Cooling at idle issue

[Eds56]

Hello Tri-Fivers,

I have a 56 Bel Air, running a 327 SBC with a Big Cam, Holley 4Brl, 180degree Thermostat & 4 speed Tranny. The original radiator was recently rodded and cleaned, it is in the v-8 position without a fan shroud. Currently I have a Derale Performance racing type fan (which I think is part of the problem).

Running down the road, the temp stays at or below 180, but when I am stopped in traffic the heat hand and gauge both rise rapidly to above 200+ (SunPro aftermarket gauge & OEM dash gauge), once I start moving a few miles down the road it settles back down. Since just always driving and never stopping to idle and or ever getting stuck in traffic is NOT a reasonable option, I figured I would ask those who have already been there and done that for some input.

Personally, I think I need to replace the FAN and add a fan shroud..... as I obviously need to get the air flow moving correctly. My question to you is, What specific manual Fan and or shroud have you had success with???

By the way, I would rather NOT move radiator to 6cyl. position therefore I'm NOT sure a clutch fan will work for me.


Thanks in advance,
Ed

[markm]

You have answered your own question and described my 56 BA ht cooling issues. I am currently running a 6 blade Speedway fan with shroud on my .060 over 350. No need to apologize to me on the 6 cyl position as I hate the look.

[chevynut]

Yes clearly you need to get more air moving through the radiator at low speeds. If you can't fix it with a good fan and shroud, I'm not sure you have many options with the stock radiator. An electric pusher fan might help, but I don't like the look of them in front of the radiator. Personally I like the crossflow radiators in front of the support a lot better than the look of any stock radiator. The nice thing is you can put a good electric fan behind them and get great cooling performance. It's just $$$.

[Eds56]

Thank You for the feedback Mark & ChevyNut,

I'm definitely starting with a new fan blade & shroud (with fingers crossed).

Honestly, I have not pushed it very much to see just how HOT it will max out at.... I'll make the changes above and see what that does for it first. Then progress to the next step.

[WagonCrazy]

Ed,
Sharing my experience with my 57 wagon here.
When I first bought it (7 years ago), it came with a 283, 3 speed column shift, and original "downflow" brass radiator. It had a vintage air system that included a "front side of radiator" mounted condensor. It had a waterpump mounted 6 blade fan.
In hot weather, stop and go, temps would rise above 200 as well.
Not enough air flow thru the radiator to allow the radiator to do it's job.
So I added a plastic shroud to the back of the radiator.
Not much help.

After finding these tri5 forums, and reading alot, I decided to spend money and upgrade to an all aluminum PRC crossflow unit, which included a new frame, crossflow radiator, a new AC condensor front mounted, and new dual Spal electric fans "rear mounted" in a custom aluminum shroud. It was about $1500 total, and more than solved the cooling problem.

I was planning to bling out my wagon anyway, so that was the start. A new 350 engine and automatic overdrive trans came later.

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Now, to answer your question:
If you don't want to spend that kind of money on a cross flow radiator setup, and just want to solve this heating at idle problem, what you need more than anything is better airflow thru your existing radiator at low speeds. A rear mounted "puller" electric fan setup with a shroud would be best in my opinion. (eliminate that waterpump mounted fan blade you have). The new electric fans can come with a shroud, are fairly thin (about 2 inches thick) and should mount up to the back of your existing radiator fine, once you remove the water pump-mounted fan blade. Danchuk or others in this industry sell them. Look online.

My dos centavos here...

[JT56]

Ed reminds me of my old setup. Had a .30 327 with 11:1 solid cam blah blah. Original radiator in the 6 cylinder mount, 180 thermostat with a 6 blade fan with an additional electric fan in front. I still had issues until I went with a cross flow with much more surface area. One thing to consider is timing and a lean condition. Yours sounds like surface area and airflow issue.

[Rick_L]

The answer as most have said is airflow.

Pusher fans are not a good choice, use only when in a money/time bind as a band aid deal.

You are limiting yourself with the radiator in the rear (V8) position because you don't really have room for a big mechanical fan and fan clutch, or even the long water pump setup. With the radiator in front you have so many more choices. Not to say you can't do it, it's just harder.

[Eds56]

Thank You for the feedback Wagoncrazy & JT56,

From what I've read lately, it seems the cross flow set up is very effective and may indeed be the where I end up at.

Today, I was fortunate enough that a local Tri-five guy, gave me a large GM 6 blade fan with the curved tips. I'm going to put it and a new thermostat in later this week. GREAT point (JT56) on the timing and Leanness of carb possible causes. I'll check that too. Just had the carburetor rebuilt not long ago and it does seem to run kind of lean, so that may be part of it as well.

