Radiator Stop leak??????


New Member
Oct 1, 2005
I have a 1991 Mustang 5.0. My mustang has a slight radiator leak. My low coolant light was on and I filled up the resevoir. 3 days later the light came back on. The resevoir is empty again. I checked the radiator and there is a very small leak. I have been driving it for 1 month now with the low coolant light on and everytime I check it the radiator is almost full. I see where the leak is in the radiator. It is in the top fin of the radiator. It is to cold out now to replace the radiator. Has anyone had good luck with stop leak or another brand. I have heard this stuff is bad to use. I just need a temp fix. Let me know everyones opinion. I just want that low coolant light off for now but I do not want to unplug it. Thanks Travis
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No better way to gum up the coolant passages and rad fins to ensure a nice clean engine install will be in your future. Well MIGHT be exaggerating a touch but that stuff is nothing but goo that will likely cause issues elsewhere in the system...my guess would be the Tstat, spend the 100 bucks and get the new rad, you can intall it in less than an hour.
I definitely would not use stop leak. Like someone else said either pinch it and solder it or possibly put some RTV silicone over it. I've put silicone over a rad. leak before and it worked.

If it's not too bad outside, put on some coveralls and get a $100 radiator and replace it. Another option would be to just pour in a little water/antifreeze every couple of days until it warms up a bit.