Oh crap, bubbles in the overflow tank.

[blitz]

'02 OBS 35,000 miles

 

I'm thinkin' I got an internal head gasket leak, ...but on a phase II motor tho?!! I thought the phase II's were prone to the external leak.

 

The irony is I think this has been going on for close to a year, but I just didn't piece it together until this morning. The thing's not overheating or showing any fluctuations in the temp gauge. It's actually been running great.

 

Anyone else heard of an internal leak on a phase II?

[1 Lucky Texan]

bad radiator cap.

[alias20035]

I had the bubble problem too and I also lost about 1 litre of coolant over the period of a month or so in my 2001 Outback. I was really worried about the head gasket, but no hydrocarbon or pressure test could find anything wrong with the head gaskets.

 

The seal on the radiator cap and the radiator fill was contaminated with yellow particles. I was due for the first coolant change at 48,000km, so I changed the coolant and cleaned the radiator cap, and thus far after 12,000 km the coolant level has not changed. I recently tested the coolant for hydrocarbons and the test was negative. The yellow particles have not returned (yet).

 

Phase II's do blow head gaskets, but a lot less frequently than Phase I's. According to the German magazine Autobild the Phase I has an 8 to 1 ratio for head gasket problems verses the Phase II. I would have guessed 4 to 1, but Canadian winters are much harder on engines than German winters which may equalize the ratio a bit.

 

FYI: The radiator cap pressurizes the cooling system to between 12 and 15 PSI (usually 13 PSI on a Subaru). If this pressure is not maintained, the boiling point of the coolant drops and you can get overheating, boil over, bubbles, and loss of coolant.

 

I had a total failure of my rad cap on my 93 Legacy, and as a result the engine burped out almost half of its coolant through the overflow.

 

The local dealer in Boulder Colorado wanted to pull the engine and change the head gaskets, but I insisted on a thermostat and rad cap only and I had no further problems once this was done.

 

Rad caps and thermostats are usually changed as a pair, but I have found that Subaru thermostats tend to last a very long time, much longer than the rad cap.

[theotherskip]

when do you get bubbles? is there an oil residue near the top of the tank? any more info?

[blitz]

Originally posted by theotherskip

when do you get bubbles? is there an oil residue near the top of the tank? any more info?

 

theotherskip,

 

Nope, no oil residue in the overflow tank or any exhaust smell for that matter. Likewise I find no evidence of coolant or moisture in the oil. I had the plugs out last month to have a look-see and saw no "washing" on any plug. They all had a perfect tan coat. The coolant level isn't dropping any.

 

Background on the problem: About a year ago as I was parking the vehicle after a spirited blast up the road, I heard a gurgling sound, like the water pump cavitating on air in the cooling system. Squeezing the top hose, I was able to force trapped air out of the overflow hose.

 

Subsequently, any spirited blast would produce the gurgle and then the squeeze-air. So out of curiosity, I opened up the overflow yesterday and saw bubbles.

 

The rad-cap is original, so I'll pitch in a new one Monday and see what happens. The thermostat was changed about five months ago to cooler zerosports unit (it's 13F cooler than stock).

[blitz]

1 Lucky Texan & alias20035:

 

Thanks for the insight. I'm gonna try a fresh cap tommorrow.

[theotherskip]

it doesn't seem like the signs of the head gasket failure of the phase 2 engine. make sure that it has been properly purged of air, and that there are no leaks elsewhere (heater core, etc). if the head gasket has blown, it will make bubbles in the expansion tank all by itself...

[1 Lucky Texan]

I need to 'tattle' on myself. All the talk of headgasket problems here and on other forums sorta had that issue in the forefront of my conciousness when the Dodge Avenger that is my daily driver (hopefully to be replaced early next year by probably an OBS) started 'gurgling' after any lengthy trip. No temp gauge abnormalities, no major coolant loss. Always just 2-3 seconds of gurgling after stopping. I thought - "Geez I do NOT want to fix headgaskets and then sell this thing in a few months" - but after really thinking about the problem I realized I had no other sysmptoms that should be assoc. with a bad HG. No oily reside nor driveability problems no sweet smelling exhaust no white exhaust vapot no choc. 'mousse' on the oil cap/dipstick no bubbles in the radiator itself. So i just stopped by and spent $8 on a rad cap from Autozone and 'Voila!' no more gurgling!

