1999 Subaru overheating


Asked by Jul 07, 2015 at 06:25 PM about the 1999 Subaru Legacy 4 Dr Outback AWD Wagon

Question type: Maintenance & Repair

My 1999 Subaru Legacy Outback with 138,000 miles, has an overheating problem. Intermittent, and unpredictable.  Coolant is full, both cooling fans run as needed, overflow reservoir is at correct level, air conditioner is off, no noticeable leaks at the water pump. That's the extent of what I know to do. Air temp can be anywhere from the 50s to the 80s and all of a sudden the temp gauge pegs at the top and I'm leaving a trail of coolant behind me. It has occurred before driving as few as10 minutes and after driving over an hour. Different garages have suggested a water pump replacement, thermostat replacement, head gasket replacement, getting a different radiator............... and I understand it could be any one of those. I know that once the hood is popped and wrenches start to turn, it will be any combination of some or all of them. The garages in this area don't have a great reputation for honesty and as for me, I can wire your house for you but when it comes to auto mechanics, I'm a full sandwich short of a picnic, no smarts at all. What do you readers think? For what little I know, my first guess is thermostat since it is the original and the miles are high. But of course, my guess is influenced by my wallet.

5 Answers

Kelly Mayo

humm...first change the thermostate..dill some holes in the new thermostat and install.add a bottle of WATER WETTER >Unique agent for cooling systems that doubles the wetting ability of water Rust and corrosion protection allows for use of straight water in racing or reduced antifreeze levels in warm climates Improves heat transfer and reduces cylinder head temperature May allow more spark advance for increase power and efficiency Use one bottle for most passenger cars and light trucks, treats 3 to 5 gallons or 13.2 to 15.9 liters. Vehicles with larger cooling systems should use two bottles. Small cooling systems should use 1oz (3 to 4 capfuls) per quart Compatible with new or used antifreeze (including DEX-COOLTM and long-life versions) to improve the heat transfer of ethylene and propylene glycol systems Satisfies ASTM D2570 and ASTM D1384 corrosion tests/anti freeze..

1 out of 1 people think this is helpful.

Try cleaning your radiator with a garden hose and nozzle or better yet a pressure washer radiator may be clogged with dirt and bugs restricting the air flow across the radiator.


Water Wetter is an excellent product and I'm not sure I'd take a pressure washer to your radiator.. Google search:: 1999 subaru outback overheating troubleshooting :: and one result is here :: http://www.subaruoutback.org/forums/66-problems- maintenance/40412-1999-outback-intermittent-overheating.html :: Lots of good reading. Another :: http://www.subaruoutback.org/forums/66- problems-maintenance/21325-indicators-bad-water-pump.html :: Plain OM said "Coolant leaks can be almost anywhere there are joints or seals where coolant flows. Assuming the water pump is the source might be premature, and costly." and I fully agree! Lots of factors. Do the reading. Register and ask for help. But don't throw money at a SUPER COSTLY water pump job that might not fix it. Clean the bottom of the engine, maybe let it idle and warm up and see if you can see the leak. Keep us posted

1 out of 1 people think this is helpful.

Never would have recommended it if I had not done it before and it worked.


If you do use a power washer do not use the jet stream use the fan spray tip.

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