Tim94gt

iTrader: (1)

2005 Sierra 2500HD 6.0l/A4

So, I drove the truck to work this morning and the heat was blowing cold. The truck was at operating temp(@210*).

After 10-15 minutes, it started to come out warm/hot but it was not constant. At this time, the coolant temp started to rise. It went up to about 220*-225* but came back down to 210* within a minute or two.

The temp does not rise as high with the heat off, but still rises a little more than normal.

The outlet heater hose feels significantly cooler than the inlet, but it is still warm.

I will pressure test after work. There is no visible leaks and the coolant level is ok. Although, I can faintly smell coolant.

I'm guessing the heater core has an obstruction but due to the mileage(112K) it could be something else. Any help would be gratly appreciated.

Thanks,
-Tim

Beatdown Z

iTrader: (18)

backflush the heater core.

Tim94gt

iTrader: (1)

I'll try that, thanks.

I might pick up a heater core on the way home, just in case a flush doesn't work.

Beatdown Z

iTrader: (18)

How does the coolant look?

Is it Dex-Cool or the green stuff?

TIM Z

iTrader: (12)

Beat down is on the right track , if you have dex cool flush it out good and put green in with Distilled water , dex cool is the devils **** , it corrodes everything .

Suburbazine

Dex-Cool isn't corrosive until someone mixes more water in with it. However it's the Devil's **** when you put GREEN coolant into a Dex-Cool system as they combine to form a corrosive gel substance which pools in the radiator and heater core passages.

TIM Z

iTrader: (12)

Yup your correct , I've had to flush way too many heater cores / systems from this stuff . Best thing you can do is get rid if it . I believe people actually think you can run this stuff 100 k like they claim , bad decision .

trxmxzx

iTrader: (7)

My truck did this back in 2009, I flushed heater core also, changed fluids, I just said screw it and put a pump on it and it did the trick for me.

Good luck

Tim94gt

iTrader: (1)

It does have Dex-Cool. Fluid level is ok and was changed two years ago.

I wasn't able to do anything with it last night. Hopefully, I'll have some time tonight, if not it will have to wait until tomorrow.

I picked up a heater core, it was only $50 so I figured I'd just replace it anyways. I do plan on switching to the green coolant as well.

livefast1

iTrader: (1)

Also, check the coolant bleed hose. Disconnect it from the upper passenger side of the radiator and make sure the hose and port aren't clogged. This won't allow air to bleed from the system and can cause the overheating and air trapping in the heater core. I've never seen a plugged heater core cause a vehicle to overheat.