Thanks again for all the replies

[Eds56]

Thanks Rick_L,

I hear ya and even agree that keeping the Radiator in the V8 position, limits my options. But I have to give it a try. Guess I'm just stubborn like that....lol.

[chevynut]

IMO opinion I wouldn't bother with a different fan unless you add a shroud. The shroud will probably help your airflow as much or more than any other fan would and I'm surprised to hear Paul say it didn't change his problem. Don't waste your time and money on a new thermostat...obviously the one you have is working correctly. A lower temperature thermostat won't fix this problem because a thermostat's purpose is to maintain a minimum temperature, not a maximum. And don't let anyone tell you that you need to restrict the coolant flow so it stays in the engine longer....that's BS.

It seems strange to me that so many guys have cooling problems at idle. It doesn't really matter how much peak power your engine puts out if it's idling because it's not generating much power doing that. In the old days we put big block chevy engines in these cars with the stock radiator with no cooling issues that I can remember.

If a good fan and shroud doesn't fix the problem, and you don't want to change the down-flow style radiator, I'd be looking at the condition of the radiator, water pump, fan, shroud, and just making sure everything you have is working the way it should and with maximum air flowing through the radiator. You might also take a look at your pulley ratio to make sure there's nothing weird going on there, causing the water pump to turn too slow. There are better down-flow radiators that don't cost as much as a crossflow too.

[Rick_L]

Ed if you can fit the 6 blade, curved tip fan in the space you have, that's probably the best you can do for a fan.

I agree with Cnut, you should go for a shroud too. There are shrouds available for the V8 radiator setup. You may have to cut on it to make it clear everything.

If that fails, get over the hangup of the radiator location and look. Put a crossflow and dual electric puller fans on it and enjoy your car.

[markm]

I have to agree with Cnut on the Shroud, they have been good for up to 20 degree drop at idle in my experience.

[JT56]

Make sure part of the fan blades are in the actual shroud. I have seen guys with both and there is a huge gap between the fan and shroud and still runs hot! Move the fan closer and fixes their problem.

[chevynut]

Good point JT. I think the fan should be at least halfway into the shroud for maximum effectiveness.

[Custer55]

I have suffered with the same issue on my 55 until recently getting it under control. I put in a better radiator (original style Dessert Cooler), electric pusher fan, fan shroud, electronic ignition with vacuum advance (Didn't do anything with the cooling but at least the engine would keep running with the temp over 220). All of these helped somewhat, but the thing that got things under control was a better flex fan with more aggressive blades. I also put on ceramic coated headers recently which has helped also. It seems the problem is the hot air just staying in the engine compartment when sitting at idle. If anyone has a car with a louvered hood, inner fenders, or even running the car without a hood it would be interesting to hear about their cooling history.
Thanks, Brian

[chevynut]

It seems the problem is the hot air just staying in the engine compartment when sitting at idle.

I have a hard time believing under-hood temps would affect the engine cooling that much. Most of the engine heat is rejected from the radiator, not the block. Also, the fan should be pushing hot air down and out of the engine compartment as more air is brought in. As long as the hot air isn't circulating back to the front of the radiator it shouldn't have much effect. This is one downside to the aftermarket hood braces with the holes cut in them. It can allow hot air to circulate back to the front of the radiator. The factory solid baffle was there for a reason.

The key to good cooling is to reduce the thermal resistance between the engine and coolant, and between the coolant and radiator surfaces for maximum heat transfer between them. That means the engine cooling passages and inside of the radiator need to be clean. You want high coolant flow rate to keep the radiator as hot as possible for maximum heat rejection and as much cool air as you can push/pull through it.

[Custer55]

Makes sense, I was just wondering if the design of the trifive chevy engine compartment doesn't allow enough air to flow through when the car is not moving since it seems like many of us have the same problem.
Brian

[chevynut]

I was just wondering if the design of the trifive chevy engine compartment doesn't allow enough air to flow through when the car is not moving since it seems like many of us have the same problem.
Brian

The tri5 engine compartment is a LOT more open and free-flowing than just about any new car is. There's a ton of room for air to escape. :)

[JT56]

I would say the different grills might have an effect on the amount of air one gets. The 55 grill seems smaller than a 56?

Laszlo I think the solid hood support directs the incoming air going across the radiator instead of over it? I have not seen any flow models or data to support that...just looks that way to me.

[chevynut]

JT, I think all the tri5 grilles are so big that it doesn't really make any difference from one year to the other, and in reality they're close to the same size IMO. I just don't think any of the grilles are an air restriction.

