302 overheats at idle - wrong water pump?
#1
Join Date: Feb 2002
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302 overheats at idle - wrong water pump?
My brother bought a custom 74 Bronco that has a built 91 302 in it. He is experiencing overheating when at idle, but as long as you can keep the truck moving, then it will run sort of cool, like about 190-200 with a 180 t-stat. When it is idling, it gets up to about 245, but if you rev the motor up to 1500 rpm, it starts to cool off. This truck has a custom aluminum radiator and such, and the fan has no clutch, it is bolted directly to the water pump. I am thinking his water flow is not sufficient at idle and the idea of having the wrong water pump on it came up. His truck has the serpentine belt, so the water pump should be reverse rotation. Without taking it apart, what I can see is that the timing cover has a boss on it for a mechanical fuel pump with a Ford Motorsport blocking plate installed.
Does the presence of the fuel pump boss automatically mean his cover and pump are standard rotation, and are therefore turning the wrong way? Since the timing cover and water pump are a matched set, is there any such a thing as a reverse rotation timing cover with the fuel pump boss?
I am trying to not tear this all apart if there's nothing wrong with it but right now I am thinking he's got the wrong pump for his serpentine belt setup.
Does the presence of the fuel pump boss automatically mean his cover and pump are standard rotation, and are therefore turning the wrong way? Since the timing cover and water pump are a matched set, is there any such a thing as a reverse rotation timing cover with the fuel pump boss?
I am trying to not tear this all apart if there's nothing wrong with it but right now I am thinking he's got the wrong pump for his serpentine belt setup.
#2
The 79-85 Mustang HO motors used a reverse rotation pump on the std rotation timing cover. It apparently didn't work well as Ford redesigned the timing cover and pumps for the 86 motors that reversed the coolant port layout in the timing cover and that resulted in a more efficient coolant flow. The 86-93 pump does not fit the earlier timing cover, this pump (and timing cover) was also used on the 86-97 pickup and van 5.0 and 5.8. You may also have the head gaskets on backwards, look at the lower front corner of the block, if the gaskets are correctly placed, there will be a section of gasket sticking out, covering the exposed deck surface of the block. If this corner of the block deck is exposed, the gaskets are on backwards, allowing the coolant to "shortcut" it's way back up to the head and out the intake, this will result in a hotter running engine.
#3
#4
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If the Bronco has the original coolant inlet/outlet radiator, that too will contribute to the overheating as the inlet is directly above the outlet allowing a majority of the hot coolant to bypass the other side of the radiator.
B.C. Broncos - 66-77 Early Bronco Engine Cooling Systems
#5
His Bronco has a Ron Davis aluminum radiator:
B.C. Broncos - 66-77 Early Bronco Engine Cooling Systems
B.C. Broncos - 66-77 Early Bronco Engine Cooling Systems
#7
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#8
The early Bronco radiator has the inlet and outlet on the same side (passenger) of the radiator. This allows the coolant to drop straight down to the outlet, bypassing half of the radiator, in effect losing half the cooling capacity of the radiator.
#10
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Sounds to me like insufficient air flow.
The early Bronco radiator has the inlet and outlet on the same side (passenger) of the radiator. This allows the coolant to drop straight down to the outlet, bypassing half of the radiator, in effect losing half the cooling capacity of the radiator.
Is the fan shroud installed? Typical indication of not running one.
#13
Yea, the gaskets should be poking out the lower corners if they're on correctly. The waterpump could have a small impeller, that's designed for high rpm operation. This type pump will not move much coolant at lower rpms. Might be worth it to swap a high volume waterpump on it to see what it does then. You don't have to spend a fortune on an aftermarket pump though. Just a trip to the local parts house will get you one. Ask for a pump for a "Police & Taxi" , or "extra cooling with A/C" this should get you a high volume, large impeller pump. But then again, with that FEAD setup, you may be stuck with std volume selections. From your description, you've got a 79-85 Mustang FEAD setup, you may also might consider a swap in timing covers and waterpumps to the 86-97 style found on pickups and vans (also on the 86-93 Stangs)
#15