knock sensor replacement question
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Joined: Jun 2004
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From: Fort Worth Texas
knock sensor replacement question
Hello Corvette family,
quick question. I have to replace a knock sensor on my 93 LT-1. I just had the coolant flushed and replaced less than a couple of months ago, so I won't need to do a complete drain (i don't think).
About how much coolant will exit the block when I take out the knock sensor? I just want to be able to refill it back to proper levels.
I do have a brand new pan that I could drain into, but I was thinking it may get contaminated coming out of the hole and I might not want to place it back into the system.
Cheers.
Marlon
quick question. I have to replace a knock sensor on my 93 LT-1. I just had the coolant flushed and replaced less than a couple of months ago, so I won't need to do a complete drain (i don't think).
About how much coolant will exit the block when I take out the knock sensor? I just want to be able to refill it back to proper levels.
I do have a brand new pan that I could drain into, but I was thinking it may get contaminated coming out of the hole and I might not want to place it back into the system.
Cheers.
Marlon
Safety Car
Joined: May 2007
Posts: 3,651
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From: Apple Valley MN
I would guess somewhere in the neighborhood of a gallon. Since it's fairly fresh, just strain it through some cheese-cloth to remove any particles.
I had to get an oil drain-plug replaced on one of my cars a while back, and the oil change shop did a trick with a shop vac, holding the vacuum over the oil fill hole while they swapped the plug, and hardly any oil was lost. Maybe search around and see if a similar trick would work with the coolant.
I had to get an oil drain-plug replaced on one of my cars a while back, and the oil change shop did a trick with a shop vac, holding the vacuum over the oil fill hole while they swapped the plug, and hardly any oil was lost. Maybe search around and see if a similar trick would work with the coolant.
Team Owner
Joined: Dec 1999
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From: Lacey WA RVN 68-69
NCM Sinkhole Donor
A gallon sounds about right. Don't bother with trying to save it as the amount you need to replace won't cost a lot, maybe $10. Unless you have a way to get the car up ona lift, it's going to be somewhat messy. Don't remove the pressure cap; that will help to hold some of the coolant back.
You should do the work when the engine is cold. Once the coolant stops draining, clean the threads in the block and remember to apply an anti-seize compound to the sensor threads before installing.
You will need to open the bleed valves when you begin to refill the coolant through the expansion tank. Add a 50-50 mix of green coolant and distilled water into the expansion tank. Once coolant comes out of the bleed valves, close them. Then with the tank filled, start the engine and let it idle. When the coolant level drops, keep filling until the coolant level stays just below the filler neck.
Keep an eye on the coolant temp; if it gets to 240 or so, stop the engine, let it cool some and start again. Replace the pressure cap and you should be good to go.
You should do the work when the engine is cold. Once the coolant stops draining, clean the threads in the block and remember to apply an anti-seize compound to the sensor threads before installing.
You will need to open the bleed valves when you begin to refill the coolant through the expansion tank. Add a 50-50 mix of green coolant and distilled water into the expansion tank. Once coolant comes out of the bleed valves, close them. Then with the tank filled, start the engine and let it idle. When the coolant level drops, keep filling until the coolant level stays just below the filler neck.
Keep an eye on the coolant temp; if it gets to 240 or so, stop the engine, let it cool some and start again. Replace the pressure cap and you should be good to go.
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Joined: Jun 2004
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From: Fort Worth Texas
A gallon sounds about right. Don't bother with trying to save it as the amount you need to replace won't cost a lot, maybe $10. Unless you have a way to get the car up ona lift, it's going to be somewhat messy. Don't remove the pressure cap; that will help to hold some of the coolant back.
You should do the work when the engine is cold. Once the coolant stops draining, clean the threads in the block and remember to apply an anti-seize compound to the sensor threads before installing.
