Where the heck is the coolant going?!

[Beachcomber86]

Need a bit of help here. Just did a 750 mile round trip to visit the daughter at school. The morning after each leg of the trip, the radiator was about 1/2 gallon low on fluid. I've got no puddles under the vehicle, no liquid on top of the engine, can't smell it driving down the road, no steam coming from under the hood, and no white smoke from the tailpipe.

Before I left, I put the beast on ramps and filled the radiator with the engine running. Kept the engine running for about 15 minutes and continued to add fluid until the level didn't drop any more. It is not drawing water from the reservoir as it is at or above the max level mark. I changed from a 20 psi to a 16 psi cap just prior to the trip.

Thoughts, suggestions, HELP!!!???!!!

 

[Mbrooks420]

It’s possible it’s going into a cylinder slow enough to not show out of the tailpipe.

 

[Beachcomber86]

It’s possible it’s going into a cylinder slow enough to not show out of the tailpipe.

1/2 gallon over 375 miles! Really?

 

[Mbrooks420]

Over 6 hours a half gallon isn’t a fast rate. Plus it might only be leaking under load, and not when you are at idle behind the truck. It’s the only likely option unless it’s leaking somewhere and you missed it. It’s going somewhere. If it were in the motor, you’d have overflowed the crank, and if you dumped that much in the tranny, I’m sure you’d have other obvious issues.

 

[naiku]

Have you looked at the little Y-pipe up at the top of the passenger wheel well? Ours was leaking coolant out of that pipe, slow enough to not ever notice any on the floor, smell any etc. but enough to notice the level going down.

 

[Tech By Trade]

I bet its sitting in the valley, and rolling down the back of the engine while you are driving.

 

[Beachcomber86]

Have you looked at the little Y-pipe up at the top of the passenger wheel well? Ours was leaking coolant out of that pipe, slow enough to not ever notice any on the floor, smell any etc. but enough to notice the level going down.

I've had that connector break and it was replaced several years ago. I've checked it and it seems fine.

 

[Beachcomber86]

Over 6 hours a half gallon isn’t a fast rate. Plus it might only be leaking under load, and not when you are at idle behind the truck. It’s the only likely option unless it’s leaking somewhere and you missed it. It’s going somewhere. If it were in the motor, you’d have overflowed the crank, and if you dumped that much in the tranny, I’m sure you’d have other obvious issues.

That's why I went to the 16 psi cap. On previous trips with the 20 psi cap, it only used about a quart of fluid. Mmmmm.

How would coolant get into the tranny?

 

[Mbrooks420]

Through the radiator. It happened on the second gens, I don’t think it’s been an issue on the 3rd gens. You are losing it somewhere, a long trip shouldn’t use any coolant. No coolant smell under the hood when it’s hot?

 

[Beachcomber86]

Through the radiator. It happened on the second gens, I don’t think it’s been an issue on the 3rd gens. You are losing it somewhere, a long trip shouldn’t use any coolant. No coolant smell under the hood when it’s hot?

No. I'm pretty good at detecting the smell of antifreeze and I can't even detect it when hot.

A little further information on how coolant would get in the radiator. Could it be that the tranny cooler line that goes in the radiator has a hole? Seems that would put transmission fluid in the radiator.

 

[Mbrooks420]

It gets in through the cooler in the radiator. A not uncommon problem that ruined many transmissions. I’m sure you’d know if this was your issue. If you were leaking it onto the engine, I’d think you’d smell it. Might be worth dumping some K seal in and seeing if it goes away.

Pulling the plugs, or a leak down test would likely tell you if you have a blown gasket or cracks between the cylinders.

 

[boominXplorer]

I had a customer the beginning of this year with an 08 explorer that her radiator filled her transmission. I've flushed the crap outo of it and so far the trans is still going but she knows it lost a few of its lives there.

 

[Beachcomber86]

Double checked. Front and rear heat works no leaks noted. Y connector for heater core shows no signs of a leak. No signs of coolant on top of the engine (it's dusty). Can't smell coolant under the hood. It doesn't seem to be drawing fluid from the overflow tank. Also, it seems to be worse with the 16 psi cap.

Averaged 19+ mpg coming back with half a dorm room inside. And I don't drive the speed limit. Mmmmmmm.

 

[hlg99]

If you have the rear climate control check the fittings on the hoses behind the drivers rear wheel. I was chasing a leak all winter and found some of the fittings there corroded out.

 

[boominXplorer]

The way to really find it is use a pressure tester. Just pump it up to 20 psi and see what happens. It's going to go somewhere and with the engine off it will be easier to find. I've had to pump the system multiple times to find those hard to find leaks like heater core or rear heater lines but eventually you'll have a puddle under the truck. If you still can't find the leak and you start the truck up and it runs like crap chances are you have a headgasket issue. Unfortunately theres no easy way to check the trans but to make sure it's not "milky" or creme colored and overfilled.

 

[Beachcomber86]

The way to really find it is use a pressure tester. Just pump it up to 20 psi and see what happens. It's going to go somewhere and with the engine off it will be easier to find. I've had to pump the system multiple times to find those hard to find leaks like heater core or rear heater lines but eventually you'll have a puddle under the truck. If you still can't find the leak and you start the truck up and it runs like crap chances are you have a headgasket issue. Unfortunately theres no easy way to check the trans but to make sure it's not "milky" or creme colored and overfilled.

I believe you, however, I've seen zero white smoke from the tailpipe, the engine purrs like a kitten, and the tranny isn't giving me any issues except for a stretched reverse band. What am I missing?

 

[Mbrooks420]

A head gasket leak doesn’t always smoke, or run poorly. It’s possible that it only leaks under load, and you’d have no idea if it were smoking. If it’s not leaking outside somewhere, it’s going into the motor. Pressure test it and look for puddles, as Boomin suggested. It’s probably the only way you’ll find it.

 

[Tech By Trade]

If it is a head gasket your o2 sensors will let you know shortly, that is if its going into the cylinder. It doesn't take much.

 

[boominXplorer]

I just had a 2003 Honda Civic with a bad head gasket (Go figure). It was blowing coolant out the radiator cap but no white smoke or miss. I put the pressure tester on it i pumped it up multiple times but found no leak. When I restarted it it stumbled really bad for the first 20 seconds then cleared up, something it hasn't done before. No real smoke this time either but clear evidence coolant was in the combustion chamber. I did the combustion gas test after and of course it failed. I don't think this is your issue but had to share the story.

 

[Beachcomber86]

I'm blowing some coolant out the overflow cap, not sure how much. When I open the radiator, it's still under pressure even though the level is low. Brand new 16 psi cap. Any ideas why it's not pulling fluid back from the overflow?