i just bought a 98 dodge stratus yesterday, and a couple times while driving yesterday and today (10 miles to my parents, and 15 to my inlaws) i noticed that the radiator reservoir was boiling after i shut off the car. it doesn't do it all the time though. when i drove 10 miles to my parents, it did it, but when i drove 10 miles back home, it wasn't... also, the temp guage shows that it is NOT overheating. the guage gets to normal operating temp and stays there.

what could be causing this problem, and how can it be fixed? i'm sure it needs the rad flushed, the fluid looks rather murkey and brown (uses the pink fluid, not the green) but the last time i got a radiator flush on my 90 olds cutlass, that caused way more problems afterwards, but the olds rad was REALLY bad...like this brown sediment would actually cake onto the inside of the rad cap....so i'm sure the radiator on the olds was shot anyway. i'm just hoping the same thing doesn't happen to this car! i really like it

 

My dad's '99 had the same "problem," with the boiling reservoir, it never caused any trouble, the rubber seal in the overflow cap was melted, replacing it stopped the boiling.
Is the fluid kind of"milky" where its brown?or does the brown fluid float towards the top? That sounds like oil in cooling system which is a sign of a bad head gasket (also happened to my dad's '99, and the previous owner of my '98, and plenty of other people).

 

Yeah brown coolent sounds like you have oil mixed in it. That will cause your over heating problems. You can't always go by your temp gauges since they could be bad as well. I would get your head gasket checked ASAP. Because if you have oil in your coolent, you have coolent in your oil and that is not good for your car.

 

no, it is not oil, its corrosion. my oldsmobile had the same problem. the oil was totally normal, no water in the oil, but someone at some point had switched it from the pink coolant that it was supposed to have, to the green stuff, and it got all corroded. it was so gross that this brown sandy sediment formed a 1/2" chunk on the inside of the rad cap. its not oil, it doesn't float, its mixed evenly throughout, its just gunk and dirt and corrosion from someone not doing regular flushes. luckily, this doesn't look nearly as bad as my oldsmobile.

and i will check the seal on the overflow.

 

another thing i just thought of, when i was looking at the car before test driving it, i opened up the radiator cap. could i have let air into the system that it was just trying to get rid of? and it just appeared to be boiling? i know the system has to be "burped" to remove air....

i thought of that because today i drove it home from work, it was hotter today than it was yesterday, i left the heater and AC OFF, and i got stuck at several red lights, and 7 miles later when i got home, it wasn't boiling at all.

PS. Where is the battery on this car? there is a positive and negative hookup under the hood for jump starts, but no sign of an actual battery?

 

when you shut the car off after running at normal temperature, it will temporarily get hotter than when it was running because there is no coolant flow. while doing this it will build up more pressure, which will 'burp' water into the overflow. btw, as a water pump seal begins to wear out, this is why you'll see a leak more after you shut it off than while its running. i'm just wondering if you heard a couple of burps. just watch your temp gauge and if its normal i wouldn't worry about it.

i recently removed and cleaned out my overflow tank. it had a nasty layer of rusty brown gunk in the bottom that could be mistaken for oil.

 

Checkin front ofthe driver's side wheel for the battery location. There should be a panel there. It's easier to get at with the wheel removed but if you cut the steering all the way left or right, you might have enough room to access it.

 

i think i figured out the secret. if i stress the system enough to make the rad fans turn on (use the AC or run it for long enough) it doesn't boil. if i get it pretty hot, but not quite enough for the fans to turn on, it boils.

i drove home today, 7 miles, the last couple miles, my husband wanted to try out the AC, so we turned it on, worked great, the guage stayed at normal operating temperature. i get home, shut the car off, no boiling whatsoever. about an hour and a half later, i drive to the grocery store, and i hear it boiling. i drive home again, and nothing. so it seems the fans are the key.

 

So the extra fans running is keeping it cool enough not to boil. Still something doesn't seem right. Have you tried changing the thermatstat?

BTW...I am pretty sure your 98 Stratusdoesn't use the pink coolent. I should be using the green stuff still. I don't think Dodge started usingthe pinktill 2000. Of course that doesn't mean that someone that before you owned the car put the pink stuff in.

 

i'm probably going to get the radiator flushed and have them replace the thermostat while they're at it.

will changing the coolant from green to pink or pink to green damage the radiator?