So I drive a 94Z basically stock.
I noticed my low coolant sensor was unplugged while working on my opti, so i plugged it back in finished up and found that it was bad...simple fix just replace the sensor and worked perfectly. My engine has been running unusually cold but I assumed it was because of the change in temperature since it has alot of desert miles on it and I now live in a very cold environment. But after about a month of driving it went off again, this time when I checked the level, it was fine. So, I opened the radiator and low and behold there was no coolant anywhere near the sensor. filled it up and the idiot light went away. Went to autozone and used a pressure testor. Brought it up to 18psi and watched it drop 3psi over the course of 2-3 min. So, on to questions

1- How can my Radiator be so low on coolant and the overflow container have plenty?

2- I know the pressure isn't supposed to fall nearly this much but I don't see an external leak. Is there an easier way of looking for an external leak?

3- If it is an internal leak, is there any notorious places for them on an LT1?
(Note: I had a guy in another state change my intake gasket about 4 months ago)

Any Help would be greatly appreciated

 

Take a look at your oil. Losing coolant could indicate a head gasket leak (worst case scenario). If it's milky there's your issue. Does your exhaust smell sweet at all or any white smoke? A slow leak into the cylinder sometimes doesn't reveal itself. If you're still at a loss, you can check all of your plugs for any steam cleaning.

The LT1 uses a dry intake manifold so your intake fix won't have an effect on it.

 

You may have a faulty cap, or a crack in the overflow hose to the reservoir. Coolant expands as it heats up, pressure builds, and the relief spring in the cap allows the valve to open and release the excess volume, to hold the rated pressure in the radiator. The released coolant flows into the reservoir. When you shut it down, as the coolant cools down, it contracts, creates a vacuum, and the vacuum causes a second (reverse direction) valve in the cap to open, and allow the vacuum to pull coolant out of the reservoir, and into the radiator, to keep it full. If the vacuum relief in the cap is faulty, or the overflow hose has a crack in it, the system can't pull the coolant out of the reservoir, and you end up with a void.

Same thing happens if you have a leak somewhere in the system. As the coolant cools and contracts, the vacuum pulls air in through the leak, rather than pulling coolant from the reservoir. The leak would explain why your system also loses pressure when you pump it up with the tester to pressurize it. The pressure leaks out of a crack or hole in a hose, or a damaged gasket.

If you have a leak into the atmosphere, you can put an ultraviolet dye in the coolant, and look for the leak after driving it for a while. If its a leak into the engine, you're either going to have white smoke in the exhaust from coolant leaking into the combustion chamber, or a milk shake in the crankcase from coolant leaking into the oil. You can also test the coolant for the presence of hydrocarbons, which would help detect a head gasket leak.

 

I have looked at the oil and I see no contamination. The exhaust does have a slight sweetness to it but every car here has white smoke, but thats do to the temperature. That could be masking the typical smoke from coolant burning. If there is coolant burning that means there is a crack in the block right?

Thanks I didn't know that about the intake on the LT1. not sure its comforting though.

 

does your heater smell like coolant? Drivers side carpet wet? This would indicate a bad heater core and would cause fluid loss. Also if your system is not properly bled it could have air inside coming out when you run it. and lastly your radiator cap could be done causing all your coolant to hit the overflow prematurely. Id check the carpet first as you said you did not see any leaking but it leaked down. Also check behind the heads for leaks from the cross over tube.

And as far as easer finding leak you can do the black light and dye in the coolant. This would work also with the oil as you would see it on the dipstick as well.

 

most likely head gasket, you can check the pressures of the cylinders or do a leak down check.

 

Could be a crack or pinhole in the block, a crack or pinhole in a head, or a head gasket leak. When its cold, the white smoke is just the normal water in the exhaust condensing, and that should not smell sweet like coolant.

 

I Have been under the dash quite a bit and have never noticed a coolant smell/ wetness.

I have done a compression check and all cylinders range from 175-190psi and holds steady.

Thanks for the quick responses guys!

 

did you do a leak down on it? Or just use a compression tester?
When you had the plugs out did you notice any that where really clean?