The solid hood support (brace) probably doesn't have a lot to do with directing air through the radiator at highway speeds. There's a lot of airflow at that time and the hot air is escaping out from under the car, plus the fan is working well to pull air through the radiator. At low speeds, with high under-hood temperatures, I think the solid brace prevents hot air from being pulled forward and back through the radiator by the fan. Same with the side baffles next to the radiator, and the one on the bottom of the radiator. I have holes in my hood brace but I also have a radiator cover so all the air going through my radiator has to come through the grille.

[Custer55]

Chevynut, When you mentioned the hood braces with the holes I remembered my hood brace has the cut for the 6 cylinder radiator (Original 6 cyl car). Do you think It would help to block off this opening?
Thanks for all the info. Brian
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[Rick_L]

I filled this on mine, but I did it for looks rather than function.

That small hole isn't going to make a measurable difference. There are quite a few that run the open baffles successfully, but that would be a concern to me. Often when you have a problem, it's not one glaring item, but a collection of small details that need fixing.

[chevynut]

I agree with Rick. That small opening is probably not a big deal, but you could block it temporarily and see if it changes anything.

[Custer55]

I'll give a try and let you know what happens.
Thanks, :)

[Eds56]

If a good fan and shroud doesn't fix the problem, and you don't want to change the down-flow style radiator, I'd be looking at the condition of the radiator, water pump, fan, shroud, and just making sure everything you have is working the way it should and with maximum air flowing through the radiator. You might also take a look at your pulley ratio to make sure there's nothing weird going on there, causing the water pump to turn too slow. There are better down-flow radiators that don't cost as much as a crossflow too.

Just thought I would give you guys and update: I installed the GM 6-blade fan and it def. helped VS. what i had. Seems to be MUCH more air moving now. I drove it about 20+ miles or so and while going down the road, she was running less than the 180 degree thermostat, i pulled over a few times and just let it sit and idle..... the temp hand still rises, but NOT as FAST or as FAR. Now it seems to top out at about 205 --- 210 after sitting at idle for around 10min. --- I THINK a good fan shroud will get me close enough.... but we will see.

I also spoke with a worker at the Radiator shop, and he said "a few of the flues had to be plugged off"..... something i was NOT told by the guy that took my money. I have another original style Radiator (out of an old parts car) i thought about getting cleaned out.... but perhaps an Aluminum replacement would be better. So now that's on my list.

Thanks to EVERYONE who took time to post and share pics / info, i now have several more things to check (like the hood support, never would i have thought about that) ---- You guys are the BEST!!!!

[Eds56]

I have to agree with Cnut on the Shroud, they have been good for up to 20 degree drop at idle in my experience.

Thanks Mark & Cnut,
I hope that's right about the shroud, because it sounds like my next item and from todays test.... i hope that gets me where i need to be.

[Eds56]

What poundage Radiator cap should be on it? It currently has a 13# but i'm not sure that's the right one.

[chevynut]

If I understand it correctly, the stock radiator cap was 7 PSI. The GM manual says the stock radiator is rated at 7.5 psi and if you use a higher pressure cap you might blow the heater core because that seems to be a weak component. Modern high pressure caps are usually 16 psi, so I think I'd leave your 13 psi one alone if it's working right. The only thing a higher pressure does is raise the boiling point of the coolant.

[JT56]

Consult with vendor...I have a PRC unit and its 15lbs. They have original style ones in aluminum, so check them out! Good people

[Eds56]

Update : Problem seems to be solved with addition of custom shroud. I made and installed one today, moved radiator as close (about 3/4") to the 18 1/4" manual fan as it would go, set shroud opening @ 1/2 the fan blade and took her out for a 30 mile test run. Now she runs under 180 going down the road and when I got back, I pulled up next to shop doors (reduced air flow, as if in traffic) and let it idle for 10+ minutes solid and it never go over 190. And that was after me running her pretty hard on the way back. I still would like to replace the radiator, as it appears pretty rough, I have feeling it's days are numbered.

Thanks again to all those who took time to share thoughts and offer suggestions,,,, YOU are appreciated!!

[JT56]

Glad its working for you

[markm]

A shroud appear to be one thing these cars missed when new, good to hear you got it handled.

