tomwu

Anyone tried Radiator Stop Leak? Could be easy fix for small leaks yet concerned if it could clog something...

If anyone used before with good outcome, can you please share brand/model of the Radiator Stop Leak? In Australia we got Nulon brand and generally pretty trustworthy. https://www.nulon.com.au/products/co...lock-stop-leak

tsuter

Shark_V8

I use Prestone. I had a coolant leak on the service record that trips to the dealer and indie shops could not locate. "Coolant residue found on engine cover, could not located leak, no fault at this time" sort of thing.
I noticed some coolant smell.

I dumped in say 3/4 a bottle when I got the car and have not added coolant since. So it does work depending on what is up with the leak.

MP4.2+6.0

+1. Net, this is where I come out. Back in my C1 days literally in the late 70s I used it. But back then the Audi motors would eat head gaskets routinely, and the entire hose set were basically only four---upper and lower and the in out heater hoses. And in the world turned upside down you would use a (same thread size and pitch) Peugeot fan switch as "more reliable" than the Audi one. Wow. By the next one, a C3, I had my first taste of a clogged internal radiator core and from then on knew adding any extra stuff was a recipe for problems longer term. Including catastrophic breakdowns on side of road. From owning even the W12 for 9 plus years and over 100K miles on my watch (and another 30K or so since), I am convinced you can find most any leak visually, except perhaps in the heater cores--which usually smell from leaks anyway. Confirmed D3 Audi head gasket or block crack type internal issues are statistically close to zero from the entire board history, and this is the largest D3 board in the English (or maybe any?) language AFAIK. You first learn to look for the pink stain stuff from the coolant--crusted on, fluff, whitish dry spray among the variety of forms you use to snout it out. And yes, you need to often suck it up to be direct (many Audi owners seem to really try to avoid it no matter what) and pull the belly pan cover to get a clear view underneath, since fluids invariably head down. After VCDS, I actually think the belly pan pull for oil changes is the other best diagnostic tool going. What you don't see can indeed leave you stone cold dead on side of road if it festers long enough. In C3 days, motors were really unforgiving and it could literally cook the whole thing inside of 10 minutes and with no nanny interventions either.

For D3 days FWIW, the leaks I had in total were: 1. slight leak at heater block hose clamp in first 10K miles that I found after dealer didn't--the dealership owner had car for first few months as his personal ride (marks on cooling bottle were the giveaway--plus service records they were probing. 2. slightly cracked radiator core right near end of 4/50--that I found w/ belly pan pull and Audi replaced w/ brand new under warranty 3. leak at rear overflow hose due to crack dealer likely first caused at the 75K service (I found their kludge splice cover up); I self replaced. Known W12 heat bake issue flagged on forum for some years now. 4. Splitter connection at front radiator hose area--crap plastic that rots; fitting is W12 specific but it may be Audi systematic since same plastic is at the elbow type fittings where the air bleed screws are that we all have 5. One air bleed screw elbow (see #4); 6. Upper hose slight clamp pullback just above (W12) water pump, leading to minor dripping I spotted--again, first during a routine oil change with belly pan pull where it had left the white dry stuff on bottom of pan.

Any of 3-6 would likely not be fixed by stop leak for even mid term. 3-5 would have at least ended up needing an emergency on road patch and several hours wasted (a few owners have posted first person it happened to them). #6 could have blown motor if clamp gave (which was inevitable with time and miles and heat) and not pulled over and flatbedded in first half mile or so. It might have worked--for a while on the radiator in #2 actually--until it really took a **** God knows when. Might have sealed #1, but then the screwdriver it took a minute to turn once I found it by methodical search was a lot more sensible. So, spin the revolver for Russian Roulette. Much worse odds though from my own experience. In at least one, your car may be dead so to speak, and in most of the rest it is either going to the Emergency Room or at least Urgent Care and maybe some bed rest waiting for parts, maybe hundreds of miles from home and/or in 105 degree weather. It may take another year or two, but the preventative real fix would have avoided the high likelihood eventual breakdown result.