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Horizontal Radiator behind SBC with twin fans, but still overheats

13K views 24 replies 13 participants last post by  boothboy 
#1 ·
I am finally getting my shopping cart rod on the road, but I am having some overheating problems. The radiator is mounted horizontally behing the engine and right above the TH350 trans. There are two 14" fans pulling air down through a full shroud. The plumbing comes up from the bottom and I am thinking that the radiator is trapping air and does not have enough liquid-to-aluminum-fin contact. I can only run it about a mile before it overheats.

The way the radiator hoses are placed around the frame does not allow me to tilt the radiator up to use the stock drain or cap to bleed off air. The system is filled and air bled from a cap above the 165 degree thermostat. I am thinking about drilling and taping a small hole in one of the end caps to bleed off any air stuck in the radiator. Anybody ever tried that? Is the plastic on the end cap of a 1988 chevy truck radiator thick enough to hold a screw and rubber washer in a 13 psi system?
 

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#3 · (Edited)
patentguy said:
I am finally getting my shopping cart rod on the road, but I am having some overheating problems. The radiator is mounted horizontally behing the engine and right above the TH350 trans. There are two 14" fans pulling air down through a full shroud. The plumbing comes up from the bottom and I am thinking that the radiator is trapping air and does not have enough liquid-to-aluminum-fin contact. I can only run it about a mile before it overheats.

The way the radiator hoses are placed around the frame does not allow me to tilt the radiator up to use the stock drain or cap to bleed off air. The system is filled and air bled from a cap above the 165 degree thermostat. I am thinking about drilling and taping a small hole in one of the end caps to bleed off any air stuck in the radiator. Anybody ever tried that? Is the plastic on the end cap of a 1988 chevy truck radiator thick enough to hold a screw and rubber washer in a 13 psi system?
With the eng. higher than rad. air trapment in the eng will be an ongoing prob.
Looks like you could easily tilt the rad. up so that rad. cap/filler is higher than the eng. (same angle as existing frame tubes) ; then figure a way to route your hoses. This will also allow a direct flow of air on the face of the rad.
 
#4 ·
Try this. Remove the thermostat housing and thermostat. This is where your going to fill your system. If your radiator petcock isn't located at the high point of your radiator attach a piece of hosing to it and raise it above your radiator. Open the petcock and until coolent flows nicely. Close the petcock and fill your system while holding the radiator hose end level with the thermostat opening in the block until the system is filled and the coolent runs from both the block and hose. Re-install the thermostat and housing and quickly re-attach the radiator hose. Run it until it get up to operating temp and the thermostat is open. Blip the throttle a few times to get any trapped air to move to the top of the engine. Let it completely cool down ( the next day) pull the thermo housing and check the level for any trapped air. re-fill as necessary. You might also want to install a thermostat housing that has a tapped hole for a temp sensor. Chevy used them. You can install a short piece pf pipe in it that becomes the high point of the system and with some pipe fittings attach a petcock on top of the engine which will become your bleed point.
 
#5 ·
Buggy project heat

1st like your hotrod. Where you have the radiator now will never work. Air will always be a problem and your fan what little air its pulling is hot air. Why don;t you just mount the thing where it belongs ,make a nice cart oriented grill and headlight piece and solve the heating problem. Looks like you have plenty of room. All the eyes are going to be looking at the cart gorng down the road,not the drivetrain.Take a look at the Baha ottroad trucks,their radiators are in the back but still mounted higher than the engine. One thing that might help would be to find an older V-8 Mustang radiator. Smaller ,taking up less space but will cool your engine fine. :cool:
 
#6 ·
Keeping air out of the horizontal radiator

Thanks everyone, always great advice here. I kept the radiator hooked up to the cooling system, but tilted one corner up until it was at the same level as the system cap mounted above the thermostat (see pic). I added fluid until it was flowing out of the bleeder valve on the radiator, closed it all up and ran the engine for a bit, let it cool and checked the coolant level again. It looks like I have all the air out of the system now and on several test runs the engine stayed at normal temp the entire time. The large truck radiator and twin 14" fans seem to be doing the job of cooling, but I guess my question now is will air accumulate in the radiator over time, creating the same situation I just fixed. The filler cap is the highest point in the system and I added a bleeder port to the top of the radiator end cap to bleed any accumulated air. If air is going to be problem, I will have to look at mounting the radiator upright somewhere else. I like the low profile look of where it's at but I need max cooling capacity. This is going to be a parade vehicle, so it is going to be idling on summer days. My other thought was to add a small vertical radiator with an electric fan at the front of the engine and run the heater hose ports to that secondary radiator.

