[Desperate for help]

Hoping some people could help, I own a 07 DTS for almost 3 years now. I had to replace the radiator and radiator fan about a 15 months ago (I'm not sure if I had the thermostat and water pumped replace too, the paper work isn't with me at school currently) and I've had no issues until recently.

I noticed when driving a few hours back home from college to my home, I had got stuck for a few hours of stop and go traffic. It wasn't very warm out only ~75 degrees and I saw my coolant temp move from sitting in the middle like normal to bump up to the line above and sometimes a little higher. Should I get this checked out at my next oil change?

Also if anyone knows where a full quart of oil would be going in-between oil changes? No smoke is coming from the tailpipe so I don't think I'm burning it.

 

[Submariner409]

You need to understand your cooling system and fan operation sequencing. In a nutshell, unless some A/C compressor or DEFROST setting is called for fans are controlled by the coolant temp sensor and a set of relays and switches. Fans run - both - in SLOW or FAST depending on coolant temp and driving conditions. There is no provision for running only one fan in our FWD Northstar cars.

If some A/C function is set both fans run in SLOW, not for cooling. but to insure airflow through the A/C refrigerant condenser at slow vehicle speeds.

Apparently, in your slow traffic case, the fans went to SLOW at about 216 degrees, the engine cooled to about 210 or so, fans shut OFF, the cycle repeats. In summer, really hot day, traffic, slow driving, fans may go to FAST at about 225 degrees and cooling begins. Normal. Fans don't even run over 30 mph or so - not needed.

Correct coolant level in the surge tank, ambient cold, is about at the tank mid-seam. Do not overfill.

If you're changing the oil and filter at 3,000 - 8,000 mile intervals then a quart is perfectly normal consumption for a Northstar. Don't be afraid to romp on it once in a while when using an Interstate on ramp. The engine likes to RUN.

 

[Desperate for help]

You need to understand your cooling system and fan operation sequencing.......

Thank You!

 

[Submariner409]

Does your temp gauge have the same number of ticks as mine? If so, the temps are the same because our engines all use the same coolant temp sender. This pic is annotated with my fan operation points - yours are a bit lower in temp, not for engine protection, but because Cadillac owners get antsy and plague the dealerships when a gauge actually moves in response to some changing engine operating conditions. Not being snarky - "modern" fact - the "gauges" are heavily damped to give the impression of calm, steady conditions. Not so - engine operation is very dynamic. Have you ever seen an oil pressure gauge move from 25 to 65 to 25 psi from stoplight to stoplight? How about an engine manifold vacuum gauge flipping from engine vacuum to almost atmospheric pressure and back in 3 seconds?

In my older U.S. and "foreign" sports cars with 4, 5, or 6 gauges in the dash they ALL moved happily any time the engine was running.

Fun video - sound and screen - I used to own one (actually, an XK-140MC) - See the knob on top of the horn button? Turn signal! Top speed in his video was just under 60 - cams are deceiving.

 

[Omac]

I had to show some of my son's friends what the gauges mean. Unfortunately learning how a car mechanically operates including what the gauges mean is not part of driver ed or a requirement to get a license.