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4.0 Back of head freeze plug


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What’s up fellas

Found out the freeze plug on the back of the head is leaking, 

has anyone has any experience with replacing one? 

What tips or tricks you did to replace it? I was thinking about dropping the trans or either pulling the head...

has anyone done it still on the vehicle? 

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What’s up fellas
Found out the freeze plug on the back of the head is leaking, 
has anyone has any experience with replacing one? 
What tips or tricks you did to replace it? I was thinking about dropping the trans or either pulling the head...
has anyone done it still on the vehicle? 


I did one in winter that the owner hadn’t put antifreeze in. I did the rubber plug with the nut to tighten it as a test which lasted till about a year ago. Make sure it’s the plug and not the back of the head gasket with a mirror.


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I had the same issue on my 98 XJ.  The easiest solution I came across seemed to be pulling the driveshaft and dropping the crossmember then lowering the rear of the trans down some.  This gives you access to take the plug out from underneath (just pay attention to the wires and cables so you don't break anything).  

 

I never ended up replacing the rear one because it stopped leaking.  No idea how or why but I'm not complaining.  I will say that I used the regular freeze plug kit from O'Reillys on the side of the block many years ago and they are still holding up strong so I'd have to recommend that kit. 

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19 hours ago, carnuck said:

 


I did one in winter that the owner hadn’t put antifreeze in. I did the rubber plug with the nut to tighten it as a test which lasted till about a year ago. Make sure it’s the plug and not the back of the head gasket with a mirror.


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I’ve heard about the rubber plugs but that’s a temporary solution...

i daily drive my xj as my mj from week to week I don’t want to do the same work twice 

19 hours ago, Dzimm said:

I had the same issue on my 98 XJ.  The easiest solution I came across seemed to be pulling the driveshaft and dropping the crossmember then lowering the rear of the trans down some.  This gives you access to take the plug out from underneath (just pay attention to the wires and cables so you don't break anything).  

 

I never ended up replacing the rear one because it stopped leaking.  No idea how or why but I'm not complaining.  I will say that I used the regular freeze plug kit from O'Reillys on the side of the block many years ago and they are still holding up strong so I'd have to recommend that kit. 

 

Might have to try this solution 

when the plugs come in tomorrow I’ll be tackling it after work and come back with results thanks 

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Might have to try this solution 
when the plugs come in tomorrow I’ll be tackling it after work and come back with results thanks 


The rubber plugs lasted longer than the truck did. On an oily environment they might only last a couple years. I have a bare 7120 casting head for $30 that needs cleaned up again (it was Checked for flat and hot tanked) because a certain idiot didn’t do the roof repairs or anything he was paid to do (after 2 years of free rent and storage they tried to kill me and claim ownership but they got shut down)


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45 minutes ago, cruiser54 said:

If that plug is leaking, how do you think this one looks in the block right below it? 

FreezePlugrear.jpg

 

25 minutes ago, Jeep Driver said:

Yep, drop the trans and do both. 

I was thinking the same, but I don’t have an impact gun to remove the bolts off of the flywheel my current one broke...

ill just do the one on the head to drive again (diving wifes car) and when I get the impact gun I’ll drop the trans to do all the plugs...

 

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Just an update 

I dropped the crossmember, took both driveshafts off, loosened the motor mounts, took off all connections that would hold the transmission in place and still couldn’t drop it low enough to clear the freeze plug...

i have it parked right now until the Comanche is ready to drive then I’ll get to pulling the head...

 

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4 hours ago, Dzimm said:

How low did you drop it? You should be able to see almost the entire head with the tranny dropped down.  

Probably still had about a foot until it was touching the ground...i had it down about a 1/4 way of the face of the freeze plug...

ill double check again when I get some time to mess with it...

2 hours ago, mjeff87 said:

Disconnect the braided ground strap from the back head bolt to the firewall, it's probably holding the engine from dropping fully.

I’ll keep this in mind the next time I try and drop the trans 

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19 minutes ago, 88whitemanche said:

Probably still had about a foot until it was touching the ground...i had it down about a 1/4 way of the face of the freeze plug...

ill double check again when I get some time to mess with it...

I’ll keep this in mind the next time I try and drop the trans 

Yeah you should be able to go until the trans is damn near on the ground unless you are lifted like crazy. 

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1 minute ago, 88whitemanche said:

Only at 4.5” of lift...

You should be able to drop the jack all the way down even at 4.5".   That's what my truck is at and my trans hung low enough to bottom out my floor jack. 

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Agree with Jeep Driver, don't pull the head, if anything pull the trans and do the other plug as well.   Even if you did pull the head, you would have an insane struggle to keep the head from sliding around the table while you try to get the plug out.  

 

As for it coming apart, yeah they do that.  Keep going but use a larger punch to spread out the load (a 1" spade type chisel/punch works well) and don't hit quite so hard.  It will come out.  If you need to, use a flat punch on the rim of the plug but be extremely careful if you do this to not scratch the surface of the block.  

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10 hours ago, Jeep Driver said:

Now that the center is out, see if you can get a brake spoon or a similar small pry bar under the rim and pop it out.

 

 

It would still be a lot less work to drop the trans than pull the head, and you can get to the other plug.

Absolutely.

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Did you disconnect the exhaust at the 4 bolt catalytic converter flange?

If not and you didn’t undo the pipe at the header then it won’t drop enough. I used a flat hook on a dent puller to get mine out but knocking it in first was easier.

If the head gasket is very old, then I would consider pulling it to do the plug and make sure the gasket is good at the same time.

 

 

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Updated 

i didn’t pull the head, I had to remove the ground cable that attaches the head to the body to get it to lower that 1/2 inch...

used a pry bar and got the freeze plug out and it took a couple tries and lucky I ordered a couple plugs to finally got in place the right way....

old plug 

 

zzGejLf.jpg

jlyCPh4.jpg

 

 

new plug

1IUUAho.jpg

 

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