Radiator coolant & blown HGs

Running *Without* a thermostat is not a good idea. Not only does it screw up the warmup time, it can actually cause an engine to run HOTTER. Before you think I am nuts read on........ The restriction the thermostat puts in the system causes the coolant to stay in the radiator longer, causing to to exchange heat better. If the water flows too fast it's been proven that it DOES NOT cool properly. The warm-up cycle gets trashed by the system not running "Open Loop" long enough due to the sensor picking up heat before it should. Engines start running lean before they should, they stumble. NO thermostat is better than a stuck thermostat...that's true.... but a good thermostat is always better than NO thermostat..

Many thanks for the reply. When I put a brand new Subaru original equipment thermostat, the engine runs hot and coolant over flows. I have heard that one should drill a hole somewhere on the Subaru thermostat. Anyone else hear of that?

Once again, BB for your reply.

R.

You shouldn't have to drill that hole in there, it should have it already. If it doesn't look for another brand (Stant #14147)The small hole allows some coolant to circulate thru the system.Stant calls it a "V-Notch" Stant is online at

(It's a USA Company) If it overheats and overflows when you put it in, there's trouble in the system for sure. Listen to the heater core in the dash for gurgling, watch the overflow tank for steam/bubbles. Feel the upper hose for stiffness. While it WILL be stiff after warm-up, it shouldn't be when cold or warming up. While Subaru is not the only company to have head gasket problems, they are VERY prone to head-gasket failure. All it takes is to run it low on coolant, overheat it or fail to remove ALL the air from the system when you refill the system.People will fight on here about it, but the fact is that the 2.5L engines ARE fragile in the head area.Some swear they NEVER had any problems, others will tell you they have lost 1 or both gaskets on their engine.Some people experience failure even when they don't abuse the engine and do the regular maintenance.

It's quite possible what you are experienceing is NOT blown HGs but trapped air in the cooling system. Have read how to 'burp' the subaru cooling system?

just asking

Carl

Dear Carl:

How do I burp the system?

Thanks.

Hi,

I'm not Carl, but if you don't mind a long drawn out description, I'll toss my 2 cents in here... (and when I say LONG, it's LONNNNGGGG! Sorry!)

First, double check your OEM t-stat. Is there a small hole drilled somewhere in the flat metal section of the housing, probably with a little jiggly thingie in it? It's even called a jiggle valve, and it's purpose is primarily to allow a tiny bit of flow thru the t-stat when things are cold. Theoretically, it should let air bubbles move thru the system. I'd be careful about standing on that theory, though!

Anyway, IF your t-stat doesn't have this jiggle valve, ask your Subie parts guy if you've got the right one. Maybe they've changed things, but the older ones all had it. I've got an OEM and a Stant sitting here as I type this: they've both got the valve, but I'd suggest using the OEM because the opening is considerably larger diameter than the Stant. Regardless of the brand you choose, most people I've talked to, and most of the books I've read, say to install the t-stat so the jiggle valve is pointed toward the outlet hose on a horizontally mounted housing, or UP in a vertical housing.

Now, on headgasket fragility and air bubbles and all that...

You're probably gonna get zillions of ideas and suggestions, all of which involve some truth, none of which tells it all! Subarus may or may not have more than their share of troubles. I've got two Toyotas in addition to my Subie, and BOTH of them have engines that are notorious for blown HGs--one's the supposedly "bulletproof" 22R 4 cylinder, the other the 3.0 liter V-6. I'm not sure what valid correlations can be drawn, but both are also genuine PITAs to bleed the air out of, and some sources blame the V-6 HG failures directly on air pockets w/ resulting hot spots (same indictment that's leveled at certain Subies.)

What I've learned from the Toys has helped w/ my Subie. It seems a horribly time consuming process for those of us short on patience, but maybe it will help you. Plan on taking the better part of a day, and probably making a mess, but you should end up w/ decent results if you're careful. (And remember, too, mine is only ONE of several methods people have found to work well. So don't take it for gospel!)

First, when putting in new coolant, mix your own using 50-50 antifreeze and DISTILLED water. There's a growing body of information that links both headgasket and premature hose failures to corrosion and other damage from electrochemical activity within the cooling system. The distilled water arguably MAY help reduce this in addition to the known benefit of NOT adding any of the minerals in one's tap water. You can buy pre-mixed 50-50 coolant, but I would rather know mine's REALLY mixed w/ distilled water.

Then put your heater on full "hot." Many Subies have a constant flow heater, unlike systems w/ shutoff valves in the coolant lines, but it's still best to do this, "just in case."

Now, fill your system SLOWLY until it's full to the top of the filler neck. You can do this on level ground, or with the nose of the car pointed slightly uphill. Point being you want the filler neck at the highest point in the system. Let things sit a few minutes to see if the level drops BEFORE starting the car.

