Heater Core Lines

[BlackSUV]

I have a 2007 Suburban 1500. I hope it is okay to ask questions here

I believe I have a leak where the coolant lines go in through the firewall to the heater corer. I can see a drip from the out-board (right side of the vehicle) line.

Before I get in to trying to remove and replace it, does anyone know of a good video showing how to do it? Any tricks I should know about?

 

[Foggy]

If it has rear heat, then it's may just be the Plastic Tee's that are a well known
issue. You can replace them with OE gm ones, dorman, dorman aluminum, or the
gruvin brand Tee's
HTH
There are a bunch of different threads on this here. Just take a really
good look at your situation !

 

[Joseph Garcia]

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, if the leak is on the engine bay side of the firewall, and you have rear heat/cooling, then it is most likely related to one of the plastic Tees, or one of your heater hoses is close to imminent failure near the Tee. The plastic Tees get brittle over time from the heat.

If you find the leak to be directly related to a Tee, then you need to replace both of them, and there are existing threads discussing how to best remove these Tees, as they can be uncooperative. IMO, use only OEM replacement plastic Tees, or the Gruven metal Tees. 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.

Last, if you have not changed ALL of your hoses related to motor cooling and heating and reservoir, you absolutely should do this as part of the project. The manufacture year is often stamped on these hoses, and they definitely deteriorate over time, and it could leave you stranded somewhere.

 

[Marky Dissod]

Pretty much what @Joseph Garcia said above, except that the plastic T- & Y- can now be upgraded with metallic replacements that should outlive the vehicle.
Think Dorman makes them (Gruven might be better, but they cost lots more).

 

[Geotrash]

I have a 2007 Suburban 1500. I hope it is okay to ask questions here

I believe I have a leak where the coolant lines go in through the firewall to the heater corer. I can see a drip from the out-board (right side of the vehicle) line.

Before I get in to trying to remove and replace it, does anyone know of a good video showing how to do it? Any tricks I should know about?

The trick to removing the tees is to push inward toward the firewall, then while still pushing, squeeze the tabs with all you can muster and they should release. Mine did on both of mine that way.

 

[Fless]

The trick to removing the tees is to push inward toward the firewall, then while still pushing, squeeze the tabs with all you can muster and they should release. Mine did on both of mine that way.

It also helps to "twist" them as you're pushing them toward the firewall. Add a shout and the Beatles would be proud.

 

[BlackSUV]

Hello Everyone. Thank you for the advice. I apologize for not getting back sooner. I just saw these replies. I think I must not have set up notifications properly, ... or something.

And, yes. It would have been a good idea to post photos. So, here they are. It looks like you are all on point. I will see if I can find the threads that talk about r&r the Tees. If you happen to have a link to any of those threads, to make it easier, I would

p.s. I agree. The photos also show the truck needs som TLC.

Thank you again.

 

[Fless]

The tees are a wear item. OE plastic doesn't age well, and there are several alternatives. Change both while you're doing it, and consider replacing both heater hoses (one of them also has a quick connect on it that @Joseph Garcia showed in a prior post).

 

[Marky Dissod]

Feel free to consider this entire post parenthetical, although it's related to rear cooling firewall connections.

The T & Y are wear items. OE plastic doesn't age well, and there are several alternatives.
Change both while you're doing it, and consider replacing both heater hoses
(one of them also has a quick connect on it that @Joseph Garcia showed in a prior post).

I still drive like a jacquesarse.
One day, I got cut off by a shmendrick before we both wound up on a torn up road, where he slowed up enough to leave me room to cut him off / back.
Taking full advantage of my Z71's suspension, I cut him off just before I struck a sharp thunker of a bump that he slowed to avoid.
I celebrated for about 10secs before I started seeing smoke ... which turned out to be coming from the Y- that I broke when I thunked that bump.
Replaced the T- as well of course. Absolutely zero damage/wear to the suspension/steering, by the way.

 

[alvocado]

This is a very manageable repair and as suggested, use Dorman or Gruven metal connectors so you don’t have to change them twice.

 

[KC 2013 Tahoe]

Worthy of adding a Sticky Thread here for the Dorman Metal Coolant Tee's:

Vehicles with rear heat use these Tee's, you need one of each:
#800-414HP
#800-413HP

Added 10/1/2025: Dorman metal fitting to replace the straight plastic fittings that plug onto the ends of the above Tee's:
#800-403HP (use 2 each)

They install just like OEM but being metal wont get brittle and break.
How GM should have done these from the very start.

 

[alvocado]

@rdezs where did you source your AN fittings? I'm only finding the -8AN female to 5/8" barb on Summit Racing and they want $33/each. I'll just cut the metal crimp off and use step clamps on the existing tubing if I can't find some fittings priced more reasonably.

 

[BlackSUV]

Can I get a little administrative help? Will one of you please tell me how to set this up so I receive an email or text when there is a response to a thread I start or follow?

 

[alvocado]

Make sure "Watch" on the top right of the thread is selected then go into your account name in the navigation at top of page, select Preferences and make sure emails are selected for the communications you want to receive.

 

[j91z28d1]

Can I get a little administrative help? Will one of you please tell me how to set this up so I receive an email or text when there is a response to a thread I start or follow?

somewhere under your profile is a setting to adjust when you get notifications. I believe it defaults to once a week. change that to instantly.

 

[89Suburban]

Besides the Tees there is also a straight plastic nipple on one of the hoses that can crack and fail as well fyi. Replace that too.

 

[Pandabird]

Irrelevant but I thought I'd share my current condition with these tees as a comparison or whatever. Got new ones already, will swap once I get to the coolant swap. But yeah these things burn off over time.