My car is running hot at idle and while driving. Drove it up the street and it got to 260. I had to replace the coolant reservoir because I notice the tee was broken on the radiator side before it started to overheat. Replaced the water pump over 11/2 ago. Just replaced the tstat and took radiator out and cleaned it and did a flush. Hoping I don't have some internal problems like a blown head gasket. I started to replace the radiator. Not sure what to do from here. Thinking about taking it to the dealer for a diagnostic test. Just tired of trying things. Unclear about blirping the system. Ready to ride for the summer. The car has 95,000 miles on it.

 

Make sure you didn't over fill it, could help to get a new reservoir cap, and a lot of guys run a 160 degree stat during the summer
Are your fans running? Kick on the A/C and see if it cools down... the coolant temp not the inside of the car ...

 

Both fans are working. It does not change with air on. I haven't tried to vent the system yet.

 

Please provide this info:

Is the system PRESSURIZED when the engine is at operating temp? (hoses should be pressurized if you squeeze them)

Did you clean the FRONT of the AC Condenser when you cleaned the radiator?

Is the radiator air intake on the front underside of the car clean and free of debris??

What is your coolant to water ratio?? If it is over 70% coolant that could be part of the issue. Most people run 50/50 or 60/40 and if you live in a HOT climate, you can run less antifreeze to water

Are the Fans running when you are at the spec for them to turn on? If you only overheat when you are in traffic or slow speeds, and it doesn't overheat at highway speeds, most likely have a cooling fan issue. Turn on the AC and see if both fans run.

There is a steam cross over pipe at the front of the engine running between the left and right head. When the engine is at temperature and the system is pressurized, Use a wrench and loosen one of the bolt that holds the fitting. If there is air in the system, it will vent. If the system is full of coolant, coolant will come out.


When the engine cools down it should draw a vacuum on the block and suck in any water/coolant that is necessary to fill the block. This may take several heat and cool cycles. If your reservoir is at the correct level, it will supply any coolant that is required to keep the block full.. Your cap also has to vent when the system is cool and HOLD pressure when the system is at operating temps. You do not want to draw a vacuum on the coolant reservoir when the system is cold.

 

This is a steam cross over pipe on the rear of the engine my 02 ZO6. I added it because the 2001-2004 LS engines don't have a cross over on the rear..

The one on FRONT of your engine will have a bolt and a fitting on each side of the head that looks exactly like that. You have a tube that runs under the manifold and connects to the rear crossover tube.



I found a picture of how your cross over pipe and system looks on your early C5 LS1 and where the fittings and bolts will be:

 

A good way to know if your cap valve is working is when the engine cools back to ambient temps see if your upper radiator hose has collapsed, if it had your reservoir isn't venting properly and could add to a air trap problem.

 

My car is running at about 217-225 now. I actually used Peak instead of Dexcool. But it's running great now. Thanks for your help. Burped the coolant system and it still was a little high, so I took the bolts off both vent pipes.

 

Cool... literally. Thanks for posting your results.