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Leaky Radiator

I have an 87 Audi 5000 Quattro, which has been our snow car for quite a few years. Not much to look at but can’t beat it on snow and ice. Recently did a few test drives with it and found a slow coolant leak. It does not appear to be coming from any of the hoses, but rather there are a couple of wet spots on the radiator core itself.

I am considering a used radiator, but was thinking of trying some of the stop leak products, just to see if they might fix it. I know it’s not a permanent solution, but I am really just trying to get another 40-50 hours of driving out of this.

My question is, are any of the stop leak additives worth trying? Do they ever work? or do they cause more damage than good?

And if they can work, which product is best for an aluminum core/plastic capped rad?


They work for certain types of small leaks. I used it on a Chevrolet metal radiator when camping in the woods of Maine; a local gas station put some in and it allowed us to finish our vacation and get back home to have it properly repaired.

I personally would not rely on it as a “permanent” fix.

The best stop leak I’ve used is black pepper. Yep! Black pepper!

Dump a tablespoon of black pepper in the radiator, fill the radiator, install the cap, start the engine and stand back and watch the leak stop before your eyes.


Just replace the damn radiator. Playing stop leak games is going to bite you in the you know where.

Before using any kind of a stop leak you need to know whats leaking. In your case i’d try testers trick with the pepper.

In my case with my 95 Taurus the seam where the plastic tanks are crimped onto the metal core were leaking. Poured in a 1/4 tube of alumaseal. Problem solved. Drove the car another 50,000 miles before trading it and it never leaked again.

Now that i know about Testers trick with the pepper, i’ll give that a try next time.