 

This was 2 weeks ago so your very detailed post led me to conclude (accurately we hope) that you have a bad rad cap. The less well/strongly they seal, the more towards 'normal' boiling point the coolant's vapor pressure moves. Probably, a little latent heat(in a head near an exhaust valve matbe?) after shutting the engine off causes a 'geyser-like effect' and after the 'phase change' removes heat from that location all goes back to normal again. Still, I suppose I could've been wrong (shudder!)

[Setright]

After replacing the coolant, it can take AGES for all the air to be expelled by boxer engines. Or did your problem occur out of the blue?

 

No wonder the VW Bug and Porsche used air cooling!!

[1 Lucky Texan]

Some newer inline 4s are tricky to bleed I hear. A mech. told me about a Toyota that has to have about a gallon put in the rad, some poured down the upper hose into the block, then a heater hose removed until coolant starts to run out.

 

My old Civic had a brake-looking type bleeder that you were supposed to loosen til coolant shot up. maybe Subaru needs something like that somewhere (where?).

[blitz]

Originally posted by Setright

After replacing the coolant, it can take AGES for all the air to be expelled by boxer engines. Or did your problem occur out of the blue?

 

Setright, yeah I 'spose you could say it occurred out of the blue. At some specific point, I heard air in the system for the first time after a hard drive, and I've been hearing it more frequently now that about a year has elapsed. Yesterday I actually looked for the first time to see bubbles flowing freely from the overflow tube while the engine is running. As was suggested, I'm hoping it's just boiling coolant due to a weak pressure cap. I'll find out tommorrow what's going on and post back.

[Setright]

Texan, my radiator has a bleed screw just above where the top coolant hose attaches. Open this and the rad cap...idle until fluid flows out, cabin heat full on. Close the bleeder, close the rad cap.

 

Then drive about a thousand miles and keep checking the system, THERE IS STILL AIR IN IT!

[99obw]

IMHO, it's not the number of miles driven that determines how long air stays in the system, it's the number of heat/cool cycles. To shorten the time the air stays in the system I recommend opening the bleeder and radiator cap after the system has fully cooled and topping it off once a day for a few days. Doing this I usually fully bleed the system in three heat/cool cycles.

[blitz]

OK, I got Pep Boys, Autozone, and all the others two miles from my house, but instead I elect to go 8 miles to the dealer and get a Fujaru part. Now I got a cap on my car that holds absolutely zero pressure. :brolleye: Should I just shoot myself or what?

[1 Lucky Texan]

I guess you inspected/wiped off the 'lip' in the neck that the cap seals on? The 'lower' one I mean. If there is a gap/erroded place in the lip, it wouldn't seal. Never thought of it before but could be an issue.

Perhaps someone here knows if there are many different rad caps in use on soobs - maybe they just stocked them incorrectly or something?

 

good luck.

[blitz]

Regarding the "no pressure" thing, here's what happened:

 

I put the new cap on at the dealer, drove home, opened the hood and noticed the expansion bottle right on the verge of frothing over with boiling coolant. I sqeezed the top hose and found no pressure. I mean absoutely zero pressure, the top hose was slack.

 

So I removed the cap, let it cool a bit, put the levels in both the radiator and the tank back to normal while fast-idling it up to temperature, replaced the cap, burped it out, and let it cool again.

 

Took it for a drive, pulling over every quarter mile or so to keep an eye on things as I built heat into the system. The frothing was gone and a small amount of pressure began to build (approx. 5 psi), but as I began to ratchet up the throttle application between stops, the bubbling described in my original post re-appeared.

 

In essence, I appear to be back at my starting point.

 

My Impreza manual calls for a 16 psi cap and that's what's installed, but I'm not feeling 16 psi (squeezing by hand) pressure building in the top hose (based on what I've felt on every other car I've owned). This defies explanation, as does the frothing episode.

 

What's next? Hydrocarbon sniff test I reckon?

[blitz]

Originally posted by 1 Lucky Texan

I guess you inspected/wiped off the 'lip' in the neck that the cap seals on? The 'lower' one I mean. If there is a gap/erroded place in the lip, it wouldn't not seal. Never thought of it before but could be an issue.

 

Perhaps someone here knows if there are many different rad caps in use on soobs - maybe they just stocked them incorrectly or something?