[Custer55]

I finally had time to test blocking off the 6 cylinder radiator hose opening a few nights ago. I let the car idle in the drive way for about 15 to 20 minutes and the temp got up to about 182 degrees (It was a cool night, 65 degrees or so) I left the car running and added a temporary block off made of thin cardboard and Gorilla Tape. The temp dropped to about 177 with the hood open while I put the block off in place, but as soon as I closed the hood it slowly climbed back up to 182 withing 5 minutes or so. I then opened the hood, removed the temporary block off and let the car run with the hood open. With the hood open the temp went down to 173 after about 5 to 10 minutes. So the blocking off the opening basically made no difference. Having the hood open helped but it's obviously not a practical solution.
I'm not sure if the results would be different on a hotter day, but that's the results of my test for what it's worth.
Brian

[Recycled Rumor]

I run my 55 without the hood. It still runs around 190-210 on the highway and will creep up slowly in town and up to as high as 230 at stop lights. I am looking for a guy in rochester who can bend me an aluminum shroud right now. Do you guys think it would be better to buy a new fan that comes with a shroud?

[Recycled Rumor]

Although, now that I look at the situation closer, do you think that a shroud would make that much difference with mine?726872697270

[BamaNomad]

Was that a 'quarter mile at a time' car? :) I don't have a great deal of experience cooling a big block, but it looks to me like you have a lot of restriction to air flow thru your radiator...??

[Recycled Rumor]

It is set up to drag race, but with no hood there is very little restriction to the radiator at all.

[Recycled Rumor]

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[chevynut]

Anything you can do to get more air through the radiator should help. If you can fit them, I recommend the dual 11" SPAL fans since they cover the entire core and pull around 2700 CFM and have an integrated shroud. My Derale dual fans are supposedly rated at 4000 CFM. A shroud might help, but my bet is your fan is inadequate, and for sure you can do better. IMO there's nothing that makes a big block inherently more difficult to cool.

[Recycled Rumor]

I'll see if I can find a shroud that fits before I spring for the dual fan system. Fingers crossed.

[Recycled Rumor]

It might be hard to tell, but the middle picture taken from above, you can see that I have almost no room between the frame and the fan right now. I hope I can find something that fits and works.

[BamaNomad]

You have several issues preventing your car's coolant from being cooled...

1. If the air which is being drawn thru the radiator has 'no place to go' (because the space behind the radiator is full of 'other stuff'), then there will be LESS air moving thru the radiator - regardless of which fans/shroud/etc that you use...
2) The HOOD is a necessary part of your cooling system, as it prevent hot engine air from circulating OVER the radiator support to be drawn back into the front side of the radiator. The system is designed to pull 'cooler air' from the front of the car, in thru the grill, and thru the radiator into the engine compartment...

[Recycled Rumor]

Well, installing a hood isn't an option at this point. I would have to fabricate a mounting system while simultaneously figuring out a way to stiffen the hood itself. I've never heard anybody say that putting a hood on a car will help with cooling it, everything that I have read has stated the opposite. That being said, you raise a valid point.

[BamaNomad]

You said your overheating issue was at 'idle'.. so I assume while stopped, which is the situation that the hot engine air would be recirculated thru the radiator with the hood missing... I think you are running into the same issues someone faces when trying to convert a 'drag only' car to a street car. If that is your goal, I'd suggest removing some of the 'drag only' items that are inhibiting your street performance.. :)

[chevynut]

Personally I doubt the lack of a hood is causing any problem. The air is being pulled through the radiator and back to the engine, where it goes up into the ambient air. I have a hard time believing it would circulate to the front of the radiator when it can rise freely out of the engine compartment. The problem, imo, is lack of airflow over the entire core. The single fan doesn't pull air through the entire radiator core when sitting still, but air moves through the area not covered by the fan when driving.

Increasing coolant flow may help some, but you need to get air through the radiator to dissipate the heat. If the Spal dual 11" fans will fit, I would recommend them if a shroud doesn't help. However, I'm not seeing how you're going to add a shroud with your electric fan. If you have 4" between the back of your radiator core and the front of your engine, the Spal fans should fit and I'll bet they pull a lot more air.

[Recycled Rumor]

That's my thought as well, I am lacking space for a shroud right now. I have a high flow water pump already. I'll look into seeing what dual fans will fit

[Rick_L]

I have seen recirculation happen in the past on a roof mounted air conditioner, like is often seen on RVs and trucks. The condenser fan was recirculating its own air. The situation would occur when the vehicle was stationary, and was aggravated when the wind was blowing in a certain direction. We installed some shrouding on the a/c unit which fixed the problem. High side pressure on the a/c unit dropped over 100 psi with the shroud.

That said, I think it' a pretty long shot that recirculation is your problem. I'd say it's far more likely if you had a hood but no baffle, where the air had a much easier chance to recirculate.

My thought is that dual 11" fans would fix the problem.

