The temperature switch sends the temperature signal to the dash’s temperature gauge. I broke the head of mine off. When I tried to remove it the wrenches (correct size) shaved off the edges without budging it - it’s brass.
I heated it with all of a can of propane, to no avail. I tried a screw extractor:
it didn’t move it at all but reamed it out.
I’ve screwed it all the way through the switch. I guess I have to clean out the
metal left on the threads. Any advice?
How best to flush out my cooling system, now that it has bits of brass in it?
'87 Toyota Pickup 2WD carbureted
If you have the new sensor, measure the thread diameter. Get a drill bit with a slightly smaller diameter and drill out what’s left of the sensor. Take a tap of the same thread as on the sensor and chase out the hole. Since brass is much softer than cast iron it should chase out very easily.
Don’t worry about the bass shavings going into the coolant jacket in the engine block. These shavings are heavy enough that they’ll sit at the bottom of the water jacket from this time forward.
Tester
From my understanding you have a thin threaded tube of brass remaining in the aluminum manifold… the carcass of the old sensor.
If you drill and tap for the same threads, the tap will not engage the old threads. It will, however, rip out the brass and leave a “double thread pattern” that will make the internal thread minor diameter too large and not enough thread engagement will occur, resulting in stripping of the internal thread.
You can try this and see for yourself. It wont matter because you will have to drill a larger hole (special drill included in kit) to completely remove the interface between the aluminum internal threads of the manifold and the brass external threads of the sensor carcass. You will have to tap it with a special tap and insert a stainless steel thread coil.
The drill, tap, and coil are sold as a kit. You need to determine the thread and thread pitch of the sensor and purchase the corresponding heli-coil kit. Look up thread repair insert or heli-coil.
After the repair, the new threads will be stronger than the original.
The manifold is cast iron. The screw extractor has made a hole 1/2" in diameter
through it. The inner diameter of the part that bears the threads (the thickness
of the unthreaded part) is 1/2". The brass has been so soft so far that I hope
I can remove the rest of it without damaging the threads. Mr Tester seems to think
so.
Were it aluminum I wouldn’t have as much hope of preserving the threads.
Are we talking metric pipe threads?? How do they do it on Japanese cars? If they are indeed a metric pipe thread, then just buy the correct tap that matches the threads on the new sender and re-tap the hole. Wrap the sender with teflon tape and screw it in and be done with it…
Then you seriously lucked out. The manifold on my 87 toyota pickup is aluminum.
You can brush it with nitric acid. It will dissolve the brass and passify the iron.
Do you have the 22R engine?
We will be sealing against coolant leakage not trying to hold the head to the block. The requirements are much lower,you can use techniques that you would not consider for a bolt in a high stress application.
It is aluminum. I was wrong. It’s the 22R engine.
I don’t have hardware that large sitting around so I will have
to take it somewhere to know for sure, but the outside of the
threads measures 5/8" (or 16 mm), the inside of them almost
exactly 1/2", between 12 & 13 mm. The ‘bolt-head’ was 17 mm.
Unfortunately taps larger than 1/2" (I have none) are rare
and expensive.
Quoth Caddyman: ‘just buy the correct tap that matches the
threads on the new sender and re-tap the hole’
Now that I know the manifold is aluminum, not iron, don’t I
run the danger of not getting it right and cutting into
the aluminum?
Alright, now we have the right engine and manifold material…
Your temperature sending unit has 3/8X18 NPT tapered pipe thread.
It is approximately .675" diameter at the thickest part (it is tapered) and there are 18 threads per inch.
The good news is that this tap is available at any good plumbing supply store for about $20 or less. Such as http://www.toolup.com/ridgid/35825.html?AdCamp=CA&utm_source=CAfroogle&utm_medium=CA&utm_term=ridgid+35825&CAWELAID=318055022
You need to drill the hole with a 9/16" drill, and only a 9/16" drill.
The other good news is that tapered pipe threads are less likely to to have the interference issue with the old threads galling out while cutting new ones. You can advance it a littler further to cut a little deeper (since it is tapered).
Quoth Bodybagger: ‘Your temperature sending unit has 3/8X18 NPT tapered pipe thread.’
Hmmmm… that’s hard to believe. I just fetched up the replacement and applied my
vernier caliper to it: it measures either 5/8" or 16 mm on the threads. It has only
3 threads, but they could be 18 TPI. The body tapers a bit past the threads but the
closest place I can measure is 12.5 mm (not quite 1/2").
Plumbing has silly measurements, so maybe this really is 3/8" in pipe threads. That
the pilot hole is drilled by a 9/16" bit would be consistent with a 5/8" threads.
9/16 > 3/8 : why is plumbing so weird? Is the point of this that a pipe with a 3/8" internal diameter needs to have walls this thick?
Trying a plumbing supply store is a good tip. Too bad the only good one is 10 miles away,
I will have to ride my bike, and 3 winter storms are headed our way, the first already
getting me a little cold and wet when I went out to check the engine’s material with a
magnet.
Harbor Freight, a bit closer, has a 3-piece set with the 3/8x18 for $15.
This is a huge help
The use of teflon pipe sealing tape is not recommended on electrical sending units as it MAY keep the sending unit (AKA switch) from grounding into the engine. Many, if not most, sending units have a dab of electrically conductive sealant applied ast the factory.
Here’s a chart for pipe thread sizes and the drill sizes used when tapping pipe threads. http://www.engineeringtoolbox.com/npt-national-pipe-taper-threads-d_750.html
Tester
I found that chart already, thanks. I don’t like plumbing
size practices and didn’t expect them in my auto’s engine.
They can be a pain but it really is the cheapest and most effective means of interfacing that sensor to the block and prevent leaks. When they do get stuck, the best removal tool is a small pipe wrench (coincidence?) since it is one of the only tools that actually applies more clamping force to the object as you apply pressure to the wrench.
Quoth TwinTurbo: ‘They can be a pain but it really is the cheapest and most effective means of interfacing that sensor to the block and prevent leaks.’
You mean plumbers know something? It’s a sad thought, but probably true.
Quoth TwinTurbo: ‘When they do get stuck, the best removal tool is a small pipe wrench
(coincidence?) since it is one of the only tools that actually applies more clamping
force to the object as you apply pressure to the wrench.’
Good point: I wish I had thought of it.
Plumbing thread is determined by the inside diameter of the standard thickness pipe being threaded.
3/8x18 thread threads 3/8" standard pipe which has an ID of 3/8" and an OD of 5/8" for standard pipe.