It was great getting this silly thing running. It rides a little stiff, but it is very stable for something that looks top-heavy:

http://www.flickr.com/photos/kathycalvin/6459572933/in/photostream
 

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#8 ·
matts37chev said:
if you already tilted up the rad so the cap is even with the top (highest point)
if you put an overflow bottle on it like the truck rad had stock
it should alow air out, but will suck fluid in if it wants some

wait, did you leave it mounted up or out it back down?
Sorry, I was not clear on that, I tilted it up to fill the system and bleed out any air and then mounted it back down in the horizontal position. The system is running with an expansion tank and so far it appears to be venting and drawing coolant back in as needed.
 
#10 ·
patentguy said:
Thanks everyone, always great advice here. I kept the radiator hooked up to the cooling system, but tilted one corner up until it was at the same level as the system cap mounted above the thermostat (see pic). I added fluid until it was flowing out of the bleeder valve on the radiator, closed it all up and ran the engine for a bit, let it cool and checked the coolant level again. It looks like I have all the air out of the system now and on several test runs the engine stayed at normal temp the entire time. The large truck radiator and twin 14" fans seem to be doing the job of cooling, but I guess my question now is will air accumulate in the radiator over time, creating the same situation I just fixed. The filler cap is the highest point in the system and I added a bleeder port to the top of the radiator end cap to bleed any accumulated air. If air is going to be problem, I will have to look at mounting the radiator upright somewhere else. I like the low profile look of where it's at but I need max cooling capacity. This is going to be a parade vehicle, so it is going to be idling on summer days. My other thought was to add a small vertical radiator with an electric fan at the front of the engine and run the heater hose ports to that secondary radiator.

It was great getting this silly thing running. It rides a little stiff, but it is very stable for something that looks top-heavy:

http://www.flickr.com/photos/kathycalvin/6459572933/in/photostream

Great job on the Cart. Here is something you might want to consider. If you think about grocery carts and how shoppers load them up, you usually see the big bulky items on the bottom of the cart; this presents an ideal opportunity for you to screen the motor/drivetrain/radiator. Replicate a giant box of Tide or other large item for the bottom, along with a few items in the basket.
 
#11 ·
Some ideas just do not work..I would get that radiator up as vertical as I could and get some shrouding on it to direct air into the radiator which will help the fans. Then lets get a fill on it above the highest level of coolant. Ford used a remote fill on some thunderbirds which had the radiator mounted very low in order to get a good fill..

Sam
 
#12 ·
70s Corvettes have the radiator at a steep angle in front, and there have been mid engine cars with the radiator installed flat in the back. I've seen a couple truck rods with the radiator flat in the back. The flat mounting won't affect cooling as long as there is adequate air flow. The mounting just effects filling, and that problem has been solved. There should be no more problems with it as is. You might want to let it idle for 3-4 hours while you watch the temp gauge just to make sure -- wouldn't want to find out there is a problem in the middle of a parade!
 
#13 ·
farna said:
70s Corvettes have the radiator at a steep angle in front, and there have been mid engine cars with the radiator installed flat in the back. I've seen a couple truck rods with the radiator flat in the back. The flat mounting won't affect cooling as long as there is adequate air flow. The mounting just effects filling, and that problem has been solved. There should be no more problems with it as is. You might want to let it idle for 3-4 hours while you watch the temp gauge just to make sure -- wouldn't want to find out there is a problem in the middle of a parade!
Thanks Farna, my plan this weekend is to let it sit idling and see if the cooling system can keep up. If the system can't handle the heat I will look at alternative locations for the radiator. I need to commit to the position before the cart gets taken apart to get ready for paint.

BTW One of my first cars was a Rambler wagon, a '63 is on my list of cars I want to own again.
 
#14 ·
I agree, that is a very cool project :thumbup:

with the filler cap on the thermostat housing and a spit can it should be fine
if you were to tilt the rad a very small amount, (maybe add a 1" spacer to the mount) and add a spit can to it, you should have no problems at all :thumbup:
 
#15 ·
That is one crazy ride, nice job.

I think you would have better luck moving the air up from the bottom rather than pulling it down with the fans. Can you mount your fans and shroud up top? or reverse polarity? hot air rises. Maybe you could fab some air deflectors to direct cool air from under the chassis up towards the bottom of the rad and that would help the air flow move up through the rad along with the fans. The rad will cool better with up flow IMHO
 
#16 ·
406 bug said:
Great job on the Cart. Here is something you might want to consider. If you think about grocery carts and how shoppers load them up, you usually see the big bulky items on the bottom of the cart; this presents an ideal opportunity for you to screen the motor/drivetrain/radiator. Replicate a giant box of Tide or other large item for the bottom, along with a few items in the basket.
Now that is creative :thumbup:

make sure to leave some room in there for the beer!
 
