Coolant smell coming through vents, engine not coming up to operating temp

Mike534x

Original poster
Member
Apr 9, 2012
894
Hey everyone! Trying to get some ideas of where to start. On Sunday I began to start smelling antifreeze through the air vents, passenger side floor board is dry/not showing signs of a leaking heater core . Windows aren't fogging up either when the heat is running, and I'm smelling a burning coolant type of smell coming from the passenger side of the truck near the front. I can't pinpoint where its coming from, nor can I see any visible leaks.

To top of it off, the engine won't go past 160 deg and seems to hold there. Any ideas? The water pump, hoses and thermostat were replaced a few months ago. I had a defective Delco thermostat and threw a motor rad one in place at the time the pump was changed out. I should mention the top radiator hose is warm, but not hot either. Any ideas? I was thinking maybe the thermostat is stuck open, the motor rad one supposedly stays in the open position (supposedly at the 180 deg mark).


UPDATE: So I was outside trying to see if I could spot a leak, and this broke when I went to move it...well there goes all the coolant to boot. Looks like it leads from the thermostat housing to the firewall.
 

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mrrsm

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Oct 22, 2015
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Sorry Mike... But that sickeningly sweet smell of PEG (Poly-Ethylene-Glycol) inside of the Vehicle Cab of the Vehicle and the fogged up interior Windshield are Dead Giveaways: There is a Rupture in the under-dash Heater Core allowing Coolant to boil through the opening.

Because of this compromise... the Engine Heat is being dissipated through that Heater Core opening and so the jacketed portion of the Engine Block Temps will never be able to rise above its present level as the Fluid Boils off. Only a Perfectly Sealed or Closed System not using Pure Water is capable of doing that.

Hopefully this Major Repair Project has some GMTN Threads and some possible "Short-Cuts" shown on Youtube Videos that will assist you with making this awful repair as manageable as possible... in addition to the secondary Thermostat & Housing R&R.
 
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coolasice

Member
Oct 27, 2013
1,019
Northern Maine
Sorry Mike... But that sickeningly sweet smell of PEG (Poly-Ethylene-Glycol) inside of the Vehicle Cab of the Vehicle and the fogged up interior Windshield are Dead Giveaways: There is a Rupture in the under-dash Heater Core allowing Coolant to boil through the opening.

Because of this compromise... the Engine Heat is being dissipated through that Heater Core opening and so the jacketed portion of the Engine Block Temps will never be able to rise above its present level as the Fluid Boils off. Only a Perfectly Sealed or Closed System not using Pure Water is capable of doing that.

Hopefully this Major Repair Project has some GMTN Threads and some possible "Short-Cuts" shown on Youtube Videos that will assist you with making this awful repair as manageable as possible... in addition to the secondary Thermostat & Housing R&R.
He did say the windows were NOT fogging up... he may have just been smelling what the heater intake was pulling in from outside.
UPDATE: So I was outside trying to see if I could spot a leak, and this broke when I went to move it...well there goes all the coolant to boot. Looks like it leads from the thermostat housing to the firewall.
Is that the water pump outlet? Cant' really see in the image.
 
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Mike534x

Original poster
Member
Apr 9, 2012
894
@MRRSM I'm not sure it is the heater core, it's a faint smell but enough to fill the cabin with a sweet scent. The windows do not fog up either, I did try scrolling through the forum in search of a guide or video but did not come across anything. I did come across the part number for the hose, but it appears to be discontinued everywhere I've checked.


@coolasice I believe it is, the hose is attached to one of the outer two out facing connectors on the water pump behind the thermostat. This one leads up along above the manifold to the firewall.
 

coolasice

Member
Oct 27, 2013
1,019
Northern Maine
@MRRSM I'm not sure it is the heater core, it's a faint smell but enough to fill the cabin with a sweet scent. The windows do not fog up either, I did try scrolling through the forum in search of a guide or video but did not come across anything. I did come across the part number for the hose, but it appears to be discontinued everywhere I've checked.


@coolasice I believe it is, the hose is attached to one of the outer two out facing connectors on the water pump behind the thermostat. This one leads up along above the manifold to the firewall.
Did the hose break or the nipple it was attached to?
 

Mike534x

Original poster
Member
Apr 9, 2012
894
Looks like the plastic connector for the quick disconnect did, the other half is stuck inside the old hose.
 

Mike534x

Original poster
Member
Apr 9, 2012
894
I think dorman makes a quick disconnect, might be able to remove yours from the hose and replace it.

I'll check it out! My original idea was to buy new quick connects and just replace the whole thing, but GM seems to have used an odd ball sized hose. I did find a new one online, downside is the rain/cold and trying to bleed the system again (gotta love the difficulty for purging air from the 5.3).
 

m.mcmillen

Member
Apr 29, 2016
554
Wisconsin

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