Hey there guys! Just bought a Z28, checked out great at the dealer despite the slightly higher mileage (150k) and replaced gaskets (performance) and refinished heads. My only two questions are:

1. The temperature fluctuates...a lot. It typically sits at just above 185 while driving, but while I am idling it always gets up there to 230 before starting to cool again. Now, I know that some of that is simply due to the fact that air flow while driving will cool the engine/engine comp. but what about idling? Is this normal? Here's a link to the instrument cluster image to see what the range is.
2. Let's say that I wanted to upgrade the thermostat to a 160 degree guy--what else could I be looking at to upgrade the cooling and keep this guy running great?

Any advice, info, etc would be great. I plan on doing some modding to the engine eventually, so extra info/help would be awesome! Keep it cool...

Justin

 

as for your tempature they tend to run extremeley hot sitting due to such a small engine bay its mighty cramped down there also i believe it has something to do with the reverse flow cooling. You shouldn't worry to much about the tempature once you move air gets in and cools it back down unless its hitting the red on the meter then id get it checked out.

as far as the thermostat i'm not to sure about i believe you should do something with the computer to let it know your putting in a lower thermostat so the second fan kicks on at the right temp then.

 

Okay, great, that alleviates my worrying considerably. I might eventually upgrade the hood to something a little more vented, but so far the temp has never passed the last line before the red zone. Any more thoughts or info on the above posts? Especially on upgrading the thermostat and fans, etc?

 

Like i said about the thermostat you can put a 160 in but i believe you'll either need a manual fan switch to kick on the second cooling fan whenever slp offers one i believe or you could make your own. if you search the forums theres a lot of debate about all this all over the boards.

 

Okay, cool. I'll check around online, too. If nothing else I might have to take the car in to have the computer programmed. Ha! Good excuse to do a little bit of tuning as well, right?

 

You can have the computer programmed to turn the fans on sooner....or run one of them all the time.

As mentioned above....your temp is operating normally.

 

I would disagree that it is normal for the coolant temp to reach 230*F when idling. The cooling system, in good condition, should allow the engine to idle at about mid-gauge (210*F). Substituting a 160* t'stat would not reduce the idle temperature, since the 'stat only determines the engine's lowest operating condition. It would allow lowering the fan on/off temps, but that would be putting a band-aid on what may be a need for throrough cleaning of the cooling system.

Have you checked the cooling system for the presence of air? Because of the reverse flow coolant, it is difficult to remove all the air from the system, and any air will cause overheating. There are two bleeder screws on the t'stat housing and the hoses to allow bleeding the system.

Shoebox has info on filling/bleeding the cooling system:

http://shbox.com/1/4th_gen_tech2.html#radflush

 

Go buy some radiator cleaner (descaler) from your auto parts store and run that through with a good fluid change. Your car is deffinatly running warm probably due to lack of service, as air would almost deffinatly cause overheating whereas varnish build-up would only hamper the cooling properties of the coolant. I went through this a couple of years back and the fix that I mentioned made a world of difference.

 

My car used to get pretty hot as well idling on a warm day. I have a 94 z28. I replaced the thermostat with an upgraded one like you're suggesting and it made a big difference- still gets warm but not hot like it did before. I'm thinking a new thermostat will solve your problem. It did for me.

 

Injuneer is definately correct buddy i had the same problem on my z when i first purchased it. It would idle around two twenty to two forty. This is after i had changed my own antifreeze. I later found out about the bleeders on the coolant system i performed this task and now the engine idles about fifteen to twenty degrees cooler than it used to but i had that exact same problem would get up to the half way mark sometimes but now after bleeding the system.

 

if it gets too out of hand... 160* t-stat and a coolant flush...if it continues then get a new water pump.

 

also keep in mind the temp sensor for the gauge is on the ds head and the temp sensor for the pcm is on the waterpump, so there's a variance between what the pcm is reading and what you are seeing.

 

In the winter, idling, the engine would take a long time for both fans to turn on and cool it down(if at all). In the summer it happens a lot quicker. I may have misspoke about the upper temp limit. Whatever the stock limit is for both fans to come on is how hot mine will get. Somewhere in the mid 220's if I recall. My LT1 has always done this....cooling system is extremely clean.

Hehe, on a hot summer day I opened the hood for a friend to see the engine and he was about knocked down by the heat wave, off the engine, when I raised the hood.