Losing Engine Coolant

[Adam A]

Reservoir has lost about an inch in the past 24 hours (have been driving).

Pressure checked the system - no leaks
Checked the oil - not milky
Looked at the exhaust - not visible at all
Engine starts/sounds fine with no overheating

Any ideas?

 

[95bajaguy]

Reservoir has lost about an inch in the past 24 hours (have been driving).

Pressure checked the system - no leaks
Checked the oil - not milky
Looked at the exhaust - not visible at all
Engine starts/sounds fine with no overheating

Any ideas?

mine does the same thing.. exept i lose like 2 inches a week or so. its not leaking and it may be.... i say may be because its been tested and they say my heads and gasket are good, but my back plugs get toasted pretty quick sometimes so i may have a small gasket leak. you cant see any smoke from the exhaust but where else could the coolqnt go. wtf. i gave up on trying to find it so i just top it off.

 

[shadetreebronco]

I had this same problem on my 2.9L but finally i started to get a small leak , turned out to be a loose timing cover bolt hidden near the lower radiator hose connection on the water pump , I coated the bolt with water pump gasket sealer and all was good.

 

[RonD]

What engine?

I had a cracked reservoir<>rad hose, leaked only when engine/rad was warmed up so evaporated pretty quickly, no visible leaks.
Next time engine has cooled down, overnight, open rad cap and see if level is low, should be at the very very top, if it is low then check that hose, it is sucking in air on cool down, instead of coolant from the reservoir

 

[Soledad]

If your engine is a 2005 2.3L then there are numous places for a slow leak to occur.

When you pressure tested, how did you pressure test and for how long?

 

[tbunch]

Hard to answer without knowing what motor you have. If its any of the V6' then I would check the lower intake manifold gasket on the back near the firewall, the coolant passages can develop seepage that may not be enough to make it to the ground or even show up on a pressure test unless you leave the tester on there for 30min to an hour. Also, although its rare, I have seen some coolant leaks that won't show up with a pressure test because heat is absent.

The older 4.0 and 3.0 engines had somewhat of a knows issue for cracked heads as well, real little cracks near the rear by the exhaust that would let just a little coolant out, often the only symptoms were low coolant levels for a long while until the cracks expand. The head design was revised I think in 97, but that doesn't mean newer models aren't immune. That's another that wouldn't necessarily show up on a pressure test.

If you have a 4banger then disregard everything I said.

Was the coolant swapped out recently? Air bubbles bleeding out will drop the reservoir level too.