: 6 years ago.
Category: GM
Expert:  goodwrench9124 replied 6 years ago.
Hello and welcome. when is the coolant boiling? going down the road? or while at idle?
Customer: replied 6 years ago.
I will be driving for about a half an hour and then hear coolant boiling at idle or wjhen i come to a stop.
Expert:  goodwrench9124 replied 6 years ago.
Ok, does the A/C seem to ok at idle? and what temp does the temp gage run at when this happens?
Customer: replied 6 years ago.
Air conditioning is fine. When i drive the truck, the temprature gauge is usually at the middle and after about 30 min or so, the gauge moves slightly to the right. Recently i had the water pump, fan clutch and thermostat replaced.
Expert:  goodwrench9124 replied 6 years ago.
Ok, great info, Thanks. if the truck is not overheating and the ac is cooling ok. the two things that come to mind, is a bad rad. cap. a bad rad. cap can cause the cooling system not to keep the right amount of cooling system pressure. the cooling system has to be around 15 psi, this raises the boiling point so the coolant doesn't boil. also another thing that could cause this, the incorrect antifreeze mixture. the system needs to be a 50/50 mix. this also raises the boiling point so the coolant doesn't boil.
Customer: replied 6 years ago.

It is not overheating but as i said, after about 30 min or so, the temperature gauge moves towards hot and i have to stop until the engine cools down. I just opened the rad cap and see coolant in the radiator.

Expert:  goodwrench9124 replied 6 years ago.
Ok, like I said, make sure the rad cap is good and not weak. make sure the coolant is a 50/50 mix. also , take a good look at the rad fins and the condenser fins in the front of the behind behind the grill. see if there is allot of dirt and bugs in the fins. if so, take a garden hose and flush out the fins real well. sometimes if the fins gets dirty, it will cause not enough air flow across the rad.
Customer: replied 6 years ago.
I have 50/50 mix. So it must be the radiator cap. Recently i took the truck to get it checked and was told that i may have a bad head gasket because the when coolant was put in the radiator while the truck was running, it was boiling, like air bubbles.
Expert:  goodwrench9124 replied 6 years ago.
a head gasket is a possibility, but to be real honest, have not seen one of this engine engines with a bad head gasket. if you want to check for a bad head gasket. most parts store have a test kit that checks the coolant for a bad head gasket. the kit is pretty cheap and easy to use.
Customer: replied 6 years ago.
What kind of radiator cap do i need? I will be going to an local auto parts store.
Expert:  goodwrench9124 replied 6 years ago.

just ask for the same pressure cap, that the factory cap calls for. most brands will do just fine

 

 

Customer: replied 6 years ago.
What would be the obvious signs that it is the head gasket?
Expert:  goodwrench9124 replied 6 years ago.
usually you will have other problems, such as, engine runs roughs and misses out, white smoke out the exhaust. losing coolant and not seeing any drops of coolant on the ground. coolant in the oil, or oil in the coolant.
Customer: replied 6 years ago.
I don't see that at all. But as i stated earlier, it just seems to run hot after about 30 min. Where should the temperature gauge be under normal driving conditions? Normally i see it right in the middle.
Expert:  goodwrench9124 replied 6 years ago.

the normal operating temp should be between 190 degrees to 225 degrees. the engine is considered to be overheated at 257 degrees. now in real hot weather with the a/c is on, the coolant temp can tun a little hotter

 

 

The IPC determines that the coolant temperature is greater than 125°C (257°F). The IPC receives a class 2 message from the PCM indicating coolant temperature.
The IPC performs the displays test at the start of each ignition cycle. The indicator illuminates for approximately 3 seconds.

The IPC turns OFF the engine coolant indicator when the engine coolant falls below 122°C (252°F).

Customer: replied 6 years ago.
Now if the cap is off, and when you start the truck and the you see air bubbles in the coolant, is it still that i need to replace the radiator cap?
Expert:  goodwrench9124 replied 6 years ago.
I would still at least at this point, try a new cap. some small bubbles doesn't necessary mean a problem.
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