Where is your water temp sender placed ?

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Hi you beer swilling, horsepower seeking, greased and spannered up gear jammers. ...  :imsorry:

I have two positions in my car for the water temp sender. In the manifold like my 02 body Sportsroof in Green - or in the Water pump block as per new red one  05 body Mach 1.  :help:

I purchased from a reputable vendor of American parts, a new sender. If I screw it into the water pump block (and I love a nice long slow screw !  :classic_biggrin: )  it reads effing high on the meter, 

if I put it into the place at the front of the inlet manifold it reads - 1/4 the way up the gauge. WTF ! 

what the eff is going on ... am I being a numpty ... should I have myself committed to the local looney asylum - or is there a good explanation? 

plz help.... oh gods of 7173  - where is your temp sender located ?

all the best to ya'aaal 

Al 

water1.jpg

water2.jpg

insane.jpg

 
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Hemikiller

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The correct location for a 351C temp sender is what you're calling the "pump manifold", which is the block front face. There is a cast-in water manifold in this location that the water from the heads flows into, and out through the thermostat and water outlet. 

You cannot take a water temperature reading from a 351C intake manifold, as it is a dry manifold with no water flowing through it. The only reading you getting is the temperature of the intake. 

Factory gauges are notoriously inaccurate, nor were they designed to be. They operate on resistance, so any issues in the engine->chassis->battery ground path will cause an erroneous reading. I would take an ohm reading from sender post to sender body, then post to block, and post to negative battery terminal. If you see a huge variation in readings, you've found your problem. IIRC, the ohm swing on the sender is like 15 to 75. 

351C4Vfordad010.jpg

 
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Don C

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Also, check the sensor body to block resistance. Some sealants also act as an insulator. Ford says to use conductive sealant, which I haven't been able to find in several years. I have an almost empty can of lead based sealant/anti-seize (no longer available because of the lead). There are a lot of copper and aluminum anti-seize compounds, but none of them state they are also sealants.

 
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This got me curious. When I installed my aftermarket gauges a couple of years back, I wanted to keep the idiot light functional as well. My solution was to get rid of the 3 port vacuum switch mounted in the water pump housing as it was not being use anyway, and install the idiot light sender there, same thread fortunately. The mechanical temp gauge sensor bulb was installed in the original temp sender location. To be honest, I'm not sure which sealant I used, I have a few types and brands laying around, so it was likely teflon based. 

So, as this got me thinking, I did a bit of digging, looking at conductive thread sealants which there are a few and reading through a couple of forums on the subject. Conductive sealants I found are Loctite GREEN, which is an electrically conductive sealant and Whitlam "TALON" copper anti-seize & thread sealant. In the forums the consensus was with a tapered pipe thread, there will be metal to metal contact between the sensor and manifold/ head/block etc. provided the threads are tight. No-one had any issues with conductivity, but all say to test with an Ohm meter. There was a strong recommendation not to use teflon tape, even though fitting to block contact should be good.

As for Al's car with the sender installed in what looks like the vacuum port on the intake, yeah, there's one born every minute I guess. He should pull it, plug it or install the proper vacuum fitting should he need to use manifold vacuum.

There are conductive high temp sealants out there, just not easy to find.

 
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I typically use High Temperature Permatex Thread Sealant (#59235). The sealant will sit at the root of the thread to prevent leakage while the threads are still making contact to allow conductivity. The issue with Teflon tape is that if it doesn't tear, it may coat the whole thread not permitting contact/conductivity.

 
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I typically use High Temperature Permatex Thread Sealant (#59235). The sealant will sit at the root of the thread to prevent leakage while the threads are still making contact to allow conductivity. The issue with Teflon tape is that if it doesn't tear, it may coat the whole thread not permitting contact/conductivity.
+1 Tony. The Permatex 59235 is what I have too and likely what I used. Your comments are as described in those forums I referred to. Basically it will be good as long as you don't use teflon tape.

 
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Hi Guys 

thanks for all the responses and helping me keep my sanity -- it didnt make any sense to me having a thermocouple in the inlet manifold 

I'll check the resistance and see whats up 

 
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One topic that is always up is the thermostat for the 351 C. It has to extend into the brass baffle in the block to change the flow of water. Most think they are extinct but went to local Advance auto and had them pull one and it is correct. They are made different. The originals had a Hat cap on the end that went into the brass baffle. Today most just have a plunger that goes into the baffle. Here are side by side pics. Always run a 195 deg. F. if you can find.

DSC_0948 (2).JPG

DSC_0949 (2).JPG

 
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Yo 

Water temp sender has been replaced with new and cured the problem

instead of 2.7Ω between outer of sender measured to the neg of battery I now have 0.4Ω - which shows how important the chassis path to neg is

thanks my old fruits 

tt copy.jpg

 

Spike Morelli

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Terry Thomas! Simply boffo.....

 
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