Subaru cooling system problems: Grassroots Motorsports forum: Grassroots Motorsports Magazine

Subscribe get a full year for only $23.95 Sample Free Test Drive—no strings attached

March 21, 2010 11:07 p.m. Travis_K Dork

I am becoming less and less impressed with subarus the more I wokr on my dads legacy. Yes, it has been reliable for over 300k miles, but so have several other cars we have had and they were alot better designed and easy to work on. But anyway, here is the lasest problem:

I just had the engine out and put it back in about 600 miles ago. I filled the cooling system with distilled water, and drained it a couple days ago, and havent driven it since then. Now, even though I filled it the same way I did the first time (when it worked fine), the lower radiator hose is cold, and although it will idle at normal temp, as soon as you step on the gas it pegs the temp gauge. Its fine if you drive with the radiator cap off, but if you pull over and put it on, as soon as you step on the gas again the gauge goes right back to the top again. Any suggestions on how to fix it? does anyone else hate subarus? lol
March 22, 2010 5:59 a.m. chaparral New Reader

I'm thinking "stuck thermostat" here, and it's the bad kind - stuck closed.
March 22, 2010 7:48 a.m. carzan Reader

Doesn't seem like it would be the thermostat if it doesn't overheat with the radiator cap off...
March 22, 2010 8:09 a.m. Junkyard_Dog HalfDork

Air in the system is my guess. And why just water? Antifreeze helps cool too.
March 22, 2010 11:14 a.m. iceracer HalfDork

Actually, water cools better than anti freeze but AF raises the boiling point plus protecting against freeze up.

How about a blown head gasket, which Subes are noted for.
March 22, 2010 11:49 a.m. Wonkothesane New Reader

If the bottom hose is staying cool, I doubt it's a head gasket..

I'm not too familiar with suby-bleeding, but I'd check some forums for proper procedures.. For example, on my friends Xterra (Nissan), there is a bleeder screw at the top of the throttlebody that I would have NEVER known about if it wasn't in the bleeding procedures..

Try that first!
March 22, 2010 1:51 p.m. Travis_K Dork

Today it seems to be working. Im guessing that the problem was a bubble of air trapped next to the thermostat so the water couldnt heat it up enough to open. It seems to be a pretty common problem from seaching on google about it, the only soultion seems to be just to try harder to get the air out. Every car has a few parts that arent designed correctly to function as a car, I guess the subaru cooling system is one of those. I also have an Mk2 jetta, and on that car, filling the cooling system works exactly how you would thing, and it doesnt have any weird problems like that.
March 22, 2010 4:38 p.m. Nashco SuperDork

I've had the cooling system empty in our Subie many times and never had to deal with an air pocket causing problems. I HAVE had a stuck thermostat on our Impreza (randomly, not related to having the system empty), but I'd hardly say that's a Subaru problem. The thermostat can be replaced for a few bucks in about 15 minutes (draining it takes some time), while you've got it empty you can refill it with 50/50 mixture of antifreeze.

I can't even begin to wrap my head around the idea of you thinking that a Mk2 Jetta is better quality and easier to work on than a Legacy. Seriously, my brain hurts right now from trying to come up with ways that could possibly have allowed you to come to such a horribly misguided conclusion.

Bryce
March 22, 2010 4:40 p.m. car39 Reader

Air bubble in the upper hose. As common as an oil change
March 22, 2010 4:52 p.m. Travis_K Dork

The thermostat wasnt stuck, I put the old one back in and it didnt help. It appears to have just been an air bubble which it took a day to get out. lol

I dont think everything on an MK2 jetta is better than a subaru legacy (for example the vw shifter linkage is a horrible design), but I do think the cooling system in the jetta is designed correctly for easy service while the subaru isnt.

The fact that the outer cv joints often sieze to the hub on subarus is also not impressive, I just pulled the cvs out of a 360k mile neon, and they came loose with a light tap with a hammer, we had to replace the entire hub and spindle assembly on both side to replace the cvs on the subaru, and the salvage yard we bought them from said that a good number of the ones they get never come apart.

There are stupid things on most cars, I think I have just had to deal with two of them on the subaru the first time i worked on it. All the rest of the job was easy though.
March 22, 2010 6:56 p.m. Hocrest Reader
The way I fill up the system on my Soob's EJ and EG series engines id simple and eliminates the air bubble problem.
- Use the top rad hose to fill the engine with straight coolant.
- Re-attach the top hose to the rad and fill the radiator with water.
- Squeeze the top hose a few times to "burp" it.
March 22, 2010 7:55 p.m. The_Jed Reader

I drill an 1/8" to 3/16" "burp" hole in every thermostat I install.

If you dislike the car that much, send it my way. I have no problem whatsoever with Subaru's build quality and engineering.
March 24, 2010 3:56 p.m. Aspen New Reader

Lol at complaining of 300k mile Subaru! My Legacy went 65k miles before blowing the HG then spun bearings at 90k miles. The replacement block burned oil like an old Ford V8. My turbo subie has been through two sets of bearings and a HG in under 75K miles. Am I stupid for still owning one? Anyway, the subaru oem thermostat does have a burp hole. They are difficult to get all the air out. I usually have a funnel that fits the rad cap to fill with fluid and let it run until hot. Burp it a few times. Drive around a bit, let cool and burp again.
March 25, 2010 9:37 a.m. dean1484 Dork

The_Jed wrote:

I drill an 1/8" to 3/16" "burp" hole in every thermostat I install.

This is the answer. I have done this many times it makes things much better.