Reader Question: Hi Austin,
This is a follow-up question to your advice regarding K & W Block sealer. You recommended we leave the sealer in and drive for 500 miles before flushing it out again.
I have a 1997 Subaru Legacy Outback with 117000 miles. After replacing the blown radiator, hoses, radiator cap, and thermostat, we have learned the head gasket (or head itself) is bad.
Once the car reaches normal operating temperature, it overheats & spits coolant within minutes of driving. There is no water in the oil, and no oil in the water. I do have bubbles in the water, and a lovely plume out the tailpipe.
First, I tried the new K & W Nanotechnology Block Sealer according to the manufacturer instructions, which had no effect. After talking to them, they believe that since it is a pure exchange between the exhaust system and cooling system, the patch was not able to take hold due to the pressure coming through the breach.
They had me identify the bad cylinder (based on spark plug appearance), and try the same patch again, only without that plug firing (left plug in, removed the cable). I did so, but once I reconnected the fourth cylinder, I went right back to the bubbles and exhaust plume.
I would LOVE to try one more fix using your 500-mile suggestion, but as I said above, I cannot drive more than a few minutes before it starts blowing coolant.
Do you have any suggestions that could help me out? At the rate I am able to travel, it would take me 50 trips just to reach 500 lol. I just cannot afford to put any more significant money into this car. If nothing else, I am just hoping to get it running well enough to use as a trade in, but I cannot even drive it to the dealer.
Thanks for reading,
Thanks for checking your auto insurance, hope you got a lower rate than you currently are paying.
I am not sure the additive is going to be of much help for you if you have that internal pressure building up that fast. I am assuming it starts “blowing coolant” because of compression gases in the radiator and not because the coolant is boiling over.
On a side note though, the additive is cheap compared to a valve job or head repair job, so you really do not have much to lose here. I would remove the thermostat, drain the coolant from the engine and radiator best you can anyway, add a can of the block sealer and top off the radiator halfway with plain water and let it idle for awhile until you can get the radiator 3/4 full of water then drive as far as you can.
I would also run the heater on full blast for a while to make sure there are no air bubbles in your heater core. Recheck your coolant level in the radiator after you run your heater.
If you can put a few miles on the engine without it overheating or puking coolant, I would replace the thermostat with a new one, do not use the one you took out. Thermostats can act strangely after they have been overheated.
This engine can be tough to bleed out the air bubbles in the cooling system. I do not remember, but there might be a coolant bleeder screw on or near the thermostat housing, which you can use to bleed out the air.
You want to get as much of this copper flake in the additive circulating around the cooling system to find and plug up the hole as long as possible.
I have yet to have luck using the product the way the instructions tell you to do.
I have my fingers and toes crossed for you, friend. Keep me posted, will ya?
Click to read my article about the K&W Engine Block Sealer Additive and how to use it.