Can I change the freeze plugs on a 4.9L without removing the engine?

I was thinking about that, epoxy of some kind. There's rust around the leaks; I'll have to clean what I can first. But almost any alternative to replacing the plugs is welcome. It's only with difficulty I can even SEE the back leak. Plus, there's another in the front. Plus, the engine doesn't run right anyway. But I suppose I'm committed.

~~ Nehmo

i would back up a bit and ask yourself why the freeze plugs are leaking in the first place. there's only two reasons - one is neglect, the other is gross neglect

for #1, if the vehicle's been run without antifreeze, frozen and the plug has been partially pushed out, you have a problem since freeze plugs only protect an engine if you're lucky, with block/head cracking being very common results regardless of whether the plug pushes out.

for #2, if the vehicle has been run without antifreeze [which is also a corrosion inhibitor] so long that the plug has rusted through, you'd be lucky if that was the only problem.

either way, i think you should focus on the big picture here - leaking freeze plugs are symptomatic of much more serious issues than simple coolant loss. if you don't have tools and don't have experience, save yourself a LOT of money and put the money you do have into a vehicle that only needs the simple stuff fixing. if this p.o.s. needs a new motor, cooling system, heater system and a bunch of peripherals because they're all cracked or filled up with corrosion and crud, it will end up being cheaper to buy something that works in the first place.

need to be committed or committed to running away?

you could always put a rubber expansion plug in.. They have a nut you tighten instead of hitting them in.

How far are you willing to go to repair this "free" truck? It will be a lot easier to get to the freeze plugs if you are willing to take off the manifolds, which might be more of a job than you can handle (particularly the exhaust manifold). If you are trying to get a few more miles out of the truck, then it is a lot easier to repalce the existing freeze plugs with the rubber expansion type plugs (particualrly if you are not familar with the drive in type plugs). See

for a picture of this type of plug. These are fairly cheap and not hard to install.

The 4.9L Six is usually pretty rugged, but I would be worried about the condition if you have two freeze plugs leaking. The expansion freeze plugs are cheap ( around $4.00 each), so if you ahve the time, replacing two of them would not be particualrly expensive. However, I suspect as soon as you repalce the freeze plugs (and the radiator cap) and let pressure build up in the cooling system you will find addtional and possibly more significant problems. It is unusal for freeze plugs to rust through on a properly maintained engine of that age. Is it reasonable to think that only two have rusted throguh (there are five of them on the side of the engine under the manifolds - two different sizes)? I think not.

There are pictures of a carburetted version of the engine at

that show the freeze plugs. I think I could change the front and rear ones without taking off the manifolds, but I doubt I could get to the middle ones, especially on a 1990 fuel injected version of the engine unless I took off the manifolds.

Ed

Not me. But I recommend popping some GM cooling system pellets in there and see if it stops the leaking. Worth a try for a few bucks.. Supposedly same as Bar's Leak Gold, but you best confirm that. It's crushed walnut shells and/or coconut fibers or something and supposedly won't hurt your cooling system. I put the GM tabs right away in a Corsica 2.2 I bought when I noticed what looked like rust stains where the head meets the block and read the head gaskets sometimes fail on that motor. Drove it for 12 years after that without a problem. Also put some in my 3.1 Lumina when I heard the intake manifolds gaskets fail.

150k miles on that with no leaks. Anyway, worth a try.

--Vic

It's possible, but you said you can't get at them, so it would not be possible in your case.

If you are careful, you can pry the old plugs out with a screw driver, but you need a clear shot with a hammer to tap the new one(s) into place.

From my point of view, the job doesn't look like a walk in the park. But sometimes someone will have done the exact job and found it possible or reasonably possible. I was hoping for someone to say something like "You just take off the exhaust man, and then the plug are easy". That would have been encouraging. Well, I'm going to try it. Why not?

~~ Nehmo

For better or worse, I've already invested a bunch of time in this vehicle. I replaced the fuel pump, a tire, and a break caliper for three things. I suppose my next step is to try some epoxy and that anti-leak junk. Then, if necessary, and it well may be, replace the freeze plugs.

Yes, I realize the maintenance of this truck wasn't the previous drivers priority. I'm wondering how he drove it with so many things failing.

It rained today in Kansas City. Tomorrow, I'm going dealing with this truck again.

~~ Nehmo

From my point of view, the job doesn't look like a walk in the park. But sometimes someone will have done the exact job and found it possible or reasonably possible. I was hoping for someone to say something like "You just take off the exhaust man, and then the plug are easy". That would have been encouraging. Well, I'm going to try it. Why not?

~~ Nehmo

No reason why not.

Keep in mind that removing the exhaust manifold is generally a difficult job. Once in a while it's easy, but not very often.

Good luck, and keep the carnage to busted knuckles because busted bolts is no fun at all.

iow, "nobody told me what i wanted to hear, so i'm going to do what i wanted to do before i asked the question".

bottom line - freeze plugs only leak if there's a serious problem. just because you've spent some money doesn't mean you have to go spend a bunch more. figure out what you're dealing with before you invest another cent on this thing. if you don't have the experience to figure it out, find someone who does.

