Help me avoid car overheating in my Subaru?

August 28, 2006 4:34 PM

Help me with my Subaru Forester overheating problem?

About a month ago, my wife, our baby, and I decided to take a trip in our new-to-us 1999 Subaru Forester. Very hot day, air-conditioning was cranked, and we were fine until we started to head into an area where it was more hilly (between Chilliwack and Hope in British Columbia).

As soon as we started climbing hills, the temperature guage climbed high...almost getting into the red. Immediately I put down all the windows, turned on the car heater, and bled off the heat (that worked very well for the car, not so well for wife and baby). It kept happening though, and we turned around and limped home. While we drove after this on the way home, on level ground, the heat did occasionally rise and I took it slow and careful until we were home. Through all of this, fluid amounts were fine, both front fans came on ok.

I took it to a recommended car repair place and they did as much testing as they could, and found no reason for it. There also appears to be no damage to head gaskets or block warping, as I've been warmed happens occasionally with aluminum blocks.

Since then we've done a lot of in-city driving, including a few multi-hour trips without incident. On Thursday this week, we are going to head on a road trip (9 hours of straight driving, but we'll take lots of breaks for the baby). The forecast is for 21C temperatures for Thursday (way down from the 32C we experienced on the overheating day).

Other than not running the air conditioning at full blast, what can we do to avoid this? Recommendations much appreciated, but abandoning the road trip plan is not an option.

posted by Kickstart70 to travel & transportation (20 comments total)

Have your cooling system flushed, coolant changed, and thermostat replaced before you go. Check the grille and the front of the radiator for obsructions (dead bugs, dirt, leaves, etc.) Spray the outside of the radiator down at the car wash to remove anything you find.

If it starts to get warm on the drive, slow down. Lower RPMs = less heat. If it gets too hot, find a place where you can pull safely off the road and let it cool before moving on. Turning the heat on was a good idea, but I wouldn't want to overheat the baby in order to save the car.
posted by mr_crash_davis at 5:05 PM on August 28, 2006

Also, warm the car in the driveway with the hood up, and watch for the fan to come on. If the electric fan doesn't kick on, you're not going to get any cooling.
posted by mr_crash_davis at 5:06 PM on August 28, 2006

Replace the thermostat? It could be sticking in the closed position and not allowing coolant to circulate back through the radiator.
posted by COD at 5:14 PM on August 28, 2006

The crash_davis program should take care of it - he covers all the usual things that could cause overheating such as you describe. More diagnostic tests will cost you money; the stuff m_c_d recommends will not cost much more, and you are probably due for those things anyway.
posted by Kirth Gerson at 5:23 PM on August 28, 2006

Aside from the excellent replace the coolant and thermostat advice, I always like to check the federal governments databases for complaints, safety recalls, service bulletins, and defect investigations.

Check out the complaints stuff for your car with respect to the engine and cooling system and see if any of it could be applicable. There seem to be some gasket issues.

Good luck.
posted by bim at 5:32 PM on August 28, 2006

My (considerably older Subaru, but with essentially the same engine design) showed exactly the same symptoms as you described, and it did turn out to be the head gasket. You say they've tested for that, though, so I'm just making a note of this for completeness. No fuel fumes coming out of the radiator?
posted by Jimbob at 6:24 PM on August 28, 2006

I had a Toyota Corolla FX with the same problem. It would work fine with just the driver and one passenger in almost any circumstance; even an additional child would cause the car to become very sluggish, and, in the summer months, prone to overheating. It also needed premium fuel to prevent the enging from pinging; given what the dealer wanted to diagnose the problem, I just kept using premium fuel (it was under $1.50 back then!)

As it turned out, I did have a cracked head gasket. YMMV (for once this is apropos the car discussion :))
posted by rasputin98 at 6:51 PM on August 28, 2006

No fuel fumes coming out of the radiator?

You're probably better off checking the oil for water and the water for oil.
posted by Kwantsar at 6:52 PM on August 28, 2006

One of the more interesting complaints. Maybe the gasket deserves a recheck.


posted by bim at 7:34 PM on August 28, 2006

Sorry for the delay.

The car shop told me they checked for oil in the coolant and found none. I'm going to get a radiator flush and oil change tomorrow just in case and get a second opinion. I can't smell and oily smell from the radiator, but not sure that means much from me.

Fans definitely come on...and did that day too.

replacing the thermostat will be problematic. When I asked about that at the car shop they said it might take a week to order it in. If that fails when we're on this trip, it's going to be even worse (I really hope that's not the culprit). However, since the fans do come on, and we've driven it for long in-city trips, I doubt that's it.

Anyway, will know better tomorrow, I hope!
posted by Kickstart70 at 7:44 PM on August 28, 2006

These cars are famous for blowing the head gasket. Definetely get it rechecked by another mechanic.
posted by fshgrl at 8:07 PM on August 28, 2006

This is gonna be long:

I hate to be the bearer of bad tidings, but I can predict your future: You'll change several parts, starting with the thermostat, drive it for a while, think it's ok, then it'll randomly overheat again. This routine will repeat itself when you replace the water pump and other cooling components.

Eventually, you'll suck it up and pay the $1,700 to get the head gaskets replaced. How do I know this? Experience. Except when I finally figured out what was wrong, I unloaded the car and bought a Toyota.

Mine was a 98, which came with a dual overhead cam. (Just in case: The cams are at the right and left sides of the engine, at the ends of the two cylinder banks in your flat-four) The DOHC, used in the Outbacks from 96/97 to 99 and the Forester in 98 only, was famous for internal headgasket leaks that only opened up when the engine was hot, letting bubbles of exhaust enter the coolant. These bubbles impede the flow of coolant, create hot spots, and eventually will cause the car to overheat. Unfortunately, when the mechanic tries to figure out what's going on, he or she never notices the exhaust gas content in the coolant, because the car never gets hot enough. That is, until you're back out on your commute...

