What pressure radiator cap?

Discussion in 'Street/strip 400/430/455' started by bostoncat68, May 20, 2018.

  1. bostoncat68

    bostoncat68 Platinum Level Contributor

    My new champion radiator came with a 15 pound cap -- I seem to recall my prior cap being 12 or 13 pounds - I notice I've really had to tighten down all the hoses to preclude drips after it runs and cools down. I wonder if the cap is a little stout for the system? 68 430 --
     
  2. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

    15 psi is the standard pressure rating for most closed GM cooling systems. Pressurizing the cooling system elevates the boiling point of the coolant, that is it's purpose. It really shouldn't be a problem at all, but if you want, you can put a lesser rated cap on it.
     
    bostoncat68 likes this.
  3. Mark Demko

    Mark Demko Well-Known Member

    16 pounds is typical
     
  4. Schurkey

    Schurkey Silver Level contributor

    What clamps are you using? How old are the hoses?

    Wild Guess: The problem is not the pressure of the rad cap, the problem is the cooling system connections. Some manufacturers are using pressure caps well above 16 psi on their cooling systems, without leaks. Adding pressure not only raises the boiling point of the coolant, it makes the pump more efficient, too.

    There was a time that I thought those stainless steel "worm gear" hose clamps were wonderful. Now I know why they aren't used by the OEMs--they damage hoses and cause leaks. Doesn't help that typical hoses cold-flow out from under clamps which reduces the clamp load and therefore the sealing. This is hose damage from worm-gear clamps on a piece of fuel hose, but we've all seen similar hose damage on cooling system hoses.

    [​IMG]
    The smooth "fuel injection" style clamps eliminate the problem of hose flowing through the slots of the clamp, but the hose will still flow out from under the clamp. It takes longer, so the clamps may not need to be re-tightened before the service life of the fuel pump is done.

    Major manufacturers are using spring clamps that cause less damage to the hose, and of course never need to be re-tightened as they self-adjust (within their range) for the life of the hose.

    Don't forget that the flanges the hoses seat on need to be reasonably smooth, too. I've seen lots of aluminum thermostat housings, for example, where the hose sealing surface was wildly eroded.
     
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  5. bostoncat68

    bostoncat68 Platinum Level Contributor

    @Schurkey I'm starting to think the clamps are the issue...but it's not for a lack of effort on my part. Like @LARRY70GS mentioned in another post, I believe a cool engine is a safer choice so I decided last fall to use my new timing cover as an excuse to get rid of any weak links. Ever piece of my cooling system is fresh save the block itself... including new gates hoses with some nice T-bolt stainless clamps on the upper and lower hoses. Like you, I've never loved the worm drives because of the way they bite into hoses. However, I think these T-bolts are my issue -- I just can't seem to get rid of drips and leaks -- upper and lower hoses -- all 4 connections. Once I shut the car off they drip and not a small amount. These clamps have some beef (nice wide bands too) so I was not aggressive at first -- so I tightened in steps. Now, I'm thinking they just don't clamp evenly enough as I don't want to keep cranking on them and create issues with the aluminum outlets? Be curious if anyone else has seen this issue with T-bolts.
     
    chrome yellow likes this.
  6. TrunkMonkey

    TrunkMonkey Well-Known Member

    Single wire spring clamps, properly sized to the hose and quality made, provide the best compression around the full circumference of the hose, but they are a pain in the butt, and hands and forearms and... when you drag against them. And if you open the hood, your gonna get bit, just standing there looking at them. Nasty bastages...

    The "double wire" are not very good at sealing.

    The "worm gear" types that have open "screw slots" are the worse. The "worm gear" clamps that only have "divot cuts" are much better. But both of these can have a leak around the area the "screw" is located, and "over tigthening" them can increase a leak at that point.

    The "fuel injection" style are better. But also can leak at the "screw side" (where the screw head is in Shurkey's pic).
     
    Harlockssx likes this.
  7. Schurkey

    Schurkey Silver Level contributor

    I've only used T-bolt clamps on pressurized air applications (turbo discharge).

    The only problems I've had with them is having the nut seize on the stainless steel bolt.

    Breeze "Constant Torque" clamps work very well. They're worm-gear, but with an inner shield so the hose doesn't extrude through the slots, and they provide both a visual indication of proper tightness, and a measure of self-adjustment as the hose collapses under the clamp over time. They're bulky, and they look "huge" on heater hoses and such. Ungainly (but they WORK great.)
    [​IMG]

    Oetiker spring-loaded clamps work very well, but they're hateful to use due to the very small range of hose diameter that a given clamp will properly tighten on. If there's a variation in wall thickness of the hose, you might have to use the next-larger or next-smaller clamp. Makes it hard to keep a useful inventory of Oetiker clamps.
    [​IMG]
    But again, if you can find an OEM-style spring clamp in the right size, you'll have the best of the best.
     
    TrunkMonkey likes this.
  8. TrunkMonkey

    TrunkMonkey Well-Known Member

    Those will work!

    V-Band clamps like we used on aircraft fuel systems would be nice, if they were small enough for hoses, cheap enough and not so butt ugly! :D
     

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