cooling issue, runs hot only at highway speeds

[DonsBolt]

Hey guys I saw 1969Sports thread about his Bronco running hot when he exits the highway. I didn't want to jump onto his thread, as I have the opposite issue. Around town, in stop and go traffic or under 65 MPH mines runs nice and cool. Though as soon as I get up to 70 MPH or above the temp creeps up.


My setup Toms Alluminum radiator, clutch fan, shroud, 180 degree thermostat in the summer, 195 in the fall/spring. If I run the 195 in the summer it will stay right at 195 under 65 mph, but jump up to 210 or higher on the higway. With the 180 once the outside temps get warm,will get to about 195-200 on the highway. It has done the same thing when I was carbed, and with the fuel injection, and I know my truck runs on the richer side, so don't think it is a lean fuel mixture issue.

As soon as I slow down, it drops back to normal

I then saw Steve posted a link with tons of info about cooling systems. I read this part and got me thinking

Some fan shrouds also include vent flaps which open at high vehicle speed to allow extra air to flow thru the corners of the radiator not sufficiently served by the fan blades. Equally (if not more) misunderstood is the bumper valance. Not merely a cosmetic addition to reduce approach angle - on some vehicles, it is critical to engine cooling. The air-damming effect it produces at high speeds results in a slight vacuum under the engine bay which dramatically increases airflow through the radiator. Without the bumper valance, air can strike the front suspension & bounce up into the engine bay, blocking the radiator's airstream. This same effect may be noted if the vehicle is lifted significantly, or if the hood is left open on the safety catch, or if the hood is vented incorrectly for the vehicle's aerodynamic flow.


I am now wondering if one of these issues might be my problem. I do have a open front hood scoop, but have taped the front shut, with no help on the highway, so I am thinking maybe I am getting a air damming effect with my lifted truck.

I am wondering if anyone else has the sam issue I am having, and what you did to resolve this issue. I am getting a little tires changing thermostats twice each year

 

[blazinchuck]

im wondering if you clutch fan is worn out? mines been holding really good lately after modifying the rad support(moved it forward to add elec. fan in front and more space between water pump and rad.

creeping temps could be a loss of air flow over,under,and around the rad. also...ive seen some high flow pumps cause issues at higher speeds...like the water is flowing too fast to actually cool

 

[DonsBolt]

I don't think it is the clutch fan, as I replaced it last year under warrantee
I am running a stock water pump, so I am thinking I am loosing airflow as the speeds increase

 

[Viperwolf1]

I think a bigger issue than airflow is the horsepower being produced to push the Bronco at the higher speed. More horsepower is required especially with more lift and bigger tires. More horsepower means more heat is generated. You might be at the limit of the stock sized radiator.

 

[blubuckaroo]

It sounds more like a coolant restriction of some sort. Pinched hose, bad thermostat, plugged radiator, head gasket on wrong. Are you running a reversed water pump on the origonal type timing cover? That will hurt your coolant flow at speed.

 

[blazinchuck]

i can see your point viper, however were only talking 3.5 and 35's...im running 5.5 and 33's right now til i install the 3.5...i have a bcb fixed fan,stock rad,stock 5.0 and it runs sweet and cool.

do ya have a large winch in front of the grill don? hard to tell from the avatar
how close is the fan blade to the rad?

 

[DonsBolt]

It sounds more like a coolant restriction of some sort. Pinched hose, bad thermostat, plugged radiator, head gasket on wrong. Are you running a reversed water pump on the origonal type timing cover? That will hurt your coolant flow at speed.

well fresh (4 years ago) ford racing crate motor, so doubt a head gasket issue, the radiator was new then, tried a few differnt thermostats, so don't think those are my issues
Stock rotation water pump, well I belive it is, which was also fresh just before I intalled the new crate motor. I did reuse it though

I think a bigger issue than airflow is the horsepower being produced to push the Bronco at the higher speed. More horsepower is required especially with more lift and bigger tires. More horsepower means more heat is generated. You might be at the limit of the stock sized radiator.

i can see your point viper, however were only talking 3.5 and 35's...im running 5.5 and 33's right now til i install the 3.5...i have a bcb fixed fan,stock rad,stock 5.0 and it runs sweet and cool.

do ya have a large winch in front of the grill don? hard to tell from the avatar
how close is the fan blade to the rad?

