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Hi, newby here..Pan M.

I want to share a recent 1994 Lexus ES300 problem and solution with the forum.

About 3 weeks ago, I lost (blew open) small water hose on the car going up a hill. Well, by the time I noticed the water temp gauge climbing I pulled over but steam rolled out of the car. I cooled it down, and tried to add more water, only to see it leave as fast as I put it in (from the small hose). So, I had the car towed home. Next day a mechanic came to my house and replaced the small hose. However, after that every time I tried to run the car with air conditioning on (and it is hot always in Panama), the car would heat up on temp gauge and water would boil out of the radiator overflow plastic container (reservoir). I started reading problems on this forum and many indicated a cracked or "blown" head gasket, cracked head, or a crack in the block. I also read many internet articles on how to fix these problems cheap by using sodium silicate in the radiator system after flushing all coolant and using only water. So, I searched products (Bar's leaks, Blue Devil, Gunk, and Heal-A-Seal) on-line that could fix this problem the cheap way, rather than a head job and not knowing if that was the only fault. In Panama I could not find Bar's Leaks, Blue Devil, but did find GUNK Block Seal, for $4.86 at Auto Parts 89 not far from my house. The Heal-A-Seal people wrote me back an e-mail with very thorough information, and the representative stated that I had hot exhaust gasses going back into my cooling system, which was very helpful. However, Heal-A-Seal was quite expensive, especially to ship to Panama.
I cleaned out the radiator and motor, poured in the Block Seal and ran it the first day 3 times at 45 minutes, 1/2 hour, 1/2 hour and was still heating up with A/C on. Next day, 2 times at 1/2 and 1/2 hours. Still heating up. Third day drove all over the city for a total of 3 hours, with some stops, and I noticed on return to home trip that the car was running smoother. So, today (day 4) I ran the A/C for about 7 miles (before would boil within 1 mile), and so far, so good, not a bit of heat, no boil over, and it looks like the Sodium Silicate (liquid glass) has fixed an apparent head gasket, head, or warp, or crack in the block. I still don't know which it was, but the first day of trying I noticed water bubbling near the head by the front exhaust headers, so I suspect it was a head gasket.

Hope this post helps somebody with an old Lexus like mine. :)