Hokie69 New Reader
10/21/15 2:57 p.m.

Would appreciate any suggestions. Daughter's van looses coolant after being parked when hot. I've replaced rad. cap and thermostat. No foaming in the oil & coolant is clean. Had garage pressure test system w/ no leaks found. Appears to be coming from bottom of rad., but w/ the panels in place, can't pinpoint any source. I can replace rad., but don't want to throw parts at it w/o knowing the cause. Thanks

Sine_Qua_Non Dork
10/21/15 3:29 p.m.

Make sure it's not your lower radiator hose being split somewhere. I changed one on my wife's a few months ago. Tiny slit and only leaks when engine is hot. Replaced it and no more disappearing coolant.

dropstep HalfDork
10/21/15 3:37 p.m.

If it has the front mounted waterpump pull the inner fender panel and check there. I thought our old 99 need a radiator but it was the waterpump leaking and being thrown forward. Puddled when parked near the passenger front tire.

moparman76_69 UltraDork
10/21/15 4:15 p.m.

What year, what engine?

tooms351 New Reader
10/21/15 4:29 p.m.

Try some of that fluorescent green dye thats made for coolant systems, you'll spot the leak real fast, hopefully.

Kenny_McCormic UltimaDork
10/21/15 5:14 p.m.

Check rear heater piping if equipped.

Hokie69 New Reader
10/21/15 5:27 p.m.

It's a 2006 w/ the 3.8 V6. During the pressure check, we looked at the heater hoses going back to the rear heater core. Will go to a more trusted garage for another pressure check. It's draining water under the left front; initially thought it was coming from the overflow, but it appears dry. Thanks for the responses.

Vigo PowerDork
10/21/15 5:43 p.m.

Water pump is in the lower rear of engine bay on the passenger side of that vehicle, so probably not related. Good thing cuz they kinda suck to do.

When you say overflow appears dry, i assume you are looking for a trail of wetness, but is the overflow at the proper level? If it's empty or close to it, that would suggest the car is pushing coolant and overflowing the bottle. Pressure testing the system usually excludes the one part you take off to fit the tester, which is the cap. A cap that is lifting off before the specified pressure can cause you to lose coolant only when hot, but the vehicle will not actually overheat until the coolant level gets too low. I know you said you replaced it, but with the right adapter a cooling system pressure tester can test the cap as well, and if you're going to have it looked at again i would specifically request that they pressure test the cap.

Hokie69 New Reader
10/21/15 5:47 p.m.

In reply to Vigo: thanks, the cap was my first thought. Will have garage check cap also.

DuctTape&Bondo Dork
10/21/15 7:32 p.m.

2002 Mercedes C230k has a reservoir with the overflow molded into a corner, the overflow chamber wall had a crack that would open up when hot and dump the entire contents of the reservoir onto the ground. Not sure if yours has that design, but worth checking.

Hokie69 New Reader
10/21/15 8:24 p.m.

In reply to DuctTape&Bondo:thanks, interesting possibility, wouldn't show up in a pressure test

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