chrisd0729

Is it possible to siphon the coolant system of an LT1? I'm trying to avoid the nightmares I've read about breaking knock sensors. If I gave a long enough and thin enough hose, is there any place I can feed it down to a low point of the coolant system and drain the coolant that way?

John A. Marker

Your profile indicates a 1980......but since you are talking about knock sensors you have to have a C4......some year.

I believe your answer is no. If you want to drain the block (which should be done every few years), then remove the knock sensor and the block plug on the driver's side. Just be careful when you remove it. It has been so long ago that I think I used a crescent wrench. That would prevent you from having a socket twist and break off the electrical connection.

chrisd0729

Thanks for the quick reply- I updated my profile to my current Vette and also added engine details to the original post .

Ill try spraying down the plug first with some PB blaster to avoid breaking it... Just wish there was a way to siphon and avoid pulling these plugs.

Thanks again.

Nowhere Man

Unplug the sensors and get a socket and ratchet and crack them loose and get ready for a green shower

chrisd0729

It's a 94 with 71k miles... Should I spray them down with PB blaster or penetrant before trying to back them out?

John A. Marker

It would not hurt to spray the threads. I would try to keep the spray ON the threads only. I have not had a problem breaking these. It doesn't mean that others have not.

If you are going to use a socket, use 6 point to match the outside of the sensor. You have a greater chance of a 12 point slipping off and that could lead to the damage.

When I pulled mine the first time, there was no coolant at all. A thin film of rust had covered the hole. It took a screw driver to break thru the rust layer to get the coolant to flow. Either way, have a large container. I think the 90's held about 3-4 gallons of coolant in the block, hoses and radiator.

Good luck.

Nowhere Man

Did my 94 the other year with over 130K miles without waisting money and time by spraying it down. I would replace the sensors too

383vett

They are not that tight. Use a 7/8" deep socket. You should have have no problems.

theadmiral94

It's been a few years since I did my 94, but I did not remove the knock sensors, but instead used a 120vAC blower (convertible shop vac) at the pressure tank fill (radiator cap neck) and it successfully pushed out virtually all the coolant (based on refill quantities) through only the radiator drain (might have also removed the thermostat).

I also then refilled with distilled water, ran the car, drained, refilled distilled water, ran, drained, blew out -- seemed to work great and saved the challenge of removing the knock sensors.

Likely I did a write-up on it way back when (circa 2005-2007), so suggest doing a advanced search in the 'tech' and this section.

chrisd0729

Tried a 7/8 6pt and 22mm 6pt, both fit very tight... the hex head is spinning inside the sensor and it's not coming out...

Any ideas on next steps?

Kmcoldcars

Large vise grips???? Also, new knock sensors.