Thread: knock sensor location?

Under the exhaust manifolds.

The rear one is basically impossible to do with the engine or the transmission in the car...the front one however...its fairly easy from the bottom

Removing the knock sensors isn't manditory to flush the system...remove the petcock from the bottom of the radiator and shove a garden hose in the radiator and start your car and run it.

Sensors like mentioned don't need to come out. Personally I mess with them as little as possible. They require torque of 14ft lbs. Too much, too little and your sensitivity is off.

Thanks for the info. I will heed your advice. The Haynes said it was necessary, but I will take your word for it. Are there any block drains on the 3800 series 3 engine, or air vents on the thermostat housing? For the thermostat air vents, I should be able to see these I guess. The Haynes also says these should be opened up, necessary? With the petcock open, and the hose running, will the radiator stay full with the engine running? Don't mean to question you, but just want to make sure. Also, is it necessary to put 2 sealant tablets in the radiator after flushing?

Most people say not to bother with the petcock on the radiator, as 90% of the time they will be stuck, and break when you put force on it.

Also, if you have the stock dexcool in there, there is a chance it will be thick and not drain properly from the small petcock hole. Everyone I've spoken to advises just dropping the lower rad hose, much bigger opening to get your potentially thickened coolant out.. more flow on the way out just seems more thorough to me. I know I've heard of people with actual chunks of dex and junk come out of the lower rad hose that would've just blocked up the petcock. The only real issue with that is the spring clamp which can sometimes be a real *****.

As for the bleed valve, it's on top of the tstat housing. Just follow the upper rad hose to where it meets with the block, that is where you will find the bleed valve. It's pointed out in the manual engine diagram if you have your manual.

I dont think you need sealant unless you develop leaks.. sometimes when you clean the coolant system, you wash away rust and junk that was blocking up holes that developed, and so you open up a leak.

And yeah, as stated you dont really need to mess with the knock sensors.

Just drain it with the lower rad hose, wash out the reservoir bottle, reconnect the hose and fill it back up with straight water, run it up to temp with the heat on... drain it again, then fill it with your flush solution if you're gunna do that and run it as per the directions. Maybe then fill and drain twice more with straight water to get all the cleaner and residue out. Get your 50/50 mixed up, maybe even slightly more coolant than water to make up for the water you already have left in your block that didnt drain. Then just bleed properly and call it done.. just open the bleed valve and fill it slowly to minimize air trapping... then I guess run it with the valve open until you see coolant start to run out and close it all up. Just keep an eye on the levels the next few days.

My advice with your haynes manual: Haynes is a good fire starter, that's the extent of that. If you want a real manual for your car, hit ebay and either get the Helm factory manuals or a GM ESI dvd that includes your year.

A factory book is priceless when trying to find or understand anything on a car.

I pulled out the front knock sensor after I flushed my coolant system. I did it to install a circulating block heater. I added an extension, and a T fitting. The knock sensor is threaded into the bottom of the T fitting and I have not had any problems. Torque to 14ft lbs and your good. It is a 22mm deep socket.

J

I changed the water pump on my wifes car a few months back. I cannot remember how many bolts there were. I did have to dismount the power steering pump and push it to the side to get access to the far left bolt. While you are at it, change the plastic elbows that connect the idler bracket to the block and LIM. They are on a help card at Advance for like 4 bucks. It will make it easier to do that at the same time because without the idler/alternator bracket in the way you have full access to the water pump.

J