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My cousin just purchased a Duralast radiator off of Amazon for his 1990 Vette.
As shown in the pictures, the radiator inlet appears to be "blocked" by a stamped aluminum sheet. Is this normal? It almost looks.like a manufacturing error of some sort...
Any assistance greatly appreciated !
Jeff
Last edited by kalayaan12; Jun 6, 2026 at 03:20 PM.
It almost looks like that is a moveable flap. Does it swing if you push on it? If it is solid it surely can't work. Dan
Absolutely agree!!!! Interesting it has "BH" stamped in ink on the blockage portion...I wonder if that stands for "Big Hole", like it's supposed to be removed when being assembled...I wouldn't be surprised if the plastic tank were removed, that there was a stenciled circle outlined for aiding the proper location for removal of material to match the hose inlet of the tank! It's like a hose to nowhere/dead-end...I don't see how that could work in any application, especially if the aluminum is right up against the tank! I would have them order in another one and see if it's the same...and if so, move on to a different manufacturer👍
Edit: Even if it is a "flap", a C4 corvette doesn't need any help warming up, nor any coolant flow restrictions!!!!!
Last edited by '78CorvetteS.A.; Yesterday at 01:28 PM.
On many Duralast radiators, the flap in the outlet is a design feature meant to prevent debris, insects, or small particles from entering the radiator core when the radiator is not in use or when coolant flow is interrupted. This is especially important for radiators that are part of a transmission cooler system or that have an extra outlet for auxiliary cooling lines Reddit.
Purpose of the Flap
Debris protection: The flap acts like a one-way valve or cover, blocking the outlet so that dirt, bugs, or small objects can’t get into the coolant passages. This helps maintain radiator integrity and prevents clogs or contamination Reddit.
System compatibility: If the radiator has an outlet for a transmission cooler or another auxiliary system, the flap ensures that coolant can’t backflow into the radiator when that system isn’t connected or in use Reddit.
Future use: Some radiators are designed for multiple configurations (e.g., manual vs. automatic transmission). The flap allows the outlet to be used later if needed, without risking contamination Reddit.
Installation Considerations
Do not remove the flap unless you are connecting the outlet to a compatible system. Removing it without use can allow debris to enter the radiator core, which can cause long-term damage Reddit.
If you’re replacing a radiator and the flap is missing or damaged, you can plug the outlet with a proper hose clamp and a rubber or barbed cap to keep it sealed Reddit.
Always ensure the outlet is connected to the correct auxiliary system (e.g., trans cooler) if your vehicle uses it.
In short: The flap in the Duralast radiator outlet is a protective cover to keep the radiator clean and prevent contamination, especially when the outlet is not actively in use. It’s a common feature on radiators with extra coolant lines, such as those for transmission coolers Reddit. S-10 Forum
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