Tank is probably a little over half full at this point. Looks to me like a slow leak as the system had considerably more fluid than that in it. Affecting performance at this point. Have an extended GM service contract. First took to a local tuner who does work on LT4s fairly regularly to bleed the system. He was unable to do so because he couldn't pull more than 9 lbs of vacuum. Took to the Chevy house and, as I understand it, they pressurized the system to 5 lbs and put a gauge on it for an hour to check for leak down. They pronounced it to be fine. I asked them if they would be willing to try to pull a vacuum on it and they declined. I asked where the fluid is going and they told me that they saw no visual leaks so they don't believe that the fluid is going anywhere. They recommended taking it back to my tuner to see if he can find the issue. If so, they claim my GM service contract will pay a third party for the work. I'll be checking on that this morning.

I have some suspicions (possible cooling block leak?), but nothing I can prove. Thoughts?

 

I would do both a pressure and vacuum test on the intercooler. You can use a Mighty Vac and some plugs and adapters to apply pressure and vacuum to the system. A plug that plugs into the intercooler fill port so you can connect to the system is available on the Cooler Bleeder website https://www.coolerbleeder.com/produc...plug-style-qc1. Use the Mighty Vac to pressurize and to pull a vacuum to see if pressure or a vacuum bleeds off over time. You won't be able to apply much pressure to the system since the pressure will tend to push the plug out of the fill port so be careful when applying pressure and maybe use a large towel wrapped around the connection to catch the plug and any coolant that might blow out of the port if you apply too much pressure.

If your tuner doesn't have a Cooler Bleeder they aren't going to be able to get all of the air out.

If there is a leak in one of the bricks that would cause an engine issue as the coolant would be pulled into the cylinders being fed by that brick. When operating the system doesn't pressurize much since the fill plug is all that seals the system and there are no reports of people losing the plug when driving for long periods on a track where everything gets very hot.

Bill

 

5 lbs seems pretty low for a pressure test, though I admit I have no idea what the correct number is. GM advised 10 psi to pressure test the LS9, but I’ve no idea if this is correct for the LT4 and wouldn’t chance it without confirmation.

see post #5
https://www.corvetteforum.com/forums...leaks-zr1.html

 

Trying another dealership. Supposedly has a master tech. We'll see how this goes. Hopefully they will figure out where the leak is.

 

If you are not seeing any visible leaks that would lead me to believe that it is the intercooler bricks leaking. Take the SC Lid off and see if you can see anything while it is pressurized. If you don't see anything on top then pull the blower off to check the underside of the IC Bricks.

 

It may come to that. I, too, suspect that I may have a leak in a cooling brick, but I've still got a Platinum extended service contract in effect. I'm going to try to find someone who can figure this out.

 

ill be in tx in march for tx2k. be happy to bring my cooler bleeder and see if it will help. pulls 35 in/hg . just need electric for the hvac pump. takes about 30 minutes from start to finish

 

Try gspeed. They have a bleeder kit for back yard mechanics for 150 bucks.

Www.gspeed.com

 

I really appreciate the offer. I'll PM you if I'm still lost in the woods. The latest Chevy Service dealer has had the car for about a week. I'm going to give them a call tomorrow and see where we are. I believe that I have a leak in one of the bricks, but haven't been able to prove it yet.

 

easy enough to test the bricks. plug off 3 ports use a Schrader valve and tube and pressurize the 4 port with air stick it in the sink full of water. if its leaking you will know in seconds.

 

Not sure what you are proposing. There are two coolant ports on the SC. Remove the coolant manifold from the snout and 4 holes under it let coolant flow from the manifold through the snout to the bricks in the SC. If the SC is removed from the engine there are still only two ports or /four holes but removing the SC from the engine permits the removal of the snout and access to the 2 ports on each brick. At that point the two bricks are independent of each other so would be tested independently.

Manifold sitting on top of Snout:


Manifold removed showing coolant holes on Snout:


Different view of holes on snout:


Front of the SC showing where Snout attaches showing the 4 ports for the two bricks with O Rings around the ports:


Rear of Snout showing where the 4 ports from the bricks connect with the Snout:


Different view of rear of Snout:


Leaks might occur where the snout and the bricks connect (there are O Ring seals around each port on the bricks) and the bricks themselves can also leak. The dealer won't go any further than seeing if there is a leak in the SC. GM's procedure at that point would probably be to replace the O ring seals under the manifold and if that didn't work they would replace the SC which can be an issue since the 2017+ SCs are on backorder.

If there is a leak it is more likely going to appear in the HX or the hoses connecting the SC to the HX and the reservoir. The HX is the most likely place for a leak to occur since it is sitting in front of the radiator and the AC condenser and can be hit by road debris thrown up by other cars. Since the intercooler system isn't pressurized any leak would probably be very small unless there is a large hole.

So which 3 ports are you blocking and where is the 4th port where you apply pressure?

Bill

 

im talking about the bricks themselves. remove them from the s/c completely and test them. if they leak he will know it.

 

The saga continues. The dealership is telling me that the "air bleeder screw" was out of adjustment. Tech was able to hold 28" of vacuum overnight after adjusting the screw. I'm not even sure where that is.

 

Isn't it up front close to the fill cap. I'd look on my car but it's outside under the car cover since i'm working on my golf simulator in the garage.

 

First things first. I can't look now, since they have the car.

 

When the original shop tried to pull a vacuum. they may have caused the extra air in the system. If there is a leak, when placed under vacuum, air will enter into the system AND you wont be able to get the vacuum levels expected which lines up to what you are seeing

Regardless, it really shouldnt be a hard diagnosis. Sometimes leaks will only show up under vacuum, other times only under pressure. I wouldnt hesitate to put 1 bar of pressure on the system and then let it sit / monitor. If it holds the pressure, then go back to vacuum. Simply touching connection points and hoses, while under vacuum, can be enough to cause a vacuum gauge to jump around if the joint is leaking. Reach out to me at www.coolerbleeder.com if you decide to fix on your own and we can set you up with the necessary tools to pressure and vacuum test, as well as bleed.

 

Well, not sure what the problem was. No parts replaced. Chevy store was able to hold 28" of vacuum. They bled the system and did what appears to be a good job. Just a couple of small bubbles at the top of the tank. I was a little surprised that they did that well until I found out the master tech that worked on it owns a 900 hp ZR1. It looks like he knows what he's doing. Putting some miles on to shake it down. Thanks for the suggestions and offers of help. We'll see how this goes from here.

 

How did the TX2K work out for you?

 

worked out great for me. road tripped my z07 from nashville 24 mpg 80 mph close to 1700 miles total narry a hiccup. weather was a bit sketchy but its all good. great racing some great racing and way to much whiskey!