High engine temp issue

[rojo23]

I have freshly rebuilt 302 with the explorer serpentine conversion and Pro-Flo 4 EFI. Yesterday was the initial start up and I was getting high coolant temps.

The pf4 was showing temps around 230. I also have a Dakota digital cluster and that temp sensor was around 150. Both sensors are plumbed into the intake so I am confused on why they are so different. These are all new parts so it is difficult to tell which maybe the issue

I have a 180 degree thermostat and I didn’t notice that opened until the pf4 was saying the temps were around 225-230

If I used an IR thermometer where is the best spot on the block to get a temp reading and what should that be?

Thanks

 

[DirtDonk]

Unfortunately, the Internet is full of stories of poorly performing temperature sensors. Thermostat too!
Normally, because you didn’t detect the thermostat opening until much higher temperature, I would suspect that the Edelbrock temp sensor is faulty. But because we’re relying on an also common fault, in the form of a poorly performing thermostat, you can’t really use that as your guideline either.
More clues, yes. But answers? Not yet.

For where to take temperatures readings with an IR gun, I’d say everywhere.
Start at each sending unit. Take readings on the sending unit, and around it.
You said the sensors were in the intake, but where exactly is each one? Is one of them before the thermostat, and one of them after?

 

[DirtDonk]

Also, be sure that your serpentine drive belt is on correctly. Usually not a problem with the water pump, but make sure anyway.
From a historical standpoint, the Explorer accessories are among the best cooling setups available. So normally you could ignore that, but it’s still worth checking the drive direction for the water pump.
Is it a new water pump, or the original?

 

[rojo23]

So both sensor are plumbed into the intake before the thermostat
The water pump is a new Napa pump for 2000 explorer 5.0 the pump rotates counterclockwise with the smooth side of the belt riding on the pulley.

Thanks for the info

 

[Broncobowsher]

Fresh build has me asking to check something else. If a head gasket gest put on backwards one side of the engine will run hot.
You will have to internet search it out. There is a way to tell if it is right or wrong by how the tabs hang out between the block and the head.

 

[73azbronco]

Shoot thermo housing with an IR gun, whats it say?

 

[sanndmann3]

Do you have a shroud on the radiator and how deep is fan into the shroud?
Possibly test thermostat by putting in boiling water to make sure it opens?
Same with temp sensor... test in boiling water to see what it reads?

 

[rojo23]

I have an electric 16” fan. I had a shop fan blowing on the front as well
Good idea about the boiling water

 

[rocknhorse76]

First, ditch that dinky electric fan and use the explorer clutch fan and a good shroud. Second, test (with an IR gun) the temps at the thermostat housing, and then at both tanks on the radiator. The housing will tell you what temp the coolant is before the thermostat. Checking both tanks will tell you whether you’ve got good flow and heat exchange through the radiator. The temp at the hot side of the radiator where the top hose comes in should be about the same temp as the stat housing, and the other side should be 30-40 degrees cooler. If you see anything other than that, your stat could be stuck closed. My money is on that PF4 temp sensor being bad though.

 

[rojo23]

So I figured out my gauge issue. I removed my PF4 and the Dakota digital temp gauges. When I unplugged then I realized I have the Dakota wire going to the pf4 sensor and vice versa.

After correcting the wire issue I put both sensors in boiling water and they are within about 5-7 degrees of each other and the pf4 matched a thermometer I had here. I am confident the sensors are correct

So Broncobowsher was correct about the head gasket. My head gaskets have one end that the corner is squared off and one that is rounded. Looks like the squared off end should be facing forward. My drivers side is correct my passenger side is not.

It makes sense, my passenger side cylinders 3-4 have a darker color on the header than the front 2 and the drivers side is uniform in color.

Guess I will be installing new head gaskets in my near future.
Thanks for all the suggestions and idea

 

[DirtDonk]

Have you run it since you swapped the sender wires? Remember, only one of them was showing high. The other one was showing low.
What are they reading now?

 

[rojo23]

I started it today and swapping the wires fixed the inconsistencies. I confirmed the sensors with boiling water and a thermometer

 

[DirtDonk]

Yeah, I got that part from your previous post. I was just wondering if it was still indicating hot.

 

[rojo23]

After running g for a few minutes they were 220ish and climbing. The thermostat did open

 

[rojo23]

Fresh build has me asking to check something else. If a head gasket gest put on backwards one side of the engine will run hot.
You will have to internet search it out. There is a way to tell if it is right or wrong by how the tabs hang out between the block and the head.

This was the issue. I replaced the head gasket last weekend and started it up this weekend. Ran for about 20 minutes without any issues getting too hot. Thanks for the suggestions saved a lot of time and headaches

 

[DirtDonk]

Sorry you had to go through the extra work, but sure glad you got it fixed!