I'm new to the site I have an 03 Yukon Denali 6.0 and I notice on the passenger side on the ground there'* a lil puddle of coolant so I check my reservoir tank and I have to add coolant not much like a bottle a month. Now before I spend money in taking it some where what should I check it not the radiator cause it would of cap out by now I no from previous experience so I had a list of some parts
Waterpump
Radiator lower hose
The radiator tank
Lower intake manifold.
So that'* all I could think of any help and also I have a Crack exhaust manifold on driver side taps on cold start then when warm goes away thank you

If its the passenger side Id take a close look at the coolant tank and the heater core. Very rarely see a head gasket, buts its possible. Lower intake manifold and gasket are separate from the cooling system.

What should I look at on the coolant tank. The inside of it has a haze to it it'* original. Maybe the rad cap possible if not the maybe or hopefully it'* the tank I would have to take it out to see if that'* all good the heater core you mention but highly doubt that but give it a look

I notice my temperature was reading low at times then it would read at the half mark then now it reads between 160-210 that would be 185. I changed the thermostat and it would do the same thing i change it could it be my coolant temp sensor going bad.

To get a most accurate diagnosis on where its leaking. You may have to pressurize the cooling system to find the leak. Either rent or buy and coolant pressure tester. If its leaking bad enough just look for the coolant trail and follow it.

Large temperature fluctuations in the cooling system can also be a sign of being very low on coolant.

Thanks all for the advice will keep an update

As mentioned I checked the hoses and all this time my low coolant must of been this hose connected to the coolant reservoir. Most be off by .25 inch so I moved the hose up and filled it to the correct measure so hopefully all is good

It'* been a week now and I still losing coolant but before I take it for a pressure test what else besides the hoses and reserivor tank should I look for. I wonder if my water pump gasket could be dryed rotted

Under the hood, the plastic "quick connect" fittings where the heater hoses connect onto the heater core will rot from the inside out. When rotten, they become very weak and may allow the coolant to seap out when the engine is warm and coolant system is under pressure.

Also, if you look on the passenger side of the water pump, you will see two smaller hoses coming off the water pump. Of these two hoses, the forward one comes off the pump, enters a "Y" pipe and splits up into two hoses. The Y pipe is made of plastic as well and will rot out over time.

The "Quick Connect" fittings mounted on the heater core. The fitting on the left is new, the fitting on the right is broken and old. They are both supposed to look like the one on the left. The heater hoses clamp onto these fittings.




And here is a picture of a water pump. If you look closely at the left side edge of the picture, you can get a partial view of the Y pipe.....they get rotten over time.