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Radiator Cap (4 pound with bottom mount)
Fits 41-52 MB, GPW, CJ-2A, 3A, M38, M38A1, Truck, Station Wagon

Part # 810391

New Radiator Cap

Replacement 4 pound cap.  Ensures proper cooling.

For bottom mount Radiators.

4-134 engine

41-45 MB
41-45 GPW
45-49 CJ-2A
49 CJ-3A
50-52 M38
52-66 M38A1
46-49 Truck
46-49 Station Wagon

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What is ment by bottom mount? I have a 52 m38a1 with the hinged front clip. The radiator appears to be original and mounts via a flange on ither side to the nose. Would this be an example of a non bottom mount? Or should I just measure the neck size and be ok? Thanks

Willys Jeep Parts Tech:
Bottom mount is referring to a radiator that has 2 studs on the bottom of it to mount on steel tabs on the crossmember its bolted to. A side mount radiator is where the radiator is actually bolted to the grille.

Hello. I bought an after market radiator for my 46 Willys CJ2A and it came with a 13lb. cap. Should I get a 4lb cap or will the 13lb one be ok??? Have driven it several times and it is working fine.

Willys Jeep Parts Tech:
We have not hand any issues with the supplied caps by the manufacturer.

is this a 21/8" inside diameter cap?

Willys Jeep Parts Tech:
2-3/4" inside diameter of the metal cap itself.

I have a '48 CJ-2A with a bottom mounted radiator. I've had trouble getting a replacement radiator cap. The inter-neck is 1-1/2" across, the outer-neck is 2" across and the depth is 1" from the bottom of the screw on cap, is the item #810391 the correct cap?

Willys Jeep Parts Tech:
If you are bottom mount yes this should be it. Make sure it looks the same as yours from the photos.

i have a 1958 CJ5 Willis Jeep. is this the correct cap? also, I don't understand the bottom mount and side mount stated for the radiator. what does this mean? thanks.

Willys Tech:
It is referring to how the radiator mounts. Either bottom mounted to tabs on the crossmember or side mounted to the grille.

I have a 1953 M38A1. What exactly do I measure to find out which cap I need? Also, I have seen 7lb and 4lb caps sold as NOS. How do I know which is proper? Which is standard for your M38A1 replacement radiator (805825)? Thank you.

Willys Tech:
We typically use a 4lb cap for the 4-134 engines. You just need to measure your neck size to confirm yours.

I have a '52 M38, the part number in the book specifies #7375030, but I'm not finding it anywhere. Will this fit?

Willys Tech:
Yes as long as you have the large neck measurement above. Which you should.

I have a 1950 Sedan Delivery with what I think is the original radiator. It looks like the radiator cap doesnt seat correctly. It looks like the depth of the radiator neck is 1 deep where as the rubber seals on the cap only measure 3/4. So when the motor heats up, the cap doesnt seal and it just goes out the overflow hose. I checked other aftermarket caps and they also measure 3/4. Does this sound correct or am I just missing something?

Willys Tech:
Sounds like you need part number: 648746 if you have the small style. This part number is for the 2-7/8 neck.
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