Confusing coolant leak

[cookiemoonster]

Hi all!

I'm hoping to find out if anyone has had issues with coolant leaking from around the water pump and thermostat housing.

I've looked it up and it's not seemingly a common issue but from what I've seen in regards to the thermostat housing using only an o-ring for sealing where the two faces meet, i imagine it could possibly be a common issue.

I have a 2004 Yukon and have experience in diagnosis and repair (took some courses years back and ran a freelance shop out of the garage in my previous house)

I have a coolant leak which isn't consistent and seems to only appear when the engine cools down (which makes me suspect it's an issue with some component shrinking when it cools and opening up a spot for the coolant to leak).

I just ordered one of those "cameras on a stick" because I couldn't see much with my mirror on a stick (side note, they're on sale right now and I'll link below; I get no commission for this, just want to share) and will be using it later today to try to find the leak.

I was hoping for some input on where i might focus my search. I do not believe it is a cracked block (would be a crazy crack to leak as much as a liter or two in one sitting) but I'm unsure of how to proceed as I've even added UV dye to try and find the source but all i get is the splatter from the belts flinging the coolant (from what little does actually leak while the engine is still hot).

Sorry for the huge post, lol. I hope I don't bore you all to death!

Best wishes!

p.s. here is the link to the camera on sale:

https://smile.amazon.com/dp/B07PBW52SF/ref=cm_sw_r_cp_apa_glt_fabc_VEECYXRY208D7SKEFGE1

 

[PNWYukon]

How much coolant are you losing?

Where does it appear? Meaning you can actually see coolant?

Can you smell coolant when it is hot?

I just had this same problem and it turned out my 16 year old radiator was leaking. After removing the water pump I was shocked how clean and not leaking it was.

 

[Doubeleive]

I would just replace the thermostat & housing if it is the 2 piece design, if it is the single piece design then then just replace the whole water pump.
you did not mention the mileage but typically anything above 150k it's time to replace the pump

 

[Doubeleive]

How much coolant are you losing?

Where does it appear? Meaning you can actually see coolant?

Can you smell coolant when it is hot?

I just had this same problem and it turned out my 16 year old radiator was leaking. After removing the water pump I was shocked how clean and not leaking it was.

come on man, lol (water pump/thermostat area)

 

[Sam Harris]

Hi all!

I'm hoping to find out if anyone has had issues with coolant leaking from around the water pump and thermostat housing.

I've looked it up and it's not seemingly a common issue but from what I've seen in regards to the thermostat housing using only an o-ring for sealing where the two faces meet, i imagine it could possibly be a common issue.

I have a 2004 Yukon and have experience in diagnosis and repair (took some courses years back and ran a freelance shop out of the garage in my previous house)

I have a coolant leak which isn't consistent and seems to only appear when the engine cools down (which makes me suspect it's an issue with some component shrinking when it cools and opening up a spot for the coolant to leak).

I just ordered one of those "cameras on a stick" because I couldn't see much with my mirror on a stick (side note, they're on sale right now and I'll link below; I get no commission for this, just want to share) and will be using it later today to try to find the leak.

I was hoping for some input on where i might focus my search. I do not believe it is a cracked block (would be a crazy crack to leak as much as a liter or two in one sitting) but I'm unsure of how to proceed as I've even added UV dye to try and find the source but all i get is the splatter from the belts flinging the coolant (from what little does actually leak while the engine is still hot).

Sorry for the huge post, lol. I hope I don't bore you all to death!

Best wishes!

p.s. here is the link to the camera on sale:

https://smile.amazon.com/dp/B07PBW52SF/ref=cm_sw_r_cp_apa_glt_fabc_VEECYXRY208D7SKEFGE1

Are you sure it’s not the weep hole on the water pump?

 

[OR VietVet]

Welcome to the forum from Oregon.

Since you said the coolant is getting on the belts I am gonna guess the leak is at the water pump weep hole in the bottom casing of the pump. I am surprised that you did not see the leak with the mirror, if in fact that is where the leak is. If is leaking there it can leak at times after the engine cools and then leaves a puddle on the ground. When you see coolant, is it on the ground and where is it on the ground in reference to the front of rig and the engine? Pressure test the cooling system.

 

[PNWYukon]

come on man, lol (water pump/thermostat area)

To be fair, the rad leak was blowing back all over the engine so it "could seem" like the obvious component was the culprit.

