'72 Eldorado Freeze Plugs Need Help

[tallredii]

Hello all, my '72 Eldo started boiling coolant out of the coolant reservoir.  Replaced the upper and lower radiator hoses along with the cap.  Drove it for a few miles and it started boiling again.  Took it to a local shop and they said that my freeze plugs are bad.  They said they will have to drop the motor as well as remove the transmission to access.  Does this sound familiar?  They are quoting me 20 hours of labor?  Thanks for the input.  Tom.

[tallredii]

Nothing?  Someone has to know something...

[gary griffin]

  There are so many reasons that radiators boil the coolant out. How long after topping the radiator off does the overheating start? First question is can you see any leakage of coolant?  If so where is it coming from. Could be heater, heater hoses, head gaskets, radiator plugged up, or fan not working correctly.  If there is no coolant obviously streaming down the sides of the block I would vote against immediatly pulling the engine and transmission.  A simple test is to first see if there are any hot spots in the radiator. a gun style thermometer could scan the radiator and find or eleminate this possibility.  Where is the coolant going, it has to be going somewhere. Hard for anybody on this forum to even guess what you need without more information. If you do not have the ability to find the problem go to a good radiator shop and get them to test the system and proceed from there.

[waterzap]

Dont quite understand how bad freeze plugs would have your coolant boiling out. Maybe could be if the pressure is let off. Coolant boils at a lower temp at lower pressure.
Get a small laser thermometer. See what the temp is at the thermostat. If the temperature is higher than say 220, you have other problems.

[tallredii]

  There are so many reasons that radiators boil the coolant out. How long after topping the radiator off does the overheating start? First question is can you see any leakage of coolant?  If so where is it coming from. Could be heater, heater hoses, head gaskets, radiator plugged up, or fan not working correctly.  If there is no coolant obviously streaming down the sides of the block I would vote against immediatly pulling the engine and transmission.  A simple test is to first see if there are any hot spots in the radiator. a gun style thermometer could scan the radiator and find or eleminate this possibility.  Where is the coolant going, it has to be going somewhere. Hard for anybody on this forum to even guess what you need without more information. If you do not have the ability to find the problem go to a good radiator shop and get them to test the system and proceed from there.

Excellent advice.  Thank you.  It is boiling out of the reservoir tank.  In researching this issue, it seems that the freeze plugs, do just that, pop if the block is frozen to relieve pressure.  I am leaning away from the freeze plugs being the issue.  Could it be just a simple thermometer issue?  Thanks again, Tom.

[The Tassie Devil(le)]

I think you have been given incorrect information regarding the Freeze Plugs.

Firstly, the holes in the block are inbuilt so that all the core sand that is inside the block during the casting process can be easily removed, and the metal plugs that are referred to as Freeze Plugs, or Welsh Plugs are inserted to fill these holes holes to seal the cooling system.   The factory uses steel plugs, but whenever an engine is rebuilt, or a plug rusts out, then they should be replaced with Brass or Stainless Steel ones.   Brass is best, because it is easier to insert, and seal.

But, if they aren't leaking, then there is no reason to mess with them.   If they ARE leaking, then the engine will have to come out.   There are ones that cannot be reached with the transmission in place, and the biggest problem, even if you can see them, is getting access to attack them.   Plus, if one is leaking, then you can safely bet that all the others will be in the same condition, and about to leak.

Your "bubbling" in the reservoir indicate to me that you could have a blown Head Gasket, and it is the leaking compression pressure that is purging the coolant.

These cars use a 15Lb Pressure Cap, and when in use, the radiator is always full, and the overflow is contained in the reservoir, and as the engine cools down, the fluid in the reservoir gets sucked back into the radiator, via the radiator cap.

Use the wrong cap, and your radiator will lose coolant as the engine heats up, but not get it back as it cools down.

There is a product that can be purchased that tests the coolant for antifreeze quality, and I believe there could be one for testing combustion gases within the coolant as well.

Bruce.

[Gene Beaird]

<SNIP> How long after topping the radiator off does the overheating start? <SNIP>

The key probably lies in the answer to the question above.  I don't see that you've answered that question yet.  Probably more-precisely, how long after you start the car from cold does it overheat?  If you're going from a cold engine to boiling coolant in 5-15 minutes, then you probably have a stuck thermostat.  If it's longer, an hour, say, then you may have a clogged radiator, or a blown head gasket.  It could also be a weak fan clutch. 

