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post #1 of (permalink) Old 06-17-2003, 11:49 PM
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Air trapped in radiator?

Well, I finished the timing chain tonight (finally), I also installed a new water pump while i was at it. Now a new question.

I let it run awhile checking to see if i had any leaks...I let it get to operating temperture, but did not notice the thrmostat opening up.

It doesnt appear the i have much movement in the radiator, and my hoses feel like its all air...

Do i have trapped air?, I can i purge the system?
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post #2 of (permalink) Old 06-18-2003, 01:04 AM
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Re: Air trapped in radiator?

Well it runs again and thats a good thing! To my understanding cj's run coolant thru the heater core at all times,and you can see the hoses attach above and below the tstat(or before and after,depending on how you look at it) so it take quite a while for the stat to open fully while sitting still. make sure its full and let it heat up and cool off with the cap on and overflow bottle would take a major effort to get a air pocket in a cj radiator! enjoy. [img]images/graemlins/40BEER.gif[/img] gas.
post #3 of (permalink) Old 06-20-2003, 10:13 PM
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Re: Air trapped in radiator?

Question about the heater core comment.

If the heater core was slightly plugged would this cause some over heating issues ?

I am runnin a 350 in a 81 cj5.

Thanks in advance. [img]images/graemlins/goodpost.gif[/img]
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post #4 of (permalink) Old 06-21-2003, 12:06 AM
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Re: Air trapped in radiator?

I've seen a blocked heater core make one warm up quicker,and not put out much heat in the winter.
But it doesnt transfer enough btu's to affect the cooling of the whole system much. Unlike alot of vehicles that have a heater control valve that controls coolant they increase the surface area when you open the valve, unlike a jeep that the coolants path is always the same,we just control a small amount of air flow. therefore check your tstat,maybe get the rad cleaned and rodded,and do you have a good pump and cap? good luck... gas. [img]images/graemlins/40BEER.gif[/img]
post #5 of (permalink) Old 06-21-2003, 08:33 AM
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Re: Air trapped in radiator?

Here's what I found out about that. One of my pet peeves are hot feet in the summer(inside a vehicle that is). Why does the heater core have to be flowing coolant all the time? I guess it's the design of the cooling system. So I put a water shut off valve in line with one of the heater hoses and stopped the flow of coolant. Started the engine and watched the temp gauge. It started to come up, and up, and almost pegged out. Now I know the engine wasn't that hot, there was nothing wrong before I put the valve in(a classic troubleshooting technique-always go to the last thing done) and it was only idling and there just wasn't enough time(maybe 3 or 4 minutes) for the engine to get that hot. About 2 seconds after the gauge pegged the needle came down real fast, then wiggled till it settled down to normal operating temperature. Here's what I think. The temp gauge sender is located in the head(rear, almost at firewall). So by blocking off the heater core flow this also blocked off the flow to the head. It only took a couple minutes for the head(and sender) to heat up(this is one of the hottest areas of an internal combustion engine), then probable by convection or by some slight flow through the thermostat, the thermostat finally felt the heat and opened up. If you have a good sender, gauge and connections you can actually see the thermostat open normally in a normal situation. The needle will start to rise, go slightly above normal, then drops to slightly below normal(t-stat opens because hot then allows cooler coolant to flow), then needle will settle down to normal(temperature stablizes). As for the Chevy small block...I have a 267 in my '79 Malibu. Had a vacuum leak. It has a heater shut off valve(vacuun operated) screwed into the port on the intake manifold, r/h side front. I bought a new one and before I installed it I hooked up my vacuum hand pump to it, mainly to see if the new one had any leaks. While it was holding a vacuum I tried blowing into the inlet just to see if it would flow anythig...totally shut. So...with this small block you can block off the coolant flow to the heater core for the summer...yes! I do not know if all small blocks are the same but I bet there close. Also I think big blocks have a little 90 degree hose that goes between the pump and the intake manifold, I think. Maybe big block cooling systems are designed like the 258 in that they need flow to the head(s) from the pump all the time. This little 90 degree hose allows coolant flow to be maintained while the heater core flow can be stopped. Also air will seek the highest point in the system, shortly after start-up and reaching operating temperature(t-stat open). If the Jeep is level or face the dang thing up hill a little so the rad cap is the highest point. Also if you have a closed(over flow bottle with inlet/outlet at the bottom) system with the rad over flow at the highest point, this will help purge the air out of the system. [img]images/graemlins/RockOn.gif[/img]
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post #6 of (permalink) Old 06-21-2003, 09:59 AM
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Re: Air trapped in radiator?

Well you got me! the heater acts as the bypass hose,re;if there isn't some small amount of coolant flow at all times, the water pump will cavitate until the stat opens.gas. [img]images/graemlins/RockOn.gif[/img]
post #7 of (permalink) Old 06-21-2003, 02:11 PM
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Re: Air trapped in radiator?

1. There are two good ways to burp a system to get the air out.
2. The first, is to remove the thermostat and drill a 1/16" hole in the rim of the thermostat.
3. There will be some fluid flow, but not much at pressure,
4. But air will pass and the engine will burp.
5. The second is to buy a thermostat with this already manufactured into it.
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post #8 of (permalink) Old 06-21-2003, 06:45 PM
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Re: Air trapped in radiator?

Hey "JimmyZ" On my AMC V-8 engine one heater hose is attached to the intake. If you block the flow of coolant to the heater , you would be blocking coolant to the intake, not a good thing. Especially since the T/stat housing is located on the intake.
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post #9 of (permalink) Old 06-21-2003, 08:01 PM
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Re: Air trapped in radiator?

you can do what LEVE said, or take it one step further: when you drill a hole on top of thermostat housing, tapp it and put a bolt (bolt should not be long). so now when you want to bleed cooling system fill the reservoir with coolant mixture to the mark, unscrew the bolt and put coolant mixture through the hole (on top of thermostat) until it spills, then tighten the bolt. start the engine and let it get to normal operating temp. loosen the bolt until the coolant spilling out is free from air bubbles, then tighten the screw and you are done
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post #10 of (permalink) Old 06-22-2003, 01:22 AM
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Re: Air trapped in radiator?

I took off the brand new water pump today, during the process i put a hole in the radiator [img]images/graemlins/shocked.gif[/img]. after picking up a new radiator (after weighing cost to repair) and installing it, i put my old water pump back on and started, as soon as the thermostat opened up and i refilled, i immediately saw fluid movement in the radiator....

So far so good, i will test drive it tommorrow. [img]images/graemlins/smile.gif[/img]
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