You will need to open the bleed valves when you begin to refill the coolant through the expansion tank. Add a 50-50 mix of green coolant and distilled water into the expansion tank. Once coolant comes out of the bleed valves, close them. Then with the tank filled, start the engine and let it idle. When the coolant level drops, keep filling until the coolant level stays just below the filler neck.
Keep an eye on the coolant temp; if it gets to 240 or so, stop the engine, let it cool some and start again. Replace the pressure cap and you should be good to go.
You should do the work when the engine is cold. Once the coolant stops draining, clean the threads in the block and remember to apply an anti-seize compound to the sensor threads before installing.
You will need to open the bleed valves when you begin to refill the coolant through the expansion tank. Add a 50-50 mix of green coolant and distilled water into the expansion tank. Once coolant comes out of the bleed valves, close them. Then with the tank filled, start the engine and let it idle. When the coolant level drops, keep filling until the coolant level stays just below the filler neck.
Keep an eye on the coolant temp; if it gets to 240 or so, stop the engine, let it cool some and start again. Replace the pressure cap and you should be good to go.
The sensor already has the coating on the threads, it's been mentioned before that adding another compound could make the sensor operate incorrectly.
BTW, Where are the bleed valves located? I did buy a gallon of antifreeze so I'm good there.
Thanks again.
Race Director
Joined: Jun 1999
Posts: 14,924
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From: Merritt Ils Fl
A gallon?All the coolant in the block,heads and what will drain back thru the lower radiator hose is going to run out. The knock sensor is just about the lowest point in the system. In fact, removing the knock sensor is a recommended method of completely draining the block. I suggest you be ready for more than a gallon. Can you reuse what comes out, yes you can. Filter it thru a coffee filter. A filter in a funnel works like a charm.
Melting Slicks
Joined: Jul 2008
Posts: 2,269
Likes: 142
From: Ottawa Ontario
A gallon?All the coolant in the block,heads and what will drain back thru the lower radiator hose is going to run out. The knock sensor is just about the lowest point in the system. In fact, removing the knock sensor is a recommended method of completely draining the block. I suggest you be ready for more than a gallon. Can you reuse what comes out, yes you can. Filter it thru a coffee filter. A filter in a funnel works like a charm.
been there, done that.
Safety Car
Joined: May 2007
Posts: 3,651
Likes: 10
From: Apple Valley MN
A gallon?All the coolant in the block,heads and what will drain back thru the lower radiator hose is going to run out. The knock sensor is just about the lowest point in the system. In fact, removing the knock sensor is a recommended method of completely draining the block. I suggest you be ready for more than a gallon. Can you reuse what comes out, yes you can. Filter it thru a coffee filter. A filter in a funnel works like a charm.
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If you remove your thermostat and have access to a 5.0 hp or higher Shop-vac, you can use its reverse thrust feature to BLOW all the coolant from the system, including the heater core. Works in minutes and saves you a lot of time by not having to remove the knock sensors. 
Le Mans Master
Joined: Feb 2000
Posts: 9,715
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From: Kempner Texas
When I changed a knock sensor, I didn't lose even a half a pint. I just had the new one ready to screw in as I removed the old one.
Jake
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Jake
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Thread Starter
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Joined: Jun 2004
Posts: 56
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From: Fort Worth Texas
If you remove your thermostat and have access to a 5.0 hp or higher Shop-vac, you can use its reverse thrust feature to BLOW all the coolant from the system, including the heater core. Works in minutes and saves you a lot of time by not having to remove the knock sensors.
Thanks.
Burning Brakes
Joined: Aug 2006
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From: Houston PA
Good idea. No need to take a lunch break waiting for all the coolant to exit.
Thread Starter
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Joined: Jun 2004
Posts: 56
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From: Fort Worth Texas
Thread Starter
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Joined: Jun 2004
Posts: 56
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From: Fort Worth Texas
Ok folks, I finally got under the car to tackle this and I had the new sensor ready to go when I pulled the old one. I may have lost a pint of fluid at the most, maybe even half that. I just want to thank everyone for their help.
Marlon
Marlon