[curly]

The product Bruce mentions is called 'BLOK Check" and you can buy it at NAPA for $15 or so.  It is a blue liquid that turns yellow if Carbon Monoxide is present in the air. You pull air out of a hot radiator and it will tell you if the Head Gaskets are bad.

X2 on what Gene said.

T Lewis

[TJ Hopland]

Head gaskets are not a real common issue with these engines even with abuse so I would not jump to that just yet.

Did a 72 have a fan clutch?  I was thinking that era tended to be fixed fans.

I'm with everyone else thinking freeze plugs have very little or nothing to do with the issue.  With no pressure at all a 50/50 mix is good to like 220 ish.  A good engine and cooling system should not get that hot on its own at idle unless its dang hot out or you got the AC on.  If its boiling at idle there is likely more than one issue.  A head gasket pushes air into the cooling system and the reason that usually causes boiling is that the air bubbles cause localized hot spots which cause localized boiling.  At some point the bubbles get to the water pump and that stalls the flow which then lets more spots boil.   With a minor bad head gasket being the only issue if you start it cold let it warm up with the cap off they will usually be fine since the air can easily escape.     

Before I got my new super modern radiator my 73 eldo used to always run warm.  240 was not uncommon and it never boiled the 10 or more years it was doing that.  Even a hot shut down with the heat soak it did not boil so if the cooling system is under pressure and the proper 50/50 mix it will hold.  Minor leaking freeze plugs could keep it from building full pressure and ultimately lowering the level.  Once you get hot spots or air in the water pump that temporarily stalls the flow things unravel pretty quickly.       

More info and details about how long this takes to happen and past history or recent maintenance or how long you have owned this car would help. 

One of those IR temp guns is a great tool for this sort of thing.  They can be had for under $50 and the cheap ones seem work just fine for what most of us would need them to do.     

[tallredii]

Thanks for all of the replies.  It takes about 15 minutes for it to start boiling and spewing on the driveway.  I don't drive it hard or rev it, I just cruise around the neighborhood.  There is no white smoke at all coming from the tailpipe.  There are no other strange sounds or issues (at this point).  I replaced the upper and lower radiator hoses as well as the radiator cap.  After these were replaced, it did the same thing, boing out of the reservoir.

Researching and from what people have said along with my '72 Cadillac Eldo shop manual, I am thinking it could be a thermostat.  I will take $7.99 for a thermostat as opposed to $2000 (labor) for replacing all of the freeze plugs.

Thanks again for all of the help.   

[Ken Perry]

Something to think about,Most of the heat leaves your engine through the exhoust! If your mufler is cloged or the tail pipe is smashed it will not let the heat out. Also timming being off will do it. I had a customer come in one time with a smashed exhoust tip,no one could figure out why the car was overheating.I sawed the end of the tail pipe off where it was smashed,end of overheating.Oh and don't forget the heat riser flap at the exhoust manifold. Hope this helps Ken Perry   

[beastly beauties]

It seems like most of your concerns have been well covered here by the replies generated. My first thought was your t/stat, the simplest to remedy. My second was the fan clutch, a very common issue with these models. Third suspect, radiator could be blocked from years of deteriorated hose particles. A professional cleaning may help cure that problem. From my own experience in changing weeping freeze out plugs on my 1971 Eldo, I was able to do all of the plugs with the engine in the car except the back of the block. I did have the exhaust manifolds off, and was detailing the engine with the front clip off. However, you can reach the plugs to knock them out with a long bar or round stock from outside your fender wells. When I removed them all, including the ones in the head (concave ones on ends of head), I spent a long time flushing out the block with high pressure water from all the openings in sequence. I couldn't believe how much black hose rubber, and to my surprise a large amount of casting sand! I wonder if these blocks were prone to retaining that much sand, creating a reputation for running so warm. I replaced the plugs with the rubber compression type. If they fail later on in life, I can replace them by loosening the nut and pulling them out. I am not really concerned with their originality, just practicality for now. They have been working flawlessly and have used these in the past on other projects and never had one fail when installed correctly. FYI, I always use distilled water with my antifreeze. The more antifreeze you use in your formula the warmer it will run. If you live in a year round warm climate or don't have to winterize for storage you can cut back on the antifreeze. Water pump lube and block conditioner is a must on cast iron engines to slow down the rusting process. I also had the radiator out so I sealed up the ends and filled with white vinegar and let it soak overnight. Could be a little risky on aged radiators but mine wasn't the original. I have never seen a cleaner core internally. Flow is 100% and runs much cooler. Thought I would share these ideas with you in case you have to go further with your issue.  "Sometimes the impossible takes a little bit longer".  Good Luck,      David Symonds

[Gene Beaird]

Wow, David, you've been very lucky with those rubber plugs.  They really are meant to be temporary.  I'd never think of replacing the entire engine set with them.  Who knew? 

