I know this sounds weird but my 94 z28 is not overheating its reading very low coolant temp.This is what happens, after starting car and letting it warm up for 10 to 15 minutes all coolant leaves the top of the radiator turning low coolant light on but while this happens I still show no temp at all on guage.Eventually both fans will turn on so I know Engine is getting hot.before I start car radiator is full and coolant storage tank is full. Any help would be greatly appreciated.

 

How do you know that all of the coolant is leaving the radiator? When you say it doesnt register does it not register on the temp gauge. First i would try to bleed the system. Then check the thermostat and make sure it is working.

You can check that by putting it in boiling water and youll see it open if it works and if it doesnt thats your problem. Is it leaking anywhere and have you done any work to the car at all that involves the coolant?

The low coolant light usually goes out on these cars all the time. Make sure that the temp sensor on the drivers side is plugged in.

 

already replaced tstat and yes sensor is plugged in.this problem started all at once no temp on guage and low coolant light.havent had any leaks at all.

 

Did you bleed it properly and i would do a pressure test to the radiator. Also would check to see if there is any coolant in the oil or tranny.

 

yes i bled coolant system properly with bleeder screws.no coolant in motor by looking on dipstick and oil fill port havent checked tranny yet.

 

just checked tranny fluid it also looks good oil looks good no foamy white colors

 

A reminder that the water level sensor is only wired to the light on the dash, not the computer, so if that light is on, either the sensor is faulty (mine has been for 7 years) or you've got a large air pocket in their.
Just mentioning this to rule out an electrical (pcm) issue. I would concentrate on the temperature sensor for the dash, which is also a simple circuit, providing a reading only for the dash (the sensor in the water pump is for the computer). Maybe somebody can comment as to how to test the temperature sensor for the dash?
Not any definite help here, just throwing a couple things out.

 

Focus on the coolant temp sensor in the driver's side head. You should check the harness wire/connector. Generally, low temperature corresponds to high resistance in the sensor circuit. If the wire is loose or damage, an open sensor circuit will leave the needle on the low end of the coolant temp gauge. If the wire is OK, and the harness connector is on tight, use Shoebox's guide to check the sensor.

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

When you bought the new thermostat, did you get the correct one for an LT1 engine?

 

replaced temp sensor after checking out resistance evry thing seems ok know temp guage works now thanks for all the help

 

My car is doing exactly this same thing.

Will report back after I test the temp sensor.

I love the Internet.

I love Injuneer.

I love shbox!!!

 

Thanks!!!

I wish everyone felt the same way.... you wouldn't believe the hate PM's and Profile messages I get from some of the members, when I have to play "moderator".

 

Maybe you need a 'pen name'?

And, this was exactly the issue with my car. Temperature Gage sensor. $26 at O'Reily's.

Was also a little low on coolant so it was 'belching' air and leading me to believe it might be overheating. Purrs like a kitten now...

 

If the radiator is not staying full, and you are sure you have no leaks, and no coolant being consumed in the combustion chambers, check the cap to insure it is holding the correct pressure when hot, and that it is opening under vacuum when the radiator cools down. Then check the hose/tube that runs from the radiator neck to the reservoir, to make sure there are no cracks or holes in it. If there are cracks or holes, the radiator can not refill itself from the reservoir when the system cools down.

 

Yeah it's got to be one of those issues... it doesn't leak coolant, it's not (obviously anyway) dumping coolant into the oil, not smoking white, etc. No signs of trouble or leaks, yet undeniably the coolant is going somewhere. Takes about 6 months to lose a gallon, so that's how I forget to check it. Maybe it's leaking so little and slowly that I can't see it, or leaking it onto the engine where it evaporates or something.

When I got the car back on the road last spring, I didn't replace any hoses. They weren't obviously bad, but they are original so they may have cracks or small leaks. I was doing well just to get it running, let alone have the cash to 'do it right' so to speak.

I didn't think to check the cap though, will do that!

 

OK so all sorts of new weirdness that has me baffled.

Ran fine until last night, started overheating in traffic. Blistering hot here with the A/C blasting, stop and go traffic, but even under those conditions it never gets over 210. It has a 160 thermostat in it and Hypertech programming so the fans are 'adjusted' for this stat.

So when it hit 260 I shut it down, and had it towed home. It boiled over a little in the parking lot, but just a little like you'd expect after getting just a little hot. Left it sitting all night in the cool garage.

This morning 2.5+ gallons low on coolant. So I'm thinking it must have a leak now that's only leaking under pressure, when the engine is at operating temperature? Confident that I'm bleeding it properly too, I fill until all the air is out of both bleed screws, close the tstat housing one first then bleed the upper one completely, close it off and top off the radiator. Filled it up and started it to let it warm up so I could watch for leaks.

Ran up to 210 and remained steady there. (It usually idles about 170-180 even in the heat so this is actually 'high'...) Stayed at 210 for a long time, not leaking a drop anywhere.

No signs of any coolant in the oil, or oil in the coolant. Runs fine. No noise. Radiator hoses get warm indicating there is 'flow' and the cooling fans turn on as they should.

Now the real puzzler, I always turn on the heater to be certain there is flow going through the core, to get out any air there. Even at 210 idling in the driveway, the heater doesn't produce an iota of heat. Zero zilch notta.

So I shut it off, thinking I'll replace the thermostat and radiator cap and see what results I get from that. Immediately after shutting it off, it gurgled into the overflow tank for a bit, then slurped down the entire contents of the (now overflowing) tank. So there was clearly air in there somewhere, but now I'm thinking "OK so the air is all out now, I'll try again."

Started it back up and did the bleed thing again, no air in the bleeders, ran at 210 for a bit, then crept towards 260 slowly. Still not a hint of heat from the heater.

WTF???

In the olden days before the LT1, now and then I'd have a small block water pump do flaky things. Some of the impellers were pressed onto the pump shaft, so they could actually fail without leaking or overheating completely. Essentially everything would 'look good' no leaks, thermostat fine, but the impeller would slip on the shaft enough to not properly flow enough coolant through the system. I have no idea if that applies to the LT1 water pump given that it's cam driven, but I don't know what it looks like inside. That was a rare/odd issue a long time ago anyway.

So, I'm going to go ahead and replace the thermostat and radiator cap, bleed, etc, and see how it acts then. None of that would explain the heater not working though, would it???

Aye yi yi...

(Of course the big Mt. Airy cruise is tonight, the 'home' of the Andy Griffith show, so I really want to cruise through in the car! Will still go in the van if we must, but watching the cruise and being in the cruise are two very different levels of fun!)

It's a good problem to have though. I keep telling myself. "My Camaro is down" is a small problem all things considered. We have a nice van to drive so it's not like I'm walking...