 

[cookiemoonster]

How much coolant are you losing?

Where does it appear? Meaning you can actually see coolant?

Can you smell coolant when it is hot?

I just had this same problem and it turned out my 16 year old radiator was leaking. After removing the water pump I was shocked how clean and not leaking it was.

it's not consistent which is why I said it's confusing. Some days I seem to lose more than a quart after a 20-30 mile drive. Other days after a similar drive it'll just be a shot glass' worth.

I do not smell coolant which is another reason to believe my block and head gasket is fine.

Everything directly under the radiator stays bone dry, so unless the leak is running along a hose before dripping off, I don't believe it's the radiator.

Sent from my ONEPLUS A6013 using Tapatalk

 

[cookiemoonster]

I would just replace the thermostat & housing if it is the 2 piece design, if it is the single piece design then then just replace the whole water pump.
you did not mention the mileage but typically anything above 150k it's time to replace the pump

That's what I was thinking, i just wanted to see if anyone here knows of a common issue with the 2000-2006 Yukons.

I've never really worked on Heavy Duty truck engines and I learned something new today: weep holes are a thing, lol.

Sent from my ONEPLUS A6013 using Tapatalk

 

[cookiemoonster]

come on man, lol (water pump/thermostat area)

I'm now thinking weep hole area (didn't know weep holes were a thing before today) lol

Sent from my ONEPLUS A6013 using Tapatalk

 

[cookiemoonster]

Are you sure it’s not the weep hole on the water pump?

I hadn't heard of them until today, and after researching it, it seems likely the weep hole is the culprit. I'm gonna look with an inspection camera later today (when it comes in the mail) and post an update here.

Sent from my ONEPLUS A6013 using Tapatalk

 

[OR VietVet]

Yea, I came up with that name, WEEP HOLE, back in 1978 and it is registered, so don't try to steal it.

Before I named it WEEP HOLE, it was just called, "THE HOLE".

 

[cookiemoonster]

Welcome to the forum from Oregon.

Since you said the coolant is getting on the belts I am gonna guess the leak is at the water pump weep hole in the bottom casing of the pump. I am surprised that you did not see the leak with the mirror, if in fact that is where the leak is. If is leaking there it can leak at times after the engine cools and then leaves a puddle on the ground. When you see coolant, is it on the ground and where is it on the ground in reference to the front of rig and the engine? Pressure test the cooling system.

I wish I still had space and time to really diagnose it. It's my daily driver and I'm so busy right now (along with not having a dedicated work space) it's hard to really take the truck apart and give it a good inspection.

Its on the ground, a good amount of it, but i'm having a hard time tracing it to the source.

Sent from my ONEPLUS A6013 using Tapatalk

 

[PNWYukon]

Taking out the whole airbox from filter to throttle body as one piece would take 5 minutes and gives you lots of room to poke around.

 

[OR VietVet]

The weep hole was designed in to the water pump housing so that when the front fan blade attachment hub bearing, in the front of the pump, started to loosen up it would allow coolant past that seal and bearing and that was to show a problem with coolant on the ground before the bearing got bad enough to allow the fan to move enough to dig in to the radiator or come completely off and pull itself in to the radiator.

 

[cookiemoonster]

Taking out the whole airbox from filter to throttle body as one piece would take 5 minutes and gives you lots of room to poke around.

yeah, I pulled that off in the auto part store parking lot trying to decide if I should just get a water pump while I was still there. Later today I'll take the air box and upper radiator shroud off and give it a good inspection.

Sent from my ONEPLUS A6013 using Tapatalk

 

[Doubeleive]

To be fair, the rad leak was blowing back all over the engine so it "could seem" like the obvious component was the culprit.

true does take some experience sometimes to figure out the source, a good rule of thumb is it flows down and will follow any surface along the way

 

[Fless]

Rent the pressure tester from your auto parts store and pressurize it to the operating pressure. If you have noticed it more when the engine is cold, do it then. Watch for pressure leakdown and start looking and listening for the leak. If you have rear heat, be sure to inspect the heater hose Ts that are near the passenger firewall.

 

[exp500]

PNW VietVet-You sure your "weep hole" isn't an unthreaded grease fitting hole? Should have seen a few of them in 78 as well!

 

[OR VietVet]

Before I was born they used to grease the water pump bearing, if I remember right.

I have seen my share of threaded and unthreaded holes in my day. The unthreaded hairy ones get my attention for maintenance.