No pressure in upper radiator hose

[Anonymous]

Hey fellas!

Not strictly a "six" question - my next door neighbor is working on a 67 stang with a 302. Engine runs really nice, but he has no pressure in his cooling system.

The car runs at medium heat, a little warmer than it should be, but not overheating.

He's replaced the thermostat twice, so that's ruled out.

No apparent leaks or drips under the car that we can see.

So, I'm confounded. Under what circumstances would the cooling system not be pressurizing?

Thanks!

 

[CobraSix]

2 possibilities that I can think of:

1) Water pump impeller is shot. How old is the water pump? If it is really old, it could have rusted to the point it is useless. Even a small hole in a pump will keep it from working well.

2) Blockage somewhere in the block.

Since it is not overheating, I'm putting stock in option #1. Just to rule out #2, hook up a water hose inline to the system with a flushing kit and see if any water comes out. If so, more then likely the water pump is shot.

Slade

 

[BIGREDRASA]

How about the wrong impeller on the pump? Don't the pumps for serpentine belts run backwards?

 

[Anonymous]

It's not a serpentine setup - good old-fashioned belt-driven. it's a '67.

The whole engine was re-built a few years ago but sat on a stand never run.

I was thinking water pump as well - is there another easy way to test?

 

[addo]

Isn't there a little bypass hose on these motors? Is it hooked up right?

Adam.

 

[CobraSix]

Yeah...didn't think of that...hoses may be on wrong. Also check to make sure they didn't give him a newer style water pump. If he went to an Autozone type store, I would definitely double check.

BTW, how do you know there is no pressure? did you remove the upper hose? Also, check to make sure the temp sending unit is working and double check running temperatures with a mechanical gauge. My new engine hardly warms up enough to even open the thermostat up (it's a 180* thermostat too), and so it appears that the system isn't charging.

Slade

 

[MustangSix]

What do you mean "no pressure"? Even when the cooling system is hot and is at 12-15psi, you can still squash the hose by hand. That's because any pressure you place there is simply displaced to the rest of the system..

OTOH, if you can remove the cap on a hot car and not experience gushijng coolant, then you need a new cap.

 

[Anonymous]

None of the hoses get hard. The water is hot, but the hoses never pressurize.

We tried 3 different radiator caps (that was my thought as well), but still no pressure.

 

[CobraSix]

All of my hoses can be squeezed...

If you are worried about that, get the hoses with the springs in them. That will keep them from doing it.

Check the temperature with a real gauge, not the dash gauge. If it is not running above the thermostat temperature (or not by much), then I say you are chasing a ghost. Maybe the engine used to have spring re-inforced hoses and that is what he is used to feeling and now thinks it is not pressurizing.

edit: If all the hoses are hot, then water is flowing. The one going into the pump from the radiator (water flow direction) should be slightly cooler.

Slade

 

[Anonymous]

What's strange is EVERY car I own, both vettes, the mustang, and my olds 442 - the upper radiator hose gets ROCK solid when the car is at operating temperature.

In this car, you can open the cap when the car is hot and nothing comes shooting out. I beleive that if you can squeeze the upper radiator hose, when the car is hot, there is something wrong.

I also noticed that there was some foaming in the coolant - in my mind that's bad since the pressurization of the system is what prevents the coolant from boiling.

I suppose I could suggest he tries another water pump.

Somone mentioned something about the thermostat - he as a 180. Could it be not opening fully?

 

[CobraSix]

if it didn't fully open, the car would be running very hot. I would still hook up a mechanical temp gauge from Autozone or anyplace. Find out what temp it is running at.

Maybe a stupid question, have you burbed the system?

Slade