The Case of the Missing Coolant

For the last couple of weeks now I've had to top off the coolant overflow bottle (about 1/4 to 1/3 gal. per week).

I get a little whiff of coolant every time I get out after driving but cannot for the life of me find a leak or a wet spot anywhere on the motor. No spots on the driveway either.

New OEM water pump was installed about 1 yr ago at the dealer. (warranty)

Best guess here guys?? :dunno:

BTW - I've checked the oil and it's not going there (thankfully!!!)

'97 Sport / 4.0 / AT / 4x4

I hate to tell you this, butt my guess is a head gasket. Probaly leaking into the combustion chamber. Just a guess, butt the best I can do with this info. Hope I am wrong!

Junkxj could be right but you'll need to completely rule out external coolant leaks. There are a number of possibilities:

Radiator hoses
Heater hoses
4-hose heater valve
Radiator (external leak)
Radiator (internal leak into tranny fluid cooler, check colour of tranny fluid)
Water pump
Thermostat housing
Freeze plugs on block/head

If there IS an external leak, it may be so small that the coolant is evaporating before you can see it.
A leak through the head gasket into a combustion chamber will show up as steam emerging from the exhaust. Check the plugs and see if any one of them looks different from the others or if it has any coolant stains (rusty-coloured).

Open your hood while it's hot and see if you can smell coolant. I've got a really slow leak out of the drain plug in my radiator. Most of the time it doesn't leave any drips on my driveway, but it's still leaking. Usually I can smell coolant while the engine is hot.

Your best bet is probably to get it pressure tested. Mine has been leaking for some time around the thermostat housing (on the to-do list, working its way up...). I get a whiff of coolant, and i can see the traces of corrosion where it has leaked, but it never looks wet.

And don't forget the obvious: how about the radiator cap?

Have it pressure tested if you can... This usually reveals where it's coming from especially if it's a slow leak... Good luck..

Will.

I have the same problem - how best can you pinpoint the leak? I heard black light can be used - is that true?

Radiator cap.


the cap has most likely become weak can can't hold proper preassure any more. It will allow steam to pass by and you won't see it while you are driving, but smell it when you stop.

Put a new cap (don't get the lever vent type.. they suck)

FOUND IT !!!!! :dunce:

Turns out it's a tiny leak around the hose clamp for the lower heater core hose right up against the firewall. I guess it's been leaking down the firewall and wrapping under the bottom of the vehicle where the wind disperses it.

It looks like the jack-leg mechanic that replaced my heater hoses used too large of heater hose. Anybody know what size they are supposed to be?