Is Bar's Radiator Stop Leak safe to use



I have a 1998 ml320 with about 130,000 miles on it that has a slight radiator leak. This wouldnt be a problem except that I live in Baton Rouge, LA where even a slightly compromised radiator can be a problem in the summer. Unfortunately business is very slow and I cannot presently afford to replace the radiator. My question is, I am thinking of trying Bar’s Radiator Stop Leak, and I am wondering if this product is safe to use in my car (I have gotten mixed opinions when researching on-line)? Appreciate your help!


I squirmed in my chair upon reading your question. On one hand, you gotta get to work or you cannot afford to fix it. I threw stop leak in my old Volvo to get by for a couple more years. I found some product partially blocking water ports in the head when I finally tore it down, but it did not cause any problem, and that high mileage Volvo engine was not worth much anyway. On the other hand, I have seen some bad stuff happen in MB water jackets that had been abused or neglected, and a Benz engine with 130k is still worth some money.

Where is the leak? If it is degrading plastic around the upper radiator hose, it will continue to degrade and Bar’s Leak won’t stop it. Similarly, if it is the O-ring seal between the aluminum core and the plastic end caps that is leaking due to being attacked by the wrong anti-freeze, then Bar’s Leak probably won’t help that either because of the movement as the aluminum expands and contracts more than the plastic.


just once
then it’s repair time.
If you use it more than once you’ll have TOO MUCH and will begin to block passageways where coolant should be flowing.
Have you asked a radiator shop about fixing the one you have instead of replacing ?


You need to tell us where, exactly, the leak is.


Put a tablespoon of black pepper in the coolant, replace the radiator cap, start the engine and watch the leak stop before your eyes.



Get a new radiator. It’s overdue yesterday. I recommend calling friends and family until you find someone who will give you money. If you do use some stop leak stuff, follow the directions to the letter or it might not work at all.


It might not have to be replaced. Radiator shops PROPERLY fix radiators every day, and for a lot less money than replacing. All those stop leak products are good for is emergency get-you-off-the-road-and-to-the-closest-shop times. I have seen some of those do more damage to an older motor, then you’re REALLY going to be spending some money. Do it right.

P.S. Always change the thermostat when you open up your cooling system.



But do they fix the plastic/aluminum one? I thought that was limited to the older brass ones.

I imagine it depends on exactly where the leak is, which we’ve yet to hear…


I have seen them change the plastic tanks on plastic ones. I have an older Dodge dually (95 model) which sprung a leak in the core. A dealer tech dropped a pair of Snap-On channel locks down in front of the radiator which wore through the core. Radiator shop cleaned it out, braised the core and pressure tested it for $65 (My cost) normally $100. New radiator at that time was a little under $400. Got a new pair of Snap-on channel locks out of it too. :slight_smile:

Also SOME radiator shops wont bother replacing tanks. The OP should call around to radiator shops to see whether they repair or replace. It would help to know exactly where the leak is.