Let me give a bit of background, as it’s probably important. I’ve got a 1995 Subaru Impreza. About this time last year, I noticed that the air conditioner was no longer working. I decided to live with it for as long as possible without doing anything about it. So, when I finally took it into a mechanic who specializes in air conditioners, he told me that the problem was not the compressor itself (which I had already figured out long before) but that a little movable baffle to cut off hot air coming into the cabin was stuck open and thus was overwhelming any cold air coming out of the air conditioner. He cut the hose that vented the hot air into the cabin and installed a little valve that I could shut when I wanted the air conditioner and open in the winter when I wanted the heater.
So, anyway, all this summer it worked beautifully as I ran around town. Yesterday, however, I decide to take the car out for its first long high-speed drive since this valve was put in. About forty miles into my trip, doing about 75 on US-70 (and in the middle of White Sands Missile Range to boot) I look down and see that the engine temperature gauge is up to maximum. I had not been running the air conditioner or the vent as it was less than 60 outside and the sun coming in through the window made the cabin temperature pleasant. So I pull over to the side of the road to do the obvious thing in checking the coolant level. The reservoir was full, just as it was when I had checked it before leaving the house. (I did not dare open the radiator on the side of the road.) I decided that it must be that air hose and tried to open the valve. I couldn’t get it open with bare hands and I couldn’t find the pair of pliers I was sure I had put in the car. So I gave up, opened the vent wide in an attempt to at least force some cold air over the engine, and drove 20 miles to the next town, where I bought a pair of pliers, opened that valve, and saw the engine temperature gauge return to normal.
So, my question is this. When I had that air hose blocked, was I really overheating the engine or was I getting a false positive on the gauge? Because I’m looking to keep this car a few more years and I really do not want to be making trips in the middle of summer with hot air leaking into the cabin just so I can keep the engine running.
Are you sure the valve was installed in an air hose? I did a similar thin to my F-350, but I installed the valve in a radiator hose (actually the heater loop).
If this is the case, which I suspect it is, you probably have one of the following problem:
Your thermostat is bad.
Your radiator is clogged
Your water pump is bad.
or, all of the above.
The reason it doesn’t overheat when the valve is open, is that everything works just well enough when it can get rid of the excess heat into the passenger compartment, but overheats when it can’t.
I’m pretty sure it’s an air hose. I don’t have a repair manual (the reviews for the various manuals that were put on the market are all bad from what I remember) but the hose where the valve is terminates in the firewall and I lose track of it (hard for me to see, but I can get a flashlight and look harder) as it heads towards the engine.
The car has about 117,000 miles on it. Other than the big maintenance at 120,000 (and the normal oil changes and such), I was hoping not to have put much more money in the car. I’m sure all of those problems aren’t too hard to fix, right?
I might go ask this question at the NASIOC forums. The reason I posted it here first was because I figured it was a general enough question that specific car knowledge wouldn’t be needed.
Regardless, you need to figure out why your engine is overheating - it shouldn’t need the interior heater to rid itself of excess heat, which brings me back to my three suggestions.
When the engine is cool, open up the radiator cap, and see if the radiator looks clogged (if you can, sometimes it’s impossible to tell).
Will do. I don’t mind replacing some things–I expect it with a car this old. I just don’t want to put the value of the car into repairs unless I have to.
If the radiator is clogged, what’s the best way to clean it out? I’ll get Subaru-specific help if I go to replace the thermostat and water pump.
Okay, you’ve convinced me. I’m pretty sure it’s not the water pump, as my parents replaced the water pump at the same time they replaced the timing belt 20,000 miles and three years ago. I don’t want to go after the thermostat unless I have to. I’m thinking of taking it to the same mechanic who did the air conditioner fix tomorrow morning. I don’t mind trying it myself, but I’m not quite sure how the radiator is attached to the rest of the car, by which I mean is it just bolted in or does Subaru solder it in as well. (I’ll take a look for guides online in a bit.)
So, buy a new radiator. Should I go to a local store and try to get one or order one online? The closest Subaru dealer is about 50 miles away. If you think I can get away with one more long drive of about 225 miles I can get it to my parents and get help from my dad. It’s also about time for a coolant replacement (SOA recommends every 30,000 miles) which I figure I’ll need to do anyway if I pull the radiator. Also, can you recommend a manufacturer?
Before you buy a radiator, may I suggest you have the system checked to see if the head gasket is blown?
In my experience* Sccoby do engines really don’t like being overheated.
It been a few years since I was near a Subaru, but back then they were famous for not liking being overheated.
First, I think you’re getting way ahead of yourself w/ all this talk of blown head gaskets, new radiators and water pumps. I’d guess that the guy who fixed it before is pretty savvy. I doubt that most mechs. would have suggested installing a valve, they would likely have told you you needed an expensive fix on the heater controls and left it at that. So I think it would be smart to go back to the same guy, let him do his thing and I’m betting you might only need a simple fix. It could be one of those other things, but there are several other, much cheaper, possibilities too. He’ll probably need a couple of hours, maybe even overnight. I’ve always found it unwise to rush people who you relying on to do a good job.
Sorry, can’t help with the OP’s problem, but I have a related question:
It says in Wikipedia that horizontally opposed 4 cylinder engines have power strokes that don’t span the full 360 degrees, which leads to vibrations along a vertical axis. OK, I get that. It also says that they have “no better kinetic energy balance than a single cylinder engine”.
Bwuh? Can someone explain this in layman’s terms? I’ve always heard that horizontally opposed engines of all stripes are designed more for performance than longevity, and thus few mainstream cars use it, but I haven’t quite been able to figure out why.
Offhand, I don’t see how or why this would differ from an inline 4-cylinder. Did the Wiki article specifically say this was a characteristic of horizontally opposed engines but not of inline engines?
I’ve never heard that. My understanding is that their advantages are smoothness, flatness (sometimes helps in packaging), and ease of air-cooling. Their disadvantages include width (sometimes hurts in packaging) and cost, which could certainly explain why they aren’t used much.
In this Wiki article I didn’t see any of the contentions you’ve relayed. What article did you read?
I thought the same thing as you did. OTOH I also hear anecdotal reports of Subaru engines almost always needing rebuilds after ~150k, with vague indications that it has something to do with the cylinder configuration. No cites.
It’s possible that either I or the other guy was just on mushrooms, but I thought I would throw it out there and see.
Just an update. Turns out it was just the combination of a bad thermostat and something about a bad radiator cap. I’m not sure what the deal with the radiator cap is. He sees no indication of damage to the engine either, so I got really lucky.
