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2001 RD688 Dump- I’ve been battling overheating when pulling a good hill for a year or so now,  I’ve just learned to take it easy but even then it still comes close.  From what I can tell, the radiators are about the same in most of the RD’s regardless of the engine.  I would think there would be a larger or upgraded one for the 460 since I’m putting more fuel and air to it.  I’m going to pull it soon and have it flow tested.  Any suggestions on an aftermarket or better one?  Radiator is clean, no boost leaks, thermostat changed, viscous fan seems to be working and water pump is pumping (from what I can tell).  Anybody have any suggestions?

Edited by USMC205
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If your putting more fuel to it your problem may me overfueling as compared to radiator problems. Is your pyrometer running hot? Sounds like you've already checked cooling system

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2 hours ago, alex g said:

If your putting more fuel to it your problem may me overfueling as compared to radiator problems. Is your pyrometer running hot? Sounds like you've already checked cooling system

It gets up to 900 when pulling a hill.  I didn’t turn up the fuel, I was just assuming the 460 puts more fuel and air into the engine.

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All the RD’s that I have seen that came factory with a 460 had a Horton air fan,  If it has a viscous fan on it might have been originally a lower HP engine then later upgraded to a 460. The RD radiator it barely big enough for the 460 HP

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2 hours ago, Mackpro said:

All the RD’s that I have seen that came factory with a 460 had a Horton air fan,  If it has a viscous fan on it might have been originally a lower HP engine then later upgraded to a 460. The RD radiator it barely big enough for the 460 HP

Should be ht550? Not a fan of them, previous owner might of done the viscous. Shit design, the little bit grease  it has gets blown out after a while and seizes up. 

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The Horton HT650 is the ones I’m thinking about..  Only issues we had was not with the fan clutch itself but the air solinoid leaking and wearing out the friction disc in the clutch.  We always installed a new air solinoid when replacing a fan clutch.  Also , sometimes the fan clutch would not fit flush on the water pump and a shin was needed . If the shim was not used , the clutch would wobble and cause the water pump bearings to go out . 

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13 hours ago, Mackpro said:

If you have the last 6 of the VIN I can do some digging for ya and see if there were any bulletins on the issue 

It’s got a viscous fan and yeah I noticed a little seepage before.  From what I can gather it came with the his clutch.  I can hear the fan roaring at higher rpm’s but not so much at lower, it kind of seems like the fan kicks in fully later than it should.  Might try a new one and see.  How hard would it be to convert to an air clutch?  I’d like to have a switch to flip before a big hill.  060231 is the last 6.  01 RD688.  Thanks guys for the replys.

Edited by USMC205
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Well I had a feeling the fan clutch wasn’t turning as hard as it should, so I went ahead and replaced the water pump and fan clutch.  Made a world of difference.  I can’t get it to overheat if I tried now.  I thought the clutch was turning just fine until I heard what it’s SUPPOSED to sound like.  Also replaced the thermostat while I was at it.  Taking the fan shroud off also gave me a new view into how dirty the radiator actually was.  The old dog stays cooler than the underside of a pillow now.

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