Coolant Temp reached over 250+ on highway.

Asked by Kristian Feb 25, 2020 at 07:14 PM about the 2001 Cadillac DeVille

Question type: Maintenance & Repair

After driving an 1.5 down the highway, I noticed my Coolant Temperature was ascending over 230 degrees, all the way over 250 degrees. It happened right near a Rest Area, where I was going anyways, so I pulled in. After I returned from the Rest Rooms, I checked for a Coolant Leak, and noticed bright green coolant was dripping lightly from my Front Passenger Side mudflap, and some underneath, leaving a good fist sized puddle of coolant.

I decided I should cancel my trip and head back home. So I waited a bit for the temperature to cool down, and journeyed on with the heat on full blast.

The temperature remained normal, and after 45 minutes I stopped for gas, and to check for leaking.  I still noticed green coolant gently leaking.

I kept driving for another 30 minutes, but this time I decided to turn the heat off and see how it did. The temperature remained fine the whole way. I pulled over to check for leaking again, and this time..there was no green fluid leaking. Just a bit of what must be dirty water from the same area.

So I kept driving the next 30 minutes home without the heat on, and the temperature was perfectly normal, between 190-196, sometimes to 201.

I really can't understand how it got up to 250 and leaked or overflowed coolant going down, but it was a normal 194 range with no leaking going back.

Several days before this I had attempted the trip, and after 1.25 hours in my ENGINE OVERHEATING LIGHT notification turned on. I pulled into a supermarket, got some coolant. A bit spurted out when I opened the cap too soon. I let it cool, added some, and kept going. After 25 minutes I was confident it was fine. But the ENGINE OVERHEATING notification came on again, on the side of the freeway. I let it cool, added more coolant, and kept going. Then I started getting a COOLANT LOW notification and decided I would just call AAA, and I got towed 2 HOURS home.

The next day I took it to the mechanic. They did a pressure test, and added dye. They said they found NO LEAK. They had no answer for what happened.

One thing I remembered is before my trip, I added 2 quarts of oil, without even checking how much I had. I just assumed I might need some. Wrong.  added WAY too much.

So with the mechanics doing the pressure test, and having no answer, I assumed that adding too much oil was the problem. I got an oil change, and tried my trip again.

This is when the temperature reaching 250 happened.

The mechanic had no answer for any of this! What is going on???

No Answers Yet

Your Answer:

Cadillac DeVille Experts

  • #1
  • #2
  • #3
View All

Find great deals from top-rated dealers


Content submitted by Users is not endorsed by CarGurus, does not express the opinions of CarGurus, and should not be considered reviewed, screened, or approved by CarGurus. Please refer to CarGurus Terms of Use. Content will be removed if CarGurus becomes aware that it violates our policies.