Another coolant leak help thread!

Disclaimer: Links on this page pointing to Amazon, eBay and other sites may include affiliate code. If you click them and make a purchase, we may earn a small commission.

2011TXDenali

Member
Joined
Jan 8, 2018
Posts
35
Reaction score
41
Hey everyone, I'm hoping to get some help with diagnosing the coolant leak on my 2011 Denali. I noticed the coolant level was pretty low in the tank and filled it up. I went out for some lunch after and when I came back out to the truck, it looked like someone basically poured out a new bottle of coolant under the engine. It has been parked for over a week and it is still slowly leaking. It is coming from above the oil drain plug (photos below). I am hoping this is something I can fix myself as I don't really have the extra funds available after Christmas to take this in to get done. Any help is greatly appreciated. Thanks!coolant leak1.jpgcoolant leak2.jpg
 
OP
OP
2011TXDenali

2011TXDenali

Member
Joined
Jan 8, 2018
Posts
35
Reaction score
41
Most likely the source is the passenger side heater hose/t's on the firewall
but.. could be other things, waterpump, hose, reservoir tank crack, radiator.coolant leak3-1.jpg
Thanks for the tip! After going up a little bit further, it looks like it might be coming from this hose.
 

repairman54

Member
Joined
Dec 26, 2022
Posts
63
Reaction score
98
Location
NW NJ
Check the T connections up on the firewall. T connection routes coolant back to the rear heater.
One of mine was leaking. Coolant drips down onto the valve cover then down the back of the engine.
GM T fitting only, aftermarket is crapola, found that out the not so easy way. I replaced my heater hoses also for a once and done. Rock auto had gm hoses but not the plastic T fittings.
My dealer had the T's in stock, that tells me it's common.
 
OP
OP
2011TXDenali

2011TXDenali

Member
Joined
Jan 8, 2018
Posts
35
Reaction score
41
Check the T connections up on the firewall. T connection routes coolant back to the rear heater.
One of mine was leaking. Coolant drips down onto the valve cover then down the back of the engine.
GM T fitting only, aftermarket is crapola, found that out the not so easy way. I replaced my heater hoses also for a once and done. Rock auto had gm hoses but not the plastic T fittings.
My dealer had the T's in stock, that tells me it's common.
Thanks, after searching the engine, it looks like the T connectors are the source of the leak! I couldn't tell which one was leaking but probably safe to replace both. Which parts would I need?
 

B-train

Full Access Member
Joined
Sep 12, 2022
Posts
1,873
Reaction score
3,050
Those 2 T connectors and the rubber hoses that go to your waterpump. Go to an online GM parts store and put in your VIN. Look under engine cooling and they should come up in an exploded diagram. Make sure to use some sort of lube when going back together so you don't roll or knick an o-ring.
 
Top