I have a 2001 DTS and I can't seem to figure out what it going wrong with it. The car starts fine and runs perfect for about 10 minutes then it starts desplaying coolant level warnings (which is full), coolant temperature hot warning A/C off (which causes the heat not to work), and eventually overheated (which causes the car to hardly run). The wierd thing is that the car never actually overheats to the point where it steams and smokes and if I turn it off and start it back up a minute or two later its fine again. I just replaced the thermostat and that didn't fix the problem so I'm wondering if it could be something electrical just telling my car its running hot and/or overheated.

 

u could have air trapped in system
or something plugged

 

Unfortunately this is the classic symptoms of a failed head gasket on the Northstar engine. Being 11 years old your engine is right in the range for this problem. To desribed the problem in a nutshell the EGR passage that runs past the rear drivers side head creates over time a heating condition that allows the head bolts to pull from the block. When cold the engine will run fine and the problem occurs over along period of time. By the time you get to ten minutes running time before all the warnings start your heads are probably warped and the engine will require an overhaul. There are a few mechanics who have mastered this repair, the best solution is to sleeve the head bolt holes in the block. It is expensive and usually costs about $3,000 because the engine has to be removed. Your car barely runs because the Limp Home mode is invoked basically running on 4 cylinders with retarded timing. The engine has reached about 250 degrees when Limp Home kicks in so this is why you see no steam as the sytem works to limit higher temperatures but it is already too late. GM did not address this issue until 2005 so if you get another Northstar keep that in mind. I personally love the Northstar engine, however this is one issue older engines experience.

 

I took it into autozone and had them hook it up to thier diagnostic thing and it came back as saying that the ECT sensor was bad. Could it be something as inexoensive and simple as that? If the head gaskets were bad wouldnt it of leaked when they put pressure into my cooling system after my thermostat was replaced? And someone told me that it would blow out alot of smoke if it were my head gaskets. I'm just trying to get a few ideas before I take it in the shop.

 

head gasket can do lots of different things depending on the size of the failure.
why did u change the t-stat in the first place??
and how did they check the ect did they say there was a code and said its bad??? if so, its not the correct way to check it. If u have air there like a pocket air(steam)it will heat up different then if it was liquid. if u test something cold u may not have a leak but if u test it hot u may have a leak. so there is alot of things one must know in order to check this motor.

 

As gmtech indicates a cold pressure test may not show the issue since it is heat that caused the heads to expand etc...Also if it is a head gasket coolant in the exhaust can cause alot of other things to go wrong. White smoke is sometimes seen but not in all cases with the Northstar.

In an 11 year old Northstar with the problems you describe, I am standing with my head gasket diagnoisis. It is unfortunate because I am sure the car looks as good as can be but I have had experience with these engines and a I know a guy who actually repairs them. Click the text links below.

Expert Engines

http://www.cadillacexperts.com/

 

So on the 2005 DeVilles there is not an issue of overheating? Just got an 05 DeVille about 2 weeks ago and it worried me to read all the posts of overheating Northstars. Trying to figure out what I got myself into.

 

Most forums are loaded with owners with some kind of concern, mostly if everything is wonderful there isn't much to talk about. Northstars are just less forgiving when it comes to overheating

 

since the problem wasnt corrected until 2005 will a 2005 or newer northstar swap into a 2001 dts y code with little issues?