cooling issue, runs hot only at highway speeds

[jw0747]

I'll be watching this thread closely, as I have the same issue. Runs at 190 in traffic, even with the A/C on, but climbs to 220+ at freeway speeds. I have the Explorer front dress, and even have the optional fan shroud extension (per the tech artical) I didn't have overheating problems on the freeway, till I installed the Explorer stuff.I tried running with and without the hood, with/without the air dams (panels between the grill and core support) 180 & 190 degree thermostats, backed off the timing, but non of that has helped. I have the sides of the rad. sealed to force the air folw through it. I feel that the fan clutch is working, because I can hear it kick in. For this summer season I have removed the A/C condensor, and I'll see if that helps.

is there a particular reason why you fan clutch guys are intent on running that type fan and don't want to even try a rigid blade fan? installing a rigid blade fan and a metal shroud has cured many overheating issues incl mine and my best buddy's.

 

[MY 4 BY]

Dirt Donk
The A/C system was on the Bronco, with the old 302 front dress, and the freeeway heating problems started after I installed the Explorer stuff. I used the Explorer front timing cover, and a new water pump.Engine RPM is 2500 -3000 @ 65MPH with 3.50 gears...same gears that I had with the 302 front dress.

 

[MY 4 BY]

When you put on the serp set-up, did you use the 302 timing cover?

Yes I did.

 

[MY 4 BY]

Check your timing before you do a bunch of work. make sure the vacuum advance daiphram in hte distributor is good if you are running one that has it. Mine use to get hot fast on the highway until I switched distributirs and got the timing right. I was timing it by ear and paying no attention to the vacuum advance.

That's good infromation, and I did test the dist. advance with my Mity-Vac vacuum gun and the advance plate moves correctly.When I first had the problem, I played with multiple timing drgree settings/adjustments, but it didn't make any difference.

 

[blubuckaroo]

Yes I did.

I think the stock 302 timing cover is made for convetional rotation and not for the reverse rotation of the serp set-up. Your flow may be restricted by the cover.

 

[Viperwolf1]

I think the stock 302 timing cover is made for convetional rotation and not for the reverse rotation of the serp set-up. Your flow may be restricted by the cover.

The explorer serp can only be used with the explorer timing cover.

 

[ransil]

anything over about 20 mph and a fan is of no use, "ram air" should be taking over

 

[DirtDonk]

Interesting thought ransil. Normally, I'd say that EB's don't do "ram air" very well. I'm thinking that, while you're correct for most modern vehicles, our Broncos have a hard time letting air get pushed through the radiator just by air pressure alone, without some added help. Especially a lifted Bronco.

Then again though, maybe it's not the generally bad air flow through the radiator that's been at fault in all these cases. Maybe it's the mechanical fan that's actually impeding that flow at higher speeds!!!!!!!
Sounds funny, but I'm thinking that it ain't so far-fetched as it sounds. It could be be setting up a literal wall of air that makes it hard to get consistent flow, or it could actually by cavitating, and wreaking all sorts of havoc on air flow.

Sounds like time for another experiment MY 4 BY!

Maybe if we took the fans off completely, more air would flow through at freeway speeds. Leave the drive working, but pull the mechanical fan off completely, to see how it cools on the freeway.
I might even try that myself, just for the heck of it.

That's assuming of course, that you can get to a freeway without having to take too many surface streets to get there.
But heck, we've done so many other types of comparisons of one thing or another over the years, to see what works and what doesn't, that this isn't too out of line with that thinking.
Maybe the best bet here though, would be for one of you that's sporting a full electric fan setup to try it. Just run with the fan switched off for a bit to see what's up.
If anyone has already done that, and found that it doesn't work, let us know. I'd sure be interested to hear.

Paul

 

[DirtDonk]

Any update for yours DonsBolt? Had any time to try some different configurations?
Don't want to forget you started this!

Paul

 

[Skiddy]

Maybe the best bet here though, would be for one of you that's sporting a full electric fan setup to try it. Just run with the fan switched off for a bit to see what's up.
If anyone has already done that, and found that it doesn't work, let us know. I'd sure be interested to hear.

Paul

I have done it and will raise a little bit but not a whole lot, i think anything under 40 mph it would start to get over 210, if i didn't have the fan there helping block the air flow maybe even better. but it's been a while since i done it. it is hard to get air flow out of basically a engine compartment like a box

 

[DirtDonk]

Good info Skiddy. Thanks!
How fast, and how far did you go?

