: 2007 Cadillac DTS Performance Overheating 66k miles; what gives?

02-15-13, 11:12 PM

First of all let me say ahead of time thanks for any help and advice you all can provide.

I literally 8 hours ago became the owner of subject vehicle, clean carfax, 2 owner just all around nice looking car.

Did my homework went around the car checking for a bad N, did not see anything major during the test drive. Signed and walked away with the car.

While in traffic mind you its 33 degrees tonight, heater and AC off, 25 minutes running, i noticed the temp gauge just above the mid way mark. It went over the first mark after half way after a few more minutes. Traffic eased up and drove over 3 miles at 55mph gauge returned just above mid point like before. Pull in driveway and leave the car running, cooling fans are not on, even as the gauge still marks above mid way.

Shut off car, no steam ,no gurgling, just exhaust manifolds clicking.

I refuse to believe this car has a blown head gasket at 66000 miles.

Can you all point me in the right direction? What should i check first?

All fuses good
coolant in overflow is orange and level
no coolant in oil
car was purchased in calumet city illinois and driven to louisville ky where i live. The dealer bought the car and just drove it here for me. what could possibly be wrong?

02-16-13, 12:59 AM
Key word is "COOLING FANS NOT ON"...
They should have came on automatically as it started to get hot.

Check to see if they come on when you turn the AC on.... They should come on then.
If not... the dealer you bought it from should stand behind getting it fixed.

02-16-13, 07:42 AM
How far past midway is it, both of the DTS's I have owned and relatives SRX, and eldorado always sit right at the half mark, they ran Cool under 45000 then sat at half way , would go over slightly, but never went much past it and would come back down and level off. Did that all the way to 122000, ran perfect,finally traded it. but having just bought your car, Now is the time to get checked to make sure. Could be a sensor might be nothing


hope it all works out for you... Good luck...send picture

02-16-13, 08:11 AM

Here is a picture of what the gauge read last night. In a few minutes i will do the first cold start up and see if it gives me any signs. This is my 3rd Cadillac, and my second blew the head gaskets, i hate to say it but it shared the same temp reading prior to completely disabling itself. What I do remember was when I started the engine cold in the mornings the engine misfired a lot. Later I found out the reason was that condensation or coolant would seep into the cylinders causing the misfires. I hope thats not the case I really love this car. Will update soon.

02-16-13, 08:53 AM
Cold Engine Start at 823 am with remote starter, 28 degrees temp outside. No rough idle, that i could tell just a normal engine sound thats not warm. At 840 engine reached the mid way mark. Still no cooling fans, turned on the AC at 60, 844 Fans came on temp stayed just above the mark like it did last night. When I say above the mark, picture the width of the needle at the tip, just that above mid way. Temp continued to raise with fans on, at 850 i shut the engine off. What could it be?

02-16-13, 09:10 AM
2005 and newer NorthStar engines don't have the same head gasket problems that the earlier ones had

they still can have a true headgasket problem like any other car but the block does not need to be tapped and inserted

that said, you may be noticing normal behavior ... temp rises, cooling fans turn on and cool it down, then they shut off because it's normal temp again

you would want to make sure that the cooling fans are coming on though

02-16-13, 09:45 AM
The thermostat is set to begin at 188 and be fully open at 206, so the engine "likes" to run at about 195 - 205. These gauges are heavily damped at the midpoint, so the tick mark at 9 o'clock represents a spread of about 190 to 205.

With no A/C or DEFROST function called for, fans go to SLOW at 224 and FAST at 236. With some A/C function set, fans run in SLOW all the time. On the highway fans never run - they aren't needed. If you're idling or in traffic with no A/C selected the temp will creep toward 224, fans come ON, the coolant goes down to 213, fans shut OFF and the cycle repeats.

Using an 18 psi reservoir cap, 50/50 coolant will not boil (overheat) until about 270 degrees. The engine could care less about its running temperatures between about 180 to 250 - it's the coolant that "overheats" and, to a lesser extent, engine oil - because engine oil is the only thing that cools ALL the internal rotating assembly and valvetrain. Engine oil should normally run at about 200 degrees in order to boil off moisture and acids for consumption by the PCV system.

(Fans also go to FAST at transmission fluid temps of 304 - yes, 304.)

You might want to go down to Discussions, Engines, Northstar Performance and read the sticky thread concerning the FWD series of temperature gauge operation.

If you're interested in watching 12 engine functions in dynamic readout, look at www.scangauge.com (http://www.scangauge.com). I use a Scangauge-II set to display coolant temp, intake air temp, ignition advance and MAP. (No, I'm not a shill for ScanGauge - years ago I bought two, at retail, on the recommendation of a local Seville driver and they work, and work well.)

02-16-13, 11:36 AM
Update: Had my mechanic that frequently works on the N*s to look at it and after an hour and a half. He came out to tell me my reservoir is leaking. I understand the theory coolant under pressure boils at a higher temp, that with a cooling system leaking the coolant can boil at lower temperature. And if such is the condition steam in the cooling system will not cool an engine down.

I now remember my first DTS when it broke the front engine mount and when it did hit the firewall. By doing that it broke a cooling pipe on the wall of cylinder 7. I waited too long to repair it and ultimately ruined the head gaskets. I realize my negligence and what ruined a car at 130000 miles that could of lived a lot longer.

Now back to me new one, it was low 1.5 gallons of coolant, mechanic estimates losing a pint a day. I will have the reservoir replaced Monday and hope this was the culprit of my overheating issue. Coolant test showed no hydrocarbons in the coolant system which proves a good seal on the head gaskets.

By the way its still 30 degrees out, after i returned home i idled the engine for a few minutes and the temp stayed at the mid way point. Feeling good so far.

Will update everyone on Monday. @ Submariner409 and Rippypartsdept thanks for that info.[COLOR="Silver"]


02-16-13, 11:47 AM
If you can gut it out, get into Amazon automotive - those GM reservoirs usually go for around $55 - $60, shipping included.

02-16-13, 11:56 AM
I can purchase it myself, and install it, but im afraid of the air pockets. Thats the only reason i dont trust myself to do it.

02-16-13, 12:19 PM
the system is self purging so no worries about air pockets

02-16-13, 02:38 PM
Provided the purge line is clear.

02-16-13, 03:31 PM
You can purge the cooling system, after replacing the coolant reservoir, the old fashioned way by running the engine with the reservoir cap off. You should run the engine till you start seeing the bubbles due to boiling coolant. Unless you have the service records of your Caddy, you should 1) check coolant strength & replace it if incorrect mixture, and 2) replace the thermostat.

02-22-13, 01:37 PM
1 of 2 cooling fans is not working .