Can additives really help? - “stop leak” products

[Deadpurpledog]

Experiencing seal leaks and considering having them replaced.  Before going to this expense, am wondering what your experiences are with “stop leak” products.  If helpful, are some better than others?

[arcticbuicks]

i take mine every morning 

[Fordy]

Stay away from "snake oil" type products that promise miracles. If you have a leak there is only one way to fix it and that is properly!

Steve

[Rata Road]

Some of the products work great in my experience. If its an older wagon that isn't worth a rebuild or your short of funds why not try.

I have several oldies, one is a 51 Rover 75. After I had it for a few months I changed the oil, as soon as i did the rear main seal spat oil and I mean it didn't drip out it pretty much poured out when hot.

I also have the original motor but not sure if i want to spend a heap rebuilding it as the existing motor is a little noisy but runs fine. 

So I poured in 1 can of rear main seal additive, as per the instructions, and the leak basically stopped (I guess it arrived with an additive in it).

Unreal!

[Leif in Calif]

I've heard that the stuff that swells rubber can be very helpful if you have an older automatic that is rarely driven.

I've also heard that full synthetic motor oil with a zinc additive is the way to go.  

[Deadpurpledog]

Do you recall the product’s name, Rata Road?

[John Byrd]

I have used "Restore" and "Blue Devil" stop leaks in a few old vehicles and one or two newer ones. Totally stopped the drips in all instances, so therefore I believe in them !  The Restore product even stopped horrible smoking in a couple of the oldies, particularly a 58 Studebaker V-8 ton & 1/2 truck that was probably my worst smoker ever !

 

Edited November 23, 2023 by John Byrd (see edit history)

[nat]

     

7 hours ago, Fordy said:

If you have a leak there is only one way to fix it and that is properly!

Steve

     Steve's advice is good but there are rare exceptions.

    In 74' I bought a 50' Buick Roadmaster that was sitting in a Wisconsin field for $50.  The engine was stuck but I got it to turn over, put a battery in, started it with a tow and drove it away.

     It ran great but the front transmission seal leaked like a sieve.  A can of "Transmedic" stopped the leak.

     I suspect that such snake oil is more apt to rejuvenate leather seals than they are to do any good to rubber ones.

     If snake oil cures the leak, buy a lottery ticket immediately.

[arcticbuicks]

I do not like additives.......but i have to agree 100% on 'transmedic'.....but not for a stop leak.......more for cleaning and seal conditioning..........it is the only additive.......i really do see working well......i also used to like rizlone engine cleaner also

Edited November 24, 2023 by arcticbuicks (see edit history)

[1949 PLYMOUTHP17]

clean the area where the drip occurs with alcohol and attach a maxi pad to absorb the oil. the maxi pad already has adhesive strips on it. laugh now but it works beautifully. we used to borrow maxi pads from the women's room at the car dealership and tape them inside the bellhousing when we did a rear main seal or transmission front pump seal. the maxi pads are cheap. maybe it will help a car that is being moody.

[yachtflame]

I’m hoping your wife doesn’t read this forum!

[plymouthcranbrook]

I have used AT 205 with some success.  However it only works on rubber so rope seals and cork gaskets are not worth the trouble.

[EmTee]

You could try one of the name-brand oils formulated for 'high mileage' engines.  I don't know if they work, but I think they'd be a low-risk option.

[5219]

In the early seventies, I owned 1969 Cadillac Deville. At about 60,000 miles (maybe-considering where I bought it), It developed an an odd transmission problem. From a cold, parked overnight, start, the car would not go forward right away when shifted into drive. The service guy at the dealership said that the torque converter was leaking into the transmission case while the car was parked. Once the car was started, the converter would fill up again and drive would work. It was expected to be an expensive fix. On an off chance, I invested a couple of bucks in a can of DuPont transmission sealer. I followed the instructions exactly. After about two days, the problem went away! The service guy at the dealership pronounced it a miracle and said that I must be God's favorite. 

     DuPont, as far as I know, is no longer in the additive business. The transmission was fine for about five years and eventually was rebuilt for 

other problems. I offer this because it is true and because there must be other, similar, stories.

[EmTee]

I had a '67 Lincoln Continental with 100K miles that would pause 3~5 seconds before engaging reverse.  I mentioned the problem to an older transmission guy who poured 2 or 3 ounces of brake fluid into the transmission.  As i recall, the problem was gone the next day and the transmission functioned perfectly.  That small amount of brake fluid was enough to swell the leaky seals.

[McLovin]

I've found that most automotive additives do very little if anything and are a waste of money. There are three that I have used though that work quite well. 1. STP oil treatment in the original blue bottle at every oil change, it's a great viscosity builder and contains zinc which is great for reducing wear in older engines. 2. AlumAseal radiator stop leak, as lame as it sounds to use it it really works on the smaller radiator, heater core and water pump leaks but is not compatible with antifreeze as it states. One needs to drain all antifreeze, refill with water and diluted stop leak, run again to temperature, finally drain and  refill with 50% antifreeze and water. 3. Iso-Heet in the familiar red fluted bottle is a great fuel line antifreeze and water remover since it's mostly isopropyl alcohol. It also helps clean carburetors and injectors for easier starts, especially in winter. One bottle treats 20 gallons, once a month is normally fine. McLovin.

