LT1 Coolant System Flushing
Thread Starter
Drifting
Joined: Sep 2003
Posts: 1,363
Likes: 7
From: 1994 LT1 Coupe 6-speed with FX3 & 2000 LS1 Vert 6-Speed with F45 Hunterdon County, NJ
LT1 Coolant System Flushing
Has anyone installed and been happy with a flush adapter (e.g. Prestone’s) in the heater core inlet hose (comes from the lower passenger side of the water pump and has the pressure/flow limiter in the hose)?
Did you do this instead of, or in addition to removing the knock sensors?
Do the knock sensors really need to be removed if flushing the engine with a flush adapter in the heater hose?
Any/all input/thoughts are appreciated.
Thanks.
I should close by saying I am about to do a complete coolant system service. I have already decided to use a 180* thermostat, completely flush the cooling system, remove the radiator and clean its fins and the AC condenser’s fins, so no need to open-up that ‘can of worms’.
Did you do this instead of, or in addition to removing the knock sensors?
Do the knock sensors really need to be removed if flushing the engine with a flush adapter in the heater hose?
Any/all input/thoughts are appreciated.
Thanks.
I should close by saying I am about to do a complete coolant system service. I have already decided to use a 180* thermostat, completely flush the cooling system, remove the radiator and clean its fins and the AC condenser’s fins, so no need to open-up that ‘can of worms’.
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Joined: Jul 2003
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From: Good health is merely the slowest possible rate at which one can die
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I feel they wouldn't be bad for doing a flush if you knew that your system was 100% But I'd much prefer to drain the block because if there is any significant rust or other contamination, that's where a lot of it is going to be.
Race Director
Joined: Jun 2004
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From: WI
I very much like having that hose fitting! After using the Prestone super flush (drained out into a bottle) I then attached the garden hose and let her flow for 20 mins. There was gunk and color for some time. I really think flushing with the hose helped a ton! I did not remove the knock sensor and just had the radiator drain wide open.
Pro
Joined: Jan 2004
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From: Syracuse Utah
Originally Posted by Aardwolf
I very much like having that hose fitting! After using the Prestone super flush (drained out into a bottle) I then attached the garden hose and let her flow for 20 mins. There was gunk and color for some time. I really think flushing with the hose helped a ton! I did not remove the knock sensor and just had the radiator drain wide open.
I flushed about 25 minutes--color disappeared after about 15 minutes, foam disappeared after about 20 minutes. Between cleaning and flushing radiator inside and out, water wetter, and electric wp, I run about 9 degrees cooler across the board.
Race Director
Joined: Sep 2000
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From: The Top of Utah
I love the Prestone flush kit. I have installed one on every car I've owned for decades. If you know the history of the cooling system and the maintenance has been kept up with, you may not have to pull the knock sensor(s). I have never drained my block (via the block drains) nor flushed with anything stronger than tap water. It must work. My radiator core has just finished it's 22nd year of service. I am now back on a once every two year flush schedule, rather than the twice a year schedule I've been in for the last 5 years.
RACE ON!!!
RACE ON!!!
Team Owner
Joined: Aug 2005
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From: Riverside County Southern California
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I use a modified thermostat. I removed the spring from it and in conjunction with the prestone "T" connector I get all the crap out 
I take the used coolant to the coolant place
I take the used coolant to the coolant place
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From: Fort Knox, KY
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Instead of draining the block by removing the knock sensors, I attach the hose of my shop vac to the coolant reservoir then reverse the motor on the vacuum to "blower" mode. The forced air moves all the liquid out of the system.
Then, refill as required. Viola! Work smarter, not harder, I always say....
Then, refill as required. Viola! Work smarter, not harder, I always say....
Pro
Joined: Jan 2004
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From: Syracuse Utah
Oh yeah, I should have mentioned, if you have an electric water pump, you can just turn it on while you are flushing and it helps move things along. Engine does not need to be running of course. Thermostat is in the way but it does have a bypass hole. You can also flush with water, run the car to open up the thermostat and mix up what stuff is left, then flush again. With the Tee in it is no hassle.
