Bus Radiator Issues

Glennman · July 01, 2020, 09:56:55 PM

My bus has a highly modified radiator system that employs 4 electric fans and 2 additional radiators (4 radiators total). The radiators on the sides appear original, then the other 2 are laying flat directly above the engine compartment. The 2 side ones have electric fans blowing onto them from the outside into the compartment where the other 2 fans are. The other 2 horizontal fans suck hot air from the engine compartment (almost directly above the turbo) into this same compartment (the compartment where the original system was). All the fans put the air into this one space, but all that hot air is really just all blowing against itself, with no real way of getting it out. The bus runs ok, but it sure does heat up quickly on the hills. I've been running the bus without the original fan compartment door, to get the heat out better. In the last couple of weeks, I cut out most of the door panel and installed some real nice stainless expanded mesh, trimmed it out, etc. I reinstalled the door, but now it gets even less air, heats up quicker, and takes longer to cool. When I ran it without the door installed, when pulling over to let it cool such as on a mountain pass, it would cool right down in about 2-3 minutes. It looks like the main problem is that the door with the new screen only compounded the issue. I have some ideas to fix all that, but my question is (pardon my long wind); in the original system, it appears that the 2 side radiators are the only 2 radiators, then there is an elaborate squirrel cage set up. Do those fans suck air through the side radiators, then blow it down onto the engine? Basically, I am just wanting to know the air pattern of the original system. Thanks for all your help. I find all the knowledge on this board to be invaluable. Glennman

benherman1 · July 01, 2020, 10:20:19 PM

The original system had the squirrel cages blowing down from that compartment onto the top of the engine. In that setup it only needs the two radiators because the squirrel cages move significantly more air than a regular fan. I have no idea why they would have rigged the fans up in your setup to blow all the air into the "sealed" compartment since there would be obvious issues with air flow. I assume the changes they made were either because it was getting hot or there was an issue with the fan gearbox and they decided they could do better. I would try swapping the fans to push down onto the engine rather than pull up. Also if the radiators are in series you can change the routing to run in parallel as that will work better. I would also make sure the fans have proper shrouds to be as efficient as possible. There is also the possibility that the stock radiators are clogged up which led to the "improvements" made. Post some pictures of the current setup as well. They will help us get an idea whats going on.

lvmci · July 02, 2020, 06:56:36 AM

What make and model bus and engine do you have? Sounds like a pre 90 MCI split dual radiator system...

chessie4905 · July 02, 2020, 06:59:19 AM

Says MC-8 with 8v-71 turbo.

benherman1 · July 02, 2020, 07:30:38 AM

Quote from: lvmci on July 02, 2020, 06:56:36 AM
What make and model bus and engine do you have? Sounds like a pre 90 MCI split dual radiator system...

That didn't cross my mind. That makes a lot more sense than someone pulling the squirrel cages.

lvmci · July 02, 2020, 09:13:42 AM

Hi Glennman, the MCI8s along with most if the pre 90 MCIs had split/dual radiators, with side by side squirrel cage fans, sucking air through the 2 radiators, thst are 5' foot up and shooting the air down past the engine to the road. sounds like they were removed and extra radiators with fans pulling up from the road in to the fan box. If that's so, your idea of taking off the door is the only way to exhaust the hot air. If your not going to replace the hi air volume squirrel cage fans, maybe if you reverse the direction of the electric fans on the flat radiators, as Ben suggested, it might start cooling again with the door on. Is the 9' fan belt from bottom of the engine to a pully on a mitre box still there, In the fan box? Pictures might help to understand what's been done...

