Replacing Temperature Sender

[Robert D]

Hey guys, I'll be getting off of work today ~4:30 and would like to replace the temperature sender so the gauge will be working when I drive to San Antonio from Austin (~70m) this evening. I'd like to be somewhat aware of what I need to do before I do it so I can knock it out as quickly as possible this evening (given I have about 1.5-2 hrs of daylight when I get off of work).

From what I've read, on my '91 350 TBI the temperature sending unit will be bolted into the head near the #3 cylinder on the drivers' side head. I will stop by and pickup a new ratchet and deep socket to fit the replacement and hope it fits the one on the truck (my tools are in California, getting a new set sent to me for Christmas). As for fluid, with this being on the head, will I lose any fluids? I'd like to be prepared with enough to replace what I lose.

Thanks for the help everyone. (I don't have my repair manual at work with me)

 

[pauly383]

Undo the petcock on the lower drivers side of radiator , your gonna have to let a lot of green stuff out , until the block and heads drain . I try to collect most of it in a 5 gallon bucket , but there isn't a great way to keep a funnel or anything on a stock truck , and get it all .

If you want to do it right away after work ,and you drove it , wait a few until the radiaotr cools enough to remove the cap . And do the drain .

Then just unbolt it like you plan on .

 

[Robert D]

Sounds like a plan, when I replaced the temperature sensor on Saturday I hadn't driven the truck all day and didn't even think of letting out the coolant before removing the sensor. SPRAY! I think it wasn't so much from being hot but from the coolant being full at the time. I'm not too worried about losing the coolant I drain out, as I have 2 full bottles of antifreeze to put in. What I am somewhat curious about is getting air in the cooling system. Is this not a problem with the 350? On the Porsche I had to bleed the system.

 

[Leper]

I am guessing the sensor for the gauge and the sensor for the ecu are different. I just replaced the one for the ecu. I put tape on the new one and pulled the old one off and stuck the new one in. Lost about 4oz of coolant.

You must be quick.

 

[pauly383]

Don't worry about air in the system . Just fill it , run it , wait for the thermostat to open , and add some more .

The overflow bottle , and the radiator cap take care of the rest

 

[4xcrazy]

if you're fast enough with the swap, you don't have to drain the system at all, you will still lose some coolant, and it's a bit messy, but remove the old one, and have the new handy, and yank n push/twist really quick...i did this once, like i said, alittle messy, but did save most of the coolant.

yes, the temp gauge sender and the ECM sender are two different units.

 

[pauly383]

Tape on it ? It needs a good ground , and won't leak without tape . At least mine don't

 

[Leper]

Tape on it ? It needs a good ground , and won't leak without tape . At least mine don't

Old habit...Tape at the top of threads. Probably doesn't need it, just habit for me.

 

[Robert D]

Good, sounds like I should be able to knock this out within the time-frame I have of daylight (otherwise I buy a lightsource from a parts store or sears). Something I noticed when replacing the other temp sensor is I could not get it to bolt all of the way in...though I plan to go back over it once I have a deep enough socket (I had to resort to a set of pliers and my gorilla hockey-grip). Don't get me wrong it isn't barely in there, it just has 2-3 threads still showing and I didn't want to torque it in too much. Thanks for the help. I plan to pickup a cheap ratchet and socket on my way home so this one will come out easier