thanser

Apparently I have a coolant leak, but I can't see where. Engine is running well and I have the oil changed at the dealership every 5k miles.

Last time the oil was changed the service rep indicated they topped off my coolant reservoir - I thought that was odd. Tonight on the way home in stop and go traffic and HEAT I had an idiot light come on - my temp guage was pegged.

I made it home and checked the coolant reservoir and it's EMPTY.

Not apparent leaks or puddles on the driveway.

If it were a head gasket the engine would perform poorly and the exhaust would be WHITE.

This is a 2004 Jeep Grand Cherokee with 130k miles on it.

So, where's the coolant going?

Bustedback

What engine?

93_xjcherokee

Is it possible that you're overheating and your coolant is evaporating?

blueseasons

It could be a pinhole leak somewhere. The fluid vaporizes under pressure. Look for a hairline crack in the top radiator tank. Have the cap checked or just replace it. I had a small leak in a heater hose once on a Isuzu. It was a connection. It dripped a bit on the top of the block and barley left a stain. I tightened all the hose connections. It went away and then i noticed the slight color variation where the leak had been.

thanser

Thanks, everyone.

I neglected to indicate this was a six-cylinder in my haste to post this question. Engine runs really well and as I mentioned I take it to the dealer every 5k for an oil change.

No drips of any kind on the ground but the occasional water from the AC.

What would it hurt to change the radiator cap? Do you suggest an OEM cap from the dealer?

Maybe the water pump is leaking? Radiator hoses?

I'll be extra careful to top off the coolant reservoir in this heat.

Thanks again.

dave1123

Just this little note; I was looking at my radiator today and I noticed a little corrosion on the top corner of the core on one side where they enter the tank flange. No moisture, no drips, no stains, but a little white powder buildup in that one spot. I'll bet it's a VERY tiny leak. I'm loosing about a quart a month.

Deepair3

I had the same issue on mine 2 years ago. Replaced the radiator and no more leaks. The filler neck actually was corroded so bad it broke when we removed it. I luckily caught mine before it over heated.

blueseasons

I don't like to preach, but I'd start doing my oil changes. Besides being much cheaper, you'll learn a lot about your engine , just by being around it. It will get familiar to you and the more you look at it, the more likely you'll be able to notice small things that may be out of the norm or changes that happen before they get critical.

When was the last time you changed your heater/radiator hoses? Or had them changed? I like to do that every couple years, when I change my coolant. I am used to driving on the beach. Engines get hotter, pressure builds up and new hoses are less likely to fail. One less thing to worry about. I change the cap as well. I prefer the solid caps , with out that pressure release on it. But the right cap, from any parts store is just fine.

Water pumps usually give you notice before they fail. They drip down, not up. If you have a leak, it's likely higher on the engine.