New build overheating

[nvrstuk]

See how the shroud covers the ENTIRE core of the radiator (part that allows air to flow thru it) and then how it attaches directly to the radiator then the fan is attach to the shroud? This example shows how ALL air coming thru the radiator HAS to flow thru the fan... at speed it just pushes thru because youre doing 40mph, but at idle the FAN is now pulling air thru every singe square inch of the radiator (without air leakage because you use window gasket material to seal it0 so the radiator now has ambient air flowing thru every sq inch and it should cool it the same as driving down the road at 40mph (IF THE ELECTRIC FAN YOU HAVE has a large enough cfm rating (air flow rating) to pull enough air thru to cool it).

WH should be able to set you up with a fan for the Derale fan, if not, call Derale and they should have a simple univeral kit. IF NOT (I love options) Speedway motors does and a decent mechanic can put it together in 2 hrs.

 

[jstek]

OK, so let me make sure I understand. Several people said I need to close the gap between the fan and the radiator. Many people said I need a shroud. But both of those things can't be true? Either the fan bolts directly to the radiator and has no shroud OR the fan bolts to the shroud that bolts to the radiator with a gap between the radiator and the fan? That's all assuming the electric fan stays. I can try and find shroud options if that is the case.
And just to be clear, a mechanical fan is better at cooling, even at slow speeds? I've read some contradictory things on the internet but you know how that goes... All I want to do is drive 15-20 mph on bumpy dirt roads without overheating. That's truly all I will do with this Bronco.
Pretty sure I never looked under a hood until 2 weeks ago, so thank you all for walking me through this.

 

[ba123]

OK, so let me make sure I understand. Several people said I need to close the gap between the fan and the radiator. Many people said I need a shroud. But both of those things can't be true? Either the fan bolts directly to the radiator and has no shroud OR the fan bolts to the shroud that bolts to the radiator with a gap between the radiator and the fan? That's all assuming the electric fan stays. I can try and find shroud options if that is the case.
And just to be clear, a mechanical fan is better at cooling, even at slow speeds? I've read some contradictory things on the internet but you know how that goes... All I want to do is drive 15-20 mph on bumpy dirt roads without overheating. That's truly all I will do with this Bronco.
Pretty sure I never looked under a hood until 2 weeks ago, so thank you all for walking me through this.

Closing the gap between the fan and radiator and using a shroud to close the gap, BOTH leave no gap for any air to come through unless that air is coming through the radiator. The only difference is that the shroud take the air from the ENTIRE radiator and the fan only against it with no gap, takes from a 17” circle.

My advice was to do the gap first and see if you notice a positive difference before wasting your time on a shroud for a fan that isn't good enough. Then, if it is, move forward on the shroud, which is even better.

If you don't notice a difference closing that gap, then absolutely, just go mechanical fan and be done with it.

 

[nvrstuk]

Again like ba123 said, we were both just trying to see if when the elect fan was still mounted directly to the radiator IF, big if, IF the electric fan when sealed tightly against the radiator would be sufficient to cool your engine & it's not. Post #47

Like mentioned in post #45, it's probably because you are only pulling a 17" dia circle of air thru a radiator that has all 4 corners w/o ANY air going thru it at idle because it is square and there are huge areas of your radiator that NO AIR is flowing thru to cool the water in the radiator (addressed this earlier also-just mentioning it). Lot going on & you are new to most of this.

In theory like you mentioned, electric fans are pulling max air all the time whereas a mech fan is pulling max air at MAX rpm, lime 6,000 rpm. Reason why this "theory" doesn't work in real life is why it's not working for you. 1) not able to move enough cfm of air 2) it isn't sealed to the radiator & or shroud (edit #3 edit: it's not an OE fan therefore it isn't up to the task as hundreds of thousdands of dollars tof research and testing to make it work as a reliable OE product was not spent on it- it was designed by some guy behind a desk that "designs fans" and was made in China. Probably the absolute truth, but not being OE means it never had a standard to follow- like true CFM ratings and longevity

So, my suggestion a long time back due to simplicity was to try the 7blade mechanical (not any other fan like -heaven forbid some cheap thing like a flex-fan! Just say No lol


Use rhe stock 7 blade fan with a very GOOD fitting shroud with the fan spaced from the waterpump pulley so appr 1/2 to 2/3 of the actual blade(s) fit inside the shroud-important.