#17 ·
Custom10 said:
That is one crazy ride, nice job.

I think you would have better luck moving the air up from the bottom rather than pulling it down with the fans. Can you mount your fans and shroud up top? or reverse polarity? hot air rises. Maybe you could fab some air deflectors to direct cool air from under the chassis up towards the bottom of the rad and that would help the air flow move up through the rad along with the fans. The rad will cool better with up flow IMHO
I like the idea of air deflectors below the radiators to move some air through the rad. The original layout drawing for the cart had the fans pulling air up from below, but as we started building someone pointed out that the principle place where the cart will be running is idling through parades where the hot asphalt and exhaust will be radiating heat. We flipped the system to use the somewhat cooler air above the radiator.

I need to give the current fan system a good test in warm conditions (hard to find in PA right now). My cooling system is not typical since it was never designed to use the air movement created by the cart cruising down the highway. But the long term goal is to make this street legal, so air movement at higher speeds will still be important.

I will try to give it a good test and then tweak the fans and radiator position. I will at least try changing the direction of the air (up vs. down) and see if that makes a difference. The blades are reversible and the motors can spin either way so changing the air direction should not be a problem.
 
#18 ·
I used a horizontal A/C condenser that was mounted under the rear of a 31 Chevy Sedan Street Rod. I did however mount it at a small angle to allow freon to flow from gas to liquid. Id like to see that radiator mounted at a similar angle(20-25 degrees) so there is no chance of an air pocket. What can happen is when the thermostat opens it could drain the block and leave an air pocket in the motor. This is just my opinion, I could be wrong, but that radiator is made to flow top to bottom leaving any air in the top near the cap.
Neat project though, Ilike the idea of big Tide box or maybe even a couple of large 12 packs. Good luck keep us informed.
By the way that A/C unit worked perfect in that drafty street rod, with 2 fans pulling down and out. I vented the running boards with several louvours to allow air. Drove that car from Florida to Syracuse one summer and Springfield the next.
I Love this Forum!!
 
#20 ·
Nice looking work, but you have another SERIOUS problem:
The roll bars as shown in 2nd photo have no strength and will fold down on your head in the event of a roll over. For them to have any strength, they must form triangles. Parallelograms and rectangles will collapse. It's not too late to add some more bars to make it strong.
 
#21 ·
graydog said:
Nice looking work, but you have another SERIOUS problem:
The roll bars as shown in 2nd photo have no strength and will fold down on your head in the event of a roll over. For them to have any strength, they must form triangles. Parallelograms and rectangles will collapse. It's not too late to add some more bars to make it strong.

Thanks for your concern Graydog, this project's goal is to be street legal but it is principally a parade vehicle. Those are not rollbars you see on the upper rear section of the basket, there will be a piece of PVC pipe running between the curled sections to make it look like the push handle on a typical grocery cart.

There will be seat belts for some level of safety, but only a few "responsible" drivers will be operating this contraption and the number one rule will be "don't do anything stupid". It will be more show than go. Lots of chrome, LED lighting, big tires, flame-thrower exhaust, etc. All while keeping it under 35 mph. Mostly a rolling billboard for my son-in-laws family grocery store.
 

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#24 ·
Horizontal radiator cooling like a champ

Just to finish up on my original questions - and give an update on the project. This is going to be idling in parades so I wanted to maximize the cooling capability. I mounted the radiator horizontally and mounted two 14" fans underneath with a thermal switch/relay to kick both fans on when the water hits 195 degrees. I also mounted two heater cores from a VW Passat in front of the engine with each of them having an eight inch fan pulling air through whenever the water is over 185 degrees (these are plumbed into the heater hose ports on the water pump in intake). I installed air bleeders on the end cap of the aluminum radiator (just a simple tire valve) and on the top of the heater cores (a small screw with a rubber washer) to be sure I do not get air trapped in the system. The filler is mounted above the thermostat and the with the overflow/recovery tank mounted back next to the transmission.

One thing I wish I had done differently - I should have put each fan on its own relay with individual temp switches, so the fans come on in stages. When both big fans switch on then can bring the water temp down quickly and then shut off. It just seems like a lot of cycling on-off-on, etc. But it works so I will likely leave it as is. Next on the list is to get it certified street-legal...







CART PROFILE PIC | Flickr - Photo Sharing!

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Untitled | Flickr - Photo Sharing!
 
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