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  #1  
Old Nov 11th, 12, 10:33 AM
Marc Marc is offline
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Join Date: Jul 2001
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Default Overheating due to air pocket

Hi!

After change of front oil seal on engine, water pump out,... I have everything reassembled and I refilled the system with fresh water and anti freeze.

180 thermostat and I didn't drilled any additional 1/8 holes.
while driving I got the temp gauge going by moment from 180 to 210 and once 240 (it goes very quickly up) and then it goes back down (after 5 sec or so).
I stopped by the road just after the needle was climbing past 210 and I noticed the big top hose on the radiator was swallowed by air.
After a moment the engine was again operating at 180, and the top hose was not swallowed no more.
Later I check level of fluid but it was still too hot and I got water going over, the water was not boiling, just hot but no harm.

I didn't change a thing to the motor/cooling system while reassemble, it is a original cooling system with mech fan, mech pump and 2 core radiator on a 327 small block and it was doing fine before.

Thinking about it, is like water is not pumped all the time to/ does not reach the radiator. Because when in circulation the water temperature goes down again as the gauge tells it - it never stays overheating.

So I come to the fact that I must have air in the system? Or/and that the thermostat does not regulate as it should and maybe pressure increases at the top of radiator going to be felt in the top hose...

What is your though on it?

Best regards
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  #2  
Old Nov 11th, 12, 11:13 AM
Steptoe Steptoe is offline
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Default Re: Overheating due to air pocket

This only happen while car is moving?
Check the bottom hose, reenforcing spring has not collasped....a good squeeeze the hose doe not collapse.
The spring corrodes away, the water pump pulls a good vaccuum, at higher rpms, being water, not air it has a strong hydrolic effect, collasping the hose and restricting flow..

What happens from here ...the spring breaks up, goes thru the system eventually bits collect in cores...restrict cores, other crud and debris gets caught in these partly blocked cores, blocking them....usually nothing is noticed at this piont because the cooling system is wasy over built.
Then a couple decades turn over , the engine gets a rebuild, new oil pump, water pump and radiator completely over looked...A few bits of gasket sealant and stuff gets flushed into the radiator.. now enough to block a few more cores, the car runs hot.

All due to a lack of maintance.

Check that bottom hose, and pull the stopcock in the bottom of the radiator , see if can hook any crud, debris out.
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  #3  
Old Nov 11th, 12, 11:53 PM
Marc Marc is offline
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Default Re: Overheating due to air pocket

Hi Steptoe, I saw your other posts on the subject, my bottom hose was replaced 2 years ago. It must still be fine.
It doesn't come at RPM, just at any moments.
Is it normal to have the top hose swallowed by air?
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  #4  
Old Nov 12th, 12, 03:09 AM
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Brian
 
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Default Re: Overheating due to air pocket

I've always had good luck with this procedure:
Refill the system to cold line left off the radiator cap and ran the engine till the thermostat opened and the radiator level dropped, monitor level and added a bit of coolant as needed then sealed and ran to temp and pressure. Then shutdown and let cool. Remove cap and check level and top to cold line.
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  #5  
Old Nov 12th, 12, 03:43 AM
Steiner Steiner is offline
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Default Re: Overheating due to air pocket

I always jack up the front of the car and fill through the thermostat opening in the manifold until full. Then install t-stat and water neck, and top off radiator.
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  #6  
Old Nov 12th, 12, 11:42 AM
Steptoe Steptoe is offline
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Default Re: Overheating due to air pocket

Look on the side of the radiator.. it has a hot and cold level... well below the height of the top hose and theromstat housing....it is not a vaccuum , it has air in it....
I have never had a air lock ...except on a LPG engine that had the converter (heated with engine coolant) above the height of the radiator and top hose....With and air lock in there and since doesnt get full coolant flow to flush, yes water can stop flowing, the expansion and drop of LPG pressure will cause it to freeze full (yep covered in ice) and car not run...
The only time an air lock has been and issue....
Jacking up the front... better still park on a slop facing up sorts that....
The bottom hose is 2 yrs old....so are we assuming it is ok then ?

Successful Trouble shooting... is no assumptions.....It is knowing.

Thu I have never seen air lock on early chevs, doesnt mean it cant happen....
U have noted u never drilled the thermostat....so it doesnt have ANY hole, even it it has a little thing hanging in it?.... have u Drilled it it 3/16" yet?
Jack the front up and fill....as Steiner says above...done that?
Quote:
Is it normal to have the top hose swallowed by air?
Yeah if the hose is old and weak, and its not air, it is pressure in the system....
Have u done a full routine maintance on the system yet?
Full flush, back flush... described in older posta many times

Complete these basic things which is 1st stop routine with any run hot/ over heating issue.
hole in thermostat.... check thermostat is working corectly in a jug
check bottom hose (all hoses)
Check behind the stopcock
Cooling system routine maintance, back flush, water pump/ clutch bearing play
replace cap
HC/ CO check of the radiator gases.
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  #7  
Old Nov 13th, 12, 03:29 PM
rj68RS rj68RS is offline
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Russ
 
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Default Re: Overheating due to air pocket

x2
Quote:
Originally Posted by Steiner View Post
I always jack up the front of the car and fill through the thermostat opening in the manifold until full. Then install t-stat and water neck, and top off radiator.
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