Freeze plugs? What now?

[Timothy Keith-Lucas]

Need a little help here. What I'm guessing (I live in Florida) is one of three freeze plugs on the right side of my Austin A engine went flying, followed by flying coolant. 

 

The conditions were: Sitting in the driveway, reving the engine following a carb adjustment, just passing 140 F, about when the 7 PSI/160 F thermostat cooling system pressurizes. The disk (first photograph) labelled 1014 and 1 5/8 (its diameter) flew off, with the coolant following very promptly. Hate to have that happen while I was driving. My other engine (second photograph) has bolts through the disks that go to bars on the back side which may be holding the disks in place. 

 

So, do I drill a hole in each of the three plugs and rig a way to hold them in place? Are these things frequent fliers? I hesitate to simply press the plug back in place.

 

So what now? 

[7Westfield]

If you go the way the 2nd engine is, you have to figure a way to seal that bolt hole...

 

I'm assuming that it's the "flat" style of plug, just a slight dome to it

 

By the picture of the plug on Moss, there should be a step in the hole for it to sit against. It just taps down to that , and then you use a blunt punch in the center to push the dome in a bit.  I don't see a mark from that being done last time. It will push the rim out a bit tighter in the hole.  

I haven't done one in YEARS, but our go to sealant was always Permatex #2

 

If the bore is straight all the way (no step) it's a cup style. They just drive in, dome to the inside. Use a big socket to drive them

 

 

Edited November 20, 2025 by 7Westfield

[MV8]

Many names for them (freeze, expansion, or core). Here is how to install them properly: https://www.mgaguru.com/mgtech/cooling/cool_105.htm

 

The second engine appears to have rubber "expansion" plugs that serve the same purpose and don't use any sealer.

 

Edited November 20, 2025 by MV8

[straightcut]

A friend much wiser on these things than myself advised that I only use brass core plugs, rather than the more commonly found galvanized steel.  The last engine I left at the machine shop (a shop that I trust), replaced the cam bearings, measured and hone the cylinder, etc. replaced my core plugs with brass.  Being the material they chose corresponded with what my old friend suggested, I figured the shop chose wisely. ;-)

[Timothy Keith-Lucas]

As usual, wonderful help. Thank you. The air-borne plug has been slightly flattened but I think will tap into place. I'll let everything dry, then put a little Permatex around the edge, tap it into place, and then give it a couple of moderate whacks with a socket, 1/2" extension, and two pound brass hammer. I've already hosed the driveway (dogs get poisoned on ethel glycol; it tastes sweet) and showered off all the coolant I got in the face. Unfortunately, the plug that thought it was a frisbee was immediately above the dip stick, so an oil inspection is on order as well. Hey, this is not the first time that MGA With an Attitude has had a very informative article.

[IamScotticus]

How old are these plugs?

I don't think reusing a core plug is a good idea.  Do you think the others will stay in place?  I suspect there is something amiss about the installation or the plugs, or the seal had sucom to corrosion, and it would be the same outcome for all eventually.

 

I'm not in the brass camp. I think surface prep and proper installation is key regardless the material.

 

Tim, this isn't your fault,  but I wouldn't trust core plugs past 20 years.  Most cars don't last 20 years, so it's not common to see them fail.

Edited November 21, 2025 by IamScotticus

[MV8]

I've had to replace several decades old steel plugs that had eventually failed/leaked due to corrosion from rust through (not the edge). I use a finger wipe of rtv on the edge before installation. The plug metal is very thin sheet metal and the first thing to go from rust. If you don't have good access with a hammer, pick up a 1-1/2 rubber plug at your local store. Here is a link to 1-5/8 but it may need to be slightly smaller to clear the recessed lip.   https://shop.advanceautoparts.com/p/dorman-help-rubber-expansion-plug-1-5-8-in.-size-range-1-5-8-in.-1-3-4-in.-10232/22140133-p?product_channel=local&store=3841&adtype=pla&product_channel=Local&store_code=3841&&&&&msclkid=cfb785ea93e114756d3ceccab7900024&utm_source=bing&utm_medium=cpc&utm_campaign=b_shopping_all_dorman_gen_gen_gen_evergreen_eng_aap_us_all&utm_term=4580221855580131&utm_content=Bing_All_Dorman - Innovation_Body&gclid=cfb785ea93e114756d3ceccab7900024&gclsrc=3p.ds

Edited November 21, 2025 by MV8

[Timothy Keith-Lucas]

Thank you both.  I think I'll proceed with the plug as a temporary until two weeks from now when I'll be driving by an Advance Auto Parts. It may be a cold weather job getting the other two out. 

 

I wanted an original Series 2 and I got it.  The constant problem is that it sat in storage for 59 years. 

 

Oops! I'm at my volunteer job, and will on the way home drive by a Carquest which is part of Advance. It's owned by my boss's boss. 

[MV8]

"Cold weather" gear in South FL? Socks?

 

I'd take a screw driver to try to clean the rust scale/deposits while they are out and flush with a water hose and the lower hose off. They tend to collect in the corners furthest from the water pump and can break free to clog radiator tubes.

[mrmustang]

3 hours ago, MV8 said:

"Cold weather" gear in South FL? Socks?

 

I'd take a screw driver to try to clean the rust scale/deposits while they are out and flush with a water hose and the lower hose off. They tend to collect in the corners furthest from the water pump and can break free to clog radiator tubes.

In defense of the OP's statement, we had a 3 hour delay of our flight in December 2010 due to snow, sleet, and freezing rain at the Tampa airport. You think SC people panic, you would have thought the world was physically coming to an end that day.

 

Bill

[Timothy Keith-Lucas]

North Florida, actually. South Florida is the home of "More cents than sense" Lamborghini owners and drunk boaters. North Florida is the origin of headlines that start "Florida Man...", multiple candidates for town idiot in each village, jacked-up tricked-out Jeeps that have never been off pavement, and family trees that don't branch. Oh, and bears. We have lots of bears. 

 

I do remember one time the temperature dropped below freezing. It was a major crisis for our Emergency Management.

[IamScotticus]

23 hours ago, mrmustang said:

In defense of the OP's statement, we had a 3 hour delay of our flight in December 2010 due to snow, sleet, and freezing rain at the Tampa airport. You think SC people panic, you would have thought the world was physically coming to an end that day.

 

Bill

Truth.  In regions that don't freeze frequently,  people aren't prepared or accustomed to freezing.  Building codes, road conditioning,  basic survival prep.  All go to crap during any freeze that lasts more than a few days.  Nature never fails to surprise us.  We never fail to be surprised.

[Alex-Ks1]

On 11/20/2025 at 5:12 PM, straightcut said:

A friend much wiser on these things than myself advised that I only use brass core plugs, rather than the more commonly found galvanized steel.  The last engine I left at the machine shop (a shop that I trust), replaced the cam bearings, measured and hone the cylinder, etc. replaced my core plugs with brass.  Being the material they chose corresponded with what my old friend suggested, I figured the shop chose wisely. ;-)

Never use a freeze plug a second time . The brass plugs don't corrode like steel ,and the rubber expansion plugs will pop out