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Author Topic: Hole in 3rd radiator  (Read 680 times)
lostagain
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« on: August 26, 2011, 07:13:19 AM »

Just finished replacing the front slack adjusters yesterday and thought I was caught up, when I noticed the coolant level was down a bit, and the 3rd rad on the right engine door was dripping, WTF... I removed it to fix it. The PO had installed it to help cool the 6V92/HT740. There was 2 24V fans on it, switched from the front when needed. They (the fans) did not make any difference anyway, on or off. The fans were attached to the rad with plastic ties that go through the rad from side to side, and they wore a pin hole in at least one spot on a tube.

So now what to do? There are no rad shops close by anymore. I have never soldered a rad before, and after reading about the procedure last night, I don't think I should attempt it.

I can easily connect the hose to bypass the rad and run the bus with just the 2 stock rads. It will work as long as the weather isn't too hot. I need the bus for another couple month before winter.

Should I then have the rad fixed ( in Calgary, anybody can recommend a good shop?), or go to a transmission cooler?

I am not crazy about that 3rd rad on the engine door because it impedes access to the pass side engine. It would be a lot nicer without it.

That would be a winter project.

JC
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JC
Invermere, BC
1977 MC5C, 6V92/HT740
eddiepotts
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« Reply #1 on: August 26, 2011, 07:45:01 AM »

I have repaired pin holes with silver solder before. It may get you to a shop that knows what they are doing to fix it if you need it fixed. Someone may talk you into removing it. I would be asking is it hurting you not having the airflow in your engine compartment. To much of anything can be a bad thing. Just throwing that out there. Opened up you may breath better back there and keep things cool enough.
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TomC
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« Reply #2 on: August 26, 2011, 07:53:06 AM »

The stock radiators should be up to the task of cooling only a 6V-92TA/HT740.  That engine doesn't put out anymore heat then a 8V-71N because of the higher efficiency of the engine with the turbocharging. Course the Allison transmission does create heat.  I installed an auxiliary transmission cooler in the right engine door with thermostatically controlled 12v fan that blows outward (trying to have that relatively small electric fan push against the big radiator fan isn't happening) and is plumbed so the hottest transmission fluid goes through the auxiliary cooler first, then through the stock shell cooler.  This takes alot of strain off the radiator and keeps the engine cooler in summer.  You should look into upgrading your stock radiators.  Good Luck, TomC
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Tom & Donna Christman. '77 AMGeneral 10240B; 8V-71TATAIC V730.
lostagain
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« Reply #3 on: August 26, 2011, 08:03:58 AM »

Going without the 3rd rad is an option in my mind. Easy enough to try. I would have to go out on a test drive on a hot day, like today or tomorrow, to see if it stays cool enough going up a mountain pass. I can't just go out like that with my family and a trailer full of dirt bikes to find out it overheats. I have a feeling that rad never did very much cooling, but maybe I'm wrong.

JC
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JC
Invermere, BC
1977 MC5C, 6V92/HT740
lostagain
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« Reply #4 on: August 26, 2011, 08:19:10 AM »

My radiators are new and I seem to remember the PO saying they are MC9 rads.

I have tried the fans on the aux rad blowing in and out, doesn't make any difference. On or off neither. The rad in about 30" X 14" and looks pretty good, but the temp when shot with IR gun is the same going in as going out. So I don't think it was very effective anyway.

The bus always runs at 180F, and I can keep it under 200F going uphill if I manage it right. So I don't have an overheating problem. It would be interesting to see what it does without the 3rd rad. I should go for a test drive this PM, it will be 85F.

JC
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JC
Invermere, BC
1977 MC5C, 6V92/HT740
lostagain
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« Reply #5 on: August 26, 2011, 02:38:28 PM »

Just back from test drive. It behaves pretty well the same without the 3rd rad as it did with it. 180F on the flat, climbs to 190F and toward 200F going uphill. I was pushing it in top gear. I could've down shifted to run cooler. Plus I could give it a shot of the rad misters, installed by PO but never used. So I think I will go without the 3rd rad for the rest of the season, and think about a trans cooler as a winter project.

JC
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JC
Invermere, BC
1977 MC5C, 6V92/HT740
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