Again... HOW do you KNOW that the truck is overheating? There is NO WAY for an Excursion PCM to see coolant temp. It does not have the ability. The dash gauge is NOT a real coolant temp gauge, it uses oil temp and intake air temp to guess at a temp "range"...

Put a coolant temp gauge in it and find out what the coolant temp is...

Right now I see a guy pissing money away on things that may or may not be the issue...

 

It's not a far fetched idea and is what happened to Krazee Matt.

His 7.3 Excursion started overheating out of the blue and after replacing the waterpump and clutch fan, it stopped overheating.

Everything else except the water pump was replaced/checked/cleaned/fixed on the OP's truck. The impeller could be spinning just enough to keep the truck somewhat cool, then when it really needs to work, it can't keep up.

Replace the pump and see what happens, although I'm almost certain replacing the pump will fix the problem.

 

Gaugepro does make a valid point about accurate information.


A handy tool for troubleshooting coolant, bearing, exhaust, injector, transmission temperatures is a hand-held infrared sensor. They have a red laser that tells you where exactly where you are measuring the temperature. I really like them because it gives you instantaneous readings for whatever you are concerned about. $50.00 or less is worth the investment in my opinion and you can use it to monitor tire, bearing temps during a trip as well.


The IR sensor can also be used to see if you have any cool spots in your radiator. If you are careful you can spot cores that are not passing their share of coolant with this tool. It is much more helpful for troubleshooting than just about any other tool that I can think of. If you shoot the laser at the thermostat housing you can get a reading of the coolant temp, (more accurate if you spray paint a small section of the housing a dull black).


Another use is to confirm oil temp-point the sensor at the oil filter for a quick measurement, especially when at high altitude with a trailer. Good luck.


Larry

 

Why are we continuing to throw parts at it, without knowing what the issue is?

I dont mean to sound like a broken record but at this point we dont know what is overheating if anything...

 

Point taken....

I've reached out to Krazee Matt so we can better understand what needs to be done.

 

Not sure how much help my experience will be after reading through the thread so far, especially after Gauge's posts about the stock temp gauge in the cluster. I will just outline my overheat and what was done that ultimately fixed it. Performance mods to mine are DP F5, 4" exhaust, 6637 intake, and I suppose the lift and 35's which are a bit harder to turn than stockers.

Truck had never had an issue before, including towing 4500lbs through Arizona hills and grades in 122* weather earlier this year. About a month ago while stuck in traffic in Houston (surprise) on a 102* day I just happened to scan the gauges and saw the coolant temp gauge was nearly pegged. Threw the heater on max blast (que misery for the next 15 minutes), and the temp dropped a hair on the gauge. Once traffic opened up and normal cruising resumed, the temp dropped further but not down to normal. As a test I got off, hosed down the radiator through the grill to help it cool down a bit faster, and topped off the coolant with water as I had a dry degas bottle and the radiator was low as well, and then absolutely hammered the crap out of it on a back road. The temp gauge would climb rapidly under hard prolonged load, but settle down cruising - the latter still never down to the normal halfway mark. I noticed the stock oil gauge was a smidgen low, which could possibly be the oil being excessively hot and lower viscosity as a result - however the stick showed full hot, and I don't imagine hot oil with a properly operating oil system would be incapable of maintaining normal pressures BUT I'm not an expert by any means. Just another symptom I noticed.
As it is my daily, I didn't have the luxury nor the time to replace individual components nor troubleshoot the exact issue. Seeing as how it had 228k on it at the time, and based off the seeming neglect on maintenance by the PO, I was ok with replacing everything that seemed suspect. Coolant was green, some silicate drop out in then to bucket when fully drained. The engine was still quite warm, and my understanding of the fan clutch is that it should not free spin once operating temperature is reached. Mine wouldn't quite free wheel when spun by hand, but it wasn't exactly stopping as soon as I left go of it. Replaced the thermostat, the fan clutch, hosed out the radiator with full strength Simple Green, and also hosed out the radiator fins as I enjoy a romp in the mud from time to time. Not a lot of fallout from the fin cleaning. The water pump showed excessive signs of wear compared to a new one I checked out at the part store - shaft has some noticeable play to it. Once the original was removed, the impeller was not in good shape - blades were worn, some were damaged and severely scored compared to the new one. There was no indications of seeping from the weep hole, nor had I been leaking when parked.