Ask WH or Tom's which shroud you need depending on whether your Bronco has a body lift or not. Then ask about the wtrpump pulley so you can BOLT the fan to the wtr pump pulley.

 

[Wild horse 75]

If you can get some weatherstrip like this:

https://www.amazon.ca/dp/B089LW37ZD/

you could try and seal you current fan in its current setup and see if that helps. Right now the fan isn‘t pulling air through the core. It’s pulling air from the area of least resistance. Which is going to be in the gap between the fan and radiator core. That gasket will close it up. If that gets it to run cool you’re done. If it makes an improvement then you need to find a shroud like this:

https://www.summitracing.com/parts/sum-381520-1

Also you haven’t answered if you drained some of the antifreeze out and got a 50/50 mixture in it. Too much antifreeze and you could stick a huge movie fan in front of the truck and it wouldn’t cool it off.

 

[jstek]

Again like ba123 said, we were both just trying to see if when the elect fan was still mounted directly to the radiator IF, big if, IF the electric fan when sealed tightly against the radiator would be sufficient to cool your engine & it's not. Post #47

Like mentioned in post #45, it's probably because you are only pulling a 17" dia circle of air thru a radiator that has all 4 corners w/o ANY air going thru it at idle because it is square and there are huge areas of your radiator that NO AIR is flowing thru to cool the water in the radiator (addressed this earlier also-just mentioning it). Lot going on & you are new to most of this.

In theory like you mentioned, electric fans are pulling max air all the time whereas a mech fan is pulling max air at MAX rpm, lime 6,000 rpm. Reason why this "theory" doesn't work in real life is why it's not working for you. 1) not able to move enough cfm of air 2) it isn't sealed to the radiator & or shroud (edit #3 edit: it's not an OE fan therefore it isn't up to the task as hundreds of thousdands of dollars tof research and testing to make it work as a reliable OE product was not spent on it- it was designed by some guy behind a desk that "designs fans" and was made in China. Probably the absolute truth, but not being OE means it never had a standard to follow- like true CFM ratings and longevity

So, my suggestion a long time back due to simplicity was to try the 7blade mechanical (not any other fan like -heaven forbid some cheap thing like a flex-fan! Just say No lol


Use rhe stock 7 blade fan with a very GOOD fitting shroud with the fan spaced from the waterpump pulley so appr 1/2 to 2/3 of the actual blade(s) fit inside the shroud-important.

Ask WH or Tom's which shroud you need depending on whether your Bronco has a body lift or not. Then ask about the wtrpump pulley so you can BOLT the fan to the wtr pump pulley.

Where do you find a OE 7 blade fan? Toms Offroad had a replica but it's out of stock. WH has a 6 blade that should fit and a shroud to match. No body lift on this. Is the 7 blade that much better?

 

[jstek]

If you can get some weatherstrip like this:

https://www.amazon.ca/dp/B089LW37ZD/

you could try and seal you current fan in its current setup and see if that helps. Right now the fan isn‘t pulling air through the core. It’s pulling air from the area of least resistance. Which is going to be in the gap between the fan and radiator core. That gasket will close it up. If that gets it to run cool you’re done. If it makes an improvement then you need to find a shroud like this:

https://www.summitracing.com/parts/sum-381520-1

Also you haven’t answered if you drained some of the antifreeze out and got a 50/50 mixture in it. Too much antifreeze and you could stick a huge movie fan in front of the truck and it wouldn’t cool it off.

I have added water to the coolant reservoir but maybe not enough. Thanks for reminding me about that.

 

[jstek]

I agree with those who said to close up the gap between the shroud and the radiator and see what that does. I had the same problem on my mustang with it overheating at idle. I had a gap between the fan and the shroud, closed that up and the car cooled fine.

