Coolant leak between transmission-manual

I know my heater core is leaking but could the antifreeze be visible under the car; because i see coolant under my car between the transmission; I’ve checked the radiator and heater core hoses and their dry; I’ve also check water pump and it’s also dry; also I’ve notice this happens every time I jack up my car from one side. What could it be?

Just some thoughts. water will travel until it finds a point to drop down.
are you sure it is antifreeze and not water from using the a/c or defroster.
If it is antifreeze, Is your carpet soaked? if it is wet, then it can be the heater core leaking and going under the carpet and finding a small hole in the floorboard.

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If the heater core is leaking, then coolant may draining from the condensate drain for the AC.



Im 100% sure it’s coolant because it’s green and I smell it it go a sweet smell; the carpet is damp but not wet;and everytime I turn on the heat it Smells like coolant

Yea I’d figured never thought you could actually see the coolant that the heater core is dropping.Thanks!!

Have fun. In the old days you could change a heater core in about 30 minutes. My Buick took about two hours. Some cars you almost need to cut it apart. Suggest checking a repair manual for the proper procedure. The good news is they are relatively cheap.

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The heater core is located in the same place as the A/C evaporator (the part that gets cold) , which sheds water that condenses on its surface, just part of normal operation. That water has to have a path to leak & onto the ground, so if the heater core has a leak, the coolant will take the same path. It’s usually pretty easy to spot that pathway from underneath the car, a small rubber-like finger-sized tube that hangs down from the floor pan under the heater core area.

One more idea, I had a water pump leak on my Corolla that I could never spot, water pump seems to be dry, but a little coolant would emerge from various places seemingly unrelated to water pump when I jacked the car at certain angles. Pump was 30 years old, so finally decided to just replace it, and during the replacement process I removed enough stuff in the way I could finally see the leak source, the water pump main seal.

I changed the timing recently and saw no leak from water pump so I think that’s fine; but thanks for the info!!

I’d experienced multiple small coolant leaks where various sensors thread into the engine cooling jacket. There’s a lot of those kinds of sensors on my older Corolla, but new cars, not so much. There’s at least one, the coolant temperature sensor, so you might want to check for the source of the coolant leak there. If it is leaking, you could try removing it and wrapping the threads with some teflon plumbers tape before screwing it back in.

I’ll keep that in mind thanks!

If you are not going to replace your known leaking heater core then just clamp off both heater hoses (or bypass it) and see if the leaks stops… If it stops then you know it is coming from the heater core, if it doesn’t then you need to keep looking… Not that hard to figure out… lol


Huh, never thought about that lol,does clamping both heater core hoses restrict the flow through the engine or do I need to connect them together

When I’ve done that I’ve always just connected the two hoses together with a short length of copper pipe in between, and hose clamps.

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I like the ways you think of going around this problems. I’ll do that till the summer when I have time to fix it.
Thanks for the wisdom!

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Some vehicle come with a heater control valve that stops coolant from flowing through the heater core for better AC… But it might be easier to bypass, and safer, the heater core then try to find something to clamp them off with that could (will overtime) come loose while driving and possibly damage the vehicle behind you…

Sometimes people, myself included, like to overthink things instead of keeping it simple…

I think my car has that according to my manual
But does that shut off when the a/c actually on or the setting is set to cold; because I have It set in cold all time but occasionally I could hear the coolant leaking( I don’t how to describe the sound but it for sure a sound of liquid escaping)

Some vehicles that use a heater control valve to manage the flow of coolant through the heater core. Depending on the system design, the heater control valve may be normally closed (blocking coolant flow until activated) or normally open (allowing coolant flow until activated).

Some heater control valves are operated via a cable or engine vacuum, while others are electronically controlled.

Your HCV could also have some crud in it allowing some coolant flow even while closed…

Just need to bypass the heater core all together…

Alright, thanks for all the help!

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I guess don’t overlook the frost plugs. They can leak. Could be behind the transmission though.

My 59 Pontiac didn’t have a heater control. The guy before me had pulled it all out so it was full blast heat all the time. In the spring I’d clamp the hoses shut and in the fall replace the hoses. Never thought about connecting them together. Pre internet. Or bce.

I will check that too thanks!