I've always liked big cars, and fords have always been good to me. I have a '98 crown vic xl hp that has a cooling system problem that has me stumped. Typically the temp guage will go up to normal (4 bars on the digital dash) and put out heat well. When it acts up it will start blowing cold air, and you can here than fan running real loud (louder than it does during normal operation). Then the temp guage starts to climb to the point of an overheat. When this is happening, and I check the reservoir with the car running, the coolant level in the reservoir is maxed out full to the top. I shut it off, give it just a little time, and then turn it on and off a couple of times, and the coolant level goes back down to within a couple inches of the top of the reservior (to the level it's at when everything thing is working normal). I can't figure out why its overheating. What is causing the coolant level to max out to the top of the reservoir and not go back down on its own? We've changed the thermostat twice, and put a new water pump on it too. Even worse, it will run great for a week, and then overheat, then be fine for another week or so. Any ideas on what's happening or what I should check next? Thanks in advance for your help. Eric

 

we had a problem with this at the police department were i work. it ended up being a plugged coolant line and water pump from what i gather. also check if i were you i would go and get the coolant flushed too and see how much crud you got in there. good luck

 

Update: flushed the system and it didn't make much difference, but it was worth a try. After some passing of time and some further investigation, we discovered a hairline crack in the intake manifold. At first, it wasn't bad enough to be noticeably loosing coolant, but apparently it was enough to affect the pressure in the system (at least that's the way it was explained to me). Sometimes when you'd remove the cap from the fill reservior, there'd be little or no pressure, and we tried replacing the cap with no improvement. Long story short, replacing the intake manifold solved the problem.

 

Thanks for posting reply of the proper fix. It does make sense that the lack of pressure would cause this problem. 15LBS Of cap pressure or system pressure will raise boiling point of coolant about 30 degrees.

 

I've seen this same problem several times before. Most manifolds rupture (burst) and it's pretty obvious. When it's just a hairline crack in the manifold it can be hard to find. Here's a link to a site with some great info in the problem and how to fix it...

http://www.autoclinix.com/Manifold.htm