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Discussion Starter #1
Thanks to all who sent me great suggestions! The sensor behind # 4 plug was NOT the temp sensor; it was a warning light sensor that alerted the driver to an overheat condition. Finally found the sensor on RH side of cyl head-then found the brown wire (it was cased in a black jacket), then proceded to try & unscrew it after grounding & seeing the temp needle go all way to right. Here is where the "fun" began: existing sensor took a 7/8" socket ? but no room to get a 1/2"drive ratchet on this sensor, obviously since it had been there for 35 years..bought new socket wrench set(now I have 5), and barely got the socket on the sensor & a short skinny ratchet in there...but it took a 3' pipe slid onto the ratchet to break it loose! Centerline tells me new one does not need a gasket? Said to use gray Permatex to get seal...
of course I have every color but gray... Well, tomorrow is another day....Would like to meet the engineer who decided to put the sensor where it is....

Chief Bre 9
 

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But Mad North-Northwest
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I don't think gray Permatex is right for that? I could be wrong, but I'm pretty sure that sensor seals with a copper crush washer.

Was there an existing washer under the sensor? If not then maybe the Centerline folks are correct. But I believe it's a straight-thread sensor with a flat under the hex where a crush washer would go.
 

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But Mad North-Northwest
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I went through my notes: I bought that same sensor in 2012 for my Giulia, and I'm reasonably confident it uses a crush washer. Like I said, verify what you took off.

If the existing sender had a copper crush washer you can re-use it by annealing it in a flame until it glows cherry red.
 

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it will have a sealing washer.
my s4 spider parts book shows one and there won't be a difference to your grad.

if you have the old one, you can probably easily match it in a store with copper or aluminium.
or, if the old is a copper one, then clean it up and heat and anneal it, as Tom mentioned.

was the sensor from centerline the same as that which you just removed?

temp.jpg
 

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Discussion Starter #5
I don't think gray Permatex is right for that? I could be wrong, but I'm pretty sure that sensor seals with a copper crush washer.

Was there an existing washer under the sensor? If not then maybe the Centerline folks are correct. But I believe it's a straight-thread sensor with a flat under the hex where a crush washer would go.
There is a washer under the existing sensor, but I have not removed it as I did not have gray permeated & it was too late last night for me to find it. So I will look today, and make more inquiries, as I sure do not want the new sensor to leak!

Chief Bre 9
 

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Discussion Starter #6
it will have a sealing washer.
my s4 spider parts book shows one and there won't be a difference to your grad.

if you have the old one, you can probably easily match it in a store with copper or aluminium.
or, if the old is a copper one, then clean it up and heat and anneal it, as Tom mentioned.

was the sensor from centerline the same as that which you just removed?

View attachment 1667922
Don't know yet, as I did not have time to get the Gray Permatex last night, but I can see that the old one does
have some sort of washer that looks like red rubber, not a copper crush washer.

Chief Bre 9
 

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Discussion Starter #7
Don't know yet, as I did not have time to get the Gray Permatex last night, but I can see that the old one does
have some sort of washer that looks like red rubber, not a copper crush washer.

Chief Bre 9
Hey, turns out the old sensor did have a copper crush washer. So, I asked Matt, the owner of Vick Auto, and he advised
that the person at Centerline I was talking to knew what he was doing, and he trusted his judgment. So, new sensor had no crush washer, but Centerline guy said he would not use old one, but use gray Permatetex w/o the old washer & all would be well. So that is what I did, and we will see soon if it sealed or not. Sure hope he is right, since it is such a ***** to get to.

Chief Bre 9
 

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But Mad North-Northwest
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Well, hopefully it doesn't leak, but I'm afraid they gave you bad advice. For straight thread senders like that a crush washer is the right way to do it. You either buy a new one, or you can re-use the old one multiple times by heating it with a torch as I described above. Crush washers work great and seal without requiring excessive torque.

For tapered threads you use sealant on the threads, but even for that silicone RTV isn't a great choice: Permatex makes a thread sealant specifically for that application.

Anyway, it'll probably be fine, but save the old washer just in case it leaks and you need to redo it right. Hopefully the new sender will fix the gauge issues too.
 

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Discussion Starter #9
Well, hopefully it doesn't leak, but I'm afraid they gave you bad advice. For straight thread senders like that a crush washer is the right way to do it. You either buy a new one, or you can re-use the old one multiple times by heating it with a torch as I described above. Crush washers work great and seal without requiring excessive torque.

For tapered threads you use sealant on the threads, but even for that silicone RTV isn't a great choice: Permatex makes a thread sealant specifically for that application.

Anyway, it'll probably be fine, but save the old washer just in case it leaks and you need to redo it right. Hopefully the new sender will fix the gauge issues too.
Well, the new sensor sank crush washer is in there, but I've not had time to get it warmed up & check for leaks yet.

Chief Bre 9
 

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when you get the chance, do let us know if the gauge now reads better than the 110 it was reading before, when fully hot
:)
 
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