[JACK M]

When I was in the boat business OMC sold a product called 'engine tuner.

It could be had in a spray can or (my preference) a gallon can.

Pour a couple of ounces down a running carburator and let it sit overnight.

That stuff would dissolve all the carbon crud and made old engines run much better.

I used to sell alot of that stuff to the Pot Lot guy down the street.

[dship]

When I owned cars manufactured in the late fifties and early sixties, I used to pour STP down their carburetor to burn out any/all crap out of it.... always seemed to work.  Also, I used a sawdust "additive" to transmissions to cure them from slipping!    

[Terry Bond]

When I first saw the topic I thought is was going to be about fuel additives and passed it over. 

My opinion on additives-everybody has an opinion. Your results may vary.

Terry

[Porsche 68]

Marvel mystery oil my friend uses it in his 28 Whippet I blew a head gasket when I pulled the head off not one speck of carbon on the pistons I’ve been using it ever since Also BG 44K is an excellent de carbonizer. John

[McLovin]

On 11/23/2023 at 1:07 PM, Deadpurpledog said:

Experiencing seal leaks and considering having them replaced.  Before going to this expense, am wondering what your experiences are with “stop leak” products.  If helpful, are some better than others?

Had a blown head gasket on an 85 tempo back in the late-90s, blowing clouds of white smoke like crazy! Went to Walmart and bought a $7 bottle of Barrs block seal. Used as directed, flushing block of antifreeze and running it with block seal and water to temp, drained, left lower hose and radiator cap off for the night to dry, filled with 50% water and antifreeze mix. No more white smoke, oil clean, and drove the car for three more years! I sold it still holding so I don't know how long it worked for! And yes I did disclose that to the new owner, knew it was the right thing to do LOL! He was just happy to get a good running car for cheap. McLovin.

[McLovin]

56 minutes ago, dship said:

When I owned cars manufactured in the late fifties and early sixties, I used to pour STP down their carburetor to burn out any/all crap out of it.... always seemed to work.  Also, I used a sawdust "additive" to transmissions to cure them from slipping!    

Dship, I was fooled by the sawdust "additive" once when I was buying a 70 LTD, thing ran great until I changed the oil LOL! Always checked under the oil fill cap for that from then on when checking out cars. McLovin.

[McLovin]

On 11/24/2023 at 4:40 PM, EmTee said:

I had a '67 Lincoln Continental with 100K miles that would pause 3~5 seconds before engaging reverse.  I mentioned the problem to an older transmission guy who poured 2 or 3 ounces of brake fluid into the transmission.  As i recall, the problem was gone the next day and the transmission functioned perfectly.  That small amount of brake fluid was enough to swell the leaky seals.

Emtee, 67 lincoln, nice car! The metal from a car like that would make probably five Kias. McLovin.

[McLovin]

28 minutes ago, Porsche 68 said:

Marvel mystery oil my friend uses it in his 28 Whippet I blew a head gasket when I pulled the head off not one speck of carbon on the pistons I’ve been using it ever since Also BG 44K is an excellent de carbonizer. John

Amazing stuff! Can be used in your fuel tank and crankcase. McLovin.

[Paul Dobbin]

My favorite for leaky transmission seals is 1/2 cup of lacquer thinner.

[avgwarhawk]

The following have worked for me or worked for others I know. 

 

1. Bars Leaks.  Stopped a radiator leak 

2. Transmedic. Stopped leak and slip. 

3. Brake fluid. Swells seals in transmissions.

[Bhigdog]

On 11/23/2023 at 2:16 PM, arcticbuicks said:

i take mine every morning 

Now that right there is funny.......bobl

[zeke01]

Many years ago I attended a seminar on oils delivered by a representative from DX oils at an AACA annual meeting. Something he said has stuck with me for thirty years or more. When talking about off the shelf oil additives he said “The best result you can hope for with an additive is that it does no damage”. He reminded us that motor oil has been developed by chemical engineers and additives have already been added. Whatever you add in addition to the oil hasn’t been accounted for in the oil formulation. It is entirely possible that your additive will not be compatible with,  and in fact counteract the additives in the motor oil. I’m not a chemical engineer. I will leave the oil formulation to someone at a higher pay grade. Zeke

[EmTee]

15 hours ago, McLovin said:

Emtee, 67 lincoln, nice car! The metal from a car like that would make probably five Kias. McLovin.