After it was all said and done, flushed the coolant system thoroughly with a cleaner (off the shelf stuff, yellow bottle that's about all I remember) and I haven't had an issue yet. I chalked it up to the water pump after comparing it's overall condition with a new unit. I did not think to boil the thermostat to check for proper operation, which is probably should have. However since I was in there anyway, I just replaced it as a precaution. To date, no further issues with overheating a based off the stock gauge, even when towing 9k through a variety of conditions a few weeks ago. That's pretty much all I've got, I don't know if it's going to be of any help or not.

Based off what the OP has already replaced, I'm inclined to think the water pump is on it's way out. On a variety of other vehicles that I've had that demonstrated similar symptoms to the OP's overheating it was the water pump in all of them. They would be in decent shape to keep up with normal driving, but when a demand was put on them, they couldn't keep up with the demands for coolant flow. It's also fairly basic that if you are a maintaining temperature while cruising and piddling around town where a significant load isn't exerted on engine, a failing pump will do fine. Put a strain on things, and the pump cannot keep up.

By no means do I claim to be an expert on any of this, just my experiences with my Excursion and previous vehicles that exhibited very similar symptoms.

 

Gaugepro, now that it's been thoroughly explained, does Matt's response answer your question/comments/concerns about "throwing parts" at the problem?

Btw, I was the one who helped Matt replace the pump on his truck and can confirm his findings as the cause of the overheating situation. It's for this reason, from my own experience, and common sense becuase it's the final piece of the cooling system that hasn't been touched, that the water pump should be replaced.

The thermostat being replaced, the radiator being cleaned with simple green, the coolant system being flushed, and the clutch fan being replaced were precautionary measures that were taken during the course of the repair, while once again, the pump was found to be the issue.

Furthermore, while the PCM may not be able to give an accurate number via the OBD2 using a scangauge or an AE, I've found the gauge on the dash to be somewhat accurate. In other words, it tells me what it's supposed to, when it's supposed to.

 

The dash gauge is telling you oil temp, mixed with a few other things to give an edumicated guess at coolant temp. Why Ford didnt just put an oil temp gauge in there is not for me to guess, but its not a coolant temp gauge.

One needs to know where the issue is, before throwing parts at it. How do we know we dont have a clogged oil cooler that is causing the oil temp to rise, in turn effecting the "coolant" temp...

All I am looking for is some conformation that the coolant was indeed overheating. You know as well as anyone how OVERBUILT the coolant system is on a 7.3, there not known for overheating even when pushed hundreds of HP more then stock towing thousands of pounds more then rated...

 

Why then, when the ECT sensor is unplugged, does the gauge go to the bottom, yet when the EOT sensor is unplugged, the gauge is unaffected?

 

Good point. I can't believe the gauge has an algorithm built into it to estimate coolant temp, while the wire from the coolant temp sensor goes nowhere. That makes no sense.

Now, if there was a way to make the gauge move smoothly with the temperature rather than stepwise based on predetermined points, that would be useful. Just knowing where the steps are would be helpful.

Mark

 

After reading all these posts...
#1 change your water pump
#2 change your radiator. I had the exact same problem. I changed water pump x2, thermostats x2, clutch fan, degas cap, degas bottle... was pulling my hair out. Would only over heat at high altitude pulling a load. Pulled radiator, flushed with high pressure hose, didn't seem plugged. Water was coming out as fast as it was going in. Long story short, I put in a new radiator and all problems went away. Partially plugged causing overheating while towing heavy loads at high altitudes. I'm betting money on the radiator.

 

Substitute all the fancy stuff as follows:
Tachometer - Already got one on dash
Digital multi meter / scan gauge
Fancy light Strobe - Timing Light (Indict off of CPM)
Idle Adjuster - Friend who knows what the far right pedal is for and can read numbers on Tach.


