Cooling system fill - Page 2 - ZR-1 Net Registry Forums

mmkkpro · 04-25-2020

That's cool secondchance, this is my first Z and I was freaking out a little over air being trapped. I ran across this air lift tool and figured I'd give it a try. I have read that if you can see coolant flowing from the little brass tube in the metal tank that means the water pump is pumping. I'm learning a ton here at the registry, hopefully as I learn more about these cars I can give back some of the help I have received. I just put new coils, wires and plugs in it, I had a slight miss and stumble off idle, took her up the road earlier and she felt good. I got a ways to go but getting there.

secondchance · 04-25-2020

One word of caution - when I first unbolted thermostat housing, bolt wiped out the thread and had to be helicoiled. Maybe corrosion between the bolt and the housing due to different metal?

Yes. Coolant flow coming from the brass tube is confirmation of the water pump working.

mmkkpro · 04-26-2020

I have not worked on the thermostat yet, so far seems to be working fine, temp Gauge is just above center. However this car sat for several years with cooling system open, hoses unhooked and marvel mystery oil in cylinders. I'm having an issue with the MM in the exhaust system, as it heats up, smokes and it leaks from exhaust connections, I mean it pools on my garage floor. I reckon maybe the valves were open on a few cylinders and the guy kept filling and it just went strait into exhaust. I have not actually driven it at speed for a long distance yet, I hope when I do so it will burn out but not sure what's going to happen to the cats. I have new o2 sensors. Headers and exhaust at some point this summer. I still have a long list, seat covers, weatherstripping, paint, have wheels refinished and so on. Have no idea when it was last tagged and on the road, 78k miles, it is all here nothing butchered, just neglected for some years. The guy I bought it from got it from original owner and it lived in SC. If you want check out my YT channel, under Michael Proulx, nothing fancy just some project updates. Getting back to the T housing, dissimilar metals especially bolts do cause problems, it's so humid here I'm sure I'm going to have to be very careful with it. Have a great day.

Matt B · 04-24-2021

Michael, know it's already been a while ago, but thanks for that great hint! I never heard about these, so far all my cars had self bleeding cooling systems. I dug a bit into the matter and apparently it's very common and even needed e.g. for some Porsche or BMW which seem to be impossible to bleed without such a tool. Nice! If it even tames a Porsche than it's great for a ZR!

One question to all: I'm thinking about cleaning the system with radiator flush or something similar. I bet my coolant is way overaged. But if the ZR cooling system is so prone to air bubbles, (how) can I flush it properly to remove any cleanser residue? In all my other cars I just remove the thermostat, squeeze a garden hose into the system and open the tap for a while. Doesn't sound as I can use the same process on an LT5, can I?
Or should I skip the cleaning and just drain/refill with fresh coolant? Any recommendations?

1991 Corvette ZR-1 · 04-24-2021

Being somewhat lazy, I bought a water heater drain pan, so it is low profile enough to get under the car without having to raise it. Works great for oil changes. Never used it for coolant draining but, it would work just as well. Whenever I drain the coolant system and need to refill, I fill as much as possible while it is on all four wheels. Then when it looks like no more air is bleeding out, I use a jack on the frame under the passenger window and I lift the whole side up as high as I feel comfortable doing, which is surprisingly tipped up pretty high.

I then pour in more coolant as I can and then I lower the car back down. Start it up and watch for the flow of coolant to begin from the tube inside the tank. I also touch the coolant tubes to feel for warmth. I have been told if the cam covers feel warm or hot and the coolant tubes do not, there is an air lock in the system. If the tubes are warm/getting hot but the cam covers are still cool to the touch, everything is working as it should. I do three short 5-6 mile drives after a system refill, each time letting the engine cool down completely. After the first drive, I add extra coolant to the overflow tank to be pulled back into the system if needed.

Never had an issue doing it this way and I have done it more times than wish I had in only three years of ownership.