I'm also in Santa Fe, I could probably give you a hand with things or advice, I may even have some of the parts you need if you decide you want to switch to a mechanical fan.

Thanks for your offer to help! I may take you up on it. Do you have a mechanic in town that you trust? I know I'll need one going forward, even if I get this fan thing worked out now.

 

[nvrstuk]

You might try the wanted classifieds here in this forum for the 7blade,.

It pulls more air than the 6 but if WH has the 6 blade in stock with a fan shroud for your no BL application then that's the way to go.

 

[71 CA Bronco]

All good advice here. But I would stick to the simple less costly stuff first.

Drain the coolant and put the proper mix ratio back in. Drain it all out not just the overflow tank. There should be a bleeder on the bottom of the radiator. You already know for a fact this is wrong. Then you need to burp the radiator to be sure there are no air pockets in the cooling system. Air pockets in a 302 have bit more than one on this board and cost another guy I know a complete rebuild on a new engine. There is a tool to do this properly but I have either parked on a really steep incline facing forward, or jacked the front of the Bronco up while warming the engine up to operarting temperature with the cap off. Once the engine has warmed up and thermostate has opened, top of the radiator and overflow tank and replace the cap. You want the front of the truck as high as you can get it. Do this all while the heater is on forcing air bubbles out of the heater core. Give it a try. It will only cost you the coolant and a little time.

 

[nvrstuk]

All good advice here. But I would stick to the simple less costly stuff first.

Drain the coolant and put the proper mix ratio back in. Drain it all out not just the overflow tank. There should be a bleeder on the bottom of the radiator. You already know for a fact this is wrong. Then you need to burp the radiator to be sure there are no air pockets in the cooling system. Air pockets in a 302 have bit more than one on this board and cost another guy I know a complete rebuild on a new engine. There is a tool to do this properly but I have either parked on a really steep incline facing forward, or jacked the front of the Bronco up while warming the engine up to operarting temperature with the cap off. Once the engine has warmed up and thermostate has opened, top of the radiator and overflow tank and replace the cap. You want the front of the truck as high as you can get it. Do this all while the heater is on forcing air bubbles out of the heater core. Give it a try. It will only cost you the coolant and a little time.

Gotta ask.

If the Bronco can drive down rhe road at 35-45mph and not overheat, how is there suddenly an air bubble that is somehow blocking coolant flow when it's driven slower or idled but never when driven at 35+?

Then this air bubble is repeating the same symptoms of being there & not being there over and over again?? Bad luck?? different if there is a leak where air is being forced in (head gasket).

Since we are talking NM and if you live where it doesn't get much below freezing??? you could drop your antifreeze to DISTILLED water ratio to 30/70. All I remember from lots of classes is you can lower temps by maybe, 10-15 max degrees when going from a high antifreeze/water ratio to a low antifreeze water ratio.
This is not your fix IMO tho, a 302 will cool just fine w/o issue with typical 50/50 ratio-than you don't have to worry about freezing in the winter.

(edit)

 

[jstek]

Gotta ask.

If the Bronco can drive down rhe road at 35-45mph and not overheat, how is there suddenly an air bubble that is somehow blocking coolant flow when it's driven slower or idled but never when driven at 35+?

Yes, that was my question too, but I did just do that test, exactly as 71 CA Bronco described. I was a bit intimidated to try it before, but it really wasn't hard. Plus, now I know I have 50/50 antifreeze/water in there. I did get several big gas bubbles out. No idea if that is significant. I can't do a test drive for a couple days, but will report back. P.S. I ordered the mechanical fan and shroud from WH. If it ends up that I don't need it, so be it. I might have found someone to install it if that's the way to go.

 

[Wild horse 75]

For what it costs before you go pulling the electric fan off I would try the weatherstrip I suggested. If it doesn’t do anything you’re only out a few dollars and a bit of time but if it does make a difference you’ll know what your next steps should be.

