medic1555

How much of a pain is it to replace the freeze plugs on the rear of the block?

mikem350

Its easy..once you pull the tranny...

medic1555

Got a quote of $500 from a local repair shop. Without a lift I don't know if I want to tackle this one.

69Vett

A big pain,... you got to pull the engine or the tranny.
you better be positive the plugs are leaking.
I vote transmission!

Tim81

$500.00 is a pretty good price, but like others have said make sure they're are leaking first.

medic1555

I'm 99% sure one of them is leaking. I've got a transmission fluid drip at the rear of the oil pan. Intake is dry as a bone, no signs or smells of a head gasket leak. Only other thing back there are the freeze (or casting) plugs. Seems to me it should be a relatively easy job although maybe a bit time consuming. Drain the system, drop the drive shaft, remove the six bolts holding the tranny, drop the tranny...

billla

Are you 100% sure it's not coming from the coolant passage at the back of the intake? Oil looks OK?

As much as I hate the garbage, I would probably try a little stop leak. It's really bad stuff and can cause other issues...but it would likely be a cheap, quick fix...

medic1555

I put the flourescent dye in the coolant. I cannot see any leaks anywhere with a black light. The top side of the motor is dry, no coolant in the oil, no oil in the coolant, no white smoke when running, no smell of burned coolant when running, no steam of vaporized coolant when running. I can see a slow steady drip that originates somewhere above the rear of the oil pan and runs down the the center of it. The only logical thing that could be is the freeze plug.

69Vett

if you hire someone they will replace them, regardless if leaking or not, and charge you.
be 100% certain they are leaking. they now make relatively cheap bore scopes,
avaliable at Harbor Freight. a camera on a stick, you might ? be able to snake behind the
flywheel and have a look-see.

have you tried to wrestle a 4-speed out with a non-removeable crossmember.
with no lift it is extremely difficult. now remove bell housing ,clutchfork, and flywheel.
now,...it's relatively easy job !

PeteZO6

While I always respect what 69Vette has to say, in this case I have to say removing a four speed tranny is not that difficult. Four jack stands to get the car up high enough to move around under the car, did it for me. I don't remember if you have drop the exhaust, but most of the job is pretty simple. The four speed with the aluminum case is light enough that a fairly strong guy can drop it without a transmission jack. If you have an auto, jackstands might not get you high enough to get a jack in there and get the tranny out.

From your posts it seems your leak is coolant and not oil? But the fluorescent dye was in the coolant and you see no evidence of it coming out of the engine. Kind of confusing to me.

Good luck with this. I'll keep to see what happens.

KapsSA

I've seen several Chevy V8s leak at the blocked off water passages at the back of the intake. Feel at the joint between the head and intake at the rear. Do you have a small mirror to look back there?
It would show up as just a drip from the bottom of the pan.
One of mine was dripping from the starter.

I've never had a problem with freeze plugs other than my beater van that had one rust through.

Steve2147

Leaking rear frost plugs ( and the front for that matter) are somewhat unusual. In the shop we typically would see lots of side ones, but seldom frt or rear.

I speculate that the reason for that is that leaking frost plugs is almost always that they are rusted out and usually when you remove them you find the bottom of the block full of rust sediment. This sediment sitting against the frost plugs accelerates the rusting. I think the end plugs are a little higher than the sides, but for whatever reason, the rust doesn't seem to accumulate there.

That said, if you are faced with the choice of removing the trans and doing the rear ones or removing the engine and replacing all of them, I would highly recommend replacing all of them. Replacing the ones under the engine mount is no picnic either. When the engine is out, none of them are hard. And if one has rusted out, you will be plagued by one after the other rusting through.

As well, if it is leaking frost plugs, they are rusted out, and you do see the sediment I'm talking about, having the engine out and all frost plugs out will make it much easier to remove the rust sediment. I am not talking about small traces here. I have seen it where it is deep enough to cover over half the frost plug and you scoop it out with a spoon. If you pull the drain plug from the side of the block and nothing comes out it's a good indication you have quite an accumulation.

And you will not get it all out. The best thing to do is to remove all the plugs and use a high pressure, high volume pressure washer. Even then, replace the frost plugs with brass.

But again, it's uncommon. I would really look long and hard before I pulled it apart.
Steve g

noonie

With the engine out, if you have enough rubber plugs , a healthy 50/50 mix of muriatic acid for 5 minutes will get the system foundry fresh.