258 running at 230-240. Is this high??????

what gage are you using? the stock electric,after market electric or capillary tube mechanical?

 

Its about 3 months and it is an aftermarket electric guage.

 

I would go buy one of those rad caps with the thermometer in it and be sure on your temp. They can't be that expensive and would be a good back up. Thinking about one myself.
They sell them at O reilly's I know.

High5

 

Radiator Cap w/Temp JC Whitney #TC001R16 $19.99

You even have a choice of colors!

 

Hey guys today I just went ahead and replaced my electric aftermarket temp guage with a brand new one and still staying around 212. Any ideas what it could be now???? Thanks.

 

sounds to me like the sending unit is FUBAR. You stated that you measured 150°and the guage read 195°. If that is truely what I am understanding you to say, then I would guess it's that or the gauge went out of calibration.

 

I just replaced the old new guage with another brand new one today. The brand new one reads the exact same as the old one and I also installed the brand new sending unit that came with the new guage today. What do you guys think the next thing to try is? Water pump?? Thanks.

 

Yeah this has me stumped...not because of the temperature...but because you say that there is no pressure at 200+ degrees. If the pressure is not being visibly released into the atmosphere in front of you (water and steam spraying everywhere)...then it is most likely an internal leak of some sort. That pressure HAS to go somewhere.
Here is what I would do...just to see what happened...Remove the thermostat...put the housing back on...make sure it has enough coolant...fire it up, when it gets up to temp...THEN see if there is any pressure.

 

Either that, or the temperature is a lot lower than you think. If there's a large air cavity at the top of the radiator, the increased vapor pressure of the water will only make a small difference in the pressure ... PV=nRT! I recall that earlier the OP said there was some water forced out through the overflow - that indicates some pressure.

Also, the sending unit is most likely a PTC thermistor, which increases resistance as the temperature increases. Any resistance in the wiring between the gauge and the sender will be added to the temperature reading. Also, how many volts do you read at the temperature gauge? Overvoltage could skew the gauge reading. I suggest you do the meat thermometer or (better) the infrared digital thermometer thing.

 

Right...and if he still has air in it somewhere...taking out the thermostat temporarily "SHOULD" get rid of it.

 

I did do the meat thermometer thing and the coolant only read a little higher than 150. Thanks.

 

Wow...really?
So you had a bad gauge or sending unit to start with...Then you replace both the sending unit and the gauge with new ones...and the new ones were both defective too? Sounds like something that would only happen to me

 

I do not know if they are defective. If the temp in the radiator is 150 does this mean for sure that the motor can't be running that hot? Its just a little odd that I have two new guages reading the same thing.

 

Is this the gauge in the cluster? IIRC the gauges in the cluster rely on a voltage regulator of sorts, and that could make the gauge read wrong. Also if the wiring has a bad connection or some other source of high resistance. Two bad gauges and/or senders in a row is unlikely, unless you've got the wrong sender for the gauge. The sender's characteristics has to match the gauge.

I think the meat thermometer is right - the coolant mixes pretty thoroughly. As I recall, the hot coolant enters at the top and exits at the bottom of the radiator, so if the hottest water should be in the top tank. You could try another, better thermometer, like a lab thermometer. Or try calibrating the meat thermometer with some boiling water. Or put the thermostat in and see if the temp goes up to 180F or 195F according to the meat thermometer.

 

The guage is aftermarket and is not in the speedo cluster. The electric temp guage came with a new sending unit and that is what I put on there. It is a 180 t-stat so I should watch to see if the coolant reaches 180 and then cools? I will try to move the wires around to see if I have some kind of interference with the guage. I have the power on the guage hooked up directly to the ignition switch as I have no fuse block. Thanks.

 

I'm pretty sure the thermostat is not an on-off device, but instead will be fully open at 180F. Thus as the temp comes up, the 'stat will start to open until the cooling capacity (flow) equals the heat output of the engine. Not much heat is produced at idle, since there's no load, so just getting near to the set point should be ok.

You can test the 195F 'stat with your meat thermometer on the stove. I think you'll see that it starts to open at somewhere above 160F, and is fully open at 195F. I'd also suggest you use the 195F 'stat that the factory calls for. If you put the 195F back in, then you can compare the temps at idle - I'd guess you'll see 150+(195-180) = 165F, within a few degrees. The vacuum controls in the block will consider anything above 160F as full operating temp, so 165F at hot idle will be ideal.

If it were me, and I were sure I had 12V at the gauge (measured!) and I used good wire and connectors to install it, I'd send both the gauges back. What brand are they? If you want to run aftermarket gauges, I'd suggest Stewart-Warner or Autometer or another quality brand, not a generic. You can buy mechanical temp gauges that rely on a physical connection to the engine compartment - see the S-W "Standard" gauges http://www.stewartwarner.com/Products/prod1.html

What's wrong with the gauge in the cluster?

 

When I changed the temp gauge I found out that the original sending unit would not work with the aftermarket gauge (Autometer Phantom). Had to put in the sending unit from autometer - it was a direct replacement that comes with the gauge.

Still nothing, so I ran a new wire from the sending unit to the gauge and a fresh wire from the gauge to a switched 12v source. Bingo.

 

Here is what I would do.. I work on instruments all the time, so this will tell you what is what. Remove the sensor and put it in hot water. Read the water temp with a known good thermometer.. Compare the thermometer reading to the gauge reading. Keep in mind that you may have to ground one side of the sensor to get it to read.

 

Hey guys I just tried putting the sensor in hot water and using a meat thermometer to tell how hot it was. The meat thermometer said about 162 and the guage in my jeep also said that so the guage has to be accurate. I don't know what else it could be. The only thing I did was change the t-stat and move the radiator up. I also still don't understand why its not boiling over. Any ideas? Thanks.