91LSMAN

I want to start off by saying that I know that no definitive solution that will 100% solve this issue will come from posting on a forum. What my hope is, is that somebody that has dealt with a similar experience might share what their solution was. And if any vendor or shop wants to chime in, that's fine too. All opinions are welcome. My Dad's 07 Z06 is still having cooling system issues. He bought this car "built"-heads, cam, etc--all already done because this car had the dreaded "head issue" years ago.
The car only has 15,000 miles on it.

Previous Thread:

From 8-4-18: https://www.corvetteforum.com/forums/c6-corvette-zr1-and-z06/4172571-coolant-issue.htm

lHead bolts that should not have been reused, were reused and the head gasket was blown. The head gasket was fixed, the heads were checked and all seemed well. Then in August he started having cooling system issues again. Coolant seemed to be getting low and possibly leaking. We took the car to the shop we have been going to for years. I had talked to them before hand and they said that they would look at it ASAP.
That day in August, when we got there they put the car on the lift while running to see if anything was leaking and the tech looked at us and said "heater core." They over nighted the heater core. Then my dad got a call the next week. (Dropped car off on a Friday). No charge for the work, we didn't have to do anything. There is no issue. We could not replicate any problem. What we thought was coming from the heater core was just condensation. They let the car idle, drove it, tested the cooling system, etc. No issue. Now, both of us felt that this was too good to be true. We had added coolant. Where did it go? Fast forward to today. He was driving the car and got the "low coolant" message on the DIC. He took the car back home. I was on my way over there anyway to wash some cars. We let the car cool down. Long enough for me to clean a car.

I looked at the overflow tank and it was almost empty. I added enough coolant to fill the overflow tank. We took the Z06 to lunch, took the freeway and when we got to the parking lot we got out and looked under the car. No low coolant messages, nothing leaking form under the car.

After lunch I looked under the car-nothing.

Where is the coolant going? There is almost always a very small puddle under the car that looks and smells like water-not coolant.

There is an issue with this car, but finding it is the problem. I'm not going to get into the personal stuff, but this is the LAST thing he needs right now. He really doesn't want to put a bunch of money into a car that he bought under the pretence that was a done and/or built car. Driving this car is supposed to be the reprieve from the other BS. The oil on the dip stick looked clean. Not sure if there was coolant in the oil, if I'd be able to see it on the dip stick. Does this sound like the heater core? Or something worse? If he takes the car back in, we'd just like to tell them to do something instead of hand it off and wait to be told they can't find any issue.

Engine Specs in case somebody wondered:
-GM LS7 Aluminum Block
-Rotating Assembly Built by Custom Built Motors,
-Compstar LS7 Crank 4.000 x 2.558 x 2.1000
-Callies Compstar 6.125" rods for GM LS series -Manley Pistons 1.115 CD FT 4.125 coated with -5 CC compression-Total Seal 4.125+5 1.5 1.5 3.0 8 Cyl
-Clevite Main Bearing Kit (LS Series) P Series
-Clevite Connecting Rod Bearings P Series -Brian Tooley Racing Camshaft: BTR LS7 Cam Kit stage 2. 230/246 .644"/.630" 115+4..660" LIft BTR Platinum Spring Kit with Titanium Springs 7.800" push rods -GM LS7 Fuel injectors modified by Fuel Injector Connection to 80lb @ 3 bar-Texas Speed Long Tube Headers
-Heads modded for Racing Performance by West Coast -C6Z06 Performance Aluminum Radiator w/EOC - West Coast Corvettes
-180' Thermostat
-Aftermarket Rocker Arms-Ported Heads by West Coast Heads - Bronze Valve guides for performance
-Oil Catch Can - Bear's Bolts and Bodies

Thanks for reading.

ss2z06

There are only two options. Either internal or external. If the oil is clean and level isn’t changing then it is external. I suggest a pressure check. The pressure should be dropping and a leak should show itself from somewhere. Granted it may be slow and obscure. Either way something should be present. Are there any other issues. Is the car overheating? Any odd smells Or stains?

zblackz06

I agree if it was an internal leak the oil should resemble a chocolate milkshake and your old level should be higher.Do you get any steaming on the inside of the windshield?.A pressure test would be one of the first things on my list.

pcguy2u

Might be good to not set the test up with pressure greater than what the radiator cap specification is.