Now take a turkey baster or other siphoning device, and remove some of the coolant until the level is just over the top of any tubes, whether vertical or horizontal. Once this is done, you can start the car, leaving the radiator cap OFF. Some models have an air bleed somewhere in the system--if yours does and you know where it is, go ahead and open it. Just let it idle for now until the t-stat opens. Check the temp gauge frequently and watch the level of coolant in the radiator. You'll see the level of the coolant in the radiator start to rise, maybe even enough to spill even though you removed some, just before the t-stat opens, then it should drop dramatically. The gauge MAY go a little higher than normal before the t-stat opens on this initial part of the drill. You may see movement in the coolant. Don't panic if you don't, though. Be sure to hose off any spillage so your neighborhood pets don't have a chance to slurp some up. It can be fatal to cats and dogs.

Now, if the coolant level dropped below the top of the tubes, add a little until they've just covered again. Keep the cap off, check that the top hose is hot, indicating good flow thru the t-stat, and check the heater hoses. Both sides should be hot and you should be getting good heat by now. If NOT, run the engine speed up a little, to 1500-2000 rpm and hold it there for a minute or so to get coolant flowing thru the heater and bleed air from the heater core.

Check the level in the radiator again, topping off above the tubes if necessary. At this point you should have good heater response, the temp gauge should be in the normal zone, and you shouldn't have too much activity in the radiator. Shut the engine off and go get something to drink, eat or whatever while you wait for the engine to cool. Give it an hour or more, depending on how hot it is outside.

The coolant should contract some as it cools, and you may have to add some to cover the tubes before starting the engine again. Keep the radiator cap off. Start the engine, let it idle until the t-stat opens again, check temp gauge, heater output and coolant level in the radiator. All good? Ok, now you want to sit in the car and run the engine up to around 2000 rpm and hold it there for at least a full minute, then let it drop back to normal idle. Repeat a time or two. Don't be surprised if you get some coolant splashing out of the radiator (or bleed valve, if applicable.) It's more likely to splash if there are bubbles in the system that are moving thru and blowing off in the top of the radiator. Watch the temp gauge. It may rise a bit, then drop, possibly more than once. If so, that's an indication there is some air that's moving thru. After a couple of cycles, check the level in the radiator. If you're getting lots of air out, it should drop a bit. Refill to cover the tubes, then shut off the engine.

Let it cool AGAIN. Once it's cool, check the coolant level and repeat the drill above AGAIN. By now, you shouldn't be experiencing much in the way of bubbling over or jumping temp gauges and all. Shut the engine off and let it cool completely with the rad cap still off.

When it's completely cooled off (radiator's not hot to the touch) you want to make sure the radiator's filled enough to just cover the tubes again, but NOT filled to the top of the tank and filler neck. Siphon some off if required. Install the radiator cap. Make sure the air bleed valve's closed IF you have one and it's been opened. Then fill the overflow tank an inch or so above the "full" line and cap it.

Now it's time for a drive. Take the car for a spin of a few miles, with some stop/start kinds of stuff, then a bit longer run. Keep the heater on full. Make sure everything's ok: temp gauge not going nuts, heater is putting out lots of heat. Then go home and let the car cool completely.

When really cool, check the overflow tank. Some of the coolant should have returned to the engine. Take off the radiator cap, and the radiator should be full. Take your turkey baster and remove coolant, putting it in the overflow tank. Leave the tubes just covered as you did before, and install the cap. Let the car sit until you need it.

First day you drive the car after this, check the coolant tank and you'll see coolant's returned to the radiator. When it's cool enough, remove the cap and siphon coolant into the overflow again. Watch everything carefully the first few days you drive the car and top up the overflow tank as necessary.

After you've done this a time or two, things should be pretty well "burped." It's a long process, and hardly exciting, but has served me well. And, just for giggles, it's always a good idea to measure the coolant that comes out of the engine when you drain it to compare with what goes back in to let you know if you're in the ballpark as for being "full." For example, when I first drained my V-6 Toy that had last been filled by the dealer, I ended up putting an entire quart MORE in the system than I'd taken out. Tell me there wasn't lots of air in that one somewhere! On the 4 cyl, it usually first appears "full" when I'm still a quart short of what I've taken out--tells me there's more work to do!

Sorry to bore you with all this, but maybe it will help you avoid a blown HG or other trouble...

Good luck!

Rick

Rick's procedure is very good. There are some write-ups a little less troublesome, and at least one I know of that recommends a hose removal. Try Rick's as described. If, after following his precedure you have coolant blow out of the overflow, 'scum' develop in the o'flow tank or see/hear bubbles in the o'flow tank - quite likely you DO have blown HGs.

Carl

Thanks, Rick, Carl , Edward and Bob!!

Rich

I would be very reluctant to recommend a nonOEM tstat. I tried that once even using a high price replacement and soon found out not all tstat are created equal. The replacement a Beck Arnely I believe, had an opening for fluid flow that was about 50% of factory part. Only tried the nonOEM part because of convenience, not price.

Mickey