Subaru OEM Coolant System Conditioner - SOA635071-2 Pack

I purchased this coolant conditioner suggested by a local mechanic for a heater core leak in my 2001 Jeep Grand Cherokee 4.0. I was having to fill my reservoir tank 2 to 3 times a week. I had a permanent wet spot in my driveway. Went to this reputable local mechanic and as he charged strictly by the book hours to replace my heater core, cost to repair was going to be $450. After turning down his estimate and deciding to live with the problem, he offered information about this coolant conditioner that he used in a dragster he owned and raced. I purchased the two bottles and installed it as per YouTube videos and within 2 days my leak was stopped and has not returned for a year now (knock on wood). I only used one bottle for my fix so I gave the other bottle to a friend that had a leaky system on a farm tractor and bam it fixed that also. GREAT STUFF! saved me $442 in repairs. Highly recommended!

I am very skeptical about miracle in a bottle like "liquid engine rebuilder" but this is a product designed and recommended by subaru for subaru's, specifically for preventing and treating small head gasket leaks. That said, I do have a small/moderate external head gasket leak of about 100cc per 1000 miles. I can't pull the engine and replace the head gaskets right now and 2 bottles of this have dramatically reduced the leakage, much to my surprise. This is not a permanent fix but I would highly recommend it to be added when changing your coolant or if you ever notice a significant drop in coolant in one of these subaru boxer motors. If you have a known coolant leak you are on borrowed time even with this product and more significantly you are in danger of serious engine problems if not addressed. You need to monitor your engine oil regularly (daily/weekly) and if it looks milky or in any way just not normal you need to get those heads done immediately. Also, you need to watch your engine temp like a hawk and if it never goes above half way, such as mine, and then one day it is 3/4 to the top, not in the red mind you, but just a significant deviation from normal, you need stop get those heads addressed immediately. Head gaskets leaks can be tricky and if it is only an external leak (big if) you aren't in real danger of damaging your engine, but coolant to oil, or combustion to coolant leaks are emergent situations in my book.That said, I'll use this again as it did work for me, again, as a temporary fix till I get the head gaskets done.

So I drove a late 90s Subaru with an EJ25 diagonally across the continental U.S. with a partially bad head gasket.That is, my coolant was not mixing with oil, and my oil was not mixing with coolant.However, exhaust gases were getting into the coolant and escaping through the overflow tank, conversely causing coolant loss and confusing the thermostat.I had this confirmed using a test designed to detect exhaust gases.I've done a lot of work to this car and sometimes wonder if I am dedicated enough to fix the head gaskets.I can't afford that yet.But here's what I did.Changed both radiator hoses. Those aren't good after 30 years.This helped with the coolant loss, as far as I could tell, but I wasn't confident enough to drive it a long distance, because typically after getting off the interstate and idling at a light is when it starts to overheat, and in those scenarios (at least before changing the hose) i would need to add a good bit of water to it to top it off again.Anyway! Even if part of the problem was the old hoses - If bubbles are coming out through the radiator, then coolant is going into the exhaust system, and thus losing coolant, one could safely assume.So, I changed the hoses. I ran it for a few days with just water to make sure I wasn't losing expensive coolant. I didn't lose any. But I feel like it was somewhat therapeutic for the corrosion to do the complete drains + fills a few times over a few days, even with the water.Once I drained the water, I added a bit of coolant, then a bottle of this, and some more coolant, and then another bottle, and then some more coolant.My thought process was that, since air cavitation makes filling these radiators super slow as you wait for air bubbles to make room for more coolant (esp. if your "breather" nut is stripped like mine) then I will probably get more "coverage" with this magic paste if i "spread it out" over the entire fill-up.I took it for a little drive immediately, not wanting it all to settle to the bottom, and let the engine idle for a good 20 minutes when I got home.After idling - ECT was 185f - Perfect! I looked in the overflow tank - NO BUBBLES! My coolant smells like coolant, instead of exhaust gases! You'd think it was flammable the way it smelled before.So, I think this pour-in stop-leak knows what it's doing when it comes specifically to Subaru head gaskets which have failed in the way of containing exhaust gases, but I wouldn't bet on it if you are already getting coolant and oil mixing.I still plan to change the head gaskets , heads machined and get the valves reseated and everything. But this stuff + the results have given me new confidence in driving this thing longer distances in the meantime. Hopefully it's a relativey long term fix.

I'm not going to comment on the fact that Subaru built cars knowing the head gasket needed this conditioner or it would most likely fail. Subaru owners already lament this. I've tried this product before, and with our Subaru on it's last legs, I bought another round to see if I can buy a few more miles before retiring it. I waited until the main radiator was down to about 2/3 level, poured in a bottle, topped off the radiator and then turned on the engine along with the heater and ran it for about 30min. Slowed my coolant loss by about 1/2 initially, but after about 1 year, it's beginning to get back to that level again. I've read that there have been people who had success pouring in 2 bottles at a time......didn't want to risk plugging up the heater core, but may try that out next. Again, not a permanent fix, so set expectations accordingly.

Exactly as described!