I know your thinking "not another overheating issue" but i've been searching and can't find anyone with my same issue. First some background on my build. 355 cid, le2 heads, intake, 228/236 cam, electric water pump, 160 thermostat, still have heater hooked up. I know all the hoses are hooked up correctly, I can see coolant flowing out of the steam pipe return and the throttle body is bypassed. My overheating issue is that it will heat up to about 215-220 (not the red) and seems to keep going but i've shut it down b/c I don't feel it should even get that hot with the 160. Heres the kicker though when i shut it off and leave the electric water pump on it immediately drops to about 175-180 degrees. The fans are not kicking on. The hoses are warm but not hot enough, after running the water pump about 15 min. after shutdown the hoses are hot. even the heater hoses. The bleeder screw has a steady stream with no air coming out with the pump on or off.

So my thoughts on this are:
-The fans aren't kick on because they read off the sensor in the water pump, which isn't getting hot.

-Why does the temp drop so quick? is coolant rushing to the sensor rapidly cooling it? As much as I don't like the thought could this be an issue of a cracked head or blown headgasket that lets a bubble form keeping coolant from getting to the sensor? This motor was built by one of the best in the kansas city area, with the best parts. Quality wasn't sacraficed to save money.

 

Just some basic questions -
Is it (PCM) programmed to turn on the fans at the lower temps?
It's an electric pump, right? Is it turning the right direction?
If you could jumper the fans to come on, then you could see if that helps it maintain. Also, you have the correct LT1 thermostat and not one for a SBC?

 

That is not an overheating issue. Your chasing a problem that does not exist (maybe why no one has your same "problem"). 160 is the temp the thermostat opens, not what temp it will run in all conditions, especially idling and the fans are not on. Unless the fans are programmed to come on earlier than the stock 226%u00B0, temp is going to rise at least that high when there is no airflow across the radiator.

When you shut the engine off and run the ewp, no more heat is being generated, but heat is being dissipated by the radiator.

 

Ok i guess I didn't provide enough info fans are set to come on at 180 low and 190 high. The computer has a base tune on it and im am 100% positive this is a Lt1 t-stat and is installed the correct direction. I understand the engine doesn't run at thermostat temp, but it shouldn't reach 210 within minutes 3-4 min idling and still climbing without the fans coming on especially with a 160 stat and reprogrammed fans. Basically with that info im trying to say there is a definate temp difference between the computer sensor and gauge sensor. Also this temp drop is literally from 215-220 down to 170ish on the gauge within 2-3 seconds so this is not a normal cool down to where the temp is disapated throughout the system. And this is what has me confused and worried.


As far as the water pump wiring goes it is correct unless there is an internal problem. Its fused and runs off a relay that activates with the key. I've triple checked that for other reasons and again for this one.

 

In that case, I would try to see what else could make it run hot like if maybe it had a vacuum leak making it run lean or some other problem like advanced timing or maybe something that you might find by looking at the running parameters if you have a way to hook up. Because what you're saying is that there is too much heat in the head, but the water pump area doesn't see the heat before it gets too hot on your gauge.

How does the engine seem to run?

 

It starts and runs amazing, its the most responsive motor i've seen. For just a startup tune its pretty close, its rich but haven't hooked up the wideband to see what the a/f is. It starts up just as fast and the same as if its sat for a week or and hour and always goes straight to idle. Heres a clip

 

I don't know what to tell ya. When I have mine apart, I bleed it once or twice and then check it again later. I've heard of folks having to do it more than once to get all the air out of it. I can't think of anything else at the moment.

 

Are you running the same pcm as what was in the car? If so it was tuned by Keith McCord for !CAGS and lower fan temps, those temperatures sound about right to what he tuned it for.

Keep in mind the gauge gets its temp for the heads and the pcm gets its temp from the waterpump (IIRC). Seems like it's warming up a lot quicker than my stockish LT1 though. Are you sure you bleed all of the air out of the system?

Car sounds pretty good, Kyler. Can't wait to see it on the street.

 

something that I noticed when I bought my 95 z28. The PO had removed the relays for the foglights and one fan. He than ran a wire from the fan relay connection to the foglights. Therefore turning on the foglights turned one fan on. Also when bleeding coolant there are 2 brass looking bleed screws on top.