Sadly I think that might be a slightly naive and trusting view of the world...Hell Razor5543 wrote:Something to remember here, Jim, is that Valeo insist that, for the warranty to be valid, you must use Forte Stop Leak when replacing a heater matrix. I would be very surprised if a recognised parts manufacturer would make such a demand if they felt it could cause damage to other components.
It all comes down to culpability - if their coolant sealing product caused your gearbox to fail 15,000 - 20,000 miles later could you really trace it back to the application of that sealant, and even if you suspected it could you prove that it was that and not abuse or some other fault ? I would say no, at least not without a detailed (and expensive) post mortem.
Would they even be aware of the potential risks in every model of car in the world that their product might be put into ? No.
Remember that a lot of oil suppliers were happy to recommend Dexron III in place of Dexron II claiming that it's fully backward compatible, but there is strong evidence (after the fact) that Dexron III has killed plenty of boxes designed for Dexron II. Who is to blame here and who can be believed ?
After what I've seen with the comparative temperature measurements between the two cars, the two year history of symptoms of the old gearbox and the fact that it actually HAS now failed as predicted, I would not put ANY kind of stop leak in the coolant at all - its simply not worth the risk.
If the coolant expansion bottle or heater matrix are leaking then just do the job properly and replace them for god sake. It's not worth writing off the car by risking destroying the gearbox.
Changing a heater matrix IS a much easier job than changing a gearbox, and about 1/20th of the cost...
They don't care how long your gearbox lasts. 
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