04-25-2020	#11
mmkkpro Join Date: Apr 2019 Location: Supply NC Posts: 124	Re: Cooling system fill That's cool secondchance, this is my first Z and I was freaking out a little over air being trapped. I ran across this air lift tool and figured I'd give it a try. I have read that if you can see coolant flowing from the little brass tube in the metal tank that means the water pump is pumping. I'm learning a ton here at the registry, hopefully as I learn more about these cars I can give back some of the help I have received. I just put new coils, wires and plugs in it, I had a slight miss and stumble off idle, took her up the road earlier and she felt good. I got a ways to go but getting there.

04-25-2020	#12
secondchance Join Date: Aug 2006 Location: McLean, VA Posts: 3,723	Re: Cooling system fill One word of caution - when I first unbolted thermostat housing, bolt wiped out the thread and had to be helicoiled. Maybe corrosion between the bolt and the housing due to different metal? Yes. Coolant flow coming from the brass tube is confirmation of the water pump working.

04-26-2020	#13
mmkkpro Join Date: Apr 2019 Location: Supply NC Posts: 124	Re: Cooling system fill I have not worked on the thermostat yet, so far seems to be working fine, temp Gauge is just above center. However this car sat for several years with cooling system open, hoses unhooked and marvel mystery oil in cylinders. I'm having an issue with the MM in the exhaust system, as it heats up, smokes and it leaks from exhaust connections, I mean it pools on my garage floor. I reckon maybe the valves were open on a few cylinders and the guy kept filling and it just went strait into exhaust. I have not actually driven it at speed for a long distance yet, I hope when I do so it will burn out but not sure what's going to happen to the cats. I have new o2 sensors. Headers and exhaust at some point this summer. I still have a long list, seat covers, weatherstripping, paint, have wheels refinished and so on. Have no idea when it was last tagged and on the road, 78k miles, it is all here nothing butchered, just neglected for some years. The guy I bought it from got it from original owner and it lived in SC. If you want check out my YT channel, under Michael Proulx, nothing fancy just some project updates. Getting back to the T housing, dissimilar metals especially bolts do cause problems, it's so humid here I'm sure I'm going to have to be very careful with it. Have a great day.

04-24-2021	#14
Matt B Join Date: Jan 2021 Location: Beautiful Bavaria Posts: 523	Re: Cooling system fill Michael, know it's already been a while ago, but thanks for that great hint! I never heard about these, so far all my cars had self bleeding cooling systems. I dug a bit into the matter and apparently it's very common and even needed e.g. for some Porsche or BMW which seem to be impossible to bleed without such a tool. Nice! If it even tames a Porsche than it's great for a ZR! One question to all: I'm thinking about cleaning the system with radiator flush or something similar. I bet my coolant is way overaged. But if the ZR cooling system is so prone to air bubbles, (how) can I flush it properly to remove any cleanser residue? In all my other cars I just remove the thermostat, squeeze a garden hose into the system and open the tap for a while. Doesn't sound as I can use the same process on an LT5, can I? Or should I skip the cleaning and just drain/refill with fresh coolant? Any recommendations? __________________ ZR-1 #638/1991 Last edited by Matt B; 04-24-2021 at 01:42 AM.

04-24-2021	#15
1991 Corvette ZR-1 Join Date: Sep 2018 Location: Florida Posts: 305	Re: Cooling system fill Being somewhat lazy, I bought a water heater drain pan, so it is low profile enough to get under the car without having to raise it. Works great for oil changes. Never used it for coolant draining but, it would work just as well. Whenever I drain the coolant system and need to refill, I fill as much as possible while it is on all four wheels. Then when it looks like no more air is bleeding out, I use a jack on the frame under the passenger window and I lift the whole side up as high as I feel comfortable doing, which is surprisingly tipped up pretty high. I then pour in more coolant as I can and then I lower the car back down. Start it up and watch for the flow of coolant to begin from the tube inside the tank. I also touch the coolant tubes to feel for warmth. I have been told if the cam covers feel warm or hot and the coolant tubes do not, there is an air lock in the system. If the tubes are warm/getting hot but the cam covers are still cool to the touch, everything is working as it should. I do three short 5-6 mile drives after a system refill, each time letting the engine cool down completely. After the first drive, I add extra coolant to the overflow tank to be pulled back into the system if needed. Never had an issue doing it this way and I have done it more times than wish I had in only three years of ownership.