Upper Radiator Hose Collapsing - Team Camaro Tech
Troubleshooting Diagnosing problems done here.

 
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post #1 of 12 (permalink) Old Apr 21st, 02, 12:37 PM Thread Starter
 
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Location: Lawrenceville, PA, USA
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I have a 79 Z28 with a 350, 30 over, 10:1 compression, 294 Comp Cam solid lifters, 650 holley carb, 4speed with 3 core radiator.

I had a 160 degree thermostat in it. The motor hasn't been broken in yet, although it has been assembled for 10 years. I put in a new 180 thermostat because I felt the 160 was too low a temp.

As I drove down the road the engine temp went to 220 and stabilized. I thought the gauge was off but decided to check under the hood anyways.

What I found was when I gave the car gas the upper hose collapsed. It literaly flattened out.

I opened the radiator cap and you could hear the pressure release and water go into the overflow. When I took the cap all the way off the radiator was down about 1/4 of the way.

I thought the thermostat was sticking so I took it out while the motor was still hot. The thermostat was open, I watched it close as it cooled down.

The thermostat housing was really hot to the touch but the upper hose was cool. The radiator cap was cool too.

Could I have an air pocket?
Bad hose?
Bad water pump?

How do I troubleshoot this?

Please help.

Thanks,
Tom
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post #2 of 12 (permalink) Old Apr 21st, 02, 01:12 PM
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The normal flow is from the lower hose to the pump, through the engine then out through the top hose.
Sometimes the lower hose will collapse, this is why the lower hose usually has a spiral wire spring inside to prevent this.
I would check the water pump to see if it is correct.
Serpentine drive belt systems use a water pump that is designed to rotate counterclockwise compared to clockwise on a regular v belt setup.
Possibly You got the wrong pump? or, Are You using a serp belt setup with the original pump?
Maybe somebody else can throw out some suggestions, but that is where I would start looking....
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post #3 of 12 (permalink) Old Apr 21st, 02, 03:57 PM
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It sounds like you had an air pocket and the thermostat wouldn't open. I've seen this exact thing happen if the engine isn't filled correctly, and revving the motor will sometimes collapse the upper hose as the pump is pulling but the thermostat isn't opening.

I like to fill the block through the thermostat housing. Then re-install the thermostat and housing and finish filling through the radiator. If you don't get the block full often the thermostat will not open and the engine will get very hot.

After doing the above, re-check the radiator level after a complete heating and cooling cycle.

Jody
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post #4 of 12 (permalink) Old Apr 22nd, 02, 02:12 AM
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If the above check out okay.
Could be signs that the upper rad hose is old,and should be replaced PDQ, It can no longer hold its shape,
If I remember correctly this hose is long, at least 24 inches, It may also come with a spring or renforced section, to prevent collapse.
You could install a spring to prevent the problem.

[This message has been edited by Rob.Canada (edited 04-22-2002).]
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post #5 of 12 (permalink) Old Apr 22nd, 02, 09:16 AM
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There should not be a spring in the upper hose.
Double check the cap for fuction and Correct type. Sounds like you have a closed system cap on an open system (with overflow) or the cap is defective and not allowing system to equalize.
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post #6 of 12 (permalink) Old Apr 22nd, 02, 10:48 AM
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if your still having a prob with your top hose try this trick. remove your thermostat an fill your system from there before replacing the stat drill a small hole in the side to allow air to escape pass the stat when closed then put everything back together. next pack the system by starting the motor cold an allow it to run for a minute carefully remove your cap an raise your idle to approx 2000 this should allow you to add more coolant and pack the system a friend to help would be great.
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post #7 of 12 (permalink) Old Apr 22nd, 02, 03:36 PM
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Okay, I'll bite. Here is my list.

First....are you sure you don't have a reverse flow pump?

Second....there should be pressure in the upper hose at all times and you have a very low pressure acting on it..it should be expanding ...not collapsing the hose.

Third....make sure the system is full.

------------------
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Techical forum/links at www.inccn.net/techforum.htm

[This message has been edited by HOTRODSRJ (edited 04-22-2002).]
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post #8 of 12 (permalink) Old Apr 22nd, 02, 07:33 PM
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Chevy uses two different (long) pumps for serpentine belt systems. Your car ('79) should be serpentine, but uses a standard rotation pump. Chevy didn't use 'reverse rotation' pumps on passenger cars until '87.
Please check the cap and coolant recovery system before you spend a bunch of money. Your system should never operate under a vacuum which will collapse the upper hose.
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post #9 of 12 (permalink) Old Apr 23rd, 02, 03:26 AM Thread Starter
 
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The water pump was on the car before I rebuilt the motor. It uses V-belts. I never had any problems when the motor was stock. I believe the motor is from a 1975 van according to the casting number.

The system may not have been full of fluid. I removed the thermostat and added water to fill the block first. I then put the thermostat back in, reattached the upper hose and filled the radiator.

I will check it out tonight and see if that was the problem. I have a new hose to install just in case the hose collapses again.

I did a pressure test on the radiator and cap with a kit from AutoZone. Everything tested fine with no leaks. The cap "opened" at 18psi so that seemed to work correctly.

More to come as I dig into it.

Thanks for the comments so far.

------------------
'79 Z28, 4spd, 3.73 10 bolt, 350 4-bolt .030 over with stud kit, 10:1 Compression, Keith Black Flat Tops, Comp Cams Magnum 294 Solid Cam .525 lift, 63cc Heads, Stainless valves, hardened exhaust seats, guideplates, Summit Needle Bearing Roller Rockers 1.5 ratio, Offy Single Plane Intake, Holley 650 Vac. Secondaries, Stock HEI (for now), Headers 1 7/8" primaries, 3" Collectors into 2 1/2" exhaust with "H" pipe and Turbo Mufflers.
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post #10 of 12 (permalink) Old Apr 23rd, 02, 03:41 AM
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Are you sure you have the thermostat installed correctly? The radiator is on the suction side of the water pump, and a blockage in the thermostat neck would limit the flow of water, resulting in vacuum in the radiator. When the radiator goes into vacuum, you will suck air through the radiator cap and your coolant recovery system. The lower hose is usually re-inforced with wire, so the upper hose is the weakest link.
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post #11 of 12 (permalink) Old Apr 23rd, 02, 04:10 AM
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Tjgerow,

I think you're on the right track. I've had the exact thing happen to me and no, I didn't have a reverse rotation pump. The thermostat was bad. I noticed the car was running hotter than normal at a friend's house, so I opened the hood and the upper hose would collapse when I revved the engine.

A change of thermostat and it's been fine since.

Good luck and please let us know if it worked.

Jody
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post #12 of 12 (permalink) Old Apr 24th, 02, 06:40 AM Thread Starter
 
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The problem was the thermostat! I changed back to the OLD 160* stat and have not had any problems with the hose collapsing.

The 180* stat was brand new. Guess you get a bad one every now and then.

Thanks for the advice from everyone!!

Now I am off to install a new HEI with a mechanical curve kit. This will probably become another topic later



------------------
'79 Z28, 4spd, 3.73 10 bolt, 350 4-bolt .030 over with stud kit, 10:1 Compression, Keith Black Flat Tops, Comp Cams Magnum 294 Solid Cam .525 lift, 63cc Heads, Stainless valves, hardened exhaust seats, guideplates, Summit Needle Bearing Roller Rockers 1.5 ratio, Offy Single Plane Intake, Holley 650 Vac. Secondaries, Stock HEI (for now), Headers 1 7/8" primaries, 3" Collectors into 2 1/2" exhaust with "H" pipe and Turbo Mufflers.
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