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replacing frost plug - technique? any good writeups anywhere?

N

NeXJ

NAXJA Forum User
Location
Los Angeles
I have a badly leaking frost plug suddenly after getting the XJ back from the shop ... but it's the third one along the block (from front) and well hidden by (i guess the motor mount?? or maybe it's the manifold?) - is there a relatively easy or maybe preferred way of doing this without having to take the engine out?
 
just had another look - seems if I can drop my exhaust header i could get to it sufficiently but as it stands there seems to be only about an inch or two in front of the plug to the header downpipe ... seems much easier than doing it from above ... (?)
 
From what I have heard removing the manifolds from these 6 cylinder heads often leads to the discovery of non-planar surfaces requiring machining to correct flatness for any hope of proper sealing after they are installed. I do not know how correct this is. I would think that if an engine is properly taken care of and does not ever overheat this is much less likely. However, I did not design the manifolds so, it may be best to err on the side of caution.

I have removed several freeze plugs in different engines using a hammer and chisel. Keep in mind you want the freese plug to rotate out toward you as much as possible. I still found it required a good pair of lock jaw type pliers and heavy pulling to remove them but, I was able to remove them without removing manifolds.
 
RAVC1 said:
From what I have heard removing the manifolds from these 6 cylinder heads often leads to the discovery of non-planar surfaces requiring machining to correct flatness for any hope of proper sealing after they are installed. I do not know how correct this is. I would think that if an engine is properly taken care of and does not ever overheat this is much less likely. However, I did not design the manifolds so, it may be best to err on the side of caution.

I have removed several freeze plugs in different engines using a hammer and chisel. Keep in mind you want the freese plug to rotate out toward you as much as possible. I still found it required a good pair of lock jaw type pliers and heavy pulling to remove them but, I was able to remove them without removing manifolds.
Click to expand...


oh dear - i'm still recovering from a REALLY EXTREME overheat i had a few years back (warped head and all) ... but wouldn't the manifold distort with the block?? hmmm ...
 
I would be willing to bet most people here have not checked their intake for being flat after removing it. I doubt you will have a problem.

I did one on the rear of mine recently. Make sure you get the block clean, I coated the outside of the plug with red loctite and then used a race driver to pound it in. You might be able to jack the engine up some to get better access.
 
If this where me I'd pull the intake and exhaust manifolds -- then you get a clean shot at all 5

And yes, while it was apart I'd by the kit with brass plugs and change them all -- and flush out the coolant jacket while your at it -- I'd also pull the 2 threaded plugs, they are the lowest part of the coolant jacket -- see if any crud comes out

Getting the freeze out plugs out is easy, just tap on one side with a punch, it will twist in the hole and you can pull it out

replacing them is a little more difficult -- Only because they need to go in straight -- you need room to swing the hammer

I use the high heat copper RTV - just a thin layer spread with your finger around each brass plug -- also a little sandpaper in the hole in the block to clean it up

The threaded plugs I use just a couple of wraps of teflon tape and then some blue monster thread sealant on top of the teflon tape -- I have never had a leak in a threaded connection if I use both tape and liquid
 
Whatever you do, plan on pulling the engine when one of the freeze plugs on the back of the block or head finally rots out. When one plug goes, the others usually are not too far behind.
If you venture far from home or the trailer, this might be something to worry about.
I was lucky and noticed dripping while parked in our driveway and not a thousand miles from home.
 
I thought it was best to use Indian Head Gasket shellac compound on the freeze plugs. I put mine in freezer the night before to make them easier to install.
 
If there is enough room, maybe you can try replacing the freeze plug with an engine block heater. It just a matter of prying the plug out, inserting the block heater and turning a bolt to seal it (IIRC it comes with a rubber gasket).
 
Mar said:
If there is enough room, maybe you can try replacing the freeze plug with an engine block heater. It just a matter of prying the plug out, inserting the block heater and turning a bolt to seal it (IIRC it comes with a rubber gasket).
Click to expand...

I would just do it the right way the 1st time. Pull the intake/exhaust and replace all of the ones you can access. You can't get the 2 on the back of the block unless you pull the transmission so I would skip those.

As mentioned before, pull the old ones, clean the surfaces, put the new plugs in freezer overnight. Apply the Indian Head Shellac gasket and install.

Pick up a new intake/exhaust gasket so you have it ready for reinstalling things.
 
ok thanks for all the helpful advice - so .. NO ONE here has tried doing it from below? i guess you'd have to take the manifold off to get to the header bolts anyway (?)
 
knowing my penchant for breaking five other things while i repair the one i might consider just taking it in to a mechanic
 
NeXJ said:
ok thanks for all the helpful advice - so .. NO ONE here has tried doing it from below? i guess you'd have to take the manifold off to get to the header bolts anyway (?)
Click to expand...

You might be able to access the 1st plug from the bottom -- gonna be a real PIA to swing a hammer to get the new one in

The intake and exhaust header use the same bolts -- can't take one off without the other -- they also use the same gasket

It's really not a bad job -- especially if you're not in a rush -- some of the bolts may be a little tricky to access but certainly not impossible
 
NeXJ said:
ok thanks for all the helpful advice - so .. NO ONE here has tried doing it from below? i guess you'd have to take the manifold off to get to the header bolts anyway (?)
Click to expand...

The manifolds have to come off to access the plugs, there is no other way.
After having two freeze plugs, on the rear of two 4.0s, blow out, I wish you luck.
 
doesn't sound like much fun for someone with sciatica ;P

i was quoted 1100 for the freeze plug job by a local shop - seemed a tad high to me - what do you think is a fair price to pay for this ...? I think I'll probably have to pay someone for this unless i can get a friend to help ...
 
I've got a freeze plug in the same location on my 4.0 that looks kind of rusty but isn't leaking yet. Replacing it's been on my to-do list for a long time, but it just seems like such a pain in the butt that it never works its way to the top of the list. (I wish I'd replaced it when I had my intake manifold and exhaust header off the rig about five years ago, but didn't notice any issue with the freeze plug back then.) Anyway, I've been thinking about the project for a while and have concluded -- consistent with what everyone else says -- that there's just no way to pry the old one out or hammer a new one in without removing the manifold and header. Fortunately, no part of the job requires a degree in rocket science. Nor does it require $1,000 worth of time and labor.
 
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