Did have a BB winch bumper last two years, but right now just a stock bumper, with no winch. Did it yesturday on my way home, maybe not as bad as with the winch, but still raised up to 203 degrees, and it want't even that warm yesturday


well hope I don't have to replace the radiator, but might come to that

 

[ransil]

I think 195 t stat years round would be Ok and 210 is an Ok temperature to run.

blocking leakage on the sides of the radiator will force mor air thru the rad and not around it.

back you timing down a bit.. get total around 32 max to see what that does

 

[Skiddy]

I think 195 t stat years round would be Ok and 210 is an Ok temperature to run.

blocking leakage on the sides of the radiator will force mor air thru the rad and not arounf it.

that is what i was thinking as well. mine runs 210 often and not a problem. efi's like the 195 t stat

 

[DirtDonk]

Even though a new/bigger/better radiator might fix it, I would optimize what you've got first. Then replace if you need to.

Air-flow:
Enclosing the radiator and grille top so that the majority of the cooling air is ducted through the radiator, rather than spilling around it (big issue with an EB actually) can make a big difference, as was mentioned above.
The air has to go through the radiator and then exit the underside of the engine compartment. A lifted Bronco has a very high pressure "dam" of air building up under there, so the faster you go, the less able it is to exit properly. Ducting/sealing the radiator area properly can help. So can hood vents. So can inner fender reliefs.
Hard to say if the sealing alone will do it, but you can easily set up a temporary air dam under the front bumper to see if it improves cooling even more.

Water-flow:
High-flow pumps were mentioned, and the "flowing too fast through the radiator" theory has merit, but I run a Flowkooler and only see temps rise ('71 w/stock radiator) at speeds in the 75 and up range going uphill with a load of camping gear in it. So even though it's a possible issue, I'd list it last.
Cavitation at high speed with a stock type pump is a bigger possibility I would think. A well designed impeller would normally eliminate that, but with most, it's a problem to consider.
If after testing different things, you feel that coolant is being pushed too fast through the radiator too fast to fully evacuate it's heat, a larger water pump pulley might do the trick. Or, a more expensive, but possibly more effective option, might be a double-pass radiator (or triple pass, or whatever pass...) might be a good option since you're thinking of a new radiator anyway. They're more efficient typically and getting even flow through the tubes and keeping the coolant in the radiator longer.

I'm sure there are probably more ideas, including different radiator designs, but these will get you going and seem to be very effective at optimizing air and coolant flow.

Good luck. Running hot sucks. But if it stays at 210 or below, you don't really have a big issue. It's when it goes over the 220 mark consistently that you really have to get busy.

Paul

 

[bmc69]

that is what i was thinking as well. mine runs 210 often and not a problem. efi's like the 195 t stat

Same here...I consider the normal temp range on my 408 to be between 195 and 210 also. I never see 210 on the highway though..only when working the engine hard at trail speeds.

I will add this to cloud the issue though...when I briefly ran a large electric puller fan..that setup overheated pretty badly at highway speeds only.

But I've been running the oversized 460 pickup truck fan with matching thermostatic fan clutch for about 6 years now with no issues.

 

[DonsBolt]

Even though a new/bigger/better radiator might fix it, I would optimize what you've got first. Then replace if you need to.

Air-flow:
Enclosing the radiator and grille top so that the majority of the cooling air is ducted through the radiator, rather than spilling around it (big issue with an EB actually) can make a big difference, as was mentioned above.
The air has to go through the radiator and then exit the underside of the engine compartment. A lifted Bronco has a very high pressure "dam" of air building up under there, so the faster you go, the less able it is to exit properly. Ducting/sealing the radiator area properly can help. So can hood vents. So can inner fender reliefs.
Hard to say if the sealing alone will do it, but you can easily set up a temporary air dam under the front bumper to see if it improves cooling even more.