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Thread Starter
Drifting
Joined: Sep 2003
Posts: 1,363
Likes: 7
From: 1994 LT1 Coupe 6-speed with FX3 & 2000 LS1 Vert 6-Speed with F45 Hunterdon County, NJ
Thanks to everyone
Everyone, Thanks.
Based on everyone's input, I will be installing and using the Prestone flush-adapter in the inlet heater core hose and using the milder Prestone flush (even though manual says not to, the system may not have been properly maintained, so since others have used it, figure better to assure system is clean and then just add the 'coolant system sealer tablets' per the manual to ward-off any leaks the cleaner might cause).
I will also disconnect the radiator hoses during the initial flushing to prevent the 'engine junk' from being moved from one location (engine) to another (radiator) until the water runs clear, and obviously protect the opti from any water. I may also remove the thermostat spring on the old thermostat (great idea, thanks PLRX787).
Also to ONEDEF92, thanks for the Shop-Vac blower idea. I did that on my sailboat diesel engine this year but forgot to consider it for the Vette. So I will be doing it to assure the system is empty, allowing for adding pre-mixed anti-freeze to prevent air entrapment from having to add the straignt anti-freeze first.
Thanks so very much. 
Based on everyone's input, I will be installing and using the Prestone flush-adapter in the inlet heater core hose and using the milder Prestone flush (even though manual says not to, the system may not have been properly maintained, so since others have used it, figure better to assure system is clean and then just add the 'coolant system sealer tablets' per the manual to ward-off any leaks the cleaner might cause).
I will also disconnect the radiator hoses during the initial flushing to prevent the 'engine junk' from being moved from one location (engine) to another (radiator) until the water runs clear, and obviously protect the opti from any water. I may also remove the thermostat spring on the old thermostat (great idea, thanks PLRX787).
Also to ONEDEF92, thanks for the Shop-Vac blower idea. I did that on my sailboat diesel engine this year but forgot to consider it for the Vette. So I will be doing it to assure the system is empty, allowing for adding pre-mixed anti-freeze to prevent air entrapment from having to add the straignt anti-freeze first.
Thanks so very much.
Team Owner
Joined: Aug 2005
Posts: 34,988
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From: Riverside County Southern California
Co-winner 2020 C4 of the Year - Modified
2018 Corvette of Year Finalist
2017 C4 of Year
2016 C7 of Year Finalist
St. Jude Donor '09 thru '20
Originally Posted by theadmiral94
Everyone, Thanks.
Based on everyone's input, I will be installing and using the Prestone flush-adapter in the inlet heater core hose and using the milder Prestone flush (even though manual says not to, the system may not have been properly maintained, so since others have used it, figure better to assure system is clean and then just add the 'coolant system sealer tablets' per the manual to ward-off any leaks the cleaner might cause).
I will also disconnect the radiator hoses during the initial flushing to prevent the 'engine junk' from being moved from one location (engine) to another (radiator) until the water runs clear, and obviously protect the opti from any water. I may also remove the thermostat spring on the old thermostat (great idea, thanks PLRX787).
Also to ONEDEF92, thanks for the Shop-Vac blower idea. I did that on my sailboat diesel engine this year but forgot to consider it for the Vette. So I will be doing it to assure the system is empty, allowing for adding pre-mixed anti-freeze to prevent air entrapment from having to add the straignt anti-freeze first.
Thanks so very much.
Based on everyone's input, I will be installing and using the Prestone flush-adapter in the inlet heater core hose and using the milder Prestone flush (even though manual says not to, the system may not have been properly maintained, so since others have used it, figure better to assure system is clean and then just add the 'coolant system sealer tablets' per the manual to ward-off any leaks the cleaner might cause).
I will also disconnect the radiator hoses during the initial flushing to prevent the 'engine junk' from being moved from one location (engine) to another (radiator) until the water runs clear, and obviously protect the opti from any water. I may also remove the thermostat spring on the old thermostat (great idea, thanks PLRX787).
Also to ONEDEF92, thanks for the Shop-Vac blower idea. I did that on my sailboat diesel engine this year but forgot to consider it for the Vette. So I will be doing it to assure the system is empty, allowing for adding pre-mixed anti-freeze to prevent air entrapment from having to add the straignt anti-freeze first.
Thanks so very much.
