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Premium Member
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Discussion Starter #1
Hey guys just picked up the new box truck today.

Driving it back I noticed the coolant temp gauge was all over the place dancing around. It never got over M in normal for a few seconds then drop right back down again.

I noticed when I popped the hood when I got back home that there was a little coolant splatter around the rad cap and at the overflow bottle. Not much but enough to see 5 or 10 drops.

I'm thinking the thermostat is screwed up. Not opening at the proper time etc.

I didn't notice any hot coolant smell or it steaming from the rad.

What suggestions do yall have?
 

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Team Shade-Tree Mechanic
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635 Posts
Do you have access to a pressure tester?
 

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Discussion Starter #4
Photos....







 

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Demon Dually
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Put a new cap on it. That thing looks original. Cheap insurance. Actually looking at the cap I think it isn't the right one to begin with. That is only a 7 lb cap.
 

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Discussion Starter #6
Put a new cap on it. That thing looks original. Cheap insurance. Actually looking at the cap I think it isn't the right one to begin with. That is only a 7 lb cap.
I was going to try that also:ford:
 

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OEM Moderator
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9,381 Posts
Gauge with rapid fluctuation sounds to me like when there is air in the system. It might be boiling over if the cap is not holding pressure causing air in the system. If it was low on coolant I might have an air pocket. I hope you do not have a bad head gasket or similar issue.
 

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Premium Member
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Discussion Starter #10
I put a new 16lb rad cap on it sat. and took it for about a 20mile ride coolant temp climbed up to O in normal but didn't flutter around and when I got home and popped the hood it didn't have any spatter anywhere.

I think the cap just wasn't seating properly.
 

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Demon Dually
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If you look at the old cap it was only rated for 7 lbs. That is less than half of what the system calls for. I am gonna guess it just plain didn't hold the pressure at all.
 

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Discussion Starter #12
If you look at the old cap it was only rated for 7 lbs. That is less than half of what the system calls for. I am gonna guess it just plain didn't hold the pressure at all.
Yea you could see where it wasn't seating at all.

So we shall see what it does:ford:
 

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OEM Moderator
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I hope that is it that would be great!!!
 

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Premium Member
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Discussion Starter #14
So far so good. I noticed with the old rad cap the overflow bottle had almost filled completely up. Now with the new cap the bottle is back down to normal and temps run normal when driving
 

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Demon Dually
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5,140 Posts
Awesome. Glad to hear the cap was most likely the fix. Nice and cheap and easy.
 

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Discussion Starter #17
Been driving it like we stole it. I think the problem was the rad cap
 
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