Why do all Subarus overheat (general answer)?

Question

Many questions on this subject have been asked, but only generally and simply answered. Here are some little known facts that will help prevent the demise of your engine:

There are several demons in the Subaru design which contribute to this problem and usually, the eventual demise of the car, worthy of a story on Forensic Files. From others I've talked to and my experience fixing 2 overheating problems in 2 Subarus, here are some contributing causes:

1. Subarus use an "upside down cooling system", with the thermostat on the bottom of the engine which slowly lets cool coolant in from the radiator as required. This may not be a good design as without coolant circulating in the radiator air or gas bubbles perhaps more easily form in the top of the engine.
2. With air in the system, the water pump can "cavitate", and not produce the required pressure to circulate water in the engine. Without circulation, the thermostat stays cool thus closed and hot water is trapped at the top of the engine at the heads and temperature sensor.
3. In this case, the engine reads hot and if you are persistent the overheated heads will warp, introducing leaks at the head gasket. As a test, note that the radiator can be cool and no warm air will come out of the heater, but the temp gauge will show hot. Use your IR thermometer to verify this condition if you have it handy. SOLUTION: If driving, drop to a lower gear, lower the load on the engine. The increased RPMs (4000) may get the water pump working. Your temp gauge will immediately come down, even if coolant is low.
4. Next, get water into it. Note that filling this beast isn't easy. To get the air out you have to open the plastic vent at the top of the radiation and slowly add water. This can take a half hour or so. Speed it up by raising the front end by driving up on a curb.
5. The whole problem may start when the engine was overheated once in the past, warping the heads. If the car was used, or if you're wife was driving, you may not know this part. The head thing can result in A. loss of coolant or B. injection of gas (bubble) into the system. So check coolant levels often. Mine loses about 8 oz a week, but less on a long trip, so checking it after 4,000 miles is sufficient. If you see even a bit of overheating, STOP immediately and get water into it. You'll have to let it cool so you can add it directly to the radiator. Plus, it there is a bubble, the radiator can't suck water from the reservoir easily. I carry water for that purpose.
6. You will see other solutions like, clean radiator, new thermostat, flush. All junk answers if you haven't followed thru as above.
7. But wait, you say you were paying attention and all the sudden the temp went to hot. Huh? Unlike old cars where the driver was expected to be responsible and you could watch the gauge creep up a bit on a hill, Subaru (another great design feature) designed the gauge so it has a dead spot. Notice how normally, the temp gauge will rise to normal as the car warms up, then stay rock solid no matter how hot outside or how you drive. Wouldn't want to alarm the driver, would we? Then when the temp starts to rise a bit in response to a problem, bang, the temp shoots up to hot. You haven't got a chance.
8. I suggest that many engines and head gaskets have been replaced because of the combination of all the overheating causes above. I've got 185K miles on mine and no warping yet, tho I've been caught a few times with unexpected heating problems. Keep in mind, when all is working, I can pull a long uphill haul full throttle in the Sierra at 106 deg outside, AC full with no overheating. With an air bubble you won't go even 5 minutes on the flat. It is such a serious problem I've added a loud alarm to tell me if the temp starts to rise from normal. And at the first sign of trouble, you have to be ready to pull over even in the dark of night to replace water, let it cool, etc., if it is worth it to you to save your engine. All worth it for this great little car, just a pain in the a**. It doesn't happen often, just once this year, but that is all it takes to turn the engine into scrap. BTW I've learned other cars are susceptible to this problem as well.
9. Good luck, Bruce

Answer 1

This isn't a question, but an answer to an implied overheating problem with Subarus in general.



I've owned and driven three Subarus a combined total of over 200,000 miles. Two of those cars had the 2.5 litre four-cylinder engine and the third was the 2.2 litre (no longer built). I've never had an overheating problem with a Subaru. I know lots of people with Subarus and have never heard one of them talk about an overheating problem.



I wonder if the "several demons" refered to in this discussion are really in the Subaru' designs, or in someone's mind?



The "learned other cars are susceptible" statement reminds me of the 'cars that leap forward even with the brake on, and with more power than they've ever had before' thing many years ago with the Audi 5000S (and then Cadillacs, etc). That turned out to be baloney too.



Added: Now that I've thought about it a bit, I realize it's almost spooky, with all those miles under my belt, that I've never had any overheating with a Subaru. Whoooo ...

Answer 2

The ONLY time I have ever had a Subaru(or any car for that matter to be precise) over-heat on me was when I failed to check the hoses and/or the gaskets for wear and tear. And of course, then I had an over heating problem. Usually followed by an engine re-build within a month if not sooner. It's only happened twice for me, once in my Subaru and once in my Chevrolet, so I've taken the necessary steps to insure it doesn't happen again. Plus, getting under the cars hood that often gives me an excuse to see if there's something I'd really like to do or improve on in regards to my car.

Answer 3

i had a 350 $ subaru gl-10 1988 i think , well anyway i got it in sumer time in slc utah 100 + degrees and one day it was getting warm - so i checked and found out that it had NO coolant and it still didnt overheat, my friends have 1 sti , 2 imprezas,1 legacy,1 baja and 1 forrester with no problems ( all in hot utah summers ) so i don't know what your talking about.

Answer 4

I've had my Impreza for 150,000 plus miles, and 2 members of my family have had an assortment of other models over the years.

Never had an overheating problem with any of them.

Answer 5

I'm on my third WRX and never had any over heating problems. What's your question or are you just rambling? Not all Subaru's over heat so stop rambling unnecessarily just because you had an issue.