I would also close up the gap between the radiator and filler panels. I don't think that's an idle issue, but could be on the road. It would force all the air to go through the radiator rather than some going around it.

[Recycled Rumor]

I took the car to a show today about a 20 minute drive away, mostly highway. The news is, that the car doesn't cool particularly well at idle, I already knew that. Now I know that the car doesn't cool particularly well on the highway either. I am sure that you may be thinking that the solution now is to buy a bigger radiator, and if I had never seen the car before I would say the same thing. My problem with this is that the car used to cool on the highway before it was parked 6 years ago. What could have changed while it was parked? I don't understand it at all.

[chevynut]

If I was you I'd start with the basics. Drain and flush the entire system. Look inside the radiator and see if it's clean or if there are any partially plugged tubes. Check your hoses to make sure they look good. Remove your thermostat and make sure it's opening all the way (put it into boiling water on the stove), or replace it with a high flow unit. Refill with new coolant (antifreeze and water) with the proper mix for your area. Run and drive it and see if anything changed. If not, make sure your gauge is reading correctly. Now you can consider any changes you might want to make.

[Recycled Rumor]

Thanks cnut, I'll keep everyone posted.

[Fladiver64]

I have some experience with a blown street car and they can be a challenge. I dont have all of the answers but I can share what I have learned with my car. First let me say that it is probably not any one thing you are going to find that "fixes" the overheating problem, everything is a balancing act and when everything is out a little bit you have problems. Even though it may look like a shroud would not help, it did with my car and there is not much of a shroud there. Second Ido not have a hood so I doubt that is your issue. I think Cnuts advice to do a through flush and clean is a great one and then see what you can fab up for a shroud even if it is temporary would help. One thing that has not been mentioned is tuning of the engine, I know on my car ignition is very sensitive, the blower seems to magnify every small issue. So check plugs (I would replace) wires, cap, rotor, coil, make sure everything is in great shape. Then on to check timing, not sure what yours is set up to run, but if you have a race track tune up in the car and you are trying to run on the street, does not make for a happy motor.

I know what you are going through, I inherited the 27 from my Dad two years ago and it took a few months of adjustments to get it running like I knew it should. Keep after it and enjoy the process.731873197320

[Recycled Rumor]

Alright gentlemen, I haven't changed anything on the car to date, but it was an unusually cool day in Minnesota yesterday and I decided to take the car for a ride to see what happened. I was pleasantly surprised to find that the car actually stabilized at 200 degrees and did a pretty good job of staying there both in traffic and on the highway.

My question is, how much of an affect does the ambient air temperature have on the cooling system?

Obviously it has some affect, but to what extent? For example, if the car stayed at 200* when it was 70* outside, how much hotter should I expect it to run when it is 80* or 90*? Does the water temp and the air temp have a linear relationship?

[Bitchin'57]

I'll see if I can find a shroud that fits before I spring for the dual fan system. Fingers crossed.
Like Cnut mentioned, you want the fan(s) pulling air through every square inch of the radiator core, so yes, a SEALED shroud is a necessity. When building the shroud, try to design it so the fan is at least 1" away from the radiator. Thin line fans are not going to cut it, because they don't pull much air and their motors are small and weak. Those weak motors might pull a decent amount of air in a zero restriction condition, but behind a radiator, particularly a 2+ row radiator with an AC condenser and/or trans cooler in front of it, it's ability to pull air through all of that goes way down. If the shroud alone doesn't work, you may have to resort to modifying your radiator support in order to move your radiator forward, so you can fit deeper, stronger electric fan(s).

[WagonCrazy]

For my money and time, I would junk the fanblade-mounted-to-waterpump and install dual electric fans with a shroud that covers the back of radiator surface completely.
Solved my problem on the 9 passenger wagon I had for many years. I live in So Cal, inland, where it gets to be 100 to 110 most summer days.

[chevynut]

My question is, how much of an affect does the ambient air temperature have on the cooling system?

Obviously it has some affect, but to what extent? For example, if the car stayed at 200* when it was 70* outside, how much hotter should I expect it to run when it is 80* or 90*? Does the water temp and the air temp have a linear relationship?

It's a direct correlation as long as everything else is constant. The heat transfer, Q, is a function of the convection coefficient, h, surface area, A, and the temperature difference between the surface Ts and ambient, Ta. In theory, the convection coefficient may change slightly due to air density but it's probably negligible.

So Q = h*A*(Ts-Ea)

If the ambient temperature goes up by 10 degrees, the coolant temperature rises 10 degrees assuming the thermostat isn't influencing the temperature at the lower end of the temperature range.