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Unread 03-25-2013, 09:48 PM   #1
Fellows45
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1989 YJ Wrangler 
 
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Location: Bowling Green, Kentucky
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Boiling coolant rushing back into overflow

Hey guys quick question.

as you know summer is coming up, and this bring a problem with my yj...

when I drive in the summer 90+ degrees, if i drive for a while, then park it at the pool or anywhere for that matter, boiling engine coolant rushes back into overflow reservoir and sometimes spills over the top, and then as the engine cools back down, it'll suck some (most) of it back up... it isn't a huge problem, it just gets a little annoying having to add coolant once a week during the summer months.

I was thinking it could be a bad thermostat, but I'm not too sure.

thanks

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Unread 03-25-2013, 10:01 PM   #2
YJinAZ
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1993 YJ Wrangler 
 
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Location: Gold Canyon, AZ
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Do you have a stock overflow bottle on your rig?Is it filled only to the "full" indicator? If so, it should have enough room for the radiator overflow, so you don't have to add coolant on a regular basis.

Usually, when I have experienced overflow, the overflow tank was overfilled.

Have you checked the condition and seal of the radiator cap?

I try to start with the easy/cheap items like these. Hope this helps...
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Unread 03-25-2013, 10:22 PM   #3
Luuca
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Quote:
Originally Posted by YJinAZ
Do you have a stock overflow bottle on your rig?Is it filled only to the "full" indicator? If so, it should have enough room for the radiator overflow, so you don't have to add coolant on a regular basis.

Usually, when I have experienced overflow, the overflow tank was overfilled.

Have you checked the condition and seal of the radiator cap?

I try to start with the easy/cheap items like these. Hope this helps...
Rad cap is cheap, but usually it'll cause overheating while driving at slower speeds. If you are getting regurgitated fluid after stopping, you may be overfilling your rad as the reply above suggests or you may have a slightly clogged radiator.

How's it run when you are in stop and go traffic? Running hot?
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Unread 03-26-2013, 12:42 PM   #4
Jeepsr4me
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Cap would be my 1st thing to replace, then the Thermostat. Over filling of the reservoir will cause it to push out what it dont need.
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Unread 03-26-2013, 05:39 PM   #5
jay-h
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I'm assuming the dash gage is not showing overheating. That is definitely not normal, there might be a little flow into the overflow but it should not be much.

First I'd change the cap.

But you could have a bad radiator. or possibly head gasket.
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Unread 03-26-2013, 06:21 PM   #6
plym49
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Two ways to check your thermostat:

1. Remove it and put it in a pan of water. Heat the water and track the temp with a thermometer. See if the thermostat fully opens at the appropriate temperature.

2. With a cool motor, be sure that the radiator is full and remove the radiator cap. Keep it off. Start the motor with a piece of cardboard in front of the radiator so the motor can quickly get hot. When the motor gets to operating temperature, if you see coolant quickly flowing in the top tank, your thermostat is fine. If on the other hand you get pulses of hot coolant geysering up out of the radiator, your thermostat is bad.
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Unread 03-26-2013, 08:12 PM   #7
Fellows45
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Thanks for the input guys, I'm gonna start with the radiator cap. then the thermostat..

There shouldn't be any way there is a head gasket leak, just had a new motor put in and really put some money into some quality parts such as gaskets and the TBI system.

Do they make an oversized engine coolant tank for the yj? that might be the way to go later on!
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Unread 03-26-2013, 08:23 PM   #8
Yams
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Water boils at a higher temperature when under pressure. Maybe the cap isn't able to keep pressure in the system. I'd get a new cap.
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Unread 03-27-2013, 12:21 AM   #9
Jeepsr4me
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Quote:
Originally Posted by Fellows45 View Post
Do they make an oversized engine coolant tank for the yj? that might be the way to go later on!
That makes zero sense... When the system is right, that tank is more than enough... Fix what you got. Cap.. Take it off, go to parts store and use their pressure tester. I just did this yesterday. Cap would not hold pressure, tested the new one while I was at the store it held to the pressure listed on the cap. Get the right one, more pressure is not a good thing..
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