question about freeze plugs.... [Archive] - Forum


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12-24-2008, 11:43 AM
after a hellacious past couple days, i've pretty much narrowed a problem of mine down to the freeze plugs. My only problm is...i know nothing about them. Dont know where they are, dont know how many i need, dont know how to get to them...i know NOTHING. I called autozone to get a price on them.....they asked me were they for the block? the block pipe? the cylinder head? or the cylinder head pipe? My cousin has a 95 Grand Am SE and he said he only had 2 plugs to replace on his. Didnt say where or anything, he just said he had to replace both his freeze plugs. I automatically assumed he only had two...hence him saying he chaged "both" of his. I dont think he has a V6 in his tho. Im stumped and any info on freeze plugs would be appriciated. Thanks to all who can provide some positive feedback

12-24-2008, 11:54 AM
Hm, I never knew what they were either... sounds like it might be a PITA to fix though.

Freeze plug is a misnomer for core plug or expansion plug, and is commonly referred to as a "frost plug." They are a subset of the plugs on a car engine cylinder block or cylinder head. The traditional plug is a thin, domed, disc of metal which fits into a machined hole in the casting and is secured by striking or pressing the centre to expand the disc.

A true freeze plug is an expansion plug located in the side of an engine block that is supposed to protect the block against freeze damage. Water expands when it turns to ice, and if the coolant does not have enough antifreeze protection it can freeze and crack the engine block. The freeze plugs (there are usually several) are supposed to pop out under such conditions to relieve the pressure on the block.

Most of the plugs to be found on an engine are actually to plug the holes where sand cores have been held. The sand cores are used in the casting process to form internal cavities in the engine block or cylinder head, for cooling water for example, and so should really be referred to as core plugs.

Freeze plugs can often be a source of troublesome leaks as a result of internal cooling system corrosion. Ease of replacement depends on accessibility. In many cases the plug area will be difficult to reach and using a mallet to perform maintenance or replacement will be nearly impossible without special facilities. Expanding rubber plugs are available as replacements when access is a problem.

A variety of block heater called a "freeze plug heater" can be installed, replacing the freeze plugs, to warm the engine before start up.

12-24-2008, 11:56 AM
And also:

Freeze plugs are normally something you change at overhaul time when the block is stripped, it has been through the acid bath, and the core is clean. Changing one on the fly is hard because you often end up with leaks worse than you had before you changed the plug. Since they are a press fit, the mating surfaces have to be in good shape. First, the only reason I've ever seen one go bad is by corrosion from using tap water in the cooling system. That is bad news because it causes widespread corrosion. Never ever use tap water in a cooling system. Use distilled water. As for the freeze plugs - when one fails, a hole will have corroded through it, usually at the edge.

Replacing freeze plugs can be a real headache. It's easy once you get enough room to swing a mallet, but very often that means removing the engine. Don't even think of using stop-leak products to try to patch a leaking freeze plug. I have successfully used another technique, though. If you have identified a leaky freeze plug, you can: (1) drain the system, (2) clean the depression in the freeze plug with Scotch-brite and a cleaner like Simple Green to remove both grease and water-soluble deposits, (3) after it dries, apply a liberal amount of putty type steel filled epoxy to the inside of the freeze plug. If you aren't familiar, they are shaped like shallow flat-bottomed cups with an inside diameter about the size of a quarter. What you want to do is to cover the hole with the epoxy from the bottom of the cup up all the sides to the rim, where there is no corrosion. This isn't foolproof, because sometimes the leak is actually not through the plug but around it. Still, it is cheap, fairly permanent, and about the easiest thing to try. Don't worry about making the plug hard to remove if/when the time comes - they are removed by placing a punch in one edge and whacking it with a mallet to knock the plug sideways. The epoxy won't get in the way of that at all. Warning - don't remove a plug unless there is room to use the mallet to seat a new one! If you do, count on removing the engine to get to it. Once it is removed, clean the area throughly with a wire brush, (Warning, do not use a grinder or sand paper). After the area is clean, you install the new plug by placing it inside the hole and hitting it dead center with a mallet and flat punch. This causes the plug to expand and seat itself. But you must have room to be able to do this. This is where the job becomes difficult most of the time. No room!

How are you sure it's a freeze plug?

