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in my '90 C4 with L98 motor. Sensor is located between no 2 & 4 cylinders in side of block. Looks like I can access it from the top. but wire harness goes down under motor. How much coolant will leak out, once I pull it? should I warm up motor a little bit? It could be the original sensor....... just looking for some tips.
Also, any recommendations on a brand name to buy? I have heard some sensors are junk right out of the box?
TIA, Mike
I would drain the cooling system first, but you are still going to get a lot of coolant out on the knock sensor hole. I would not warm up the car first, the exhaust will be very hot if you do. Are you sure you are looking at the knock sensor and not a coolant temp sensor ?
Coolant temp sensor.
Knock sensor.
Removing the knock sensor will empty the water jacket on that side of the block, as well as any coolant above it. In other words, a lot. Drain the radiator first, then yank the KS. You might need to poke through a blockage of sediment in order to get coolant flowing out of the KS hole, but do it if necessary. Pulling the knock sensors and draining the radiator is the best way to get nearly all of the coolant out of the system.
Yes, that can work if the goal is to minimize coolant loss. But, there's no better time to completely drain the system than when the knock sensors are coming out anyway. Few owners do coolant replacement on a schedule, so most are overdue for this basic maintenance.
Removing the knock sensor will empty the water jacket on that side of the block, as well as any coolant above it. In other words, a lot. Drain the radiator first, then yank the KS. You might need to poke through a blockage of sediment in order to get coolant flowing out of the KS hole, but do it if necessary. Pulling the knock sensors and draining the radiator is the best way to get nearly all of the coolant out of the system.
Live well,
SJW
Ya, I should prolly drain the coolant. Just not an enjoyable job. I want the threaded hole to be dry, when I put in a new sensor. I did change one, a while ago in my L98 IROC-Z, and I think I just did the quicky method, pull the sensor and stuff the new one in place quickly. That engine has headers, so more room to work around. I thought of just warming car up, for a few seconds, would help with getting the sensor out. Certainly do not want to break the sensor off, with thread portion still in block.
Check out my picture, not a lot of room to work around, but certainly not impossible.
Thanks fer all the tips!
Ya, I should prolly drain the coolant. Just not an enjoyable job. I want the threaded hole to be dry, when I put in a new sensor. I did change one, a while ago in my L98 IROC-Z, and I think I just did the quicky method, pull the sensor and stuff the new one in place quickly. That engine has headers, so more room to work around. I thought of just warming car up, for a few seconds, would help with getting the sensor out. Certainly do not want to break the sensor off, with thread portion still in block.
Check out my picture, not a lot of room to work around, but certainly not impossible.
Thanks fer all the tips!
That is a coolant temp sensor, not a knock sensor. The knock sensor is located on the lower side of the block, just above the oil pan.
Patsgarage above gave you two excelllent pictures of a coolant sensor and a knock sensor. You apparently are dealing with a coolant sensor in the head. If this is what you want to remove, you don't need to drain the radiator. Just work quickly.
That is a coolant temp sensor, not a knock sensor. The knock sensor is located on the lower side of the block, just above the oil pan.
Crap, you are right! Prolly a temp sensor for the gage in the dash, its not the engine coolant sensor. That has a different 2-pin connector. Mine has a single metal post, and the connector slides onto it. Similar to the knock sensor.
This explains a few things. Last fall, I was tuning for spark retard, and looking at the knock counts. I did some electrical checks on this "fake" knock sensor, and now the readings makes sense. I still want to replace the knock sensor, but cannot even see it from the top of the engine!
This job might be for someone else. C4 is going into shop for some other things, and it will be on a lift. One more thing to add to that list!
Knock sensors are installed in what had formerly been the block drain plug holes on earlier SBC engines. They are accessible from underneath, and are normally easy to remove. If you do the replacement, be sure to torque to the proper value, and use no sealant on the threads.
Knock sensors are installed in what had formerly been the block drain plug holes on earlier SBC engines. They are accessible from underneath, and are normally easy to remove. If you do the replacement, be sure to torque to the proper value, and use no sealant on the threads.
Live well,
SJW
Thanks, good info. I think I will let my trusty mechanic do it, along with some other normal maint. I dont mind doing my own work on my rides, but certainly not afraid to pay my best mechanic to do the work!
I just looked at my 1988 L98 IROC, and the sensors in the block are in different locations than my C4, so maybe that engine got me confused.
Crap, you are right! Prolly a temp sensor for the gage in the dash, its not the engine coolant sensor. That has a different 2-pin connector. Mine has a single metal post, and the connector slides onto it. Similar to the knock sensor.
This explains a few things. Last fall, I was tuning for spark retard, and looking at the knock counts. I did some electrical checks on this "fake" knock sensor, and now the readings makes sense. I still want to replace the knock sensor, but cannot even see it from the top of the engine!
This job might be for someone else. C4 is going into shop for some other things, and it will be on a lift. One more thing to add to that list!
Replacing Knock Sensor....
All's well that ends well.