Slight coolant loss and cabin smell | Ford Explorer Forums - Serious Explorations

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Slight coolant loss and cabin smell


Well-Known Member
October 4, 2007
Reaction score
City, State
Glendale, AZ
Year, Model & Trim Level
1998 Explorer 4.0 4x4
I have a slight coolant loss. I top off the overflow container every few hundred miles. Car heats up normally, maintains steady temperature (torque app confirmed). No visible leaks, no steam, no drips, or puddling. Upper and lower radiator hoses are newer. Cap is good. No coolant in the oil or trans. Spark plugs look normal. I notice that at start up, if I have the fan on and windows closed, I can detect a slight sweet smell, chemically sweet like coolant. What could use me smelling coolant inside the cabin, but not visible leakage on the outside?

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Heater core may have a leak.

If must be a very small leak (or the fluid might be exiting the cabin via the A/C drain). Changing the heater core is a huge job. I'd try a bottle of K-Seal on it. It works really well and won't hurt anything. I've stopped some pretty major leaks with it. Plus it stays in the cooling system to prevent future leaks and it's considered a permanent repair. I prefer to remove a little coolant from the radiator and install it directly, rather than just adding it to the overflow reservoir. It stopped both my leaks in less than 30 minuets and neither vehicle has leaked a drop since. That was 18 months ago.

i'll try the kseal

If the heater core gets worse, would it drip inside the cabin? from under the dash?

If the heater core gets worse, would it drip inside the cabin? from under the dash?

Most likely.

I don't know why it isn't now, unless it is and you just can't see it.

Heater core isn't that bad , I've done so many in rangers and second gen explorers I can do it in about three hours ,

Having the same issue with mine right now. Taking it i this week to have it checked.

Just because you can smell the coolant inside the truck doesn't necessarily mean it's the heater core. Mine did that, too...and, it was the thermostat housing that was leaking. Coolant would pool in the intake valley and once engine warmed up, the odor would get pulled inside the cabin through the vents. Was very difficult to determine the source of the leak as it wasn't readily apparent it was the t-stat housing just by inspecting it for signs of residue.

What's the best way to troubleshoot this? I'll pull up the front carpet and look for residue.

My next guess was t-stat housing :)

I would think also that as a heater core heats up, it's metal expands and it could close a small leak. In theory...

I am assuming you have colored (usually green) antifreeze and not water in the system. If so, check what's dripping out of the A/C condensation drain, on the passenger side close to the firewall. If you see clear water it's not the heater core. If you see the color of your antifreeze, it is. In addition, clear water evaporates quickly, but antifreeze feels oily to the touch and evaporates slowly.

What's the best way to troubleshoot this? I'll pull up the front carpet and look for residue.

I use the green stuff.

I did more trouble shooting and notice that I dont smell it when the windows up/fan off and when the fan it set to recirculate (max ac). But if the vents are open I smell it. So it could be coming from under the hood.

I just ordered a UV dye and pen blacklight to get to the bottom of this. In the mean time, I have coolant and kseal in the back in case I need an emergency fix.