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Old 03-09-2006, 12:21 AM   #1
Corellian Corvette
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No pressure in upper radiator hose. Is this normal?

Still working on getting my "new" 1974 Chevy pickup up to snuff and trying to 'undo' all the cusomizing by the previous owners

One thing I've noticed is that the upper radiator hose never gets any pressure. This seems unusual in that every single other vintage car I own gets a stiff upper radiator hose when the engine is at operating temp.

Now, the car doesn't overheat as verified by 2 gauges, IR thermometer and my hand.

P.O. says there is a 195 deg. thermostat which also is verified by the above gauges.

There is no coolant in the oil, no oil in the coolant, and no water leaks that I can see. I ran the engine with the rad cap off just to make sure the system is purged of air and there are no bubbles that might indicate a leaky head gasket. I'm told that the water pump is new.

Is it normal for these trucks not to pressurize the system? Again, the engine doesn't appear to be overheating but the lack of pressure has me worried.

Thanks!
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Old 03-09-2006, 12:24 AM   #2
cliffsta
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Re: No pressure in upper radiator hose. Is this normal?

Mine has pressure, I believe. I'm 99% sure.
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Old 03-09-2006, 02:39 AM   #3
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Re: No pressure in upper radiator hose. Is this normal?

Does the upper hose get hot like it flowing coolant?
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Old 03-09-2006, 03:17 AM   #4
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Re: No pressure in upper radiator hose. Is this normal?

My 1970 is not pressurized. I didn't think that 74's were pressurized, Do you have a picture of the radiator?

Even if it was pressurized at one time, it could have been swapped out to a nonpressurized system.
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Old 03-09-2006, 10:35 AM   #5
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Re: No pressure in upper radiator hose. Is this normal?

When the upper hose seems to never get pressure, then there is usually a problem. First, is the core full of water? Sometimes the air that is trapped, when you fill the readiator, is more than the makeup bottle can handle (if you have one). Second (you won't like this one) there may be a head gasket leak and it has pushed the water out and there is a lack of fluid in the radiator. This can be found by most radiator shops, most have a carbon monoxide tester to see if you are getting gases in your cooling system. By chance do you have the wrong radiator cap on the radiator? There are basically two kinds, one that vents and holds and then there is one that vents and allows water to be pulled back in from the overflow bottle. Last but not least, what pressure rating is the cap, it may be two low.
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Old 03-09-2006, 11:40 AM   #6
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Re: No pressure in upper radiator hose. Is this normal?

OK all good questions.

1. Rad is full of fluid.
2. Yes upper hose gets hot and coolant is flowing - I ran the car with the rad cap off, and I could see when the thermostat opened to let all the hot water flow in.
3. I checked for typical head gasket leak (bubbling in the water) but the water is still. That doesn't rule out a head gasked leak as you say.
4. How do I tell a pressurized vs. non pressurized system? There is an overflow bottle, and the rad cap appears to be a standard AC Delco type unit from the 60's/70's.
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Old 03-09-2006, 12:19 PM   #7
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Re: No pressure in upper radiator hose. Is this normal?

Just for safety's sake---Get a new rad cap..15 psi.
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Old 03-09-2006, 04:32 PM   #8
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Re: No pressure in upper radiator hose. Is this normal?

If you have the car running and can see the fluid cycling into the radiator from the hose I would thing your fine? The hose will be stiffer the newer it is, but you should be able to squeeze it when the engine is running wiht the cap on.
It not a high pressure system so-to-speak, but I would still be careful opening the cap when hot!!!
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Old 01-03-2015, 01:37 AM   #9
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Re: No pressure in upper radiator hose. Is this normal?

I'm having the same problem on my 84 c10 I was under the impression my water pump maybe bad but there's no water leaking anywhere not in the weep hole or any where else, I've already changed the thermostat a d the upper hose the fluids in the radiator are up. My temp gauge will shoot up to about 230 the drop to about 170 /185.
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Old 01-03-2015, 02:38 AM   #10
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Re: No pressure in upper radiator hose. Is this normal?

Think of it this way, IF you boil or heat water in a confined space, it will expand and create pressure. That is a law of physics. So the older systems did not have a collection/return system on them, they just pressed up to a point that they would hold pressure and not boil or they lifted the relief on the radiator cap.. The later systems had a radiator cap that relieved to a bottle and then had a small orifice that would allow water to return to the radiator when the system cooled and the coolant inside shrank back down. The upper hose should get firm or somewhat solid as the system presses up. If it is not pressing up, then something is letting pressure out and your water is going to boil at a lower temperature. If you want to, you can change the cap to a later style and add a return catch bottle to you truck.
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Old 01-03-2015, 04:02 AM   #11
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Re: No pressure in upper radiator hose. Is this normal?

'74 should have a coolant reservoir bottle. Does yours? Some people remove them to "clean up" the engine bay. I strongly recommend you use one. Google it; you can get NOS and repros on-line.

Chevy radiator caps are only good for so long, and I have had premature failures as well. Replace yours with a 15 PSI pressure cap.
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Old 01-03-2015, 07:04 AM   #12
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Re: No pressure in upper radiator hose. Is this normal?

Quote:
Originally Posted by three80three View Post
I'm having the same problem on my 84 c10 I was under the impression my water pump maybe bad but there's no water leaking anywhere not in the weep hole or any where else, I've already changed the thermostat a d the upper hose the fluids in the radiator are up. My temp gauge will shoot up to about 230 the drop to about 170 /185.
Have you pressure tested the cooling system to verify you have no leaks? Why bump a 9 year old thread for your issue when you already have a thread going?

As far as the temp spiking, IMO, it's the nature of the beast. Thermostats don't "snap" open. They slowly open, allow warm coolant to flow out of the block, cool coolant is allowed to flow in. In the meantime, the running engine is still producing heat, allowing temp to spike briefly while thermostat is opening.
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