Glennman · July 03, 2020, 01:21:34 PM

I've added some pictures. The system is pretty sophisticated, as you can tell they put a lot of thought and engineering into it. There was apparently a huge scoop on the back that the original designer built that shot air into the fan compartment. The previous owner removed it, and just drove it with the door off. He tossed the scoop. The system works, but I think it can be improved. I am surrounded by mountain passes for the most part. I'm not afraid of completely redoing it, modifying it, etc. For some reason I am only able to get one picture to attach, but I think it tells the story.

chessie4905 · July 03, 2020, 03:49:12 PM

Consider changing to 1 large radiator with a hydraulic fan motor, if it is at all feasible. Change transmission cooler to air cooled, and ditch the oil to oil cooler. Hayden has some pretty large coolers and have recommendations for your trans. Will need to add electric cooling fans with it also. On a thermostat, if you dont want them to run all the time, but also add a bypass switch when you see those looong strrp grades coming up.

lvmci · July 03, 2020, 05:16:20 PM

Interesting, I've never seen anything like it. With 4 fans all blowing into the fan box, the only way to exhaust is to have the door open or a screen door, as you said. If you reversed the flow of air thru the original split system radiators, could you get enough CFM to suck out the hot air thru the fan box and out the radiators?...

Glennman · July 03, 2020, 10:44:27 PM

Quote from: lvmci on July 03, 2020, 05:16:20 PM
Interesting, I've never seen anything like it. With 4 fans all blowing into the fan box, the only way to exhaust is to have the door open or a screen door, as you said. If you reversed the flow of air thru the original split system radiators, could you get enough CFM to suck out the hot air thru the fan box and out the radiators?...

I'm thinking about installing the radiators in a vertical position across the front of the fan compartment doorway so that the fans are on the outside sucking air out of the compartment through basically all 4 radiators. I could block off the engine compartment so that no hot air from it will be going through the radiators.

Or, flip the fans so they are installed under the 2 radiators so they are sucking through the radiators blowing downward into the engine compartment. Then I could have the air either come from the outside (ambient), or I could (like my first scenario) have the air suck through the 2 side radiators and install an airtight door again.

One more idea that is the least expensive (doesn't hurt if it doesn't work) is to install a small scoop on the sides above each of the 2 side radiators so that air is blowing into the fan compartment while driving down the road, which would expel the hot air out. I could easily cut a 5" by 7" hole on each side and install a corresponding scoop. This would move a lot of hot air from the compartment.

I think it is a given that I install a transmission cooler as well.

Chasing down all these theories can get costly and time consuming. Oh well, this isn't my first bus. I'm kind of getting used to it!

Jim Blackwood · July 04, 2020, 07:10:11 AM

Do you need more cooling when at speed? Will there be enough wind to be a benefit when climbing long hills?

Jim

TomC · July 04, 2020, 07:56:43 AM

MCI ran the 8V-92TA. which is thee hardest engine to cool, with the dual radiators and squirrel cage belt driven blower quite successfully. I would suggest you get rid of all the electric stuff-mainly electric can't ever come close to the power of a belt driven fan. Get the two 8V-92TA radiators and again belt drive it. I know that long belt is a pain, but it is also the simplest. You could add misters. Add an oil to air transmission cooler with electric fan. I have one that is plumbed that the hot oil first goes through the oil to air cooler then to the normal shell cooler. This takes most of the heat out before hitting the engine. Good Luck, TomC

luvrbus · July 04, 2020, 08:02:02 AM

Quote from: Glennman on July 03, 2020, 01:21:34 PM
I've added some pictures. The system is pretty sophisticated, as you can tell they put a lot of thought and engineering into it. There was apparently a huge scoop on the back that the original designer built that shot air into the fan compartment. The previous owner removed it, and just drove it with the door off. He tossed the scoop. The system works, but I think it can be improved. I am surrounded by mountain passes for the most part. I'm not afraid of completely redoing it, modifying it, etc. For some reason I am only able to get one picture to attach, but I think it tells the story.

A lot of time and money was spent there,it is hard for electric fans to replace the 40 to 50 hp engine fans because of the high and low pressure areas a bus creates it takes a lot of radiator and fan to reject the almost 3000 btu per minute x each hp to cool a 2 stroke engine

lostagain · July 04, 2020, 11:36:58 AM

I've been thinking what TomC just said: just go back to the OEM squirrel cage fans. The belt is not even a bother: it will last a couple hundred thousand miles.

chessie4905 · July 04, 2020, 11:42:31 AM

Do not run oil to oil and oil to air together. You are defeating half the benefit. If you want transmission to run warmer in the cold weather, it is simple to bypass some of the flow with a crossover pipe with a shutoff valve in it. You can adjust the valve to control the bypass flow. Whatever you do, add a transmission temperature gauge.