C5 Z06 overheating while in BG
 

I missed any posts you made about overheating. What temps are you seeing? The C5 technically isn't overheating unless you hit 235F and the fans haven't/won't kicked on, or are on and can't keep the temps down.

It maxes out, ding and check gauges..with the AC and fans running...

I'll move this to C5 Tech

Damn. Hitting ~270F w/the fans on sucks. I'm sure you've considered the obvious: crap in front of the radiator, stuck thermostat, water pump, air in the system.

Water Pump is next...

Water Pump done...no change...crap...

So the options left are:

1. The radiator (Blockage)

2. The Engine Block (Blockage)

3. The Engine Block (Cracked)

Am I missing anything?

Fans kick on at the right temps/speeds and right direction, Thermostat is new, Water Pump is new, Engine Oil is not milky or foamy.

*sigh*

Sure it's not a faulty temp sensor? Coolant reservoir cap maintains pressure? Air in the system?

From a cold start, does the engine warm up normally (and w/o any errors) and progressively overheat? Or is it fairly quick to overheat?

Not sure on the sensor...

New Cap.

I'll check for pockets..

Progressive,I guess, took about 20 with the AC on and the fans on high speed.

BTW, where is the sensor... (I'll probably look it up but I'm book lazy this AM.)

Access to temp gun? Could ck. specific locations. Back home ? I've got one...

Got one, thanks.. !:D

When it overheats, does it still blow hot air through the vents? Does the coolant in the reservoir boil over? Are both the inlet and outlet hoses hot?

Don't think it's the sensor atm. The dash gauge works off a signal from the pcm and the failure mode is to lock the dash gauge ~215F. The sensor is behind the alternator screwed into the head.

Not sure if it is boiling Lutzdog was watching it. Put it this way, the AC gets lots warmer.

Update:

Took the cars temperature...

Hose 1 = 198

Hose 2 = 203

Temp shown on DIC - 234

Thoughts?

Reading some threads over at CF, one member was able to reduce his temps by messing w/the crossover tube between the heads in the front of the engine. Apparently that is a place air pockets and get trapped. Here is the post from CF about it

GMpartshouse has the sensor for ~$21. I'm not sure if the temps can vary that much from where the sensor sits to either of the coolant hoses.

The cooling fans are controlled by the PCM. From the factory, low speed is set for 226F and high speed is set for 236F. The temp on the DIC is what the PCM thinks the temp really is. I don't remember, will it overheat, meaning the fans can't keep the temps below 236F, at idle w/everything off, or just when the A/C is running?

Also, what oil temps are you seeing on the DIC?

It only gets above 230 with the AC on.

240ish

Very Interesting....How does one "burp" the system?

Well, since the oil temp is close to your coolant temp, I would say that you are seeing the actual temp. Since it is only happeneing w/the A/C, what about a slipping belt, bad tensioner, etc?

Concur

Doubtful, new belt... tensioner seems good.

I'd like to burp it, not sure how.

Found the procedure below here

Here is The factory service procedure for draining and filling.

Draining and Filling Cooling System

Caution: With a pressurized cooling system, the coolant temperature in the radiator can be considerably higher than the boiling point of the solution at atmospheric pressure. Removal of the surge tank cap, while the cooling system is hot and under high pressure, causes the solution to boil instantaneously with explosive force. This will cause the solution to spew out over the engine, the fenders, and the person removing the cap. Serious bodily injury may result.

Important: If the procedure below is not followed a low or high coolant level condition and/or vehicle damage could result.



Park the vehicle on a level surface.
Remove the surge tank cap:
Raise and suitably support the vehicle. Refer to Vehicle Lifting.
Place a drain pan under the drain ****.
Open the radiator drain ****.
Allow the cooling system to drain completely.
Inspect the engine coolant for the following:
Discolored-follow the flush procedure below.
Normal in appearance-continue with the next step.
Notice: When adding coolant, use DEX-COOL coolant. If silicated coolant is added to the system, premature engine, heater core or radiator corrosion may result. In addition, the engine coolant will require change sooner-at 50 000 km (30,000 miles) or 24 months.

Notice: Refer to Fastener Notice in Service Precautions.



Close the radiator drain ****. Tighten the radiator drain **** to 2 Nm (18 inch lbs.).
Fill the cooling system through the surge tank.
Fill the cooling system with a 50/50 mixture of DEX-COOL coolant and deionized water.
Start the engine.
Allow the engine to idle for 1 minute.
Install surge tank cap.
Cycle the engine RPMs from idle to 3000 in 30 second intervals until the coolant temperature reaches 99°C (210°F).
Shut off the engine.
Remove the surge tank cap.
Start the engine.
Allow the engine to Idle for 1 minute. Fill the surge tank to 12.7 mm (0.5 inch) above the COLD FULL mark on the surge tank.
Install the surge tank cap.
Cycle the engine RPMs from idle to 3000 in 30 second intervals until the coolant reaches 99°C (210°F).
Shut off the engine.
Remove the surge tank cap.
Top off the coolant as necessary, 12.7 mm (0.5 inch) above FULL COLD mark on the surge tank.
Rinse away any excess coolant from the engine and the engine compartment.
Inspect the concentration of the engine coolant.
Install the surge tank cap.

After reading all the posts, I'll give this a try tomorrow evening. If it works, I'll be smiling...