Subaru attempted to address this problem in '99 with a new SOHC (single overhead cam, likely what's in your '99). That engine, which essentially remains in use today, was more famous for external leaks (that is, they leaked coolant out of the engine and onto the outside of the block). This was what the coolant conditioner mentioned in the previous post was all about. Unfortunately, they still go internally, too, just not as frequently. I'd bet the farm yours has, since if it was leaking externally, your mechanic would have seen it staining the block, and registered the coolant loss. No amount of special conditioner is going to fix it, and you won't notice it as coolant loss.

A foolproof way to find out for sure is to take the car out for a spirited drive, get her good and hot, and then, while the engine's idling, look in the plastic coolant overflow tank (not the hot radiator!). If you see oily bubbles rising up, that's exhaust, and the only way it gets in there is through an intermittent head gasket leak.

Good luck.
posted by M.C. Lo-Carb! at 8:54 PM on August 28, 2006 [1 favorite]

I hate to be the bearer of bad tidings, but I can predict your future: You'll change several parts, starting with the thermostat, drive it for a while, think it's ok, then it'll randomly overheat again. This routine will repeat itself when you replace the water pump and other cooling components...

M.C.Lo-Carb speaks the truth. He pretty much described my entire experience, except replace "bought a Toyota" with "bought a Hyundai".
posted by Jimbob at 9:23 PM on August 28, 2006

Thanks for the unfortunate news :-(

I'm really screwed.

Well, I'm going to have to take this trip with the car and hope for the best...taking it slow when I have to. All I can do is hope to hell that we last through it. Once I get back, I can look at finding out for sure if it's the head gasket and replacing it. I owe too much on the car to not fix it, so no real choice there. We've only had it for a few months now (bought from a reputable dealership) and had hoped for better than this, especially considering we did not underpay for this car/odometer reading.
posted by Kickstart70 at 10:04 PM on August 28, 2006

I have a different vehicle with similar symptoms, and I just plunked down $29.95 for a combustion leak test kit. Basically it's a kit that allows you to check for hydrocarbons in the coolant, which can only come from a bad head gasket. It's not hard for a civilian to use -- pretty much all you have to do is open the radiator and pull air through a bulb filled with test liquid. I don't know how it will work if the gasket gaps are open only when the engine is really hot, but it's worth a try before replacing everything else in the cooling system in an attempt to fix the problem.
posted by harkin banks at 11:26 AM on August 29, 2006

That looks like a possibility. This page gives a little more info, but I'm not sure what air you are talking about...the radiator is full to the brim with coolant.
posted by Kickstart70 at 11:56 AM on August 29, 2006

You can use the hydrocarbon tester in the overflow tank, too. But if there are bubbles coming up in it, you can save the money - your gaskets are toast. The problem with subaru is the head gaskets can leak intermittently, as the engine expands and contracts, which means sometimes you won't get a reading at all. This is why many mechanics just keep throwing parts at them.

We had high hopes for the car, too, and this was a long, expensive and very frustrating process. We also bought our Forester from a reputable dealer. I feel bad admitting this, but it was Subaru's reputation for reliability (which I feel is quite unwarranted) that allowed us to get rid of it without taking a bath -- they tend to have high resale value.

We have a hyundai too, Jimbob, and holy crap, can that car take a beating...
posted by M.C. Lo-Carb! at 2:09 PM on August 29, 2006

Followup: I took the car in for a complete fluid check and replacement. After testing everything, we could find no sign of any leak...internal or external. The coolant is clean as new, no coolant in the oil (which badly needed a change...as I said I haven't had the car long and the previous owners hadn't done it recently). In short, all looks good.

Since the only time this happened was when I was running the car on the hottest day of the year, up hills, with the air conditioning at full blast...right now I think this was an idiosyncracy of the vehicle.

I can hope, anyway :( We'll see what happens when I push it harder on this trip.
posted by Kickstart70 at 7:24 PM on August 29, 2006

Further followup: The car was fine for the trip except for the last day, on the way home. But again, as soon as I got on the flat roads of the city it was all back to normal.

On that day, we did discover bubbles in the coolant tank, but I haven't yet done a check to see if that's exhaust. It could, according to various automotive sites, be just the effects of boiling coolant. In other discussions with people, they suggested that at least doing a coolant flush and then possibly doing a water pump change would at least settle the cheaper possibilities before resorting to a very expensive head gasket change.

On the other side, I slowly grow to hate this car for doing this. Everything else about the car is great, but I'm really wary of it doing this again with a new gasket after replacement. I can't afford to keep paying out gobs of cash.
posted by Kickstart70 at 2:32 PM on September 8, 2006

Kickstart - I just came back to this thread to find out what happened. Sorry to hear you're still having problems. As much as I hate to say it, I seriously doubt the water pump and coolant flush will have any effect at all on your problem. Plus, the water pump'll require a timing belt change, as well. I tried all these things, as have many, many other subaru forester and outback owners.

Coolant shouldn't be boiling, that's why the system is under pressure. Those bubbles, as much as you don't want them to be, are going to be exhaust.

If I were you, I'd start saving for those head gaskets, because that's going to be the final chapter of this unfortunate story. I feel your pain.

FWIW, I hated my forester for doing this, too. It was very expensive and frustrating for my wife and I. But I loooove my Toyota. Good luck to you.
posted by M.C. Lo-Carb! at 3:48 PM on September 15, 2006