Start the engine and allow the engine to idle throughout this test. Allow the engine to run for 10 minutes, then record the ECT voltage. Record the ECT voltage every 60 seconds. When the ECT voltage trend changes direction or only changes slightly (0.03 voltage or less) from the previous reading, record this as the thermostat opening voltage. Use the voltage and corresponding coolant temperature chart listed below.
Scan gauge /AE / Etc. You can even do the testing with a DMM so long as the ECT is tapped and not removed (the PCM will throw a code "even though it doesn't monitor it".....)

Coolant Temperature °C (°F) ECT (Volts)
22 (71) 3.00
43 (109) 2.01
71 (159) 1.01
82 (180) 0.75
91 (195) 0.059
97 (206) 0.050
105 (221) 0.040

If the thermostat opening voltage is greater than 0.75 volts and less than 82°C (180°F), replace the water thermostat. If the thermostat opening voltage is less than 0.75 volts and greater than 82°C (180°F), the water thermostat is good and should not be replaced.

On the following test, it the temp volts increase above norma, its your Radiator

Fan Clutch Test

Spin the fan blade (8600) by hand. A light resistance should be felt. If there is no resistance or very high resistance, the minimum and maximum fan speeds must be checked as follows: Fan Clutch Test—Minimum Speed Requirement Use a suitable marker to mark the water pump pulley (8509), one of the fan blade retaining bolts and the crankshaft pulley. Connect a tachometer to the engine. Install a throttle adjusting tool. Connect the Digital Photoelectric Tachometer. Start the engine and run it at approximately 1500 rpm until the normal operating temperature has been achieved. Adjust the engine speed to 2300 rpm. Operate the strobe light at 3000 rpm (on Diesel engines 3600 rpm's) and aim it at the water pump pulley. Adjust the engine speed until the light flash and the water pump pulley mark are synchronized. Aim the strobe light at the fan blade bolts. Adjust the strobe light until the light flash is synchronized with the marked fan blade bolt (the fan blade appears to stand still). The fan blade speed must not be greater than 1500 rpm (on Diesel engines 2000 rpm's) at
3000 water pump rpm.

If the fan blade speed was greater than 1500 rpm (on Diesel engines 2000 rpm's), replace the fan clutch.

Fan Clutch Test—Maximum Speed Requirement: Perform Steps 1 through 5 of the Fan Clutch Test—Minimum Speed Requirement.
2. NOTE: The temperature should be above 96°C (205°F) for maximum fan speed. Block off areas on each side of the radiator in the engine compartment and the front of the radiator grille. This will raise the temperature of the air striking the fan clutch and should cause the fan blade to operate at maximum speed. Place the climate control function selector switch in the MAX A/C position and the blower motor switch in the HI position. Adjust the strobe to 3000 rpm (on Diesel engines 3600 rpm's). Start the engine and adjust the engine speed until the strobe light flash and the water pump pulley mark are synchronized. Aim the strobe light at the fan blade retaining bolts. Adjust the strobe light until the light flash is synchronized with the marked fan blade bolt (the fan blade appears to stand still). If the fan blade speed is less than 2300 rpm (on Diesel engines 2950 rpm's), replace the fan clutch.

 

How are you so sure of this? Do you have any evidence to back this up?

I'm sure we'd all like to see what you have on this.

It's rare to hear of an oil cooler clogging on a 7.3, you'd have to seriously neglect the cooling and oil system for that to happen. Parts have already been thrown at the truck and the only part that hasn't been replaced is the waterpump.

You're right about the 7.3 cooling system as THEY'RE not known for overheating. However, when the waterpump can't keep up with the demand due to failure within the pump itself, it will overheat. The same applies if the wrong thermostat is used, the cooling system is seriously neglected, or someone uses "stop leak" radiator fix in a bottle.

 

Plug in your scanner... Cold motor and look at coolant temp... then tell me you have a real coolant temp gauge in your truck.

 

Huh? We all know the PCM doesn't see coolant temp on the auto trucks, but that has nothing to do with what the temp gauge on the dash is connected to.

Mark