Went out for a drive tonight and noticed my 04 Z06 was running hot. Temps got to 243 and would drop to 237. Normally my coolant temps are under 190 on highway regardless of outside air temp. In the winter they typically stay in the 170s.

Came immediately home and noticed that the coolant cap was cool and the lower hose to the thermostat was also cool while the upper hose was very hot.

​​​figure it's the thermostat or water pump but not sure how to test. Car only has 56k miles so kinda odd it would be the water pump no? No other telltale signs.

I have a new Lingenfelter 160degree thermostat on the shelf so I guess I will swap it but I'm not sure what thermostat is currently in there. Car has bolt on mods and a tune and based on my normal running temps, I assume it has a 160degree stat but want to be sure. Anyway to check?

​​​​​thanks in advance

 

Probably a bad thermostat.

The thermostat will indicate the opening temperature, check the Lingenfelter.

My car runs 190 with a stock thermostat. The only change with a 160 is lower opening temperature which may not be beneficial.

 

Sounds like a thermostat, a water pump fails by leaking or bearing failure. On very rare occasions the impeller can come loose-never heard of it happening on an LS engine-when the impeller comes loose you overheat real bad real quick.

 

As above swap your thermostat.

It may be tempting to swap for the 160, but seeing you live in LINY the 190 might be a better option if you drive in the fall or any cooler weather.

 

Thanks for the replies. Just ordered a 190 stat and housing from rock auto. Had to also order drain valve. Didn't realize it's not threaded so yeah.....I broke it🤭.

To anyone draining your coolant, turn no more than 90 degrees and you will see a pin. Line that up with the slot on the radiator housing and pull.

Will update once it's all installed.

Thanks again.

Mark

 

So just finished the stat swap....all good. Was definitely the stat.

I swapped in a GM 187 degree stat which is what it called for based on the advise here.(thank you) I will say the car now idles ato 207 degrees and then drops which substantially higher than before (it was at about 180 consistently before) so I assume it definitely had a lower temp stat previously. My only concern is that the car is tuned so not sure if the original tuner (prior to me owning) changed anything for the old stat. I guess we will see.

The Lingenfelter I had on the shelf was the smaller integrated stat for the older style so it wouldn't work anyway. Much smaller and completely different design.

Regardless....one last question. How do I burp the system? There is no bleeder anywhere.

Thanks again!

Mark

 

Here is the FSM method.

 

Thanks Jim

 

Don't know if you have the 4 corner steam pipe setup, or just the two in front setup. Either way, it's best to park on a steep incline, if you can find one, like a buddies angled driveway, a steep knoll, or use a floor jack to raise the front. What you're trying to do is raise the front end as high as possible to let the air bubbles find their way out. Remove the fill cap, and add coolant, varying rpm up to maybe 2,500rpm and back down to idle, then rev, then idle, etc. I always drill a very small, say 1/8" diameter, in the stat body, before installing, to help let the air thru. Hope this helps....

 

I have not posted this in the past because most will not do it -- but it is the absolutely certain way to get air out of the heads after a coolant change.

Five coolant changes so far, it works. Never a high temperature after.

2001 and later C5's do not have rear head coolant air bleed piping, but the heads do have the ports with bolted on block offs. These cars can have the rear ports activated when the intake manifold is off using a modified front pipe from a 2001 and later car and extending 1/4" heater hose to tee into the front coolant air bleed line which goes from the throttle body to the radiator on the right top side. There have been some reports blaming lack of rear head coolant air bleed piping for on track loss of cylinder #7. Maybe old wives tales but the last time I had the intake off, I added rear head coolant air bleed piping and hose to my 2001.

The picture below shows the rear head coolant air bleed hose coming from the left to a tee in the coolant air bleed hose coming from the front ports on my car ( I bypassed the throttle body a decade ago):


After a coolant change, I disconnect the connector with two band clamps, block the hose leading to the radiator and run a clear plastic hose from the coolant air bleed system to a bucket on the floor by the passenger fender.

When the engine is run in this configuration the coolant system tries to pressurize, forcing coolant and air bubbles out the coolant air bleed system through the clear plastic hose into the bucket. Be prepared to stop and refill the surge tank from the bucket several times. During the last coolant change on my car, about one and one half gallons mixed with air bubbles came out of this cobbled up bypass before the bubbles finally stopped. The reason for the clear plastic hose is so you can see whether the bubbles have stopped.

After the bubbles stop, I reconnect the connector and top off coolant.

 

Thanks for the replies...honestly, I have been just idling and reving it slightly with the cap off and squeezing the hose...seems to have gotten most out.

I will keep an eye on it but thanks again.