TF running hotter on highway than in-town.

[roger55]

Anyone else experienced this?

I'm trying to figure out what is going on and what to do about it.

I've got a 305 TPI engine with a 180 Stant thermostat that I can verify that it does open at 180.

The radiator is a new American Eagle (Champion)with 2 -1" cores and an internal tranny cooler and is advertised to cool up to 650HP
It has a 16" Maradyne electric fan mounted to a shroud covering 100% of the core. The fan switch turns the fan on at 190 and I've verified that. The differential is low though and it will cycle it off after cooling only about 1 degree.

I've sealed around the radiator and condenser well so air entering the grille area cannot go over the top or around the sides.

The truck has Vintage Air A/C and all the testing I've done is with it turned on and the ambient temperature at 95 degrees.
After some extended in-town driving, the water temperature runs at 192-196. Getting on the highway and running at 65MPH (2000 rpm), it will warm up to 210 after about 10 miles. I Transitioning back to in-town driving, the temperature will come back down to 192-196.

These aren't damaging temperatures but what concerns me is a hotter day maybe up to 106-110 and pulling a highway grade. With what I've got, I have no room for the extra heat those things would do.

Here's some photos of my setup and how I sealed it:

During initial mockup with a good angle to see the shroud and fan:


During final assembly:


Foam seal and tape to insure air coming thru the grille can't go over or around the condenser/radiator:



Underneath side. Another seal between lower radiator tank and the splash pan:


Header panel back on.


Here is a snapshot output from my ECM running at 65 MPH. Note: The speed is wrong in my ECM and the temperature shows 196 because I had just got on the highway and it hadn't warmed up from there yet. The mixture says lean but it alternates back and forth from lean to rich constantly. I believe that's what it's supposed to do.
And btw, my dash temperature gauge is right on the money with what the ECM reports.

[57chevyman]

not sure if this is relevant to you, but when i first got my truck, i was sure it was running hot and i was scared to drive it and overheat it.. but it turned out that the engine wasnt running hot at all. in my case the temp gauge wasnt grounded good enough and it was reading higher than the actual temp. if you havent already, i'd confirm the temp is what the sensor is telling the computer

[roger55]

Originally Posted by 57chevyman

not sure if this is relevant to you, but when i first got my truck, i was sure it was running hot and i was scared to drive it and overheat it.. but it turned out that the engine wasnt running hot at all. in my case the temp gauge wasnt grounded good enough and it was reading higher than the actual temp. if you havent already, i'd confirm the temp is what the sensor is telling the computer

Thanks for your response.
The new Autometer electric gauge is spot on with the ECM reports. When starting cold, I can see the water temperature as the thermostat opens. Goes to 180 and opens, cools down a little and then rises back as the thermostat throttles it.
When the temperature reaches 190, the fan starts. Right where my block-mounted fan switch was advertised as cut-in temp.
Since nothing is conflicting, my confidence is pretty much 100% on the reported temperatures.

[FirstNation]

My brother had the same problem, around town driving running hot. He had the same setup as you, a puller electric fan and the AC condenser, both blocking the flow thru the radiator- he replaced the AC condenser with a unit that goes under the car and moved the fan to where the AC condenser was. That solved his problem. Extra bonus was making the fan a pusher rather than the less efficient puller..

The Chevy truck hood isn't vented up front like a GMC hood, and that header panel sure doesn't look like it lets any airflow thru. Appears that you're only getting airflow mostly to the middle area of the radiator, and the puller fan is also probably struggling to get air as well when it kicks on.

[69chevytrucker]

not to change the subject but was i hard to put that engine in how much did you need to take out of the third gen to make it work i have a third gen and i was thinking of doing the swap into my 69

[CMACDONALD1]

Do you have enough room to run a clutch fan? I was having overheating problems with my car and changed the electric fan setup I had a couple of times. Decided to ditch the electric fans and go back to a mechanical fan and all my problems went away. I know lots of guys run electric fan setups but I hated being paranoid about overheating. This is my 2 cents anyway...

[roger55]

Originally Posted by 69chevytrucker

not to change the subject but was i hard to put that engine in how much did you need to take out of the third gen to make it work i have a third gen and i was thinking of doing the swap into my 69

I've detailed everything with that in my build thread. It should be helpful to you. I take photos of everything. If you have follow up questions about it, feel free to ask me there.

