Knock Sensor Removal

[TimmyATC]

I recently tried draining my cooling system as much as possible. I read in my the Oldsmobile Service Manual that to drain the most fluid you should drain the radiator, turn the bleed valve on the thermostat and also drain each of the knock sensors to get at the fluid still in the cylinders. I was able to remove the knock sensor from the farthest front of the car (the left side of the engine) but have had no luck in trying to reach the sensor nearest the firewall (the right side). I can see the sensor, but cannot fit any of my sockets or tools in the tight area. I managed to weasel one of my smallest sockets in the area, but cannot get it to grip the sensor. I was just wondering if anyone else has had this issue or at least tried getting at the knock sensor? Also, does it make that much of a difference to totally drain the system by doing the knock sensors? Thank you! I have a 1999 Oldsmobile Intrigue 3.8L.

 

[Cutlass350]

Hmm, seems like the 1999 Intrigue came with either the OHC 3.8L or the DOHC3.5L.

I have a 2000 3.5L. Regardless, there's no real need to yank the knock sensors to bleed the coolant. In fact, IMHO, that's a very extreme measure! Those generation Knock Sensors are semi-garbage. By that, I mean that they do not like be over torqued, dropped, looked at in a nasty way, etc.

In other words, properly, you should not remove a knock sensor and use it again.
Also, don't even think of trying to put one in without a low-torque value torque wrench.
And, as you've seen, good luck getting a wrench in there, much less a torque wrench.

Yea, I found out the hard way when my brand-new knock sensor ended up being bad. It was a massive pain to change it. Mine is right against the firewall, and well hidden under the passenger-side tranny mount.


As for flushing coolant, it is a good idea to flush coolant. Yea, drain it. But, doing a number of flushes with clean water is the best way. Think of trying to get sauce from a pan. You can drain the sauce. But, doing a number of flushes is what's really needed to get it off the sides of the pan.


Also, IMHO, use and buy only a GM/Delco knock sensor.
I've read many bad things about the cheap ones. Then again, the people that use/buy the cheap ones are also people that are likely to just crank the sensor into the engine without a torque wrench (or knowing that they go in with very little torque).


Good Luck!

 

[dosintrigued]

I have had the same issue with the knock sensor. Front one will come out pretty easy and the rear one is not accessible. Go ahead and flush out and don't worry about it. I usually fill with water a couple times and drain to get the old coolant out of the system.