Good luck. Running hot sucks. But if it stays at 210 or below, you don't really have a big issue. It's when it goes over the 220 mark consistently that you really have to get busy.

Paul

Thanks for the tips, and after reading the tech article I posted, I am thinking it is the high pressure under the truck that is causing my issues. I agree I am not concerned about running at 210 degrees, I am just concerned about it running hot on the highway. I can idle all day or run in stop and go traffic all day, and the temp never moves. If I could keep the temp between 195-210 with a 195 thermostat I would be a happy camper, but if I try to run the 195 thermostat in the summer, it will go past 210 at speeds of 70 or higher. If not the way people drive around here will get runned over if I drive to slow

I will try experimenting, and see if I can funnel the air into the radiator better, and figure how to reduce the high pressure under the truck
thanks for the advice

 

[jw0747]

trade in the clutch fan for a rigid blade and your temp will hold steady. nothing wrong with running at 210 degrees. my GMC truck won't run right unless it's clocking 210 all the time. Ford efi engines need 195 thermostat year round. changing it back and forth must be a pita.

 

[TBS-POPS]

Don, check to see that both your radiator hoses have the internal springs in them to keep them from collapsing. I have seen that to be an issue at high speed running. I have a stock 3 core,flex fan, winch, hood scoop with 5.5 lift on 35's and never have a cooling issue.

 

[DonsBolt]

Don, check to see that both your radiator hoses have the internal springs in them to keep them from collapsing. I have seen that to be an issue at high speed running. I have a stock 3 core,flex fan, winch, hood scoop with 5.5 lift on 35's and never have a cooling issue.

Could it be that simple
I do have a internal spring in the lower hose, but not the upper hose
I will have to look into where to get one of those springs for the upper hose??
Any idea where to find one??

would be funny if all this time was as simple as a little spring

 

[DirtDonk]

Could it be that simple
would be funny if all this time was as simple as a little spring

Of course it could. This is an EB after all!
And that's why they make all those other expensive and time consuming alternatives. Just so you can go through all that, BEFORE you find out it was the first thing you thought of, or the thing the 9 year old kid from across the street told you his older brother's Camaro had a problem with, or the thing your Mom suggested, but that you immediately eliminated as a not possible piece of mom-nonsense.

Heck, otherwise Bronco life would be easy!

Paul

 

[MY 4 BY]

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.

 

[DirtDonk]

For this summer season I have removed the A/C condenser, and I'll see if that helps.

Makes sense. Heck, you've done almost everything else! Let us know if that makes any difference. Have you had any initial results to report at this point?
Sounds like you're the test-bed for all the tricks that have been thought up so far.

Did you have the A/C condenser installed before the Explorer serp stuff? If so, and you didn't have any issue, I would think that's not it either. But hey, it's already off, so might as well run with it.

If it happened strictly after the new setup, then it sounds like a water flow issue to me. The fan changed too of course, so there was still a change in air flow patterns, but so did the hose layout and the pump design. Either the pump is pumping too much, a hose is collapsing, or the radiator is just slightly insufficient to be dialed in to the Explorer pump.
On the opposite side of that coin, could it be a bad pump? Is it new, or was it original to the Exploder? If original, I wonder if the impeller was worn down? Seen it happen, just not that often on late model stuff.
The Explorer pump should be slightly more efficient in flow than the old Bronco pump (I believe, but don't know for a fact) and was intended to spend most of it's life and much lower rpms and pushing coolant through a modern radiator of respectable size. Lots of surface area, but only a couple of rows of larger tubes if I remember.
What engine speed are you running at freeway speeds? If geared low, and you're running in the 3000 rpm range at 70 or so, maybe that's it?

So if that turns out to be the case, I guess slowing the pump down, increasing the efficiency of the radiator, or making sure that one of the hoses is not collapsing would be your next step.
If the A/C condenser went on at the same time as the rest though, it'll be interesting to hear how it goes with your testing.

Good luck to both of you.

Paul

 

[blubuckaroo]

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

 

[00gyrhed]

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.