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Discussion Starter #1
My 95 FWB-

@!#$ knock sensors: Aagh. I've been carrying around new knock sensors for a few years because the old ones wouldn't come out.
All I accomplished this time was to make the tack-welded tops on both knock sensors break loose and spin.. Great.
Can't fit a pipe wrench or vise-grips in there. Can't fit a basin wrench in there. Don't have a welder to re-weld the socketed tops to the sensors. Ahh, well, reconnect the wires and forget it.

"Use-whatcha-got" flush trick--I didn't have any suitable rubber caps around so, after disconnecting and back-flushing the heater core, I reinstalled the heater lines and clamped them off to prevent circulation. Disconnected the steampipe hose to the coolant reservoir and plugged it with a bolt. Okay. The radiator and engine top were empty, but how to get out old stuff from the bottom half of the engine? See picture below. I removed the thermostat (breaking a bolt in the process). Used vise-grips to pull the rest of the bolt out, then scrounged for half an hour to find a suitable replacement bolt. Disconnected the hose from the bottome of the radiator, put the old outflow hose on the thermostat housing, flipped around the new silicone top hose to direct outflow to the ground, added a 1x6board to direct the flow, stuck a garden hose in the top hose and cranked the engine. Watched it belch out old coolant for a minute until it ran clear, then shut it off. Put as much as I could of 2 gallons new antifreeze into the thermostat opening and radiator, re-installed the thermostatre and connected/unclamped all hoses. Yes, it's now a mix of Prestond and tap water, but I didn't really feel like going to the store for ten gallons of distilled water to flush the system, and I suspect the Covid-19 hoarders would have bought it all, anyway.

Bleeder clog--I have the brass bleeder fitting that was sold on this forum years ago. Love it. Works great with a piece of vacuum line to keep the engine front/Optispark dry, but this time it wouldn't bleed. BUT, if you have one, the next time you do your antifreeze, take the needle all the way out (not the fitting itself) and poke down into the thermostat housing with a wire or tiny screwdriver--after several years the small hole in the seat can gunk up, like mine did.

New KS approach? I'm still unhappy that I can't truly drain the block and replace the knock sensors. I have in my mind's eye a socket I've never seen in real life--a socket which doesn't have flats inside, but has tiny angled sharp teeth like those on a pipe wrench, that could be gently tapped down on a round item like a knock sensor, then be used with a regular socket wrench to remove. Or, maybe a crows-foot for a socket wrench, but with sharp teeth--like a basin wrench, but more compact and stronger. Did a little hunting online, didnt' find anything that fit the concept.

Any ideas on specific wrenches/tools to remove the knock sensors, other than removing the engine?
Water doesn't compress, so setting off a stick of dynamite in the engine's water jacket might shake them loose, but that could cause other problems...
I also thought about finding someone with a Browning .50 cal and buying them some API ammunition (still shaking my head that us ordinary folk can actually buy such ammo, lol), removing the wheels, drilling some access holes, and having someone shoot out the knock sensors, but that seems like a lot of work and problems, although it might help burn off any interior engine deposits
Seriously, though, any thoughts? It bugs me that I can't concoct a solution. I'd happily drain/flush the whole system again if I knew I could get those sensors out.
Mark
193243
 

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There are lots of flavors of stud / bolt extractors. I have the latter set:

193244



193245
 

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Discussion Starter #3
Thanks! That second set is a great start. I'll have to find something that matches the OD of the knock sensor. The replacement ones are 38.5mm, I'll get under tomorrow to check the original ones.
 
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