1998 blazer 4.3L I think i need a new radiator cap. The overflow tank is full and overflowing. a couple of days ago i cleaned the overflow tank and then filled it halfway with antifreeze,everyday since then ive had to add 1-2 cups of water to the radiator because it was low. I havent seen any wat…

If the resivour tank is filling up I do not think the radiator cap is the problem. Easy check when cool remove the radiator cap and see if the radiator is full. A failing radiator cap will in my experience allow fluid to escape via the cap and never make it to the resivour.

When GM built your vehicle, they didn’t make the cooling system pressure cap. It was purchased from a vendor/supplier. So if you buy it from the dealer/parts store, you’re probably getting the same part. One major supplier to the auto industry for pressure caps is Stant. Tester

no it`s not full, i have to add 1-2 cups of water everyday. i only filled the overflow tank halfway and now it`s full, water is going in to it from the radiator but not going back out to the radiator.

Thats what i was going to replace the plastic cap with, a metal stant cap. maybe the plastic cap is suppose to have a spring or did have a spring but it doesnt have one now. This cap has a 15psi pressure release but all the stant ones that the local parts stoer has are 16 psi pressure release, will…

The radiator has just a plastic screw on cap too.like i said it doesnt even a spring on it so i dont know how it releases pressure, that`s why i want to get a new cap.

It’ll be okay. All 1 PSI will do is just slightly raise the boiling point of the coolant. Tester

this is what it has now: [image] I want to get one of these: [image]

If it screws onto the radiator, it should work. Tester

Replace it with exactly what came off. Don’t try to force that different cap on it.

The cap’s design depends on the dimensions of the place where it screws on. The cap has to match up with those. Especially important is the distance between the top surface (on the Stant photo above, the surface corresonding to the bottom of the red lever to the lower rubber washer.) The spring …

OEM or aftermarket radiator cap?

Maintenance/Repairs

circuitsmith November 25, 2016, 7:57pm 21

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OEM or aftermarket radiator cap?

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