[hgiv]

Got a small leak from a freeze plug on my 69 Firebird 350. Basically all original.
Small leak means that after sitting for a couple weeks it might fill a shot glass. Then it seems to stop. I don't smell antifreeze when its running. Coolant level is not noticeably down.

Obviously the best course of action is to get it fixed. But that will likely require pulling the engine. Honestly I don't want to spend money on this right now.
How "big" of a concern is this in the short run? I know it's one of those questions that is kind of stupid. But is the thing likely to blow out or can I just keep an eye on it for now? I would like to at least drive it the rest of this summer/fall and deal with it over the winter.

What about some stop leak? Some people would rather give finger than dump crap in their engine. Understood. Others have had good luck. I'm generally not a fan of the "can mechanic" route but as a band aid maybe.

[25stevem]

Get yourself a tube of this product.
It will 100% not harm anything!

[mgarblik]

I would recommend GM cooling system pellets you can buy from a dealer. Or Bars Leak cooling system pellets which may be the same thing. They look like giant pills. Crunch them into powder and put them in and drive it around 1/2 hour once warmed up. That should take care of it. The GM pills were installed for the first time ON THE ASSEMBLY LINE when Cadillac was selling the HT 4100-4500 engines. If that stuff can seal those terrible engines, it will seal your Pontiac freeze plug. They put 6 pellets in each new car. What an engine!!!

[25stevem]

Question for theOP, is this leaker a block or a head plug?

[Goatracer1]

If a core plug is leaking at all it is only a matter of time before you have a major leak. Stop leak might fix it for a short time but don't go far from home. Can you get at it enough to put in one of the expandable rubber plugs?

[zippy]

IF it's a block plug, and you can get to it to punch it out and remove with pliers. Get a Block heater, or similar style plug. They are rubber and have a tightening bolt. I've had engines with 1/2 of the plugs replaces in frame with block heaters. Not used as heaters, Just as plugs because it was cheaper than pulling engine. Sealed for ever.

[Schurkey]

HOW OLD is this core plug that's leaking?

Is it steel or brass?

Have you checked the coolant for "radiator voltage"?



If this is an old steel plug, you're courting disaster by pouring in "Stop-Leak" products. There may not be enough left of the plug to hold pressure; stopping a leak now may mean the weak part of the plug blows-out catastrophically later.

If this is a newer steel, or a brass core plug, it's likely leaking around the edge from improper installation, or improper sealer being used (RTV silicone, or some other crap.) GM is installing core plugs using "Blue Loctite" lower-strength (removable) thread locking compound.

It's worth verifying that the coolant isn't acting as an electrolyte. If there's voltage in the coolant, it'll tear-up the metals of the cooling system.

[mgarblik]

Yes, in my stop leak post post, i just assumed the plug was leaking around the outside by not sealing well into the block and head. If it's rusted out, it needs to be replaced. Ever wonder why the first freeze plug to fail is right above the starter? Shurkey nailed that one. Electrolysis, voltage in the coolant is extra corrosive right above the giant electromagnet, we call a starter. If you haven't checked coolant for voltage, set your DVOM to low voltage scale and drop the positive lead in the radiator neck just into the coolant. Ground the negative lead. If you see voltage over .5 volts, you need to change the coolant ASAP. I have seen 5-6 volts in some old, dirty coolant.

For installing new plugs, my favorite sealer is a liquid. I use Permatex avaition form a gasket. It's a brown, sticky, nasty, non-hardening sealer. Comes in a brush top plastic jar. Nearly impossible to get out of clothes, and hard to get off your hands as well. But plugs WILL NOT leak when installed with it. Lightly coat both sealing surfaces and drive in.

[P@blo]

To take this a step further disconnect the battery when doing the first test. If getting voltage flush and replace coolant.

Then hook the battery up and do the same test. If you are getting voltage start pulling fuses looking for a bad ground.

Two possibilities: acidic coolant or bad grounding.

[hgiv]

Sorry for a bit of delay...

Yes it is leaking right above the starter. Hmmm. The leak isn't large... yet. No voltage in the fluid. The freeze plugs are original from 1969. Hopefully it can get it to seal up with stop leak stuff until I can pull the engine and get a bunch of stuff done.

Also have leaking rear main seal and a drip of tranny fluid from somewhere TBD. Thank god for drip pans.

[flat-bill]

Permatex avaition form a gasket can be cleaned off your hands or parts with alcohol. Billk

[Formulas]

there is worse ones to change, but if its original anything short of all new core plugs is futility they are all thin by now

get under it and visualize access to that plug without the starter in remember to disconnect battery before starter removal if you go that way

[Schurkey]

Originally Posted by hgiv

The freeze plugs are original from 1969. Hopefully it can get it to seal up with stop leak stuff until I can pull the engine

Pull that engine sooner, rather than later.

I wouldn't trust any of 'em, including the ones that don't obviously leak.

[hgiv]

Originally Posted by Schurkey

Pull that engine sooner, rather than later.

I wouldn't trust any of 'em, including the ones that don't obviously leak.

This beg another question, probably worth another post...

If you are going to pull an engine what are all the things you should do while you have it out? Regardless of the why. I realize this list could get out of control but there should be at least a few things we all agree on.

[25stevem]

Well you say it’s basically all original so let’s do the timing chain and gears, pull the pan to reseal it and if you have a oil pump with only a 5/8” pick up tube ( 45 psi pump ) replace it with a 60 psi pump with a new HD driveshaft to power it while your at it.

I myself would like to check some rod bearings like number 2 way up front and I would be tempted to change the rear main seal, but that’s a much bigger job.

I would pull numbed 4 main cap to look at the thrust bearing face after I check what thrust clearance I have.

Remove the drain plugs on each side above the pan rail and open them up if they are clogged.

If your valley pan has any signs of leaking then now would be the time to get that done also.

If it’s a auto trans car then look the flexplate over carefully for signs of cracks starting.

Any spark plugs or other bolt holes that may have funcky threads would be game for getting a helicoil fix while the motors out also.

If you ever foresee adding headers or HP exh manifolds then now is the time to ball peen hammer on the heads of those bolts so they can be removed and replaced with new ones fully coated with Antiseize compound.

[25stevem]

The two long timing cover studs can be a real problem to get out of the face of the block .
To make this less painful, double nut the end of them and once again beat on them with a big hammer to jar the threads loose.

To even get these two nuts off the studs in the first place on these two studs soak the crap out of them overnight with PB blaster brand rust breaker.
To pop the balancer free once the 15/16” headed bolt is removed the claw end of two hammers works nicely.

[hgiv]

Some good thoughts.

My list:

Freeze plugs
rear main seal
open her up and inspect. Get timeline for rebuild if nothing else.
Helicoil on one bolt of fuel pump. (in but not good)
good degreasing on everything
clean and paint (spray can) engine bay.

[zippy]

If your replacing main seal, and have heads off while out. Might as well put new rod and main bearings and a set of rings in her if your not doing a full rebuild. Re and Re we used to call it.