Where is my coolant going?
 

2008 Hyundai Santa Fe, 105k miles

Two mos. ago while doing my last oil change I noticed the coolant reservoir looked empty. I opened it up and it looked bone dry. I filled it up with 50/50. Just checked again, and it was down to the minimum level line. I checked the oil dipstick. No foam, oil looked as clean as honey. Car doesn't smoke, engine temp gauge never goes above about 40%, no leaks under the hood or car, no crusted antifreeze stained around engine. Where is this coolant going and what's causing it?

Transmission cooler? Brake booster?

Have you pressure tested it?

I had the same problem. It was a slow leak that was getting into the combustion process so it was being burned off. Compression check (to the radiator) confirmed leakage.

This is engine coolant. So how does it get into combustion process if a radiator leak? How did you fix it?

It could be a head gasket issue.

Radiator cap getting weak? Hat was the issue with my 944. Cap spring was weak letting it dribble out a little while running.

Rick,
He did not suggest a radiator leak. He is suggesting a head gasket or perhaps a cracked head. A pressure test, done at the radiator cap, should give you an idea of how much leakage and perhaps reveal where the coolant is escaping.

Best of luck.
Les

Yeah, I suspected a head gasket too. But shouldn't there be foam on the oil dipstick or some other evidence?

No , not necessarily. I had a 1980 Chevy Citation 4 cylinder (Iron Puke) that did the same thing. The seepage just burns off in the combustion process and never makes it to the crankcase.

If the leak is directly into the cylinder, it might be passed as steam through the exhaust.

Best
Les

Arent you coming up on major service like timing belt, and water pump ? Maybe some weepage from the water pump , would be imossible to see without dis assembly .
Just a thought
I am not aware of them having problematic head gaskets, at least not in this climate. I'd look real good around the crank pulley, and see if you can see any crusty-ness

I had the timing belt done 20k miles and two years ago. Runs like a top.

My one time experience is occasionally I would get a misfire (Money Light) that would go away.

It was suggested I get a Harbor Freight Radiator tester and pressurize the system a couple of times. Take the plugs out and you will see a blast of coolant when you crank it.

I'm taking it in for a pressure test today. $35 and he said it'd take 30-60 min.

Have you checked the integrity of the line going from the overflow tank to the radiator?
I'd expect a leak from a head gasket to show bubbles in the radiator when cold.
Good luck with the pressure test.

GF's VW Tiguan does the same thing. We've had to add coolant a few times.

you smelling it?

my wife's subaru was maddening. we would smell it. no visible leaks, cap was tight, etc.

pressure testing it didnt show much. turned out there was a micro crack at the thermostat housing. i used a flashlight at night and saw the wisp of steam. easy enough fix.

I'm ashamed to say we once owned a Taurus wagon that did the same thing. Turned out there was corrosion stress fractures to the head bolts on the aft bank of the V-6 and the coolant trail down the backside of the engine was out of sight until it was put on the lift. It had done this from just about the time it was new too.

A dye kit will tell you instantly if it is combustion related .