Overheating Issues

[left285]

Okay so my motor is freshly rebuilt. It's got less than 2 hours run time on it. I was having issues of it getting hot. By hot I mean 260. So I flushed the system removee the thermostat and bought a new radiator. Which fixed the overheating issue. Now my temp gauge on the dash doesn't work. I tried 4 different dash clusters and none of them registered any temp. So then I changed my temp sensor and I still have nothing reading on my gauge. Anybody have any ideas?

[adricar1]

Originally Posted by left285

Okay so my motor is freshly rebuilt. It's got less than 2 hours run time on it. I was having issues of it getting hot. By hot I mean 260. So I flushed the system removee the thermostat and bought a new radiator. Which fixed the overheating issue. Now my temp gauge on the dash doesn't work. I tried 4 different dash clusters and none of them registered any temp. So then I changed my temp sensor and I still have nothing reading on my gauge. Anybody have any ideas?

have you checked that the timing is correct? what colour are the plugs ? it could be timing related or a week fuel mixture also. Buy an add on temp gauge and try that at least you will know the temperature until you get the motor running , until you sort out the heating issue.
try earthing the temperature lead and see if the gauge moves on the dash mounted gauge.if so the wiring is correct,

[Dead Parrot]

It is possible your overheat problems didn't really exist and were a prelude to total temp gauge failure. After trying a couple of different sensors and gauges, I thought I had a pair that worked together. But every so often, the gauge would read very high. After swapping thermostats a couple of times, purchased an aftermarket temp gauge and installed the sensor in the passenger side head hole. That let me run both gauges and compare the results.

The new gauge shows a 200 degree temp with a 195 thermostat. The stock gauge with a sensor pulled from a salvage motor reads low now. The first sensor was reading near full scale while the aftermarket gauge was showing the 200 temp.

The $25 cost of the aftermarket gauge is well worth the piece of mind while dealing with trying to get a matched pair of stock gauge + sensor and wondering if that 260 reading is real or a gauge malfunction.

[Tucson38]

The first thing that comes to mind when a gauge is showing something abnormal is "is it the engine or the gauge?" You'd think something as simple as a water temp gauge would seldom fail but that's not always the case.

[left285]

Timing was checked when the issue first started. It was 50 degrees advanced, which is now set back to 0. I have a temp gun that I've scanned different water outlets and they are seem to be reading normal.

There was a true overheating issue with the motor. When it was hot tanked the tank was dirty because the shop i had it tanked at didn't do a good job of cleaning it. I run the antifreeze that can mix with anything (the green kind) and when i emptied the system it was a rust orange color from being inside the block.

I bought a new sensor and that still didn't fix the issue of nothing reading on the gauge. And that's why I'm stumped right now with it. i really want to put the truck on the road and start driving it but I'm afraid to without being able to keep an eye on the temp.

[greg64]

If you ground the green sender wire out at the temp sensor, the temperature gauge should peg all the way hot. Since you've changed gauges, I've got to think that the gauge is good. I'm suspecting the sender wire has a break in it.

[kalbert]

So the factory guage was showing 260? What did your temp gun say when pointed at the thermostat housing? What does it say now with no thermostat?

I'm guessing your guage, sender, or wiring isn't working and the guage read 260 when it was actually 180-200. Now with no thermostat installed the engine is probably 100-150 and not hot enough to make the guage move.

[S10Fan]

Just a note about aftermarket gauges...........I fought an overheating issue with my V-8 S-10, gauge kept showing 210-215 but the truck never boiled over. Went through everything, timing, water/coolant mix, tested the radiator, you name it. I finally called Sun (SunPro gauges) and their tech told me the gauge tolerance is + - 20%, yeah 20%. You get what you pay for. I installed a set of Autometer gauges and suddenly the heating issue went away.

There's an old saying, "Buy Nice or Buy Twice"

[Dead Parrot]

One problem with buying replacement sensors is the commonly available ones from the parts stores rarely match the resistance/temperature curves of the OEM parts. Usually, the gauge will read way low. Also, make sure the parts place gave you a gauge sensor, NOT an idiot light sensor. As others have suggested, ground the temp wire at the engine block. If things are good with the wire grounded, the gauge should read full scale.

There are several threads on this forum about the aggravation of trying to get a sensor that matches the gauge. Gauges from different years require different sensors.

Another issue often mentioned is the sensor has to be grounded via the threads to the block. If you used too much thread tape or plumbing dope, you might not have a good ground. No ground = 0 reading on gauge.

[left285]

I grounded the sender wire and the gauge pegged, so the wire and the gauge are good. I did notice when i installed the new sensor there was a lot of thread tape on it so im going to pull the sensor again and clean up some of the tape.

[hatzie]

Originally Posted by Dead Parrot

One problem with buying replacement sensors is the commonly available ones from the parts stores rarely match the resistance/temperature curves of the OEM parts. Usually, the gauge will read way low. Also, make sure the parts place gave you a gauge sensor, NOT an idiot light sensor. As others have suggested, ground the temp wire at the engine block. If things are good with the wire grounded, the gauge should read full scale.

There are several threads on this forum about the aggravation of trying to get a sensor that matches the gauge. Gauges from different years require different sensors.

Another issue often mentioned is the sensor has to be grounded via the threads to the block. If you used too much thread tape or plumbing dope, you might not have a good ground. No ground = 0 reading on gauge.

I thought this was the case too. This guy seems to have a differing opinion about tape on the threads.
http://www.lbfun.com/warehouse/tech_...eCF-Thread.pdf
I can't believe it wouldn't sometimes be a problem. I'd test the resistance from the tang to the sender body and then tang to the block/head, just like he did, to see whether Teflon tape is really insulating your sender.

There are at least 3 different temp sensors between 73 & 87 with slightly differing curves. They will all drive the gauge but it will not be accurate without the right one.
The 1513321 Nail Head sender used up through sometime between 78 & 80 is no longer made by GM. The AC Delco G1852 / 12334869 and aftermarket replacements are less than stellar replacements.
Letric Limited makes an exact replacement for the 1513321 sender.
http://www.lectriclimited.com/mainpage.htm

[MikeB]

The first thing I do with any new water temp gauge is check it for accuracy. I connect the gauge and sender to a 12 volt bench power supply, and set the sender in a pan of boiling water. I also have a digital thermometer to check the gauge at lower temps. I suspect a 0-250 degree glass thermometer would probably be more accurate.

I have found Autometer and the older Stewart-Warner gauges to be very close at 150 to 212, but some cheapies can be off by 10 degrees or even more.

On another note, if you have an OE water temp gauge with no numbers on it, you can use the above procedure and put marks on the gauge face at any temps up to 212, assuming water boils at 212 where you live.

[hatzie]

I was looking for this article and I finally found it... http://forum.73-87chevytrucks.com/sm...?topic=25339.0

He outlines how to build a DIY gauge tester made from discrete components that you should be able to by at Fry's Electronics or even Radio Shack.