I just want to share this happy ending.

Several weeks ago my 94 Eldorado overheated to the point where the engine shut down to an idle and a little bell went off. Then when I looked at the instrument panel it told me my coolant was overheated, in fact this happened three times. After the last time I parked the car and walked away, Oh I started up every once in awhile but it always ran really rough.

Then a couple of weeks ago I decided to take it into the dealer, but first I drove it around the neighborhood for a while, but no matter how much I drove it, it still ran rough. So I took it home and opened the hood, just to see if any coolant had overflowed, then just before I was about to close the hood, I noticed the PCV valve. I pulled it out and cleaned it. After I installed it, I started the car and to my surprise the engine ran smmooooothly.

I’ve been driving the car everyday, freeway, slow city streets and ran it at idle for long periods and no more overheating! I replaced the PCV and can only guess that when the old valve stuck shut, the car overheated and when it freed itself the car ran normal. Total cost to repair was $3.80 for a new PCV valve.
:)

Can't imagine a PCV valve would cause an overheat, but glad she's running good again.

Can't imagine a PCV valve would cause an overheat, but glad she's running good again.A PCV valve can't cause an overheat. Hey maybe everyone overheating needs to check their PCV valves first. :)

where is pvc valve located on 94 Eldorado?

It's on the passenger side of the rear cam cover.

What about on a 2004 DTS?

Here is my best guess, keep in mind I'm no expert nor mechanic.

The PCV valve can effect the engine idle at all RPM by restricting the air flow. If I were to pull the hose off the top of the valve the rpm will increase, if I place my hand over the hole and block air flow the engine will die. So I think that the old PCV which was badly gummed up would get stuck and restrict crankcase ventilation, maybe the computer tried to compensate and sooner or later the engine ran too hot. My only interest is driving my Eldo on a regular basis, so if I'm wrong and it overheats again I'll post that here too.

What about on a 2004 DTS?
The 2000+ Northstars don't have a PCV "valve". They have a metered orifice. I think it is in the same place.

well it has now overheated so you screwed any way, no?

So far the Eldo is running like a top :)

Here is my best guess, keep in mind I'm no expert nor mechanic.

The PCV valve can effect the engine idle at all RPM by restricting the air flow. If I were to pull the hose off the top of the valve the rpm will increase, if I place my hand over the hole and block air flow the engine will die. So I think that the old PCV which was badly gummed up would get stuck and restrict crankcase ventilation, maybe the computer tried to compensate and sooner or later the engine ran too hot. My only interest is driving my Eldo on a regular basis, so if I'm wrong and it overheats again I'll post that here too.

The PCV is a calculated vacuum leak. By disconnecting the hose, you're making the leak bigger than what the engineers calculated, so it acts like you opening the throttle. By clogging the tube with your hand the computer needs to compensate for the lack of air going to the intake by opening the throttle a little bit. It shouldnt make it run rough, just lower the idle speed (or kill the engine) because it's starving for air.