Strange external coolant leak

Every morning, after I have driven to work and parked my car I see coolant leaking. If I open the hood I can see steam and a coolant trail in a valley on the exhaust crossover pipe shield. This leak only occurs in the morning after I have driven maybe 1 mile. For the rest of the day there is nothing.

I took the car to the dealership and had the cooling system pressure tested and inspected for coolant leaks. They could find nothing wrong. I looked with the tech as he thought maybe it was coming from the clamped area on the upper rad hose where it meets the metal piping. Also thought maybe bleeder screw which is also located there, but could find nothing. The strange part is it only happens first thing in the morning after my car has been driven mile and then no sign of a leak after that. Any possible ideas?

Thanks,

Dollar to a donut says the leak is from where the hose connects to the thermostat neck and it's from a build-up of deposits on the neck sealing surface. Remove the hose and with nylon brush polish up the neck and reinstall.

Do you mean rad hose that connects to thermostat housing. Also, why does the leak appear first thing in the morning then no symptoms after that?

Thanks much

Yes, your picture shows the correct hose & connection. I can't explain why the problem goes away, but I bet it's probably related to how much the gooseneck expands as it's heated by the hot coolant...

Thanks, it is starting to make sense now.

Yes, your picture shows the correct hose & connection. I can't explain why the problem goes away, but I bet it's probably related to how much the gooseneck expands as it's heated by the hot coolant...

Close but not quite.

It's the rubber hose that expands and contracts with the temperature.

When the hose is cold (ie: sitting overnight) the rubber contracts INSIDE the (now loose) hose clamp (and if the hose has age cracks at the end) a leak will occur.

As the rubber warms up, the hose expands UNDER the clamp and closes the leakage opening.

You can tighten the clamp(s) but that may not fix it.

The hose is new - maybe 5 months old. It is attached to the Thermostat housing pipe with a new screw down clamp. In the past when checking my hoses I have notice that the screw would come loose, and could not figure out why. Right now it is on there as tight as possible.

I will check the deposits and clean it up with a nylon brush. If that doesn't work I guess I just have to get a new hose.

The hose is new - maybe 5 months old. It is attached to the Thermostat housing pipe with a new screw down clamp. In the past when checking my hoses I have notice that the scfew would come loose, and could not figure out why. Right now it is on there as tight as possible.

I will check the corrosion and clean it up with a nylon brush. If that doesn't work I guess I just have to get a new hose.

In that case, it may not be the hose.

When you clean the neck look very closely for a crack.

Yes, I will. Aside from the leak problem,there is some sort of vibration causing the screw to loosen. A small crack would make sense.

The hose is new - maybe 5 months old. It is attached to the Thermostat housing pipe with a new screw down clamp. In the past when checking my hoses I have notice that the screw would come loose, and could not figure out why. Right now it is on there as tight as possible.

I will check the deposits and clean it up with a nylon brush. If that doesn't work I guess I just have to get a new hose.

Ah-ha....this is new information! Did the leak start shortly after installing this new hose? Why was the original spring clamp replaced with a worm-gear clamp? Believe it or not, but those spring clamps do a remarkable job of sealing the connection. And yes, the worm gear clamps do loosen up...!

No, I did not notice any leak after the hose was replaced. I noticed the leak after the radiator was replaced which was 4 months after the hoses were replaced.

I don't know why they used the screw down clamps. They replaced my heater hoses and other hoses with these clamps as well because the spring clamps were rusted.

Update: In the past week I drove about 800 highway miles to SC and no coolant leaked. As you all have suggested I am convinced that it is the cold that facilitates the early morning leak. Now that I am in the South and the car is parked with complete exposure to sunlight I have not seen a drop of coolant leak and screw on clamp is still tight.

I haven't had time yet but will remove the radiator hose and look for deposits or small crack somewhere.

When I was back north I could see the coolant dripping (about 1/8 of a cup) after driving first thing in the morning and now no coolant loss. It is a amazing what such a slight leak can do.

Doe's this car have a Dual Climate Control Valve (DCCV), and a Dual Air Temp Control (DACT)?

When the car is cold and the heat is on, at a certain temp there's 100% coolant flowing through the DCCV, this will give heated coolant for the dual heater core.

If you turn the heat off during the warm day , the plumbing is turned off, so you wouldn't beable to see the leak.

Do a water pressure test with the engine at normal operation Temp with the heat temp on MAX.

venturenot, I wouldn't bother removing the clamp if it's not leaking. I think the problem was fixed when you tightened the worm clamp up. Just keep an eye on the clamp - if it requires continual re-torqueing, maybe look for the correct clamp. If it holds its torque, forget about it....

Doe's this car have a Dual Climate Control Valve (DCCV), and a Dual Air Temp Control (DACT)?

When the car is cold and the heat is on, at a certain temp there's 100% coolant flowing through the DCCV, this will give heated coolant for the dual heater core.

If you turn the heat off during the warm day , the plumbing is turned off, so you wouldn't beable to see the leak.

Do a water pressure test with the engine at normal operation Temp with the heat temp on MAX.

I don't know if I have these valves, but I will try the pressure test with the heat on max.

venturenot, I wouldn't bother removing the clamp if it's not leaking. I think the problem was fixed when you tightened the worm clamp up. Just keep an eye on the clamp - if it requires continual re-torqueing, maybe look for the correct clamp. If it holds its torque, forget about it....

I hope that it is just the clamp. However, it was as tight as could be when I was up north and it still leaked. I really believe it has something to do with the hot and cold. It was so strange, every morning when I was up north ( clamp on tight ) after driving about a mile and turning off the engine it would spill out coolant and after that no problem.

It was almost like the van had morning sickness... Maybe a little Venture will pop out the hatch.