Straight Six Running Hot

[tanman]

My temp gauge was stuck near low. I grounded the temp sensor wire and the gauge went full tilt so I know the gauge is operating. I replaced the temperature sensor and Eureka! I now have a working temperature gauge.

Now that the gauge is working, it appears that the engine is running hot. All my other fords had a temp gauge need that rode center or a little to the left of center.

I just got this truck in June 2020, and it looks like it has a new radiator. I can feel the pressure in the hose from the radiator to the motor when the truck is running.

I don't know where to begin troubleshooting. Any ideas how to troubleshoot this? I've added a photo and the gauge climbed even higher when idling in traffic.

[old55pete]

Just a few questions

1 Does it have a fan shroud?

2 is it the correct fan shroud?

3 is the thermostac fan clutch locking up and pulling air through the radiator?

4 You say that it "Appears" to have a new radiator. When was the last time the thermostat changed?

5 What is the temp of the upper radiator hose while the engine is running at the temp on the guage?

[tanman]

Just a few questions

1 Does it have a fan shroud?

2 is it the correct fan shroud?

3 is the thermostac fan clutch locking up and pulling air through the radiator?

4 You say that it "Appears" to have a new radiator. When was the last time the thermostat changed?

5 What is the temp of the upper radiator hose while the engine is running at the temp on the guage?

Steve, thanks for the reply. To answer your questions:

It does have a fan shroud. I don't know if it's the stock shroud or not.

I don't know how to tell if the clutch is acting up but I will do some searching on this.

I don't know when the thermostat was replaced. I just got the truck in June 2020. I will look into replacing this.

I don't have a temperature gun but I'm always looking for a reason to buy a new tool.

[tanman]

Steve, thanks for the reply. To answer your questions:

It does have a fan shroud. I don't know if it's the stock shroud or not.

I don't know how to tell if the clutch is acting up but I will do some searching on this.

I don't know when the thermostat was replaced. I just got the truck in June 2020. I will look into replacing this.

I don't have a temperature gun but I'm always looking for a reason to buy a new tool.

Found some info on troubleshooting the fan clutch here

The gist: "To confirm the diagnosis, start with this simple test: Spin the fan as hard as you can on an engine that has not been started that day. If the fan rotates more than five times, you can bet the clutch is bad. You should feel some resistance and the fan may spin up to three times, depending on the ambient temperature."

I will let the truck cool down and test the fan clutch tonight.

I also looked up the thermostat. It seems like a straightforward part to replace and it's inexpensive so I'll go ahead and change it out.

Thanks again for the tips Steve!

[old55pete]

Found some info on troubleshooting the fan clutch here

The gist: "To confirm the diagnosis, start with this simple test: Spin the fan as hard as you can on an engine that has not been started that day. If the fan rotates more than five times, you can bet the clutch is bad. You should feel some resistance and the fan may spin up to three times, depending on the ambient temperature."

I will let the truck cool down and test the fan clutch tonight.

I also looked up the thermostat. It seems like a straightforward part to replace and it's inexpensive so I'll go ahead and change it out.

Thanks again for the tips Steve!

A few things to also look at on the fan, look to see if there is oil leaking out of the shaft at the water pump, look to see if there is oil leaking from the front seal where the temp sensing spring is.

Another thing to look at is the radiator cap, if any of the rubber seals are cracked, hard or broken, replace it. Test the cap with a preasure tester. I want to say that you should have a 13 lb cap but look it up and find out for sure. If the coling system wont hold preasure, it wont cool properly.

[Ford F834]

Before you get too far into troubleshooting, I would confirm the temperature with a decent quality gauge. The factory temp, oil and fuel gauges are powered by a pulsing voltage regulator and they are notoriously approximate. With age, the approximation becomes worse... the temperature gauge on my 1981 straight six reads quite high... I have replaced the sender and I have plugged in a couple spare clusters (to test if the ICVR and/or gauge itself had issues) and it still reads high. My mechanical VDO fluctuates right around the advertised advertised thermostat opening temperature of 195*F so I know my cooling system is okay. One day I will revisit trying to get the factory gauge to read correctly (whatever that is on a gauge with no numbers or units) but the mechanical gauge will stay regardless because I refuse to put full trust into the factory electric gauge.

This may or may not be your issue, but I wouldn’t chase my tail diagnosing the cooling system based on what the stock gauge reads. Just my .02

[old55pete]

Before you get too far into troubleshooting, I would confirm the temperature with a decent quality gauge. The factory temp, oil and fuel gauges are powered by a pulsing voltage regulator and they are notoriously approximate. With age, the approximation becomes worse... the temperature gauge on my 1981 straight six reads quite high... I have replaced the sender and I have plugged in a couple spare clusters (to test if the ICVR and/or gauge itself had issues) and it still reads high. My mechanical VDO fluctuates right around the advertised advertised thermostat opening temperature of 195*F so I know my cooling system is okay. One day I will revisit trying to get the factory gauge to read correctly (whatever that is on a gauge with no numbers or units) but the mechanical gauge will stay regardless because I refuse to put full trust into the factory electric gauge.

This may or may not be your issue, but I wouldn’t chase my tail diagnosing the cooling system based on what the stock gauge reads. Just my .02

As you saw, I wasent advocating changing parts just because the, less then accurate when new, now 30 plus year old gauge is reading a little on the high side. Instead, I was asking questions that would ether lead him to the fact that his cooling system is in fact doing it's job and the gauge is wrong. Or there is something accutaly wrong with his cooling system that needs to be addressed.

Like you, I have a similar problem with my temp and gas gauge. When it rears it's ugly head it means that I need to pull my radio and clean the ground stud that is welded to the inside of the firewall and it goes away for a couple of years.

[Ford F834]

Like you, I have a similar problem with my temp and gas gauge. When it rears it's ugly head it means that I need to pull my radio and clean the ground stud that is welded to the inside of the firewall and it goes away for a couple of years.

Thank you! I will try this!

[Gary Lewis]

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.

[old55pete]

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.

Still, with all of this being said, he still needs to figure out if his cooling system is doing it's job or not. There does need to be some trouble shooting to make sure everything is operating with in what it was designed to do.