[Speedbumpauto]

A non running fan is pretty high resistance to air flow at highway speed. An interesting experiment would be to tap into the fan circuit and manually turn on the fan at a low temp then drive it on the highway and see if you experience the same problem. One of the slickest things I ever saw was on a VW liquid cooled Rabbit.(or such) It had little doors in the shroud that would open up as air flow velocity increased on the highway and at low speeds they were closed so the fan drew all the air through the radiator. I've thought of modifying my shroud as I'm fighting the same problem here in AZ. I'd go to a clutch fan in a heartbeat but with the big block, I don't have the room.

[dwcsr]

The fan and shroud you have is very restrictive. You would be better off with no shroud with that fan or change it to a fan that's open in the back (spal) and larger.

Option two is put some air flaps in the areas that are flat sheet metal so at highway speed the air blows through and at low speed the flaps pull shut and direct the air through the fan. Some Camaro fans use the flaps. If the engine is hotter at hi speed its a clear indication you don't have enough air flow.

[mr48chev]

I'd say Speedbumpauto hit it right in post 8. While that fan will probably suck a cat though the grill at idle or low speed the fan and shroud may be blocking air flow a bit at road speed. With the perfectly flat and square to the radiator surfaces of that pretty shroud may be causing a buffeting effect at speed when the air hits it at 70 something causing a turbulence that isn't letting the air flow smoothly though the radiator and through the hole in the shroud.

You only have between an inch and an inch and a half between the radiator core and the flat surface of the shroud from what my eyes see and when the air flow hits it going down the highway it is hitting the flat surface and bouncing back and smoothly flowing to the hole. With the fan pulling air at low speeds you don't have that problem because the fan is somewhat directing the air flow.

Production fan shrouds for most rigs including the ones on our trucks are tapered from the edge to the hole to help air flow.

[roger55]

Originally Posted by dwcsr

The fan and shroud you have is very restrictive. You would be better off with no shroud with that fan or change it to a fan that's open in the back (spal) and larger.

Option two is put some air flaps in the areas that are flat sheet metal so at highway speed the air blows through and at low speed the flaps pull shut and direct the air through the fan. Some Camaro fans use the flaps. If the engine is hotter at hi speed its a clear indication you don't have enough air flow.

Agree that it would be restrictive if the fan weren't running. The question is would it flow as much air with the fan running as it would if it and the shroud weren't there on the highway. My feeling is that it does flow as much when the fan is running.

The fan is a 16" and I haven't seen larger ones. Two 12" fans will fit but the area of two 12's is barely more than a 16 and if you account for the addition fan hub, it's probably about equal. Maybe two 12" flow have more total cfm though.

I don't care for those rubber flaps much. Seems to me they wouldn't work very well. I wish someone made some nice aluminum shutters of some type. I think those OEM ones where hinged plastic shutters.

I wonder if these OEM ones to assist when the ECU commands the fans to shut down above a certain speed. Then, I can see the merit to them. Otherwise, it comes back to that question about the total flow when the fan is running.

I keep coming back to the possibility the radiator itself doesn't have the capacity I need. At 95 ambient, the truck runs about 195 which is 15 degrees warmer than the thermostat temperature (180). That's warmer than I want it to be too.

If I have to put money into this thing to solve my issue. I'm going to go all out and spring for one made by AutoRad.
At 32" wide, it's wider than anything else out there.
It comes with the Aluminum core support and overflow bottle. I'd get the shroud, dual fan setup and condenser that they offer. It would be a $2K deal. Just want to be sure there isn't something simple I've overlooked. But I don't want to nickel and dime a bunch of times trying stuff that may or may not work either.

[roger55]

Originally Posted by mr48chev

I'd say Speedbumpauto hit it right in post 8. While that fan will probably suck a cat though the grill at idle or low speed the fan and shroud may be blocking air flow a bit at road speed. With the perfectly flat and square to the radiator surfaces of that pretty shroud may be causing a buffeting effect at speed when the air hits it at 70 something causing a turbulence that isn't letting the air flow smoothly though the radiator and through the hole in the shroud.

You only have between an inch and an inch and a half between the radiator core and the flat surface of the shroud from what my eyes see and when the air flow hits it going down the highway it is hitting the flat surface and bouncing back and smoothly flowing to the hole. With the fan pulling air at low speeds you don't have that problem because the fan is somewhat directing the air flow.

Production fan shrouds for most rigs including the ones on our trucks are tapered from the edge to the hole to help air flow.

Yes, there's 1 3/8" clearance in there.
You guys might be right. I can test it on the highway without my shroud (and fan) on there and see what temperature it runs.
Let's say you are right and it does run cooler.

