Freeze plugs, Blew one out. What ?

[MopART]

I blew a freeze plug out of the '71 340 Sat. night. Should I repalce them all or just that one? The one that blew out is on the passenger's side at that back. Can someone tell me what sizes I need?

Can they be change in the car?

thanks,
ART

[ehostler]

I would replace the one and inspect the rest. It can be replaced in the car, however it will not look like the factory plug.

The ones for replacemen in the car are made of rubber. It is sanwidwiched between two metal discs. A stud is attached to one disk and passes through the rubber and the the opposing disc. you insert the rubber plug with the nut sitcking out. Once the plug is in, you tighten the nut.

Ed

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'96 Dodge Ram 1500 SLT CC 360 4X4
'68 Charger 383-4

[SB Racer]

Well, I would change them all at the same time. Otherwise you'll end up replacing one by one in every few weeks. Plugs are not going to last forever anyway. Most of them you can change with the engine in the car. But not the two in the back of the block, behind the flywheel/flexplate. How can you check them as ehostler said? I don't know. Because they start to rust inside, they can look completely new from outside but suddenly start to pee from a needlehole caused by rust. By a complete kit thats made from brass, they'll last longer. Use thread sealer, for example Loctite red when hammering them in. At least chance all those that you have access to, and hope for the rest to last. BTW, I've never seen any of those sandwich type replacements that ehostler said, sounds neat.

TeRo http://www.angelfire.com/mo/racevaliant

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[bemiller]

I had one of those back freeze plugs give up on my Dart at the worst possible place ever. We had just paid our entry fee ($75)to race for the big bucks at Tri-State Dragway in Ohio. Anyway as soon as I started the car to pull it off the trailer poof a little hole popped open and started spraying all over my headers. So not wanting to lose my rather spendy (for me) entry fee I dashed over to the Quick-E-Mart across the street and voila...a can of Stopleak. Woo-hoo. We ran back to the car drained most of the water out of the radiator and put in the stopleak and crossed our fingers. It worked!! We ended up making it all the way to the semifinals that day...with the radiator cap left just a little loose!! Just thought I'd share.

[MopART]

ehostler,

I thought those expandable plugs were just a quick fix type thing and not for permenant replacement.

SB Racer,

You got me worried now..... hadn't thought about the plugs in the back of the block.

The thing is that this is a fairly newly built motor, about two years ago. Seeing how the whole plug blew out and not leaking from a rust hole, maybe it wasn't seated right..... I dunnno - guess it's up to me. I think that I'll change the ones that I can get to and take my chances.

thanks,
ART

[Hans]

MopArt
If you have to replace the freeze plugs, best deal is to pick up the brass plug pack from mp (P5249706). The plugs are 1 5/8 and 1 1/4.
I just replaced all mine on the 340. It sounds like maybe it was just installed wrong...not in far enough? I had assumed that you ment the plugs at the back of the block. Does the inside of the plug look corroded? The rest are probably in the same shape.

[MopART]

Hans,

The one that blew out is the one at the back on the passenger side of the block. I have no idea what the plug that came out looks like, it's on the track somewhere.....

Since the motor got *really* hot - 250 degrees - with no water in it, I'm gonna take the whole car to the local engine shop and have them do a leakdown and comp test depending on how long it's gonna take. However, the next morning it started right up with no rattles, pinging, tapping or knocking. I'm gonna get them to replace all the plugs with brass ones while it's there.

I'm just about worn out on DIY stuff right now and I don't feel up to pulling the motor.

[MopART]

Could this have happened due to too much pressure in the cooling system?

What would cause such a build up of pressure?

ART

[AJ]

I would also check the thermostat and/or the water pump, a frost plug should not have blown out if it was installed properly.

[MopART]

AJ,

You are da' MAN! Good diagnosis.

I just went and got me one of those neoprene expandable plugs and installed it. The water was not circualting b/c the thermostat is stuck closed. I beleive this is what caused it to blow out along with the possibility that it was installed wrong.

No water in the oil, no rattles, ticking, or knocking --- what a relief!

[pishta]

Yeah, those expansion plugs are a lifesaver, and alot easier to install on your back at night in a parking lot than a brass or steel freeze plug. I read people coat the inside of new freeze plugs with a layer of RTV so as to retard the deterioration, what a neat trick! I had a freeze plug blow on a 351-C Rustang on an onramp to a rather speedy freeway here in So. Cal. I thought my friend hit the nitrous, there was such a power surge. With no water, my water pump gave up all its drag. We installed an electric water pump drive kit the next weekend. Amazing..