Leaking coolant from lines by firewall.

Hey guys, new to the forums and hoping y'all can help me. I recently inherited a 2008 Tahoe LTZ from my grandfather. The truck sat for about 1.5years unused while they had a live in nurse. When I picked up the truck I noticed the coolant reservoir was very low, so I refilled it. Fast forward about 1k miles, I started getting a faint smell of coolant through the vents when the air was running. When I checked the tank, it was damn near empty again. I found the leak from this connector next to the firewall, I'm hoping someone can tell what the name of this part is so I can order a replacement and change it. TIA

Heater hose T's.
There have been hundreds of threads here about them breaking and needing to be changed.
Do a search

Dorman now makes metal ones, as @mattbta posted:


GM part numbers in this thread (and many others): https://www.tahoeyukonforum.com/threads/what-pipe-hose-is-this.149975/post-1901529

Welcome to the Forum from NH.

Lots of knowledgeable folks here who freely share their knowledge, experiences, and perspectives. Knowledge is power.

I hope that you will become a participating member in the Forum's discussions.

Pics of the truck, please.

You are already receiving sage advice from the knowledgeable folks on this Forum.

Yes, it is a common issue. These Tees are plastic and get brittle over time, and they eventually fail. You can replace these Tees with GM (only) plastic Tees, or get the Gruven or Dorman metal Tee replacements.


When you change out the tees, be sure to wear gloves, as the firewall insulation is quite aggressive, and your hands will itch for days.

I got a truck from my Grampa too. A truck is something really special to inherit and you got a really good one that’ll go 300k with a little love.

You got good advice on replacing the heater hose T’s with the metal version. If the coolant was low and the truck didn’t ding you that means the sensor integrated into the coolant reservoir needs replacement too.

GM permanently moulded the sensor inside the reservoir. The whole thing needs replacement. Your coolant pressure will go back up to normal so keep an eye on the system for new leaks like the plastic radiator end tanks.

After your heater T and reservoir are replaced, a pressure test may be a good idea to stave off any surprises in the future.

The retainer clips for the T's can be tricky to get to let go, but once you figure out where to squeeze, they pop off fairly easily.
When you install your new T's, I would remove the O-rings and lube them with some coolant or silicone spray, insert them back into the T and then install the assembly.
Trying to shove dry O-rings onto those metal heater lines can be difficult and it can cause the O-rings to roll and possibly pinch them, resulting in a premature leak down the road.

My advice is, when you replace those T's, replace all of the rubber lines leading to them, along with the one that goes to the coolant reservoir.
If you are unsure of the age of the upper and lower radiator hoses, I would replace those as well.
And, since you'll be staring right at it, swap out the thermostat.
You may as well knock out what you can while you have the system open.

Congrats on the new truck, taken care of, they will provide many years of reliable service.

Edit: Did Gramps install a second battery?
That heavy red cable looks like it would be routed for a second battery in the engine compartment.

Disconnect the hose to the t fitting first. Then reach back by the firewall where you will find two tabs, press them in, push the fitting towards the firewall briefly and then pull toward you. Then do the connection pointed down last. Assembly is the reverse order.

If you're going to stay with the plastic tee's, stick with genuine GM or ACDelco. The aftermarket ones have a different plastic and they don't hold up. Nothing wrong with the metal ones, but I question if they're worth the price. I just replaced them on the 2014 Escalade at 168,000 Miles as preventative maintenance..... I figured new genuine GM ones will last at least that long yet again.

Something to think about is you also have two quick connects at the rear heater core. Behind the passenger tire if you look up the fittings are right there. The two flexible heater hoses back there get exposed to all the elements, and rot.