Then where is my best place to put money? I think it would be impossible for me to get a rounded shroud in there with either an electric or clutched mechanical.
Kind of makes me lean to the expensive AutoRad that I like the looks of.
Btw, I have the AutoRad setup in my '55 Bel Air. Runs between the fan cut-on and cut-off temperatures (185 to 190) all summer long in any driving condition.

[mr48chev]

Out of curiosity I went out and looked at the stock fan shroud on the radiator out of one of the 1-1/2 tons I bought a couple of years ago.

The surface of the shroud is flat but it sits a tad over 2 inches off the core.


Also the hole for the fan is much larger at a bit ofer 18 inches and the measurement from hole to top is 2 inches


It's about 6 inches from hole to corner at the top corners.


While the stock shroud is flat it doesn't block near as much air flow on the road as yours might.

I was just pondring, do you have room to move the shroud back away from the core even a half inch or inch? that might open up the air flow a bit at speed.

[roger55]

Originally Posted by mr48chev

Out of curiosity I went out and looked at the stock fan shroud on the radiator out of one of the 1-1/2 tons I bought a couple of years ago.
The surface of the shroud is flat but it sits a tad over 2 inches off the core.
Also the hole for the fan is much larger at a bit ofer 18 inches and the measurement from hole to top is 2 inches
It's about 6 inches from hole to corner at the top corners.
While the stock shroud is flat it doesn't block near as much air flow on the road as yours might.
I was just pondring, do you have room to move the shroud back away from the core even a half inch or inch? that might open up the air flow a bit at speed.

That hole on your stock shroud is one inch larger than mine all the way around. Not a lot of difference there but in square inches it's significant. I still think the question is is how much air my electric fan moves. It doesn't run all that cool in town either.
The other thing is that if my truck didn't have A/C and condenser was gone, I'm pretty much convinced the whole issue isn't there.
Even with the A/C turned off, the in-town temperature goes to 190 and the fan cuts off. From 196 with it on, it goes to that 190 in less than a minute.
Again, all 95 degrees ambient.

And to answer your question. No, I can't move my shroud out at all. The air intake pipe is very close to it and there's only about 1/2" from the back of the fan hub to the water pump pulley bolts.

Pretty much any change I make large or small is going to require some work and money.

[Hampshire]

+ + on the general theme of comments by dwser & mr48chev....

I have a similar setup on my 49 ( & running a Spal fan) & I have talked to a couple other forum members (wish I could remember who) who had the same problem - heating up at highway speeds. The problem was always traced to the restriction of airflow at high speeds at the base of the shroud - which is very close to the radiator surface. The solution was to use a stepped drill bit and drill a series of holes in a pattern at the lower corners of the shroud.

The guy who helped me on my build does vintage race cars, often sets them up with electric fans and most often has to drill holes in the bottom of the shroud to cure high speed heating problems.

[roger55]

Originally Posted by Hampshire

+ + on the general theme of comments by dwser & mr48chev....

I have a similar setup on my 49 ( & running a Spal fan) & I have talked to a couple other forum members (wish I could remember who) who had the same problem - heating up at highway speeds. The problem was always traced to the restriction of airflow at high speeds at the base of the shroud - which is very close to the radiator surface. The solution was to use a stepped drill bit and drill a series of holes in a pattern at the lower corners of the shroud.

The guy who helped me on my build does vintage race cars, often sets them up with electric fans and most often has to drill holes in the bottom of the shroud to cure high speed heating problems.

If that is an issue, I still have the issue that it still might not be where I want it to be for around town too.
So then the question is one of whether my fan is powerful enough or whether I require a radiator with more cooling capacity.

Interesting about the holes as a cure. It seems like while sitting or when traveling slowly, the fan would pull hot air in from the engine compartment and make things worse. I'm reluctant to try that.

I wish there were 4" electric fans available. I would have room for one in each corner of the shroud.
Like I said, I don't care for the idea of rubber flaps but if there were nice shutters or a hinge flapped louver of some type, it would be something easy to try.

Btw, this is the fan I'm running:
http://www.maradynehp.com/m162k.html

2170 cfm rating at zero static. On the highway the pressure should be positive so the flow should be more than that.

[Hampshire]

Interesting about the holes as a cure. It seems like while sitting or when traveling slowly, the fan would pull hot air in from the engine compartment and make things worse. I'm reluctant to try that.

Myself and all those I mention use pullers - not pushers ( which seems to be more the CW).

My radiator is from PRC http://www.prchotrod.com/ They have a lot of customers out there in restomod truck world.

