G'day, Iv got a 94 c4 LT1 350 lately I have noticed it's been getting a bit warm when idling or driving slowly around city doesn't do it on open road and just noticed for first time after I turned ut off after driving for about 20 mins I could hear the coolant boiling? What do you all think please?

 

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Clean between the radiator and fins. And burp any air out.

 

Thanks Il do that,was sort of worried it mite b head gasket on the way out,havnt had to much of a look yet tho

 

This is common for the C4 LT1 which is designed to run a bit hot for emissions and fuel economy purposes. Higher cylinder temperatures promote more complete burning of the fuel for lower emissions, and the ignition system incorporates knock sensors to prevent excess detonation due to higher engine temps. Reverse flow cooling also plays into the system.

On the digital temp gauge, the fans automatically turn on low speed at 228*F and high speed at 235*F if I recall correctly. The fans do not automatically trigger above 35mph since at that speed it's pulling air across the radiator as well as the fans could. The system works pretty well as it is designed, I think. But many people are not comfortable with an engine that regularly reaches 228*F in traffic. I'm not either.

Assuming your cooling system is healthy and working properly (see replies above)... turning on the A/C or defroster will trigger the cooling fans, and this will bring down the engine temps. Otherwise you can have the ECM reprogrammed to turn on the fans at lower temperatures.

Anything between 195-215 I would consider normal temp. Don't worry too much about anything in the 220-225 range, as long as it's not going there too often and it's not staying there when it does go there. If you hit 235 or above, and the fans are not helping, I would start looking for a place to pull over. And ignore the analog gauge, it's misleading.

My strategy... when I'm at long red lights (90 seconds or more), I just turn the engine off and restart for green. It saves gas, and idling for longer than about 30 seconds isn't good for gas engines anyway. In stop & go traffic where I can't reasonably turn off the engine, I use the A/C as needed. I see 220 maybe 5-6 times per year, that's the number where I turn on the AC (and the fans). I intend to reprogram the ECM for 220 and 225 but have not yet done this.

Hope this helps you.

 

Thanks mate tht give me less worries now ,but will keep an eye on it and have a good look when I get time cheers