Let's start with some background info.

Brand new 355 installed 3 weeks ago.

I replaced me heater core 2 weeks ago because I had a green pond in my passenger floorboard.

I replaced my heater control valve today because it was leaking out of the underneath side of the top (if that makes sense ...). I thought this was the main source of me losing coolant recently.

I clamped off all hoses with vice grips near the hcv before removing the clamps & hoses so I would lose minimum coolant and not have to drain the system.

After replacing the HCV, I drove the car around for about 10 minutes. During the drive, I cycled the HVAC controls through all settings, making sure the heat worked like it should. Also ran the air on max, norm, bi-level and also ran just the vent.

When I pulled into the garage, I had coolant dripping very rapidly onto the floor. The drip was coming from somewhere between the back of the engine and the firewall. It eventually stopped after leaking about a pint onto the floor.

I thought "crap ... I must have cracked or pulled loose that ?-shaped hose that comes out of the heater core ... or I might even have ... gasp ... a leaking freeze plug!"

I looked all over the back of the engine and firewall as much as I could, but it is so cramped back there that I couldn't see hardly anything. The one thing I know for sure is that it isn't leaking out of either of the two hoses that connect to the heater core (at least the top of the ? one).

I started the car and backed it out of the garage. Let it get good and warm. Cycled through all of my HVAC controls and ... nothing. No leak at all. Left the heat on for about 5 minutes ... not a drop. Left the air on for about 5 minutes ... not a drop. Turned the system completely off ... not a drop.

So, I drove the car another 10-15 minutes, cycled through my HVAC controls again, stopped for gas about 5 minutes into the drive and looked under the car. No dripping. Drove home and pulled into the garage. No dripping. Turned the car off. Still dry. Not a drop since the first time it leaked earlier today. I watched the temp gauge all the way through my drive and it never broke 200 degrees.

So, I topped off the coolant reservoir to replace what leaked out, and now I'm posting this.

Any ideas?

 

I'm somewhat in the same position that you are in. I drove to my girlfriends house and in twenty minutes my temperature was cycling from 190-220. This is ODD. my new 358 always runs at 160..

I get to her house and me and her dad check my radiator, it was DRY. So i leave it there and get my other car. Once it cooled down we checked to see if there was a leak, we poured water down the radiator and it leaked right out the bottom!

So we decided that weekend we would take it out... But randomly i decide to check the radiator the next day, and it was full!! wtf! We took the radiator out and it was fine, filled it back up and drove it around.. thermostat opened and it ran consistantly at 155-165.

Week later on the way to work it leaked coolant out again!

I'm going to try a 7psi cap, since i have a 15psi cap now. Maybe its too much pressure?


I just checked it today and nothing leaked? This is blowing my mind

 

M1tch I would stick to the cap you have as the higher pressure will keep the boiling point of the coolant down.
Also if your sure it was coming out of the radiator change it. Don't drive it if you need to be somwhere, but when you see it again, look at it and figure out where it is coming from, then fix it.
Also 15 psi is normal and not to much by any means.

gcgarner, other then the heater hoses I don't have any coolant hoses at the rear of my engine, and I belive your's should be the same.
I would take a shot at the head gaskets. That's really the only other thing back their, but you may also want to try to run it alittle more to see if you can locate your leak better.

 

try a system press. tester , you can rent these at many parts stores . the one i used had a rubber bulb like a blood pressure tester . my leak was the hose going to manifold at dist. base , very hard to see . good luck .