Straight Six Running Hot

[ratdude747]

Before you get too far into troubleshooting, I would confirm the temperature with a decent quality gauge.

YES! Get an infrared thermometer and check the temp at the thermometer housing. I doubt you have a problem.

I have mechanical aftermarket gauges on Big Blue with a brand new engine, water pump, hoses and brand new aluminum 4-core radiator - with new coolant to boot. And with a new 195 degree 'stat my temp varies from 200 to 205.

In addition I've put a very accurate voltage regulator in place of the original ICVR, which means my factory temp gauge is very stable. I just walked in from a 160 mile drive and the factory temp gauge was glued on the M of NORMAL for the whole trip. But if I wanted it on R or A that would be easily done by lowering or raising the voltage on the regulator - although that would also change the oil pressure and fuel level gauges.

Basically I'm saying is that the factory gauges are decent with a good ICVR powering them. But even then they are approximate. If you want precision get a mechanical aftermarket gauge. Mechanical because most of them have a 270 degree sweep and you can read them pretty easily.

Agreed. When I put in a 195 T-stat into mine, my temp readings when driving around town tended to be a bit past mid-gauge... so this might be normal. IR thermometer would be the way to go if there is a concern.

[ArdWrknTrk]

Agreed. When I put in a 195 T-stat into mine, my temp readings when driving around town tended to be a bit past mid-gauge... so this might be normal. IR thermometer would be the way to go if there is a concern.

I'd add that it's best to put a piece of masking tape on any bright metal surface before measuring with a non-contact IR thermometer.

Reflective surfaces effect emissivity.

[FuzzFace2]

I'd add that it's best to put a piece of masking tape on any bright metal surface before measuring with a non-contact IR thermometer.

Reflective surfaces effect emissivity.

As said you need to check just what the cooling system temp as that factory gauges are not great.

He would only have a clutch fan & shroud if the truck has AC.

Non-AC trucks don't use a clutch fan and only have a small top of fan shroud so the fan will not eat you if the motor is running.

If he does have a full AC shroud the fan blades need to be half way or a little more inside the edge of the shroud.

Now I have just the reverse of you.

My temp gauge only get s up to the 2nd line on the cold side.

2 new 195* stats, new radiator and hoses, new sender and all grounds are good as I made sure when rebuilding the truck. The oil & gas gauges work great.

Now I do have AC, new condenser and full shroud I had to come up with.

But I am using a non-clutch 5 blade fan and have a lot of air flow thru the front grille using the paper test.

Even the IR gun give a good temp so it has to be a gauge issue so I am not going to worry much.

Oh the gauge will go up a little more when it is 100* out and I have the AC on and taking back roads home from work but still no where to the center.

First you need to see what the system temp is.

Air flow thru the grille at idle, does the paper stay to the grille?

Being this happens at idle it looks like an air flow issue.

AC condenser plugged with dirt?

Does the lower hose have a spring inside it? Check when motor is cold.

Dave ----

[tanman]

I’m glad my cooling issue is a HOT topic.

I’m ordering an IR thermometer and will post my findings.

My truck has an aftermarket AC system. I will post pictures when I get the thermometer.

[tanman]

I’m glad my cooling issue is a HOT topic. http://www.garysgaragemahal.com/uploads/6/5/8/7/65879365/laughing-25-x-25_orig.gif

I’m ordering an IR thermometer and will post my findings.

My truck has an aftermarket AC system. I will post pictures when I get the thermometer.

I got my thermometer and took some readings.

[tanman]

I got my thermometer and took some readings.

I spun the fan and the fan is stiff and doesn't rotate easily by hand so I think the fan clutch is okay. There is coolant leaking from the heater core. It's not a major leak that has a large impact on the coolant level. I do notice some vapor in the dash vents.

 

[Gary Lewis]

I got my thermometer and took some readings.

The reading off the radiator hose of 159 is the one to use. The one off the engine of 251 is probably getting some heat from the exhaust system, but it doesn't really matter as we are concerned with the cooling system.

But the 159 reading is lower than I would have expected. Was your engine really/fully warmed up? If so, I would have expected it to be close to whatever thermostat is in there. And, unless that reading is an error, your engine certainly isn't overheating.

And your fan seems like it is working well.

So, if you had driven the truck and it was fully warmed up, then I'd take a few more readings on the upper radiator hose and thermostat housing. If they are consistent at ~160 I'd assume there's a 160 'stat in there. Then you have to decide what you want for a thermostat. Personally I like the factory 195. But I'd want to know that the readings you are seeing are consistent with the 'stat.

Then you can troubleshoot the temp gauge, knowing that the cooling system is "right".

 

[old55pete]

I spun the fan and the fan is stiff and doesn't rotate easily by hand so I think the fan clutch is okay. There is coolant leaking from the heater core. It's not a major leak that has a large impact on the coolant level. I do notice some vapor in the dash vents.

It sounds like the thermostat is ether stuck open or is too low a temp as it should be around 195 by the book.

You might want to give a thought to changing the heater core as well. If you remember what I said about the radiator cap earlier, it is supposed to hold a certon amount of pressure in the cooling system. I am pretty sure that yours needs to be 13 lbs, but you need to look that up and be sure. In any case, the cooling system needs to be able to hold that amount of pressure to do it's job.

[Machspeed]

I spun the fan and the fan is stiff and doesn't rotate easily by hand so I think the fan clutch is okay. There is coolant leaking from the heater core. It's not a major leak that has a large impact on the coolant level. I do notice some vapor in the dash vents.

For what it is worth, I had normal temp readings until I changed my sensor to an aftermarket one. The gage now reads just a little less than yours. I do not believe I am running hot but will be delving further into it.

[ArdWrknTrk]

For what it is worth, I had normal temp readings until I changed my sensor to an aftermarket one. The gage now reads just a little less than yours. I do not believe I am running hot but will be delving further into it.

You could put it in boiling water and quickly ohm it out.

Then follow the ohms as it cools, using the IR gun to determine 210, 200, 190, 180, 170, 160F

Resistor combinations at the sensor end of the harness would allow you some idea of '200 = the high side of M" "190 = the low side of M"

or whatever....