2004 Z with a 187 degree thermostat has been running around 199 degrees on the highway and up to 230 degrees in stop & go traffic. I replaced the fluids, thermostat, and the 3 fan relays. I suspect the high speed fan kicks on at 230 degrees and brings the temp back down to 199'ish, but do you think it's running at around 199 degrees because the low speed fan is shot? Is there a coolant sensor that also is in play here?
Thanks.

 

Have the fans been reprogrammed to work with the cooler t-stat?

 

I'm confused here...with the stock t-stat those temps are right were they should be and perfectly normal. I see you said you replaced the t-stat but it didn't say you went with a lower temp so I assume it is still stock temp. I don't think there is anything wrong unless I am missing something.

 

With the stock thermostat and stock fan settings, your temps are normal. In order to lower your temps, this is the sequence of actions you should take:

1) Inspect the radiator closely; clean out any debris that's stuck in it, being careful to not bend any of the fins. A wire brush is useful, but blowing pressurized air or water through the radiator from back to front is probably the most effective technique.

2) Seal up the edges of the radiator shroud, using tape or something like this:
http://forums.corvetteforum.com/c5-z...t-cooling.html

3) Have your fan settings adjusted to come on at a lower temp.

4) At this point, you should be running at a good temperature under pretty much any conditions (aside from heavy track use). If you still want to run cooler, then the last thing you should do is swap the tstat to a lower temp unit (and adjust the fan settings accordingly).

 

It used to never it 230 while idling, that's what prompted me to change the t-stat. I ordered what I thought I was stock and I believe it was stamped with 186.7 degrees on it. I'll also follow skyavonee's 4 step process.
Thanks guys.

 

I live in South Florida where it's always hot. I have the stock Tstat and I never hit 230, I would flip out if I did. Buy a new radiator there not that expensive.

 

Check/clean the radiator and ac condensor?? Ud be surprised how dirty they get!!!

 

I'm guessing that its the control mod, it's not kicking on the low speed fans. I'm going thru the same thing right now, and that's what I discovered.

Mark

 

I know 217 is about normal on mine and it can go higher on a hot day and in the right circumstance. 230 doesn't sound too far off from normal to me. As other said, changing the T-stat does nothing unless you change the fan settings.

 

I do run the 187 but I did talk my tuner into lowering the fan on temp. He didn't want to do it but I begged.

 

I was hitting 235 at Sebring this past weekend. I do have a Doug Rippie oil cooler that blocks some of my flow though.