Frost plug leaks coolant / 307

Roy Ale

Member
Oct 20, 2020
55
11
8
Victoria BC
I have another frost plug leaking coolant .
The first frost plug i replaced was corroded and leaking coolant , it looked like the seal between the engine block and frost plug was fine , it looked like surface rust bubbles in middle of frost plug , when i scratched it to see how deep the bubbles were , it popped a hole and lost all the coolant , not good really shut the car down ! That first frost plug was drivers side , above the engine mount .

Now i have another frost plug leak on the other side of engine , again above the engine mount ! So Question ? whats going on that both frost plugs above the engine mounts are in bad shape ? as all the other frost plugs look to be ok .

There is a heat shield over the engine mount . Looks to me like the heat shield is to protect the engine mount / deflect or block heat from exhaust manifold . so the frost plug is between the heat shield and the exhaust manifold . does this have anything to do with these frost plugs failing before the other frost plugs ? my engine is a 307 in a 1982 Delta 88
 

Olds 307 and 403

Well-known member
Oct 4, 2018
882
263
63
Melville, Saskatchewan
Roy, what shape is your coolant in? I haven't seen any frost plugs fail on an Olds V8, saw quite a few of them come through working in shops 20 years ago. It may be a freak thing or the rest may be on borrowed time. I never even had one fail, even on an engine that sat for years in a car and the coolant looked like mud. Good luck.
 
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Rocketman269V

Member
Feb 26, 2020
55
15
8
South Central Florida
Where did the car come from? I worked at a gas station and for an Olds dealer in Buffalo, NY years ago and never had to change any freeze plugs. I moved to South Florida and it's an all to common issue. Difference: the water down here sucks. Up North the water was clear and clean. Down here there are a lot of minerals in the water that promote corrosion of steel freeze plugs; hence, we use brass as replacements and on new engine builds.
 

Roy Ale

Member
Thread starter
Oct 20, 2020
55
11
8
Victoria BC
Melville so you have never had one fail , so what is the average life span of a steel frost plug ?
The coolant in car now is good , and i test it with PH strips . But the car was in storage for close to 20 years . Before i departed from Saskatoon the car blow the first plug . So maybe that is where the problem started , past history of coolant.

Rocketman , Interesting that the water might make a difference . The car was sold new in Saskatoon Sask . not sure if water would be same as Melville Sask ? Car is now in Victoria BC . These must be steel frost plugs . Brass plugs thats interesting ! South Florida a common issue ! so in S.F. would you use distilled water ?

so maybe all the frost plugs in engine are now a bit off ! how many do i have ? looks like 3 on each side . are there any i cannot see like maybe between the engine and trans ? How to get at the frost plug above engine mount ? lift engine ? remove exhaust manifold ?
 

Rocketman269V

Member
Feb 26, 2020
55
15
8
South Central Florida
........... how many do i have ? looks like 3 on each side . are there any i cannot see like maybe between the engine and trans ? How to get at the frost plug above engine mount ? lift engine ? remove exhaust manifold ?
There are the 3 on each side as you stated, plus 2 smaller ones in each cylinder head. Olds doe not use any in the front or rear of the block, for the cooling system. There is one at the back of the camshaft tunnel, which gets oiled, so no corrosion there and a small one on the left side in the rear, that covers access to the pipe plug, with an oil metering hole, for distributor gear lubrication. Again not subject to corrosion. I've changed all (4) in the heads, with the engine in the car ('84 H/O); I don't recall doing all (6) in the block that way,
 

Olds 307 and 403

Well-known member
Oct 4, 2018
882
263
63
Melville, Saskatchewan
Saskatoon has pretty good water. I saw coolant turn to mud in a car that probably sat that long. It actually rotted the shim head gasket out but none of the frost plugs failed. I put that Olds 350 in a 94 Z71 4x4 truck and ran it at least 5 years till the truck burned to the ground from a circulating block heater.
 
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Roy Ale

Member
Thread starter
Oct 20, 2020
55
11
8
Victoria BC
Thanks for all the plug locations , i will look for the smaller frost plugs in heads .

about water , i do not add tap water , i top up the coolant with a ready to use 50/50 prediluted product . There would be water in that product . but this car dates back to 1982 before a 50/50 mix was available .
 

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