I think it's both and I'm going to rely on testing and data to prove it.

Right now I think we have sufficient water flow for an empty truck going down the road or cruising through town. The problem comes with speed, and at this point testing data is pointing to the shroud being the issue. Temp drop of 20° across the radiator in the shop will keep it below 160°. The best temp drop we've seen on the highway is 14° associated with a slow temp creep. We can pull off the road and watch the radiator outlet temp drop, followed by engine temp.

When starting the test, the engine temp only starts climbing following the radiator outlet temp rising(water temp into the radiator stays steady as outlet temp rises, then followed by engine temp creep). This is the main point of the test IMO. I wanted to see what was leading the climb, its obvious it's the radiator with the truck unloaded. If the radiator was working as desired we would see the temp drop remain at 20° but engine temp creeping, we don't see that at all. Instead we see radiator temp drop go from 23° to 14° and engine temp start climbing.

It's possible that after we get it fixed in an unloaded condition, that with a load the engine temp starts the match. But we have the FlowKooler impeller and a new lower radiator hose to put on as well.

Right now, all the data is showing that our radiator/fan/shroud package is the issue, but not far off. I think if we can get to 20° temp drop going down the road empty, that the problem is pretty much fixed. The impeller should help move more water when the engine is really making heat, but wouldn't make any difference now as the radiator is already on the losing side of the equation. More water flow without more air flow would not improve the situation as we have already proven via a 3,000 mile test haha. It made a big difference at idle or crawling through town. But zero effect at speed. Only improving the radiators ability to dissapate heat made any difference(cool water spray).

I've been working on the shroud all day. I'm almost done with all the flaps and opening the center to fit the fan better. The picture below is just the start.

I don't want to spike the ball early, but the first test with the changed shroud was very promising. It is cooler outside than our testing yesterday, but we rolled back into the shop at 158° after a 10 mile drive. Normally we were 185° and climbing at the 3 mile mark. the highest temp seen was 168° and it actually dropped back to 161° once we got back up to speed 55mph. This is the first time I've seen a temp drop at speed without water spraying on the radiator. Idle cooling was still really good about 27° temp drop so our holes/flaps did not negatively impact slow speed cooling!

Interestingly we were only seeing a 12° temp drop across the radiator. It makes me think the 14° we saw yesterday was a fallacy and the 7-8° results were closer to reality with the 10° being more realistic as a before condition.

High flow impeller install tomorrow! I'll add the last line of holes across the top of the shroud when I pull it to change the water pump.

It really sounds like airflow is the key when the engine is generating a lot of heat.

If your fan is only capable of 3000CFM maybe it isn't sufficient.  It might also be why Flex-A-Lite suggests a 6000CFM for the Superduty F250/350 trucks.

The right amount of airflow should allow you to put 7000lbs on the hitch and maintain a safe temp going up a long hill.

I was so worried about enough airflow across the rad that I bought a (Hayden)  transmission cooler that has it's own fan so I can mount it in the back somewhere.  And since I am planning A/C, I want to make sure airflow is not going to be a problem.  So the OEM 6-blade larger fan/clutch from a 429/460 engine

In my 55 F-600, the original fan is only 4 blade and there's a lot of gap between the blades and the shroud. (and of course, it only had about a 90hp inline 6-cyl engine)

I am thinking (and hoping) that your improving the airflow makes the difference for you!!


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1955 F-600/272/E4OD// Disclaimer: No animals were injured while test driving my F-600 except the ones I ran over intentionally!

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This post was created using OpenSuSE Linux x64 and Firefox

I think we finally got it.

Got the FlowKooler impeller installed today. It made a slight improvement. On my 20 mile test drive it never got over 178°. Before the shroud and water pump it would have been 200+. The shroud flaps made the biggest difference, about 15° I would say. The FlowKooler impeller was worth about 5° steady state.

Although it certainly improved coolant flow, it sounds like maybe the impeller wasn't necessary after all?



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1955 F-600/272/E4OD// Disclaimer: No animals were injured while test driving my F-600 except the ones I ran over intentionally!

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This post was created using OpenSuSE Linux x64 and Firefox

I think it'll really be evident when we get it loaded. It has helped, but it's not dramatic. I think it's contribution is more in temp gain/loss slope vs total temp. Something that is really hard to measure outside a lab in the actual world, but after watching the digital temp guage for a few thousand miles, the butt Dyno says it's slower to heat up and cools quicker.

Also we learned that temp drop across the radiator is not the right data set to evaluate. I think absolute temp outlet temp, or outlet temp vs ambient would be a better evaluation. The in vs out temp can lead you astray as with improved cooling we actually noticed a drop in the in/out delta, but cooler overall temp. Looking back at the data our "rad out" temp stayed relatively stable, it was the higher inlet temp causing a greater delta across the radiator. This is where the added water flow made a difference. Rad out temp stayed the same, but the water coming out of the engine was cooler. Lower operating temp, but lower radiator temp delta.

Not helping things, our brand new Klein thermocouple decided to drift and become unreliable. The real evaluation is long term temp control and recovery at speed, which for the moment we have achieved, unloaded.

Update time!

The truck runs great!! We've hauled a little over 200yrds of fill material around our new shop. Of course it has a completely new bed hydraulic system now....

The good: temps are much better than before. I can pull a 2 mile hill loaded to 17k lbs, 8-9psi of boost and get to the top of the hill under 180°!

The bad: the Summit Water pump pulley just exploded. Luckily Summit is great to work with and is overnighting me a new one. But it's down for the weekend while we wait.





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