My roommate's 1991 W126 350SDL has either a bad head gasket or a cracked head. Or both. The fan blades cut a hole in the radiator and it lost its coolant and overheated. After repairing the cooling system, the engine acts like it has dead cylinders and idles poorly, smokes white out the exhaust, the upper radiator hose builds pressure fast when cold and holds pressure for hours after the engine is shut off, and smoke comes out of the coolant reservoir, even when cold. Oil and coolant aren't visibly mixing, though. The engine temperature also swings wildly and acceleration is poor.

So should I pour Bar's Leaks head gasket repair liquid into the cooling system and call it good? Are there any downsides to using it like clogs or it coating parts and causing overheating? We don't want to deal with the expense of replacing a head gasket, or worse; a head right now.

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1967 W110 Universal Wagon, Euro, Turbo Diesel, Tail Fins, 4 Speed Manual Column Shift, A/C
1980 W116 300SD Turbo Diesel, DB479 Walnut Brown, Sunroof, Highly Optioned, 350,000+ Miles

leak down test

Good idea. Is there any question that the head gasket and head aren't leaking, though, based on the symptoms?

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1967 W110 Universal Wagon, Euro, Turbo Diesel, Tail Fins, 4 Speed Manual Column Shift, A/C
1980 W116 300SD Turbo Diesel, DB479 Walnut Brown, Sunroof, Highly Optioned, 350,000+ Miles

Head gasket in a can like Blue Devil will work, basically it is Sodium Silicate ( AKA Water Glass ) . This chemical remains in suspension while mixed with water / coolant and won't clog heater cores. What happens is the fine " glass " fibers interlock as water is strained out by the leak. Heat then fuses the fibers together.

I've used this on a few engines with massive head gasket leaks but only one slight leak engine that I used long term. It greatly reduces coolant use but there may be some slow lingering consumption. The engine in question was iron head / iron block that developed a quart every few thousand miles consumption. Blue Devil took this to a quart every 4 K or so over the next year.

Doing a leak down I determined what cylinder was the problem, at 100 PSI the rad level rose ever so slowly, it was that small of a leak. After lifting the head, the gasket looked great with only a bit of silicon silicate in the area where the head had a low spot. ( both heads actually and in the same spot ) There were no signs of anything else clogging due to the sealer and the engine was reassembled with a set of milled heads.

I'm thinking that the leak was too slight to get a good rush of sealer in before cylinder pressure forced it back.

sealers only work for leaks not involving the combustion chamber ie coolant to oil etc.

if the leak is between the combustion chamber and the coolant passage then the combustion pressure will destroy any sealer

Sodium Silicate sealers will actually seal / dramatically slow down a combustion to coolant leak. Hot gasses fuse the fibers locking them together.

this may or may not get you by for a short while.

the only real way to approach op's concern is to:

1. Do a leak down test

and if a leak is found into the coolant:

1. have the head checked for cracks etc...

2. change the gasket

I have first hand experience with Blue Devil across probably 8 cars with one being my own. I've also repaired / rebuilt countless engines over the 40+ years I've been in and around the car business. These builds have ranged from " I know it will run but not last " to " It is as close to new as possible ".

While Blue Devil and the like isn't a permanent fix, it will dramatically reduce coolant loss stop coolant in exhaust smoke.

I don't know how well the 7 or so other cars fared but they did drive away without coolant smoke / pressure in the rad. These were car lot rejects on their way to the sub prime auction so no fear that my guy was going to retail them. The car lot I did work for buys directly from new car dealers and not at even a high end auction. The lowest end car on his lot right now is probably $ 5,500 but he stops short of higher end semi exotic stuff.

New car dealers bundle used cars together in order to get rid of junkers. Get 3 good ones but you have to take a junker.

I used Blue Devil on an OM603 and it bought me 12 months and about 15k miles. The crack was so bad that it hydro locked the engine but Blue Devil fixed it. I eventually replaced the head. It may be caused by further cracks and not the Blue Devil itself but one would never know. It will buy you time to sell it. If you intend to keep the car then a new head or gasket is in order.

If you use it, follow the instructions to the letter and REMOVE the thermostat first. Good luck.