... They are in the USA and make their radiators for vehicle specific hot rod applications. Their radiator (made for my truck) with the 16" Spal puller fan is per their recommendation. I run at 180 all the time & run the fan all the time. I had the temperature sensitive switch system and changed it out for an on/off switch. (just my thing, but simpler & less electronics) Haven't decided whether to drill holes or not as at the worst, I've only seen a 5 degree rise at sustained highway speeds.

[roger55]

Originally Posted by Hampshire

Myself and all those I mention use pullers - not pushers ( which seems to be more the CW).

My radiator is from PRC http://www.prchotrod.com/

... They are in the USA and make their radiators for specific hot rod applications. Their radiator (made for my truck) with the 16" Spal puller fan is per their recommendation. I run at 180 all the time. Haven't decided whether to drill holes or not as at the worst, I've only seen a 5 degree rise at sustained highway speeds.

Yeah, pullers. That would have add possibility of recirculated heated engine compartment air through open holes in the shroud around the fan. Thus why flaps or shutters are used.

Do you have A/C? As I said in my earlier post, I'm pretty convinced I wouldn't have an issue with my setup if I didn't.

[69chevytrucker]

just a little fyi i have owned many camaro's and T/A's and i have a T/A right now and i have to say they all run very hot at highway speeds it has alot to do with the air flow if you look at how GM slopes the rad in the birds its to make more air cover more sq in of the rad and the elc fan is never enough most guys that own camaros and T/A's put 2 fans on to help cool them if your going to use a camaro engine i suggest asking this question on a camaro forum you might get the answer you are looking for some smart guys there too lol

[diceman50]

Originally Posted by roger55

Agree that it would be restrictive if the fan weren't running. The question is would it flow as much air with the fan running as it would if it and the shroud weren't there on the highway. My feeling is that it does flow as much when the fan is running.

According to Ron Francis this is not true. They found that cooling increased at 55-60 MPH when the fan is turned off. They even sell a switch to do just that. (CS-07 cooling fan shutdown kit)

Also I have seen this problem cured more than once with flaps in the corners as has been previously suggested . I'm not sure why you object to them, but it's your truck. It seems like a better solution than a new $2K radiator/fan combo.

[roger55]

Originally Posted by diceman50

According to Ron Francis this is not true. They found that cooling increased at 55-60 MPH when the fan is turned off. They even sell a switch to do just that. (CS-07 cooling fan shutdown kit)

Also I have seen this problem cured more than once with flaps in the corners as has been previously suggested . I'm not sure why you object to them, but it's your truck. It seems like a better solution than a new $2K radiator/fan combo.

It's the rubber flaps I object to. If they made some nice hinged shutters/louvers, I think they would work and look better.

I guess I am coming around to that the idea that it doesn't flow as well with the electric fan and shroud on the highway even if it's running. But, the flaps wouldn't do anything for me around town and I don't like those temps either. That's what makes me lean to going a whole other route with this. Even if I was able to improve the in-town/highway difference I have now, I still think my radiator cooling capacity is lower than I want it to be with the airflow I can get with a 16" electric fan. I guess if it were easy for me to put an 18" mechanical clutch fan on there, I wouldn't object to trying that. But, I'd have to buy the stuff and cut the hole in my shroud larger by 1" all the way around. I don't have one to try either and am not convinced it would improve my around town temperatures. Could even be worse. Not sure I want to deal with the trial and error stuff. Like I said, I have the AutoRad setup in my '55 Bel Air. It would be a spend-the-money and do-the-work thing and I'm confident I'd never have any issues to deal with heat again.

Btw, I have 2 things on order right now to make sure I don't have any water flow problems. A FlowKooler Robertshaw 180 high-flow thermostat to replace my standard style Stant and a spring coil for my lower radiator hose to make sure it's not collapsing on me. I don't think those things are a problem but I just want to eliminate the possibilities.

[diceman50]

P.S. Spal does make a 4 inch fan. Part # 30103018.

[diceman50]

By the way "Nice Truck".

[roger55]

Originally Posted by diceman50

P.S. Spal does make a 4 inch fan. Part # 30103018.

Thanks for the compliment!

I had found that Spal 4" fan just a little while ago. I went out and looked at my truck afterwards. I can't do all 4 corners but I could do 3 of the 4. They are 150 CFM each so that would give me 450 more. They run about $60 a piece so that would be a couple hundred investment. But would it solve my issue(s)? No one knows until it's tried.

[diceman50]

They should serve the same purpose as the vents by eliminating the stagnant airflow in the corners. Also, I found the Spal 4 inch fans on Amazon for $40 each.

Amazon