Overheating after changing temperature sender

[1989GMCSIERRA]

Is that Teflon paste I see on the sending unit? It’s a one wire sending unit.?

 

[stutaeng]

Is that Teflon paste I see on the sending unit? It’s a one wire sending unit.?

It did look like Teflon. I watched it and didn't leak, so that's good.

Yes, single wire sender.

 

[1989GMCSIERRA]

The problem is that on a single wire sensor the sensor body usually acts like the ground. The paste may be interfering with creating a good ground and creating a bad or intermittent ground so the sensor is malfunctioning so you’re appearing to overheat. It may be a bad sensor. You can test it

I usually put a tiny blob and then thread it on. Sometimes they come with some sealant already smeared on the threads.

 

[Pinger]

The problem is that on a single wire sensor the sensor body usually acts like the ground. The paste may be interfering with creating a good ground and creating a bad or intermittent ground so the sensor is malfunctioning so you’re appearing to overheat. It may be a bad sensor. You can test it
.

That's my concern also. Which is why (after a coolant change) I fitted the driver side drain plug with thread tape but on the other side (what I now know is the knock sensor) fitted it without anything that could compromise a good ground.

Those two fittings into tapers - what's the sketch re tightening them? I'm more used to fittings with parallel threads and a shoulder - like a bolt. Do tapered fittings need a lot or a little tightening? (Really don't want to crack the block!)

 

[evilunclegrimace]

That's my concern also. Which is why (after a coolant change) I fitted the driver side drain plug with thread tape but on the other side (what I now know is the knock sensor) fitted it without anything that could compromise a good ground.

Those two fittings into tapers - what's the sketch re tightening them? I'm more used to fittings with parallel threads and a shoulder - like a bolt. Do tapered fittings need a lot or a little tightening? (Really don't want to crack the block!)

They do not need a lot of torque, the KS is 14 Lb. ft. ( 18.9 M m). You do not have to worry about the KS being grounded as it generates its own signal. It comes from the factory with sealant on it.

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There is no reason to worry about sealant interfering with a ground path as one side of the tapered thread on the sender will be in contact with the corresponding side of the thread in the cylinder head/ block/intake.

 

[evilunclegrimace]

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[stutaeng]

Those gauges are notoriously imprecise. My '97 sits right at the 1/4 mark at 180, 195 is about 1/2 & 200 is 3/4.

Yes, it is NPT, basically plumbing threads. No signs of leaking.

Ok, I double checked my guages on my other trucks: '99 Silverado 4.3 and '06 suburban 2500 6.0, both GMT 800s; Silverado is about 3/8s and Suburban is halfway mark. I guess the K3500 reads "a tad low."

The thermsotat on the Silverado and the K3500 were replaced by me, and I believe I went with the slightly lower temperature rating sold at the local auto parts store. Is it 190F? When I took it out and tested it I didn't see any markings. The Suburban is new to me, so don't know if it was factory thermostat.

Thanks everyone for your help. I've been chasing my tail trying to "fix" the problem, when there appears to be nothing to fix, LOL. The moral of this story is that the gauges on these trucks are more like, "low, medium, high," as some have noted.

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[1989GMCSIERRA]

I rarely have to gorilla tighten the brass fitting in a block. I Just tighten and then check for leaks if it leaks I just tighten a bit more but usually a tight till it starts to feel Like it is almost bottomed out and then maybe 1/4 turn is good enough.

 

[AK49BWL]

I went through two senders and a gauge, even tried a different cluster before I said screw it, it's just gonna read 160 when it's actually 194... My 93 was the same way even. I look at it this way... If it gets to 210, there's a problem lol.

The later trucks read a lot more accurately because they're getting info from the PCM over the serial data bus instead of a direct feed from the temp sender itself -- you'll note those trucks only have one temp sensor unit. In the case of the 06, that gauge is a stepper motor, not an electromagnetic coil == even more accurate.

 

[HotWheelsBurban]

Well guys, good and bad news. The good news is that I'm not overheating. I went and picked up my new sender BWD WT723 and installed it.

I added coolant and installed that Lisle funnel and was getting a lot of bubbles, so I new air was coming out of the system.

I ran it for 25 minutes and the needle in the guage pretty much hovered at the 1/4 mark. I ran it at 2000 RPM for a few minutes and could see the needle going back and forth from the 4 and 5 tick marks, presumably from thermostat opening and closing?

At this point I'm thinking my original sender was okay and my instrument cluster guage is not calibrated correctly...

Well guys, good and bad news. The good news is that I'm not overheating. I went and picked up my new sender BWD WT723 and installed it.

I added coolant and installed that Lisle funnel and was getting a lot of bubbles, so I new air was coming out of the system.

I ran it for 25 minutes and the needle in the guage pretty much hovered at the 1/4 mark. I ran it at 2000 RPM for a few minutes and could see the needle going back and forth from the 4 and 5 tick marks, presumably from thermostat opening and closing?

At this point I'm thinking my original sender was okay and my instrument cluster guage is not calibrated correctly...

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Well guys, good and bad news. The good news is that I'm not overheating. I went and picked up my new sender BWD WT723 and installed it.

I added coolant and installed that Lisle funnel and was getting a lot of bubbles, so I new air was coming out of the system.

I ran it for 25 minutes and the needle in the guage pretty much hovered at the 1/4 mark. I ran it at 2000 RPM for a few minutes and could see the needle going back and forth from the 4 and 5 tick marks, presumably from thermostat opening and closing?

At this point I'm thinking my original sender was okay and my instrument cluster guage is not calibrated correctly...

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My truck-- according to the gauge-- is usually around 150 degrees. That needle really doesn't move much unless I'm in bad traffic or something. I almost thought it was broken until that evening when I ran the radiator almost dry. Then the needle moved so fast it was scary to watch! Water got in the oil, changed that and filter, put a jar of bars leaks copper in it and it's been behaving.