Upper radiator hose blowing off...Any ideas

[night rider]

Hey guys.. I picked up a beater chevy parts chaser about a mo. ago with a 350 in it.

Ran great for about 3 weeks then this week it started blowing the upper rad. hose off the water neck.

Crank it up, runs good then about 20 min later the hose will pop off the water neck and around a gal of coolant spits out everywhere.

It's got/had 50% anti frezze mix in it, I replaced the old hose with a new one. No water in the cyl. when I removed plugs, no sign of oil in water, or water in the oil.

I have always heard blowing off hose = cracked head/block, or maybe blown head gasket.

Yall got any ideas on what to check??

 

[Kamikaze]

A couple of strange things come to mind...

Check the thermostat and maybe drill a couple of 1/8" holes near the poppet to act as a bypass.

This one doesn't make sense since you stated it ran good for a few weeks but I was thinking that there's a blockage and the water pump may be a reverse rotation that's backing up against the thermostat???

 

[Camaro75LT]

I'd pop the t-stat out completely and run it, just see if it stops the hose from blowning off. I have seen compression bleed off into a cooling system from a cracked head, but it will usually pop a radiator, hose clamp or a weaker part of the system.

 

[night rider]

Ok guys.. Been working on it some more. Pulled the T stat out.. Still does it.

Looked in rad. with car running, I can see water flowing through rad.

 

[Marv D]

Apparently it's the wrong radiator cap or the cap would be releasing the pressure, and not blowing hoses. If you fix the hose thing and don't fix the problem,, next it will be blowing the ends off the radiator.


1. find out if there is, or is not, combustion pressure entering the cooling system. (simple pressure test the system and see if it's leaking down)

2. Find out why the radiator cap isn't releasing the pressure.

 

[BowHunter]

Did you put a new clamp with the new hose or use old clamp ?? Just thought I'd ask! If new! Double clamp that sucker and see what blows then! (JK) on see wHatt blows then!

 

[night rider]

Ok, Thanks guys I'll give those ideas a shot here in a couple of hours.

BTW.. Yeah new clamps on both ends of new hose.

The rad cap looks good, Don't seem to be but a couple years old and its a 16 lb cap.

I'll put the one off my camaro over onto this rad and see how that does. I know my camaro's cap is good.

 

[camaro454]

I had the same problem I bought a new rad cap and tried it out blew the upper hose right off the radiator. Placed old cap back on and no more problems. Sounds like you might have the wrong cap.

 

[Air_Adam]

Sandblast or replace the water neck... I've seen more that one thats so smooth, for one reason or another, that a hose just can't "grip" it. Of course, even then, it still takes pressure to blow it off - more than is normal.

You should try doing a pressure test on your cooling system, get it up as high as you can and try to blow off the hose like that. If it blows off at normal cooling system pressures (10-18 psi) then the hose coming off is the problem and not just a symptom of a bigger problem. If you can crank the pressure way up and the hose doesn't move, then excess pressure is coming from somewhere else when the engine is running - possibly a leaking head gasket, possibly a SEVERE overheating problem you don't know about, or something else.

 

[Marks71BB]

I agree with Marv and Air,

I bet its a chrome water neck and bad rad cap.