4.0 L Core/Freeze Plugs

Hello - I recently replaced all five 2" core plugs on my 1997 4.0L Cherokee with brass plugs due to corrosion of the original steel ones. The Cherokee ran great for about two months, and then, under a moment of hard acceleration, one of the new plugs blew out. Fortunately the engine was not damaged, and I again replaced the one that blew. The folks at NAPA said that this can be a common problem when replacing core plugs if the cooling system is not bled properly. My question to you masters out there is this: is this the probable cause, and if so, what is the best way to ensure that this will not occur again? I may have saved $600, but the tow cost $100!

Thank you all so very much!

Reply to
Quattro GR4
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Quattro GR4 did pass the time by typing:

After running for two months you shouldn't have any air left in the 4.0 block. It's a closed system that vents air and sucks back in extra coolant from the overflow bottle. It's more likely the plug didn't sit correctly and worked it's way out. Not all those holes are perfectly round. Wouldn't be the first time a plug popped out on someone.

Hard acceleration doesn't increase coolant pressure except directly between the pump and thermostat. Overheating/boiling can but that pops the radiator safety valve.

Reply to
DougW

Which one keeps blowing out? Is it the rear freeze plug?

Reply to
billy ray

Reply to
L.W.( ßill ) Hughes III

This has only happened twice - the first time was due to corrosion, then I replaced all of them. The second time it was the 2nd one from the firewall, and this one blew out after driving the vehicle less than

100 miles over about 6 - 8 weeks (was using another vehicle most of that time). Now I just want to be certain I have it fixed properly!

Thanks again!

Reply to
Quattro GR4

Hi Bill -

You say "Nope," meaning that bleeding the cooling system had nothing to do with this blowing out? What do you think caused it, and what should I do better to make certain it doesn't happen again?

Thank you very much.

Reply to
Quattro GR4

Reply to
L.W.( ßill ) Hughes III

The right tool for the right job. Coasty

Reply to
Coasty

"and of course drive it correctly straight in from the it's center using the tool:"

Thanks Bill - I totally agree, and I did actually order a complete core plug installation kit on eBay. It helped only a little, but I believed the plugs went in true. When I redid the blown one I double checked all the plugs to make certain they were seated flush with the block. I hope it was just a case of poor installation the first time!

Merry Christmas!

Reply to
Quattro GR4

You just got unlucky in my opinion. The plugs are a press fit. The rad cap is supposed to blow at 15 psi or so. That means you had less than

15 psi pushing on it and it just let go.

If it happens again, I would think about gluing the next one in....

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail >
Reply to
Mike Romain

Quattro GR4 did pass the time by typing:

flush, as in the outside edge is flush? That's not seated unless your talking about a dome type plug. There has to be an edge for the plug to catch on.

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is what they should look like.

Reply to
DougW

That's what I was thinking. I always try for enough edge to be able to stake it at 2-3 points around the hole.

Reply to
Will Honea

LOL! Man is that 'ever' one reversing image! At first it looked like a plug in half way and inside out. I had to download it to look closer, then the aspect managed to change to look right....

I agree with them being set in a little too. The metal needs an edge to grab.

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's Canadian Off Road Trips Photos: Non members can still view! Aug./05
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(More Off Road album links at bottom of the view page)
Reply to
Mike Romain

You don't say! There in lies a good part of my problem. I will take the manifolds off again and reset these in like the picture (third time

- I should be able to do this in 15 minutes LOL).

I'm curious that the tool that is supposed to help me install these sets them exactly flush, not in-set like that picture. Live and learn.

Thank you, and everyone else, very much for all of this great technical info.

Reply to
Quattro GR4

Does it look like this

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I just borrowed mine from the local AutoZone.

Reply to
DougW

I just looked at it again.. it's got to be the angle I took that photo at. :)

funky.

Reply to
DougW

Reply to
L.W.( ßill ) Hughes III

Dave Milne did pass the time by typing:

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What do you call them ? Spud Wrench
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Although there are a few other names and not all "spud wrenches" are that type.

Commonly used for high-iron/aligning bolt holes in beams and girders where fingers dare not tread.

Reply to
DougW

Okay everyone, thank you all for such great help. I've installed the new plugs (using permatex sealant), and recessed them into the holes (and only slightly smashed one finger). I've taken a picture of each plug and placed them at:

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So for those of you who love to look at pictures of Jeep 4.0 L freeze/core plugs, here's your chance to see all five! Of course, I would love feedback to see if everyone seems happy with this before I put the manifolds back on.

You guys are truly awesome, and your help is very much appeciated!

C.R. Starr (don't have a website of my Jeep yet, but soon)

Reply to
Quattro GR4

Well... You know you are going to get a little flack over #2 anyway, eh?

I personally don't like the dents and if I dented one, I would re-do it. Even with the permatex....

#4 has a couple dings too....

They might hold, but I would expect a leak down the road someday.

Just my $0.02,

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail >
Reply to
Mike Romain

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