Coolant Temp Sensor Question

[RIMoparGuy]

Hey guys, new to the forums, just acquired a 1979 C10 350. I have a question about installing a coolant temp sensor. I'm not a full-on mechanic, so I just want to check something before I do this. When I remove the old sensor, is the majority of the coolant going to come out? If so, how do I go about refilling and bleeding the system? Thanks!

Here's pics of the truck.

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[350runner]

nice truck! drain some fluid from the radiator peacock on the drivers side. should help.

Sent from the dust in front of you!

 

[smoothandlow84]

Wow...rust free truck in Rhode Island? Nice btw. You won't lose much coolant. Just be sure not to over tighten the new sensor. They usually have tapered threads and can break easily if over tightened. Use thread sealant, I use the liquid thread sealant teflon instead of tape.

 

[PrairieDrifter]

An easy trick to not have to drain any coolant and barely lose any is to have your new sensor with thread tape or paste on it and ready to go in one hand while removing the old one with your other hand and quick put the new one in as soon as you take the old one out.

 

[RIMoparGuy]

Thanks for the tips, much appreciated! Is the system going to need to be bled or do these older trucks work the air out themselves? I'm used to working on more modern cars and I know how much of a pain in the ass it can be if you don't properly bleed the system.

 

[PrairieDrifter]

These older trucks aren't too picky just do that quick swap and then run it to normal operating temp for like 5 minutes then let it cool down and check if you have to fill any coolant and it should be good to go.

 

[rich weyand]

Yup, that's how I did it.

1) engine off, truck cold, pressure relieved by opening the cap, then put the cap back on and seal it so no air can get in the other end. that's what slows down the coolant from leaking out.

2) put liquid teflon pipe sealer on the threads of the new sensor. you don't need a lot, just some in the threads all the way around.

3) loosen the old sensor and get it almost all the way off.

4) holding the new sensor in your RIGHT hand (assuming you're right-handed), spin the old sensor the rest of the way out with your LEFT hand, then thread the new sensor in with your RIGHT hand. I say do it this way because it needs more dexterity to start a thread than it does to spin something out.

You should lose about two tablespoons of coolant total.

 

[MadOgre]

These older trucks aren't too picky just do that quick swap and then run it to normal operating temp for like 5 minutes then let it cool down and check if you have to fill any coolant and it should be good to go.

Do it with the cap off the rad though and any air will cycle out

 

[rich weyand]

Do it with the cap off the rad though and any air will cycle out

Do NOT replace the sensor with the cap off! The coolant will run out like crazy! Instead of a small glug-glug-glug, it will pour out.

Once the sensor has been replaced, idle the engine for a bit with the cap off to help cycle the air out.

MO, I think that's what you meant, but I want to be sure it is not misinterpreted.

 

[MadOgre]

Do NOT replace the sensor with the cap off! The coolant will run out like crazy! Instead of a small glug-glug-glug, it will pour out.

Once the sensor has been replaced, idle the engine for a bit with the cap off to help cycle the air out.

MO, I think that's what you meant, but I want to be sure it is not misinterpreted.

Run the engine with the cap off to cycle out the air!

Lol you just said what I said as your second sentence lol

 

[rich weyand]

OK, that's what I thought. I didn't want the OP to think that having the cap off during the swap was what you meant. We're good.