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Not MBZ nor A/C trained professional but a die-hard DIY and green engineer. Use the info at your own peril. Picked up 2 Infractions because of disagreements. NOW reversed.

W124 Keyless remote, PM for details. http://www.peachparts.com/shopforum/mercedes-used-parts-sale-wanted/334620-fs-w124-chasis-keyless-remote-%2450-shipped.html

1 X 2006 CDI
1 x 87 300SDL
1 x 87 300D
1 x 87 300TDT wagon
1 x 83 300D
1 x 84 190D ( 5 sp ) - All R134 converted + keyless entry.

My experience with Blue Devil: combustion leak into coolant, it did not work. When I called customer service to get a refund ( guaranteed to work or your money back ) they told me that their product rarely works on that type of leak. Since that product is guaranteed or you get your money back, there is little risk in trying.

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Greg
2012 S350 BlueTEC 4Matic
2007 ML 320 CDI
2007 Leisure Travel Serenity
2006 Sprinter 432k
2005 E320 CDI
1998 SLK230 (teal)
1998 SLK230 (silver)
1996 E300D 99k, 30k on WVO
Previous:
1983 240D, on WVO
1982 300D, on WVO
1983 300CD, on WVO
1986 300SDL 237k, 25k on WVO (Deerslayer)
1991 350SDL 249k, 56k on WVO - Retired to a car spa in Phoenix
1983 380 SEC w/603 diesel, 8k on WVO
1996 E300D 351k, 177k on WVO

Sorry I can't add to this thread but i do wonder . Did you get your refund?

Yes. After my call, they contacted the retailer and authorized the refund. The retailer credited my charge card. No hassle.


As far as I know, the glass only forms when the liquid comes in contact with air. So best for coolant leaks to the outside of the engine, not so much for internal, liquid to liquid, leaks.

__________________
Greg
2012 S350 BlueTEC 4Matic
2007 ML 320 CDI
2007 Leisure Travel Serenity
2006 Sprinter 432k
2005 E320 CDI
1998 SLK230 (teal)
1998 SLK230 (silver)
1996 E300D 99k, 30k on WVO
Previous:
1983 240D, on WVO
1982 300D, on WVO
1983 300CD, on WVO
1986 300SDL 237k, 25k on WVO (Deerslayer)
1991 350SDL 249k, 56k on WVO - Retired to a car spa in Phoenix
1983 380 SEC w/603 diesel, 8k on WVO
1996 E300D 351k, 177k on WVO

The fusing to the water flow passages was real on several engines. Again it was a favorite trick of used car dealers. So the amount put into the system is open to real questioning. This was also years ago. It actually looked like a very even and nice glass type coating on the water passages.

Barr's Leak has walnut shell or some other stuff. I would only use it in an emergency. I have tired Blue Devil on a Neon. It slowed down the leak. I did put on a new gasket. I did not replace the torque to yield head bolts. There are the ceramic sealers. Haven't tried them. I think you have to remove radiator fluid, flush, then run the stuff with a mixture, then remove and refill.

For a suspected head gasket leak I personally do not think this is the way to go. I have seen a glass coating remaining in passages of engines I have taken apart. The water glass was applied a long time before.

How much they put in was an open question as it used to be a favorite with used car dealers. You could order it and still might be able to from some drug stores. Just was a lot cheaper.

Until someone enlightens me otherwise. I will continue to believe that no matter what the labels and claims. It is still just water glass. Used originally to stop leaking boilers perhaps even before the advent of internal combustion engines .

By the same token I would use it if a car or engine was near enough to the end point. Otherwise I might suspect some issues with heat transfer through the glass coating. Although glass conducts heat pretty well.

They lie if they claim it does not also do this over time. Yes it will fuse at the hot spot though usually. Far more times than not. Then again I have no ideal of how much was put into those cooling systems on the engines I dealt with.

Head gaskets on old engines are kind of a right of passage. Cracks are another beast. Part of problem with cracks. I have always suspected is shutting down engines before letting any hot spots cool down.


Especially when you roll off the highway at high speed up to a fuel pump. Idling it for a couple of minutes first can do no harm. Otherwise if the coolant boils off the hot spots there are stress issues. Eventually they take their toll.