 

[nvrstuk]

Yes, that was my question too, but I did just do that test, exactly as 71 CA Bronco described. I was a bit intimidated to try it before, but it really wasn't hard. Plus, now I know I have 50/50 antifreeze/water in there. I did get several big gas bubbles out. No idea if that is significant. I can't do a test drive for a couple days, but will report back. P.S. I ordered the mechanical fan and shroud from WH. If it ends up that I don't need it, so be it. I might have found someone to install it if that's the way to go.

Just to clarify what's been done and where you are now, what test? Was that sealing the fan gap to radiator that was suggested right after you posted the large group of pictures or putting a 50/50 mix in?

So many suggestions, timelines & posts get mixed up as to what is being done and why.

 

[jstek]

Just to clarify what's been done and where you are now, what test? Was that sealing the fan gap to radiator that was suggested right after you posted the large group of pictures or putting a 50/50 mix in?

So many suggestions, timelines & posts get mixed up as to what is being done and why.

Yes, lots of info to read through! I did several things. First, I made a temporary shroud around the electric fan - no help. Most recently, I drained the cooling system, put in a fresh 50/50 mix and "burped" the system. Have not had time yet to take for a test drive to see if this has changed anything.

 

[jstek]

Gotta ask.

If the Bronco can drive down rhe road at 35-45mph and not overheat, how is there suddenly an air bubble that is somehow blocking coolant flow when it's driven slower or idled but never when driven at 35+?

Then this air bubble is repeating the same symptoms of being there & not being there over and over again?? Bad luck?? different if there is a leak where air is being forced in (head gasket).

Since we are talking NM and if you live where it doesn't get much below freezing??? you could drop your antifreeze to DISTILLED water ratio to 30/70. All I remember from lots of classes is you can lower temps by maybe, 10-15 max degrees when going from a high antifreeze/water ratio to a low antifreeze water ratio.
This is not your fix IMO tho, a 302 will cool just fine w/o issue with typical 50/50 ratio-than you don't have to worry about freezing in the winter.

(edit)

It does freeze here quite regularly. We actually get pretty cold winters.

 

[ba123]

It does freeze here quite regularly. We actually get pretty cold winters.

And that's how Anti-Freeze helps you, it is not called Anti-HEAT. It doesn't cool like water does, but water freezes so you have to mix them to find the right balance. Hope doing that does it for you!!!

Let us know.

 

[71 CA Bronco]

Gotta ask.

If the Bronco can drive down rhe road at 35-45mph and not overheat, how is there suddenly an air bubble that is somehow blocking coolant flow when it's driven slower or idled but never when driven at 35+?

Then this air bubble is repeating the same symptoms of being there & not being there over and over again?? Bad luck?? different if there is a leak where air is being forced in (head gasket).

Since we are talking NM and if you live where it doesn't get much below freezing??? you could drop your antifreeze to DISTILLED water ratio to 30/70. All I remember from lots of classes is you can lower temps by maybe, 10-15 max degrees when going from a high antifreeze/water ratio to a low antifreeze water ratio.
This is not your fix IMO tho, a 302 will cool just fine w/o issue with typical 50/50 ratio-than you don't have to worry about freezing in the winter.

(edit)

Ha Ha. I didn't catch the no overheat at 35-45 mph. I didn't read all the posts either. Just trying to start with the easy stuff first before going down the rabbit hole. I've never been a fan of electric fans. I agree the mechanical one with proper shroud is the way to go. I cramed a bunch of stuff under the hood on my Bronco during the 5.0 swap and it has never heated up using the factory Explorer front dress and fan.

 

[DirtDonk]

I’ve got a question that I don’t think was touched on yet. If it has been, sorry for short-term memory loss!
But when you were idling and the heat came up, was the hood still up, or was it down?

 

[blade]

Thanks for your offer to help! I may take you up on it. Do you have a mechanic in town that you trust? I know I'll need one going forward, even if I get this fan thing worked out now.

I mostly work on my own vehicles so I don't personally have a mechanic. I spoke to a friend that I know who works with local mechanics, he recommends Angelos Auto 505-795-9096.