 

good luck.

 

Yeah I did actually wipe it out and it's spotless. No nicks in it or anything. Likewise the cap has no flaws in the rubber seals. I lifted up the little back-flow check valve thingy to check for possible detritus and none found.

 

I think it's the correct cap. All the visual dimensions are identical to the original part as is the labeled pressure. The parts guy used my VIN# to establish the part I recieved.

 

I'm wondering if the bubbling is just a normal phenomemon on this vehicle. There's a good chance that I'm just freaking out over nothing.

[blitz]

Today's my day off, so I spent some time doing searches on Subaru cooling system phenomenon. Found this quote to be interesting: (it's from an aircraft conversion article)

 

 

"The 2.5 liter Subaru is sensitive to air bubbles in the coolant. It only takes about 1/2 cup of air in the engine block to cause heat transfer problems. This engine is particularly sensitive. Trapped air is easily 10 times more significant than any other cooling parameter. It's pretty conclusive that trapped air causes local boiling in the block. This affects the entire cooling sys and rapidly degrades heat transfer."

 

"During initial ground testing I did multiple high speed taxi runs. I would see the coolant temp elevate after each run. It would get to the boiling point after 4 runs down the 5000 ft runway. If I continued, the cooling sys would boil over. I deliberately did this many times. If I aborted any further runs, then after shutting the engine down I could hear it gurgling. This was the fluid boiling internally. "

 

"All of these problems were caused by a small quantity of air trapped in the block at the highest point. Eventually, I added a small diameter tube to this block high point. This allows all the air to exit the block and move to the small reservoir under the radiator cap. Unfortunately, all of my deliberate overheating caused the heads to warp. This allowed compression gasses to flow into the cooling sys during high power settings. My computer detected this problem. 3 seconds after applying full throttle, the coolant pressure would rise to 24 psi. It would then slowly drop 5 seconds later. "

 

"So trapped air causes head warp, which causes air to enter the cooling system. It was pretty amusing that at the same time I discovered this entrained air sensitivity in the 2.5 engine, so too did the auto dealers. Head warp caused by customers changing their coolant is now the number one warranty item with this engine. All caused by an engine block that was not plumbed to dynamically remove air from the high point. Subaru has since changed their cooling system design. "

 

"It's essential that the 2.5 liter coolant crossover tube atop the engine be drilled and tapped. This allows user to add a small tube from there to the coolant reservoir. Any air inside the engine block then automatically purges. Proof of effective purging is that I can now drain all the coolant from the entire sys, then refill. Every drop can be refilled without hesitation. Before adding this air purge, I would end up with a few cups of fluid that I could not get back in to the system. Also, I now can't get the engine to gurgle after a hot shut down. "

 

 

If I'm reading this correctly, the author's claiming that the phase I head-gasket problem is directly attributable to a small quantity of trapped air.

[99obw]

I think blaming trapped air for all head gasket failures is an oversimplification. Many folks that have not changed their own coolant have had head gasket failures. Have you had your coolant tested for exhaust gasses yet?

[1 Lucky Texan]

I would say you still have trapped air and it very possibly could've been the whole issue. Did you or the dealer recently do a coolant flush or otherwise have a reason to open the coolant system?

 

I have read where some folks will drive the front wheels up on ramps to help 'burp' the system. Or maybe one 'side' to get air to crossover?Or somehow pulling a vacuum may help (though I suspect hoses would collapse before a hard vacuum would form). maybe it would help to also ensure the climate control is set on 'heat' to get flow through the heater core?

 

Sounds like someone should make a crossover pipe with a bleeder in it.

 

you're to be commended for sticking to this and I appreciate you posting back. Sorry it wasn't the rad cap.

[1 Lucky Texan]

Just finished re-reading the thread. At one point you did say you were watching bubbles coming out the O/F tank with the engine running. If it does do this perhaps it is time for a sniff test and/or a cylinder compression test.

 

Um, after the engine is shut off, does coolant get sucked back in from the O/F? I would expect any overhated air in the system would contract quite a bit and pull in some coolant. These are the cycles I would expect are 'normal' for this engine that setright and others refer too. Perhaps there is some restriction or debri sin the overflow tube itself? Or some type of weird oneway leak allowing air to be pulled in instead of coolant? After you changed the thermostat, was everything OK? Did you notice a notably lower postion on the temp needle? Have you ever seen one of the rad hoses collapsed?