Any smoke out the exhaust?

c5racr1

Pb82 Ronin

Start simple first...I agree pulling plugs and checking pressure.

91LSMAN

Thanks for your thoughts everyone. It's appreciated.

The car does stink-it's catless, so it smells like that. The previous owner had air fresheners in the glove box and shoved under the passenger seat.

The car did overheat right before it said "Low Coolant Level"

I'm not sure about steaming at the windshield. I'll ask him. What would that indicate?

92rsz

Check the water pump gaskets. I had one in my 5.3 truck that leaked very slowly. No drips but I was losing coolant.

pcguy2u

Heater core/feed tubes at the firewall...

Sox-Fan

Put dye in it and pressurize it with a hand pump. let it sit under pressure. see where the dye is. if that doesn't reveal anything then drive it till warm and again check for dye. You'll need a UV lamp. A light and dye can be bought on Amazon cheap.

91LSMAN

No abnormal condensation.

Thanks for the thoughts everyone.

91LSMAN

OK:

After reading the thoughts above and thinking about it my thought is to take the car in and tell them to do the following:

Change the Oil-and of course check the oil
Check the Water Pump Gasket up close
Pressure Test the cooling system

Wouldn't those 3 things cover most of the potential causes?

One question I have-and this might sound weird. Is there any coolant line anywhere on the car that only has coolant in it or is only pressurized when the car is in motion? Wouldn't have coolant in it when just up to temp and idling? (My thought is coolant running through a hose when the car is in motion, causing the hose to heat up, leaking from a small hole. When the car is just idling or off, the hose is cool, doesn't expand, and therefore doesn't leak. Maybe I'm reaching here. )

zblackz06

I dont think you need to change you oil unless you notice that the oil level is higher than normal or has a chocolate like color to it, this would indicate a coolant leaking into the motor/oiling system.
The vehicle being in motion has no effect on the coolant leak once the engine starts heating up it starts to build pressure so if you have a leak all that built up pressure will escape through leak forcing coolant out along with air.
Start by putting a dye in the cooling system and get it pressure tested that would be the first thing I would do.

fake

Change all your hoses if you have not done! Use new clamps only the original type not the band type. Change your antifreeze to G-20 Zerex and flush the existing with distlled water only. Start the car with hood close and let it get to temperture . At least 15 minutes. Open hood with car running use a LED light to look for seepage Do not forget to fill expansion tank to mark on container .

c5racr1

NemeZ

91LSMAN

Myself-I'm not touching anything. I'm just wanting to establish a list of things for my dad to have checked, because it's already been to the shop once and he was told there isn't a problem, when there evidently is. Cars don't overheat and lose coolant for no reason.

So here is the "list" as of this moment:
Check the oil/level
Dye in the cooling system/pressure test cooling system (Although they did say they already pressure tested it back in August)
Visual inspection of water pump gasket
Trans Fluid

And I was thinking about suggesting that all the coolant hoses be changed if none of the items above resulted in a solution.

ALTRDTA

Have the expansion tank cap pressure tested. If that fails it may be intermittent and leaking while driving to where you don't notice it anywhere on the ground

WhiteDiamond

AND

as mentioned many times:

Pull the PLUGS.

pcguy2u

And in case the reason for pulling the plugs is not obvious, compare the condition and color of each to the other. Be sure to put each on a piece of cardboard, marked with the number of the piston that it came out of (doesn't make any difference if you don't know the proper numbering, just so you know where it came from); then take photos. Armed with the photos/information, only then take it to a shop. Always good to have information on your side...