Vehicle fluids, such as engine oil, automatic transmission fluid and even power steering fluid are highly specialized. Engineers take a multitude of factors into account when specifying these fluids. Damage can be done by using the incompatible fluids or by using stop-leak additives.
Leaks in vehicle systems are always a symptom of another problem
For instance, a common leak is a power steering pump. As the pump wears the shaft bearings develop slack. The rotating shaft no longer runs true and the seal starts to leak. A proper repair involves replacing the worn parts, cleaning all debris that has been generated from the system and refilling with the proper fluid.
Such a repair will involve some expense, but addresses the cause and prevents further issues. Contrast this, with adding stop leak to the system. Power steering stop leak usually softens and swells the seals in the system. The swollen seals may temporarily push more firmly against the rotating shaft and slow the leak. Unfortunately, all rubber, exposed to the fluid, undergoes the same swelling. This includes the seals in the rack and pinion, hoses and other components attached to the system.
The original bearing continues to worsen and now there is noise. Debris from the failing bearing has spread through the system, further damaging the softened and swollen seals. There is now a much larger issue and the original problem still exist. A proper repair would have been far less costly and would have prevented the additional problems.
Automatic transmissions are much the same. Foreign additives can attack clutches and friction materials. All seals in the transmission are affected. The transmission may be ruined, when a proper repair could have been inexpensive and easy. There is no substitute for a proper diagnosis of the problem. Adding stop leak to any system attempts to address a symptom, it never cures the problem.
Worse are stop leaks added to an air conditioning system. Many of these products work with moisture-curing chemicals, that harden when exposed to moisture. This cannot seal a mechanical problem such as a leaking shaft seal. Because of the original problem, moisture may leak into the system, causing the product to react. This creates a much worse situation and the original problem still exist.
By Federal law, all shops reclaim and recycle refrigerant in an air conditioning systems they service. This requires very expensive recycling equipment. Systems are tested for contaminants before recycling. Improperblendsofrefrigerantsandsealerswillshowascontaminatedwhentested.Whenthisoccurs,veryexpensiveremovalanddisposalprocedureshavetobefollowed.Thedebasedcontentscannotberecycled,anditisillegaltoreleaseitintotheatmosphere.Addingsubstandardrefrigeranttoanairconditionermaycostthevehiclefarmorethantheyexpect,forremovalanddisposal. The costs of this procedure can be shocking.
Unfortunately the sale of stop leak products are unregulated. They are widely sold by auto part stores and the buyer needs to be careful to avoid them. Often a proper repair would have a cost far less, than the problem created by the stop leak.
Ask the vendor, if they will stand responsible for the cost, if this product damages the vehicle? If the answer is no, why would you trust such a product
Leaks are always a symptom of another problem
Repairing symptoms will not fix the problem
Proper diagnosis of the actual problem is the least expensive route
No chemical or additive will effectively stop a leak
Incompatible chemicals added to a system can cause thousands in damage