why does my car only leak when its cold?

[markus]

I just noticed lately my car has been peeing coolant when its parked but only when its real cold. We will say less than 40 degrees. And usually happens when the car was just shut off after being run.

Example: I came home last night from my gf's houst at about 12.30. Wake up this morning to check and see if the car is leaking. Nope and the temp today was in the 40s. Well I go back to her house at 6.30 tonight and leave and come out and see decent sized puddle on the ground. Not so much coolant loss to put on the "CHECK COOLANT" light on the dash. It must be a lot to drip down past my splash guard to make it noticeable on the ground. Its also on the passenger side. Anyone have the same problem? Im going to take the shilds off tommorow and have a peek. Hopefully I will find something.

[schnell944]

where is it leaking from? it it is just weaping coolant from the weap-hole up front at the water pump, that means that the bearings in it are starting to go. but since it's a fair amount of coolant it might be leaking out of a hose that has deteriorated and seals up when it is warm, allowing it to leak when cold.

[markus]

i have to determine that tommorow. findling leaks sucks ass.

[shogun]

Tighten all hose clamps. Lessons learned in school: warm material expands = closing leaks, cold material= leaks start to show up.

[ironie]

One would want to be careful not to overtighten the hose clamps on a plastic radiator, espcially when it is cold out, as cold makes plastic a lot more brittle.
The water pump suggestion is the most likely, next runner up is the thermostat houseing.

[Russell]

expansion tank lower 0 ring could be the problem. However, the 540 has expansion tank on the firewall. So may not be same propblem.

Mine does the same every winter. May replace 0 ring or expansion tank next radiator flush.

[shogun]

the 540 has expansion tank on the firewall. So may not be same propblem

Yes, still could be the problem, they tend to get haircracks at the lower part where the halfs and connected. Check the expansion tank at the bottom.