[blitz]

Originally posted by 99obw

I think blaming trapped air for all head gasket failures is an oversimplification.

 

 

Mmm... well, stated in that manner it actually is. I believe that between the lines he's saying that a complicated series of intermediate steps ensue. Something to the effect that the trapped air is stationary at the highest point of the cooling jackets which surround each of the cylinder bores, so that the topmost side of the bores are not being cooled. This then causes physical distortion, which in turn causes uneven torque across the head gasket, which then begins to lose it's seal under high engine load. Or something like that.

 

 

Many folks that have not changed their own coolant have had head gasket failures.

 

 

Good point. I can't answer that one.

 

 

Have you had your coolant tested for exhaust gasses yet?

 

 

No, but I 'spose that'll probably be my next move. I appreciate your help.

[theotherskip]

again, i agree with 99obw. i didn't have any trouble purging air from the system when i was refilling my system. parked it on a slight incline (front higher than rear), opened the bleeder screw, and slowly filled the system. reinstalled the bleeder, put on the cap, added to the min line of the expansiong tank. then drove for ~1 hour. let it cool. it had sucked some back through the expansion tank. topped off the rest of the radiator, and that was it. i checked it a few times over the next few days, and it didn't budge.

 

the article that you found seems to be someone who put a 2.5L in a plane. this can open up a whole host of problems, such as it not being at its intended angle, different radiator/hose pumbing, etc. it also was most likely a salvaged/used engine, and there is no telling if he bought it with a blown head gasket, then overheated it a bunch of times, then warped the heads. when my head gasket blew, it was not detectable by doing a compression test. the article guy seems to have really overheated his engine, which is definately going to cause things to warp...

[cookie]

since I have seen them blow on cast iron to cast iron. Rare and so would this be. This would be the first phase 2 I have heard of like this.

This stuff is not new guys. They were blowing head gaskets on flathead Fords. Just nowhere near as much as on new alloy engines.

I look forward to the results of a gas test and hope I am wrong.

[blitz]

Originally posted by 1 Lucky Texan

Just finished re-reading the thread. At one point you did say you were watching bubbles coming out the O/F tank with the engine running. If it does do this perhaps it is time for a sniff test and/or a cylinder compression test.

 

 

I'm thinking that's the direction to go, but the bubbles seem to be clean (as in water vapor, rather than combustion byproducts). After reading the trapped-air quote I got fresh inspiration that maybe seeking and purging trapped air out of the block is the answer. I'm going to try the ramps thing, thanks for that.

 

 

Um, after the engine is shut off, does coolant get sucked back in from the O/F? I would expect any overhated air in the system would contract quite a bit and pull in some coolant.

 

 

Yeah, as it cools, it pulls coolant back into the system like it's supposed to, so I figure that after burping all the air out as the temp rises to normal, then allowing it to suck coolant back in as it cools would eventually purge the system of air, but this dam* thing handily generates more gas bubbles everytime I drive it.

 

 

These are the cycles I would expect are 'normal' for this engine that setright and others refer too. Perhaps there is some restriction or debri sin the overflow tube itself? Or some type of weird oneway leak allowing air to be pulled in instead of coolant? After you changed the thermostat, was everything OK? Did you notice a notably lower postion on the temp needle?

 

 

The tube is free, I've run water through it (you see, I've been doing more that pestering the board). :cool: I was checking some specs in my manual this afternoon and the full-open temp for the stock stat is 196F, and this replacement stat I have is 183F, so it's not really a "cold" stat. So to answer your question, naw, I can't see any change in the temp gauge. It did lower my octane requirement by about a point and give me about 2 ft./lbs. of torque in the critical 3-4k RPM cruising range. It's a real Fuji stat too, it looks exactly like the stock unit. Other than the heat-shield rattles, dash-rattles, cold piston slap, lousy fuel mileage, brake squeal, and steering "bonngle" noise when entering a driveway, I really like this car.

 

 

Have you ever seen one of the rad hoses collapsed?

 

 

No, this is the confounding thing about this bubbling problem. The engine and cooling system both seem to be in perfect shape. I think I'll take a couple days off from the problem. Thanks for all your help. -Danny