The casting sand would lie at the bottom of the block, where coolant really isn't needed that much, so I doubt the casting sand would contribute to the engine running hot. 

[tallredii]

I got back from the shop today and it is the freeze plugs.  One on each side of the block is leaking.  Does anyone know exactly how many freeze plugs there are?  And their locations?  How many in front, sides and rear?  Thanks to everyone for the suggestions and replies.  I really appreciate it.  Thanks, Tom.

[The Tassie Devil(le)]

So, if it is boiling, and the overflow is running into the Reservoir, I cannot see how the leaking Freeze Plugs could be causing the problem.

If the Freeze plugs were leaking out all the coolant, then there wouldn't be any coolant left to overflow into the Reservoir.

But, there are three Freeze Plugs on each side of the Block, one in each of the heads, and it is only the block ones that ever give strife.

Personally, I have never used the Rubber replacement plugs that David mentioned, but have seen them on engines I have brought in from USA for rebuilding, but they are the first things I toss out.   I think they are only meant for emergency repairs.

Bruce.

[tallredii]

So, if it is boiling, and the overflow is running into the Reservoir, I cannot see how the leaking Freeze Plugs could be causing the problem.

If the Freeze plugs were leaking out all the coolant, then there wouldn't be any coolant left to overflow into the Reservoir.

But, there are three Freeze Plugs on each side of the Block, one in each of the heads, and it is only the block ones that ever give strife.

Personally, I have never used the Rubber replacement plugs that David mentioned, but have seen them on engines I have brought in from USA for rebuilding, but they are the first things I toss out.   I think they are only meant for emergency repairs.

Bruce.

And this is the reason I want to start beating my head on the wall... ..the mechanic showed me the leaks and swears up and down that this is 100% the only issue and told me that if I would like, I could bring any "Cadillac guy" that I could find and he would show it to them.  He said I am the 1 in a 1000 case that this happens to.  He's going to do 6 plug replacements and hopefully that will get it back on the road.  Thanks to Bruce and everyone else that has helped me with this problem.  It is very much appreciated.  Tom.

[The Tassie Devil(le)]

In his defense, it is very hard to diagnose any problem over the internet, phone or however, without actually being hands-on.

I have seen Welsh Plugs that have been leaking, but there is sufficient "gunk" built up behind the holes to really slow down the outward flow.

I would be having a compression check done on each cylinder to eliminate a blown head gasket.

Bruce.

[Bob Hoffmann CLC#96]

Tom,
I don't think it's freeze plugs either. Get a second or third opinion.
HTH, Bob

[TJ Hopland]

Only relation to freeze plugs I see would be that they are leaking enough to keep the pressure from building so if it was running hot anyways the lack of pressure may be enough to push it over the edge.  Like someone else mentioned there is usually enough other crap in an old engine to plug up slight leaks.  The only time I have had freeze plugs cause more than just little annoying dribbles is when they completely fall out which I have had happen and leaks are a sign that that could happen soon so getting them replaced is not a bad thing but I / we are concerned that there may be more that needs to be looked at while its out / apart.

If this mechanic is 1000% sure is he willing to significantly discount this repair if it does not completely solve the issue?

If the engine and transmission are getting separated you want to be sure the timing set has been replaced.  Originals all had a plastic covered cam sprocket.  Age and mileage were not kind to these things so even if you don't have a lot of miles you have the age on it now.  Problem with the Eldo is that to properly do the job the oil pan has to come off and in the Eldo its partially blocked by the transmission.   Oil pan ideally comes off because of the way it fits and seals into the timing cover the timing cover was designed to go in first then the oil pan.  Also the oil pan and oil pickup tube will be full of cam gear bits.   Don't get a store brand timing set get a Cloyes brand.  Cloyes is a common brand in engine parts so they are not hard to find and they make 3 grades, all are fine for a stock engine.  The least expensive is a stock type.  The other 2 are roller (bicycle) type chains.   Pulling the distributor will usually get you a slight look at the chain and sprocket.  If the engine is real dirty inside it can be hard to tell what you are looking at but you can usually determine if its coming apart because if it is plastic it will have cracks at this age.