Paul

 

[Skiddy]

Good info Skiddy. Thanks!
How fast, and how far did you go?

Paul

was going a little over 50 on back roads about 10 miles, going to my brothers house to put my Taurus fan on because the two cheapies that were on there stopped working and never cooled good anyway. I think if maybe there was a dam around the radiator to force air just through it may have done even a little better

 

[cbford]

I had this problem too, cool in traffic; heated up on longer runs.

I thought it was the flex fan since it looked a bit sketchy. So I put in a clutch/fixed blade. Only change I made at time. After that, it made much less fan noise, ran cooler in traffic but still heated in longer runs.

One day I was a bit cranky about how hot is got, pulled over and opened the hood.... and sure enough the upper hose was flat as flat can be, just past the curve at the radiator end. Bought a new Gates hose, no more problem.

 

[MY 4 BY]

blubuckaroo
I answered your question incorrectly...sorry. I REPLACED the 302 timing cover with the Explorer timing cover.

 

[MY 4 BY]

cbford
What radiator do you have...coolant return on drivers side or pass. side? I using the original Bronco rad. with coolant return on the drivers side, and the crossover tube to the pass. side for the suction to the water pump.

 

[Rustytruck]

Try driving on the highway without putting it into over drive and see if it still overheats. With your 35" tires and 456 gears your great for a stock engine but with overdrive you may not be so great. You may have enough Hp to pull it but creating so much heat the water pump may not be turning fast enough to feed the radiator. By gearing down you reduce the load and spin the motor faster increasing flow in both the fan and the pump. If this works you may need to change the water pump pully to a smaller diameter.

 

[ransil]

Interesting thought ransil. Normally, I'd say that EB's don't do "ram air" very well. I'm thinking that, while you're correct for most modern vehicles, our Broncos have a hard time letting air get pushed through the radiator just by air pressure alone, without some added help. Especially a lifted Bronco.

Then again though, maybe it's not the generally bad air flow through the radiator that's been at fault in all these cases. Maybe it's the mechanical fan that's actually impeding that flow at higher speeds!!!!!!!
Sounds funny, but I'm thinking that it ain't so far-fetched as it sounds. It could be be setting up a literal wall of air that makes it hard to get consistent flow, or it could actually by cavitating, and wreaking all sorts of havoc on air flow.

Sounds like time for another experiment MY 4 BY!

Maybe if we took the fans off completely, more air would flow through at freeway speeds. Leave the drive working, but pull the mechanical fan off completely, to see how it cools on the freeway.
I might even try that myself, just for the heck of it.

That's assuming of course, that you can get to a freeway without having to take too many surface streets to get there.
But heck, we've done so many other types of comparisons of one thing or another over the years, to see what works and what doesn't, that this isn't too out of line with that thinking.
Maybe the best bet here though, would be for one of you that's sporting a full electric fan setup to try it. Just run with the fan switched off for a bit to see what's up.
If anyone has already done that, and found that it doesn't work, let us know. I'd sure be interested to hear.

Paul

I did gather up a few pressure & temperature sensors at one time and was going place them in different areas in and around the radiator and see what kind of pressure & temps I was seeing, pretty much like most of my projects they only get 3/4 done.

 

[blubuckaroo]

I'd take the hoses off the radiator and check the flow through it with a good garden hose. I've seen excess RTV sealant clogged up the side where the coolant leaves the intake manifold and you couldn't see a problem looking into the filler neck.

 

[cbford]

My4 - Stock radiator. I am guessing that my issue with the top hose going flat had something to do with the system pulling water back into it from the overflow tank. But I had already checked the tank, line to radiator filler neck and radiator cap so I knew they were good.

So apparently the soft, but not totally failed upper hose caused my problems by collapsing when negative pressure assiciated with overflow recovery came along. I guess I could have tried a lower pressure cap, but I am comfy with my 18psi Stant lev-r-lok.

 

[DirtDonk]

It can also occur when the pump is pulling hard on the lower (intake) hose, and there is a restriction in the upper (inlet) circuit. Likely caused by a low-flowing thermostat or perhaps even a restriction in the hose. Though that probably doesn't happen that often, I wouldn't think.

It probably doesn't really take much of a difference in pressure to collapse a really soft hose though, so just about anything could do it when the hose gets old and soft enough.

Paul