SloopJohnB@mac.com

But can't see where it's coming from, LOL.
Pressure tested to 20psi…pressure slowly drops, but no coolant.
Puke is on the driver's side of the car so it's not the 4.2 coolant transfer tube plus I can't see any leak on the passenger side of the engine by that cooler.

With the pressure tester on at 20psi and engine running, the pressure climbs..i shut the engine off at 22psi. I'm going to do the same with the OEM cap on when wifey brings the car home and see if it's coming out the bottom of the expansion tank (there's no indication/dried stuff on the underside).
I'm thinking there's a leaking head gasket so I'm off to test with combustion leak tester, but any ideas?

Huskerbob

I think the coolant temp sensor is at the driver's side rear on your engine. 'O' ring or clamp?

SloopJohnB@mac.com

Wife brought the car in, no coolant leak.
I put a wad of paper towel under the expansion tank….hour later the paper is still dry and about ½" of coolant from the tank is on the floor!!!

Short of lying under the car and waiting for it to go…what the heck is it coming from? With the belly pan on, the leak is from the front of the belly pan right under the headlight. It only seems to happen after the car is shut down for awhile.

There is no secondary auxiliary coolant pump on a 2K4.2A6 is there? Something that would only leak after the car had been shut down for awhile?

rallymarty

Sloop, I have this problem as well. Thought it might have been the windshield washer tank at first, but noticed the loss of coolant after the display showed low coolant on instrument cluster.

Only seems to happen when it's cold out, noticed no loss (at least didn't add any) this summer during warm weather. Never leaks in my garage, only if car is outside.

Possible bad hose connection or loose clamp? I haven't looked myself, planned to during next oil change when the undertray is off.

SloopJohnB@mac.com

I have two activities in mind when I get the combustion leak detector kit.
1. Test for combustion leak (unlikely, I think..there are no bubbles or discoloration in the coolant, but who knows).
2. Run the car to hot, then put it up on jackstands, drop the belly pan, and wait underneath for it to puke…hopefully not on me!!!

Other than that, I'll just take it to the shop and let them figure it out. Two years ago a heater hose blew on the way to downtown DC…I'm glad the shop did it because the hose was kind of spendy at $165 (quick disconnect on one end..amazing) and it was difficult to get to. A 2000 4.2A6Q with 181K miles simply isn't worth doing a head gasket on unless I do it myself…not.

UncleScar

Leave belly pan off to get a better idea of leak. The pan collects the fluid and drains out the nearest hole. Grabb a mirror and a flashlight and wait for leak to start.

socalclimber

I had same symptoms: engine hot= no leak (even pressurized), next morning=coolant puddle on driver's side, near left side of radiator in the area near drain plug, but it was not the drain plug. My leak was radiator and was replaced under CPO warranty at the dealer. My radiator only leaked when it was cold (overnight).

Maybe leave belly pan off and do your paper towel test overnight under radiator?