No. Nobody here knew how best to replace the freeze plugs on that truck. That includes you. He's going after it without your advice, which was worthless anyway. One minute into it he'll know more about how to replace the freeze plugs in that that truck than you can dream of. Then maybe he can advise the next guy who asks.

The only "serious problem" mentioned here is one or more thin metal freezes plug have rusted and are leaking. That's his "serious problem." It's common enough when the coolant isn't kept up to snuff. He already said the thing was poorly maintained. If he replaces the plugs and keeps a 50/50 mix he'll be fine with his serious problem. You got the "serious problems" all ass-backward. Or maybe you want to invent problems that don't exist, and nobody else mentioned.

untrue - don't put false words in my mouth.

apparently you missed the bit about me not saying how to do replacement for a reason.

ok, then when he reports back that the block is cracked and/or that a piston is seized because of local heating caused by a blocked water channel after years of the coolant not being "kept up to snuff", what are you going to say? "oh, sorry, i wish i'd had more experience and had bothered to assess the problem properly first", "uh, whoda thunkit" or "just keep blindly spending money on it bud"?

fact: freeze plugs don't just leak unless there is a serious problem.

fact: every cent spent on not addressing that serious problem first is, to use your own words, "ass-backward".

and i suspect you already knew that but just wanted to bitch.

In25 years as a working mechanic, and another20 sinse, I've replaced a LOT of seeping front plugs (technically they are "core plugs" on lots of engines - Most of which had been neglected - but some that actually rusted from the OUTSIDE in, with no coolant quality issues.

A VERY small percentage had other problems related to the plug failures that showed up later, making the replacement of the plugs a waste of money and effort. (like head gaskets). Unless they had been seriously overheated, cracked heads and blocks were almost never an issue.

If he's talking about the plugs on the side of the block, removing the manifold on a 300 inline six makes replacement pretty straight forward

- and don't waste your money on the rubber plugs.

When the old plugs are popped out is a good time to flush the crap out of the bottom of the cooling jackets - and then clean up the bores of the core-plug holes, coat the plugs with Permatex Gasket Sealer, and pop the new plugs in.

When you have the manifold off, replace all the plugs you can reach. For the $4 or whatever they are worth, don't leave the middle one and chance having to pull it again. Before replacing the manifold, fill with water and pressure test.

... and as problemg go, this one isn't really very serious. Freeze plugs fail for two reasons, they are pushed out because the block froze, or they rotted. If they are pushed out because the block froze, they are doing their job, and by definition this isn't a "problem." It's more of a pain in the ass than a serious problem.

Frankly, fixing the freeze plugs from the bottom of the motor is the easiest way. Put the truck on a lift and work on it from underneath. There should be no need to remove the exhaust manifold from the head, but it might be necessary to take the exhaust pipe off of the manifold -- remove the muffler bearing -- and move it out of the way.

I don't think that there is enough JB Weld in the universe to fix a freeze plug leak.

Cooper is on the right track here, Beam has jumped the rails.

Now, the rest of the story ...

The FUNCTION of a freeze plug is to be the weak link in the event that the coolant freezes. The plugs are supposed to be pushed out by the expansion of frozen coolant. Freeze plugs can rot away or be pushed out, if they rot, then the coolant really isn't coolant, it's water, and if they are pushed out, again by freezing coolant that isn't really coolant, then they are doing what they are designed to do. (Having just pointed my crroked little finger at water, it's entirely possible that coolant/anti-freeze can actually freeze, so perhaps the mixture of coolant and water is proper and the freeze plugs leak anyway.)

Doing what the design intent is normally is not considered to be a problem. You want frozen coolant to push the freeze plugs out because this is what prevents the block from cracking, that's why there are freeze plugs in the first place. I'm just saying ...

Not really. People call them "freeze plugs" but they are are in the block becasue they are needed to provide a means of locating the interior portions of the sand casting molds (i.e., the core) and to allow the sand to be cleaned out of the interior passages after the casting cools and the core has been reduced to sand by vibrationg the casting. I suppose at some point in history in some engine the plugs used to seal these opening must have been pushed out when water in the block froze, but for modern engines they are not designed-in to prevent the block from being damaged by frozen coolant. I think you'd have to be very lucky to have an engine "saved" from freeze damage by the core plugs. I think in most cases, if forzen coolant pushed out the core plugs, you'd likely have more significant damage. I've only ever seen one block damaged by frozen water and the core plugs weren't pushed out at all - the whole side of the block had been pushed out and cracked.

Ed

I replaced a leaking plug in the side of a 1967 Mustang 300 CID. I don't remember how I got the old one out, but I was going to try prying the new one into place with a "blue bar" without taking off the exhaust manifold. That didn't work. After taking the manifold off, it was pretty easy to put the new plug in. I would think an F150 would have more side room than the Mustang, and wither one of them... you are working with a straight six in an engine bay where a V8 fits, so I wouldn't expect any maneuvering room problems.

There were another three or four years and quite a few miles put on that car before it was sold. No hidden problems partially exposed by a leaking piece of tin in a 30 year old car.

They are NOT frost plugs. They are CORE plugs. By the time they pop in a freeze-up the head and/or block is often done. They are there to facilitate removal of the sand casting cores. There location is optimized for core removal, not for freeze damage protection.