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View Full Version : Exhaust Manifold freeze plug - 81 tristar


AHUNTER
05-15-2010, 02:27 PM
Just dewinterized & found an exhaust manifold freeze plug that had popped out. All other potential issues aside, any experience out there in replacing this plug? Much appreciated.

Mr_Woodcock
05-15-2010, 02:40 PM
Prolly just drill it out and tap it and put a plug in it. I speak out of experience=)

AHUNTER
05-15-2010, 02:41 PM
Thanks, are the plugs available through general parts stores or only MC?

Wait - are you saying to plug it with a bolt?

Thrall
05-15-2010, 02:48 PM
I think that's what he's saying, but I'd replace the freeze plug. Looks like it did it's job once. May have saved you from major damage.

JimN
05-15-2010, 04:42 PM
Just dewinterized & found an exhaust manifold freeze plug that had popped out. All other potential issues aside, any experience out there in replacing this plug? Much appreciated.

Who winterized it?

Technically, those are for removing the sand when the part is cast, but they work well enough when water freezes inside. It's a common part and can be bought at most parts stores. The thing is, it needs to be installed correctly, or it will be too easy/hard to pop out when needed.

AHUNTER
05-15-2010, 05:13 PM
Who winterized it?

Technically, those are for removing the sand when the part is cast, but they work well enough when water freezes inside. It's a common part and can be bought at most parts stores. The thing is, it needs to be installed correctly, or it will be too easy/hard to pop out when needed.

Did it myself - same as for the past 6 years. I put the new quick drain valves on 4 yrs ago from skidim. As I was closing the valve this morning, which is all of 6 inches from the plug, I noticed the plug popped out. Had a real hard winter here in North Texas - must have been just enough water in that bottom corner of the exhaust to do the job on a weak plug. Don't know.

Is a common freeze plug that right part to request?

83SuperSlot
05-15-2010, 05:35 PM
They sell universal expansion plugs at the auto parts stores... just bring the plug and they'll match the size... they are brass & rubber.. less than $5... Good luck with it!

JimN
05-15-2010, 07:19 PM
Did it myself - same as for the past 6 years. I put the new quick drain valves on 4 yrs ago from skidim. As I was closing the valve this morning, which is all of 6 inches from the plug, I noticed the plug popped out. Had a real hard winter here in North Texas - must have been just enough water in that bottom corner of the exhaust to do the job on a weak plug. Don't know.

Is a common freeze plug that right part to request?

Since it's the lowest point where water can exit the manifold, why not do as someone mentioned, and tap it so you can install a brass plug? You could do the same on the other side and include removing tehm as part of the annual winterization? The brass plug should be tapered, which is standard for plumbing parts. If you were to use a cast iron plug, the chance of it rusting in place is about 100% and brass won't do that.

JLeuck64
05-15-2010, 07:37 PM
That core plug did not pop out due to your hard freeze last winter. It rusted out due to age. There is still a good portion of the plug in the casting. Spray it down real good with something like PB Blaster and let it soak in good! Take a pin punch and drive that plug into the coolant jacket. Then turn it sideways and pull it back out through the hole.

Clean up the core plug hole in the exhaust manifold with some 180 grit sandpaper. If that machined hole is in really good condition, no pits and heavy rusting, then measure the diameter and buy another core plug to fit. Coat the new plug with Aviation Form-A-Gasket and drive it into the hole. I like to use a half inch socket that just fits inside the new core plug. Put a short extension in the socket and drive the plug into the hole just enough! You just want the edge of the plug to sit about a 1/16 inch below the edge of the exhaust manifold. Look at other freeze plugs to get a good idea for the proper depth.

If the machined hole does not clean up very well you have a several options as stated in previous posts. If you want to use another freeze plug on a heavily rusted manifold best practice is to have a machinist clean up the hole down to good material, cut it oversize. Then you could install an oversize freeze plug.
HTH...

Oh and one more thing to think about...
That plug failed because the water skiing Gods are smiling down on you. Better check the rest of your engine and manifold plugs and fix them too. I would bet a few more are paper thin like that one was! Better to catch them now than to over heat your engine out on the water this summer!

AHUNTER
05-16-2010, 11:41 AM
That core plug did not pop out due to your hard freeze last winter. It rusted out due to age. There is still a good portion of the plug in the casting. Spray it down real good with something like PB Blaster and let it soak in good! Take a pin punch and drive that plug into the coolant jacket. Then turn it sideways and pull it back out through the hole.

Clean up the core plug hole in the exhaust manifold with some 180 grit sandpaper. If that machined hole is in really good condition, no pits and heavy rusting, then measure the diameter and buy another core plug to fit. Coat the new plug with Aviation Form-A-Gasket and drive it into the hole. I like to use a half inch socket that just fits inside the new core plug. Put a short extension in the socket and drive the plug into the hole just enough! You just want the edge of the plug to sit about a 1/16 inch below the edge of the exhaust manifold. Look at other freeze plugs to get a good idea for the proper depth.

If the machined hole does not clean up very well you have a several options as stated in previous posts. If you want to use another freeze plug on a heavily rusted manifold best practice is to have a machinist clean up the hole down to good material, cut it oversize. Then you could install an oversize freeze plug.
HTH...

Oh and one more thing to think about...
That plug failed because the water skiing Gods are smiling down on you. Better check the rest of your engine and manifold plugs and fix them too. I would bet a few more are paper thin like that one was! Better to catch them now than to over heat your engine out on the water this summer!

The skiing Gods smile down on me every time I post a question on this forum! Thanks to all for the responses!

jparris0916
03-08-2014, 01:42 PM
I just found the exact same thing on my 91 prostar. What did you end up doing to fix this. . any help would be great. Thanks