It was a really nice car that I wouldn't mind owning today.  Bought from a coworker when I lived in Sunnyvale, CA.  He bought the car when it was ~2 years old.  He and his wife had no kids and the back seat looked brand new.  Silver with a perfect black vinyl top.  The paint on the hood and deck lid was burned-off to the primer in spots, but the paint on both sides was perfect.  100K miles and it ran like a Swiss watch.  After I changed the idler bearing in the compressor clutch it was dead silent at idle.  The PO had installed a Frantz oil filter (the kind that used a roll of toilet paper as the filter media).  That was fun!  I drove it cross country and my wife's comment was that it was like putting your livingroom on cruise control!  Traded it on a new '83 Mazda B2000.  The Mazda slowly dissolved, but I'll bet the Lincoln lives on somewhere...

 

Oh, and back on-topic, these are recommended by GM and work (even with antifreeze):

 

 

...and the identical product from the source:

 

 

Edited December 16, 2023 by EmTee (see edit history)

[Angelfish]

I use Seafoam in pretty much everything I own.  In the gas more than in the oil, dump it in before a road trip or when parked for the winter.  Mostly because I like the color. 

 

Techron fuel system cleaner did seem to clear up an old fuel injection system. 

[plymouthcranbrook]

My late neighbor had a home based auto repair business in his garage for years. One time a customer brought a big early 80’s Cadillac to him with an antifreeze leak from somewhere on the block. The customer insisted he use a particular treatment that he supplied for the repairs. Some type of “glass” compound.  Pretty complicated repair process that involved draining and refilling the system a few times. My neighbor did it while being  doubtful if any success. The leak stopped much to my neighbor’s surprise and did not return for the rest of the time his customer owned the car. Several years anyway.  Unfortunately I do not remember the name of the product though some of you might know it.

[Bhigdog]

10 minutes ago, plymouthcranbrook said:

My late neighbor had a home based auto repair business in his garage for years. One time a customer brought a big early 80’s Cadillac to him with an antifreeze leak from somewhere on the block. The customer insisted he use a particular treatment that he supplied for the repairs. Some type of “glass” compound.  Pretty complicated repair process that involved draining and refilling the system a few times. My neighbor did it while being  doubtful if any success. The leak stopped much to my neighbor’s surprise and did not return for the rest of the time his customer owned the car. Several years anyway.  Unfortunately I do not remember the name of the product though some of you might know it.

Sodium silicate or water glass......bob

[Andy J]

For small radiator leaks or other minor coolant leaks,I have used ground black pepper.Put a couple of teaspoons of pepper in the radiator and drive away.Of course,it is just a temporary fix,but a few times it lasted up to three years for me.An old mechanic I used to work for showed me this trick.

[JACK M]

19 hours ago, Paul Dobbin said:

My favorite for leaky transmission seals is 1/2 cup of lacquer thinner.

Tell us about this.

[McLovin]

55 minutes ago, Bhigdog said:

Sodium silicate or water glass......bob

That's what the lot attendants used at the Dodge dealership that I worked at for many years on cars taken in for the Cash for clunkers program where they had to intentionally kill the motors before they sent the cars to the junkyard since the motors we're not allowed to be resold. They would pour it in the crankcase and run the car at 2000 rpm until it froze up. Most engines seized up in about a minute but I remember an older Ford conversion van with a 302 that went on for almost 5 minutes before it finally gave up, it was sad to watch as it could have gone on for many more years! Sodium silicate is great in your cooling system for leaks but don't accidentally put it in your crankcase! Lol! McLovin.

[McLovin]

59 minutes ago, Andy J said:

For small radiator leaks or other minor coolant leaks,I have used ground black pepper.Put a couple of teaspoons of pepper in the radiator and drive away.Of course,it is just a temporary fix,but a few times it lasted up to three years for me.An old mechanic I used to work for showed me this trick.

1 hour ago, Andy J said:

For small radiator leaks or other minor coolant leaks,I have used ground black pepper.Put a couple of teaspoons of pepper in the radiator and drive away.Of course,it is just a temporary fix,but a few times it lasted up to three years for me.An old mechanic I used to work for showed me this trick.

That old remedy is about as old as it gets, I've never tried it but it's supposed to work! 🙂

 

[Deadpurpledog]

Who knew?

[Harold]

5 hours ago, McLovin said:

 

My father used oatmeal instead of black pepper.  It worked.

[EmTee]

I've heard people use a raw egg -- never tried it myself.  The active ingredient in the GM and Bar's leak tablets I posted above is Ginger Root!

[tcslr]

sawdust was old power plant condenser leak ‘tricks’. Finding condenser leaks is laborious. Coarse ground pepper would be a reasonable trick in small systems.
the ‘trick’ was always a temporary fix like when pricing was high or one was concerned with performance metrics. 
it was NEVER a good thing. Sometimes, it didn’t work - about 30-40%? 
as far as oil additives in transformers and turbine lube oils, IF the chemistry indicated it, ok. But one then deals with varnish on bearings. One is almost always ahead of game draining, flushing, repairing properly and using fresh oil or fluid. And turbine oils and transformer mineral oils are expensive. Still - cheaper.