12-24-2008, 02:11 PM
Each head has 2. Are those leaking? There is 1 in the block. Is that leaking? You say you narrowed it down to them but you dont know what they are so how did you do that?

12-24-2008, 02:19 PM
because im basically goin off of word of mouth from this website among others. Everybody is telling me the same by that meaning ive narrowed it down to being those. Not the heater core, not the heater core hoses, not the water pump and not the LIM. whats left then? Freeze plugs. Thats why im here also....if i dont know about them wouldnt it make sense for me to do as much research on them as possible? I dont know how you work on things vegeta that you arent to fond of, but its worked for me so far and until i get bad advice....ill then decide to change up my modes of attack. ill say from friends, websites, auto parts stores.....9 out of 10 people told me to check those after checking my heater core hoses. so yea.....

12-24-2008, 02:52 PM
and by my not trying to be a **** about it either. Im jus really frustrated with this damn car. I know people are intitled to give their personal opinion about things but im here to seek professional advice about my car. Some things can be taken out of context due to the simple fact of people not reading it the same as the person typed it. Prime example....vegeta answered my question perfectly....but insulted my intelligence by saying the last line in his comment. Thanks again and hopefully i can get this problem resolved.

12-24-2008, 03:43 PM
I won't "insult' your method again. Replace all your freezeplugs and let us know if whatever your problem is now goes away.

12-24-2008, 05:16 PM
freeze plugs dont commonly leak though. if they are you might want to consider overhauling the entire motor while its out. honestly, watch VERY CLOSELY to any and all connections where water is. could be nothing more than a hose that may have been over looked.

if it is the plugs, i HIGHLY recommend that you take it to a machine shop and have them put the plugs in. if you havent done it before, DONT try it on this. unless you enjoy taking the motor back out. while its in have it tanked and what not to make sure its not a crack in the block somewhere. bad castings happen. from what i understand the 3400 block is a fairly good block, but even the best block in the world can have bad castings.

Good luck

12-24-2008, 07:06 PM
I would use the best stop leak product before I removed a engine to replace freeze plugs.

I replaced one years ago on a Jeep but it was out in the open. It had a block heater that rotted out. I used a rubber plug with a bolt in the center.

12-24-2008, 09:00 PM
yea thats an option you can take. but BE SURE you have your heater running full blast the whole time. if you dont your heater wont work anymore. lol

gagt Mechanic
12-24-2008, 09:27 PM
freeze plus are used when casting. they are passages that are used to remove sand from hard to get to areas when the parts are cast. they are generally aluminum or ss. I have run across a couple of bad ones over the years. you need a special tool in most cases to change them out in the car. you need to get the car pressure tested at a shop before you get to much more into it, costs $30 where I work and youll know for sure. cheaper than guessing

12-24-2008, 11:14 PM
AlumAseal works pretty good i used it on my first car a 93 beretta with the 2.2l 4cyl in it when a

small corner of the headgasket decided it didnt want to stay sealed anymore and i drove it for 2

years after putting that stuff in and no problems and the guy i sold it to got another 2yrs out of

it before getting t-boned.

12-25-2008, 11:50 AM
where can i go to get it pressure tested? like, what places do you suggest? you said your job charges $30? where do u work?

AlumASeal.....where does it go? just pour the entire contents of that lil bottle in the coolant reservoir or what? is the powder better than the liquid or vice versa? THANX A TON GUYS.

12-25-2008, 02:49 PM
yeah just pour it in the coolant bottle and run the car for awhile i forget the exact direction but they are on the container. it goes something like that though

12-25-2008, 07:53 PM
I've used Barsleak in many vehicles over the last 40 years. Last summer I replaced the questionable orange stuff (warranty problems) in my 2003 Grand AM GT with Peak and Barsleak. I've never heard of a freeze plug leaking, and on most FWD engines they are not usually easy to get at. Whatever is leaking, a $4 jug of Barsleak is a good economical first step.

Since the reservoir is pressurized and above the radiator, I suggest you drain most of the radiator, mix the Barsleak with 50/50 antifreeze, then refill the mix thru the top radiator hose, replace the hose, then top off the reservoir tank. Run, cool down the engine a couple of times to make sure the radiator gets filled and the magic sawdust gets circulated. There is a bleed valve on the V6 engines.