: 1998 Deville overheating



Jason Henry
12-02-07, 12:43 PM
Greetings,

As recently as a few days ago I had my coolant reservoir tank
completely replaced. There was a bad leak which caused the car 's temp to rise to 260. Today I drove the car about 20 miles on the freeway with the new
tank installed and the temperature rose to 228, but did not go above
that reading. On my way back home, I drove the freeway in the other
direction for 20 miles and toward the end of my journey the temp crept past
231.

I parked the car to enter the grocery store. I returned 20 minutes
later, drove home (which is about 5 miles) and the car's temp rose to 237.

I have heard that the car's temp isn't supposed to rise above 228, then
I heard that a normal temp is 240.

I am in need of assistance as I have had this temperature issue since
March. Also, I have had numerous mechanics run a diagnostics on my
vehicle and no-one is able to pinpoint a cause of the temp rise. Thanks"

misfit6794
12-02-07, 01:58 PM
There's a couple things that could cause it. Do a search on the forum for "purge line" as it could be clogged. You could have dislodged some crud in the system replacing the tank. Also make sure your cooling fans are kicking in. BEFORE you start throwing any more money or parts at it, have the coolant tested for exhaust gases, you can buy the kit urself at pepboys or napa, etc, very cheap. You could have a failing headgasket, and if thats the case its between a 2500-3500 dollar repair, and there is nothing you can pour in the engine to fix it cheaply. Some of the syptoms of a failing hg is having coolant in your tailpipes (stick your finger in there, if it comes out slimey, thats coolant), bubbling or overflowing out of the coolant resevior, white smoke out the exhaust (thats burning coolant, not to be confused with water vapor burning off). There is a TON of info on this site about headgaskets, do a little bit of searching. Hope its not that, but it probably is. After my headgaskets were done my car never went over 197, when they were failing between 225-235 and the 255-265

Ranger
12-02-07, 10:34 PM
Normal running temperature is 205-215. In addition to the purge line, have the cap checked to be sure it is holding pressure. Check the water pump belt tensioner.

Jason Henry
12-03-07, 12:23 AM
Thanks for the help. I am a novice when it comes to cars, so bare with me. When I take the car back to the auto mechanic, should I ask for a test on the purge line?

-JH

chubbyranger
12-03-07, 06:12 AM
Thanks for the help. I am a novice when it comes to cars, so bare with me. When I take the car back to the auto mechanic, should I ask for a test on the purge line?

-JH

Yes - have the purge line checked.

misfit6794
12-03-07, 07:49 AM
Have the mechanic check the purge line and cap, but if he wants to start replacing high dollar items, make sure he tests the coolant for exhaust gases before doing so. All too many times forum members replace just about every part of the cooling system only to find out it was the hg's.

Ranger
12-03-07, 08:56 PM
Thanks for the help. I am a novice when it comes to cars, so bare with me. When I take the car back to the auto mechanic, should I ask for a test on the purge line?

-JH
No need to take it to a mechanic. See the 3/8" line attached to the surge tank near the top? That is the purge line. Loosen the clamp and slide it back on the line so you can pull the hose off. Then start the engine (cold so as not to burn yourself). Pull the line and if it spits coolant. If so, quickly plug it back on. Shut the engine off and replace the clamp. If it does not spit coolant (flow increases with higher RPM), then there is a clog. THEN take it to your mechanic if you are not comfortable clearing it.

sahtt57
12-06-07, 11:53 PM
Greetings,

As recently as a few days ago I had my coolant reservoir tank
completely replaced. There was a bad leak which caused the car 's temp to rise to 260. Today I drove the car about 20 miles on the freeway with the new
tank installed and the temperature rose to 228, but did not go above
that reading. On my way back home, I drove the freeway in the other
direction for 20 miles and toward the end of my journey the temp crept past
231.

I parked the car to enter the grocery store. I returned 20 minutes
later, drove home (which is about 5 miles) and the car's temp rose to 237.

I have heard that the car's temp isn't supposed to rise above 228, then
I heard that a normal temp is 240.

I am in need of assistance as I have had this temperature issue since
March. Also, I have had numerous mechanics run a diagnostics on my
vehicle and no-one is able to pinpoint a cause of the temp rise. Thanks"

Before anything else, you need to have your compression checked. If your headgasket is blown everything you will do will be in vain and will never resolve your heating issues as they slowly get worse over time. Right now you may be able to replace the head gasket and be ok, if you continue to drive on it and it's indeed partially destroyed then particles will enter your combustion chambers and cause excess wear. After you figure out if your compression is ok and consistent, [assuming you check the purge line first because it's very easy] you can pressure check your coolant for leaks etc. and figure this out more accurately. Try here for cadillac over heating (http://www.forumdig.com/search.aspx?q=cadillac+over+heating) solutions.

Zorb750
12-09-07, 10:28 PM
Not compression test, leakdown test. Force air in and watch for bubbles. Compression test is less accurate (And less dramatic if it "fails").