: Freeze plugs ( So called )

12-03-03, 12:43 AM
A guy asked me why the 4.1/4.5/4.9 and the Northstar don't have freeze plugs. It seems he was worried about cracking the block if he ever had the coolant freeze...Here's the real deal...They really aren't freeze plugs. Those plugs that people call freeze plugs are really plugs that seal up holes left in the block casting by the sand cores. The cores need support during the casting process...they are supported via extensions on the core that leave the holes in the side of the block... So, those holes have to be plugged. The holes are machined and the cup plugs are pressed into the holes. I have no idea where the idea that they are freeze plugs came from. I suppose that someone looking at them figured that they would pop out if the block coolant froze and protect the block from cracking. Unfortunately, if you test this theory you will find that the block will still crack when the coolant freezes. The plugs are really core plugs...not freeze plugs...so not having them on the 4.1/4.5/4.9 or the Northstar does not put you at a disadvantage. I hope this clears up what is one of the most common bits of misinformation about your engine.

12-03-03, 01:00 AM
Interesting, I've seen then on other cars I've owned and never knew what they were for until someone ID'd one for me. Everytime I saw one I thought, hope it doesn't fall out. LOL They look pretty flimsy if one got dislodged. A friend had one on a 5.0 Mustang, and it looked like it was not "set" properly, angled, etc.

12-03-03, 01:03 AM
They're in there pretty good Ralph, You try pulling one out and you'll see what I mean. The way I usually get them out is to push them in and turn them and then pull them back out through the hole sideways

12-03-03, 01:11 AM
OK, no new Caddy for you if you go around doin' things like that! ;) OK, why would you want to remove one, are you talking about some old engine you rebuilt? If so, why would they have to be changed. How many on a typical engine. Why doesn't the 4.9 have them? You asked for it, now I have to learn about them! :bighead:

12-03-03, 01:19 AM
OK Ralph, The reason you would have to change them is that occasionally they will start to leak ( They're much thinner material than the block ) When that happens you just pop them out and install new ones. The number of "freeze plugs" varies Usually you'll have a couple on each end of the block and two or three on either side depending on what engine configuration you have. The 4.9 and the other engines I mentioned don't have them because they're not manufactured the same way.

12-03-03, 01:27 AM
Some people including myself have experienced "diasppearing coolant" syndrome as I'll call it. There are no leaks, yet after a couple thousand miles or so, the coolant level in the recovery tank just lowers! Have you heard of this, experienced it, or think it could have been the cause? The big-ass Merc my dad wanted from me when I got his old Caddy is still experiencing this "syndrome." I know someone else recently started a thread on this, but I don't bother with everything anymore, computer too old and slow. :annoyed:

12-03-03, 01:36 AM
Cars consume coolant for a number of reasons. The most common are....Good old evaporation and leaks. If there isn't any coolant leaking out, that pretty much eliminates the leak option. It is normal for coolant to gradually evaporate due to the fact that you're getting it hot and the stuff vaporizes and then it is no longer in your recovery tank. That is the reason that you're supposed to periodically check your coolant level. It's really that simple.

12-03-03, 01:45 AM
OK, I guess I thought if the coolant strength to water was strong, it shouldn't evaporate, but with more heat I guess anything is possible. I notice it a little on the 4.9 but not much. It is noticable on the 5.0 Ford. Aluminum (4.9) is supposed to run cooler than a cast iron or ? block, so maybe the latter evaps more because of the excess heat? But what about new cars, this shouldn't be normal, one might think. No prob, I'll just keep an eye on 'er.

12-03-03, 02:58 PM
Another thing those plugs are supposed to do is protect the block from excessive corrosion by rotting out quicker in severely neglected cooling systems. I have no idea who came up with a protection mechanism that usually ends up with an overheated block due to coolant loss, and it usually doesn't work that way anyway. A way to tell if yours are leaking a small amount is look for powdery wite stuff down the side of the block. When antifreeze dries, it leaves that residue. One thing freeze plugs are good for is cleaning all of the crap out of the waterjackets during a rebuild. You punch them out before putting the block in the parts washer, and everything comes out nice and clean.

12-03-03, 04:36 PM
At our marina, we take out the freeze plugs every winter when the boats sit outside.... Maybe thats why they're called FREEZE PLUGS....

12-03-03, 11:05 PM
Both interesting answers....But both are based on the wrong information....The manufacturers do not build in safeguards for poor maintenance....They rightfully expect you to maintain the vehicle to specs. if you don't it's YOUR problem. You do not need to remove the plugs in the winter to prevent the block freezing..You need to have the proper mix of anti-freeze and water to prevent this. ( But I forgot you already know everything there is to know about everything....My mistake. ) This information was given to me by a Cadillac engineer that I know. ( But he probably dosen't know anything either. )

Big Jim
01-07-04, 04:39 AM
Whoa there, maybe you didn't read the post. He is removing the plugs from marine engines. Most marine engines don't have things like closed cooling systems or radiators. They suck in water from under the boat, pump it through the engine, and dump it back out. Unless it it using a heat exchanger system, there is no good way to put antifreeze in a marine engine.

01-07-04, 07:46 PM
YES!! He gets it!

01-07-04, 09:26 PM
But other than Fleetwoods....Were not talking about boats here!