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Major Coolant Leak Underneath Car (w/ pics)
Posted: Fri May 15, 2009 5:37 pm
by oneone1onezero0
1996 3100 base automatic w/ 149,000 miles.
Symptoms:
- smell of coolant through heat vent when fan on
- cool air blows when heater is on
- gurgling sound coming from underhood (exact location unknown)
- coolant leaks only when engine is warm/ran for a while
- Coolant overflow tank is bone dry and drains quickly while being filled
- "Low Coolant" light is not on
Other info:
- Front Passenger side under dashboard is dry.
- New radiator early 2009
- Replaced water pump 2008
- Oil is clean & at normal level
There is what looks like some value that's missing some sort of plug. It looks like is't made out of plastic, and it points straight down. It's somewhere behind the engine block.

Re: Major Coolant Leak Underneath Car (w/ pics)
Posted: Fri May 15, 2009 10:32 pm
by 3X00-Modified
Your heater core blew out and thats the internal core box drain, it prevents the coolant from dumping in your car on the passenger floor.
Replace your heater core and you'll be good to go.
Re: Major Coolant Leak Underneath Car (w/ pics)
Posted: Fri May 15, 2009 11:52 pm
by oneone1onezero0
Two thoughts come to mind:
1. Wow, that wast fast. You guys rock.
2. crap. The heater core. That means I gotta rip out the dashboard and whatnot. I'd better clear my schedule.
Re: Major Coolant Leak Underneath Car (w/ pics)
Posted: Sat May 16, 2009 2:14 am
by 6r8ph1X
i second the notion as it has happened to me before also.
Re: Major Coolant Leak Underneath Car (w/ pics)
Posted: Sat May 16, 2009 12:30 pm
by NewNann
You definitely do not need to take your dashboard out to change your heater core. I replaced mine this passed fall and the only thing I took out of the car was the passenger side seat. Then everything from underneath the passenger side and driver's side foot well.
Either way you can bypass it for the time being. I bought a small tube with lips on both sides from NAPA's "side of the road" help section. They are two different diameters on each side because the tubes running into / out of the heater core are slightly different diameters.
Re: Major Coolant Leak Underneath Car (w/ pics)
Posted: Mon May 18, 2009 11:26 am
by oneone1onezero0
Is there a step-by-step guide to bypassing the heater core?
Where should I start? Does anybody have pictures? The last time I was under my car, everything looked like everything.
Re: Major Coolant Leak Underneath Car (w/ pics)
Posted: Mon May 18, 2009 12:07 pm
by 3X00-Modified
Take the two lines that are going in to the firewall, remove them from where they are connected to and hook them together with what NewNann described.
There was a heater core write up somewhere... I'll see if I can find it and bring it back to life.
Re: Major Coolant Leak Underneath Car (w/ pics)
Posted: Mon May 18, 2009 12:34 pm
by 3X00-Modified
Re: Major Coolant Leak Underneath Car (w/ pics)
Posted: Mon May 18, 2009 5:12 pm
by oneone1onezero0
Fucking awesome. Now that's how you (excuse my french) write a how-to. If I ever become competent enough to do my own repairs, I'll be sure to take beaucoup pictures.
Re: Major Coolant Leak Underneath Car (w/ pics)
Posted: Sat Jun 27, 2009 7:24 pm
by oneone1onezero0
Okay, so you guys were right. I went through hell taking apart the dash. I dunno why GM thought it would be a good idea to put such tiny screws in such unholy places. Anyways, I got the 2 black boxes under the radio (well I broke one of them, but it didn't connect to the vent hoses, so I wasn't worried.)
The old heater core was a piece of crap aluminum heater core with plastic hoses. The hoses were cracked so I tried to pull the hoses into the passenger area, but they broke.
Someone told me that the actual clamps for the heater core inlet/outlet hoses are in the back of the engine, but I can't get to them from under the hood. It looks like I can get to them by taking out the AC condenser, but I'm already weary from battling the heater core.
Is there a way to get to the hoses without having to take out the condenser?
Re: Major Coolant Leak Underneath Car (w/ pics)
Posted: Sun Jun 28, 2009 10:51 am
by 3X00-Modified
Go from under the car and un-clamp the hoses. Taking out the condenser will NOT help you in any way.