2006 OB coolant bubbling, overheating, combustion gasses not present

[Pauldoug]

Let me answer a few questions. The radiator was replaced as a result of a fender bender to the front left of the car, about two years ago. The body shop guy told me that they had finished all the work and they noticed some kind of minor damage on the radiator that made it unusable. I don't remember what he said. In fact they might've broken it when they were doing the work. So the original radiator was otherwise sound ( presumably not clogged, not leaking).

 

As for the "bubbling", sometimes I'll see that there are a few bubbles in the overflow ( like gently blowing into a straw that's immersed in water), and the coolant level in the overflow is normal. Perhaps this is when the condition is just starting. Other times, I'll open the overflow, and the coolant will be very high and at what appears to be a rolling boil. This often will continue for almost a minute after the engine is turned off. Note that the car is not always overheating at this point, ( actually, usually not) by which I mean the temperature gauge is at dead center.

 

I'm working to get the car in at an independent Subaru repair place I found in northern Jersey. It's run by true Subaru enthusiasts. So they should really know the car very well. They do list a leakdown test as one of the services they offer. I'm hoping they're not on vacation; I'm waiting for a call back.

 

Meantime, I'll be glad to answer any other questions or clarify anything I've said before. Thanks for all the advice so far.

[Pauldoug]

Ok: I took the car to a well-respected Subaru repair facility - AZP Installs in Kennilworth, NJ (azpinstalls.com). Took 50 min of highway driving to get there, so the car was warmed up. They tested for HC, and watched the coolant temp with a Snap-On diagnostic tool. Test drove the car.

 

Verdict: Not the head gasket, not a cracked head.

 

In a few days, I'll post what it was, thought in the meantime some of you would want to take another stab at what it was. Two hints: at least one of you guessed correctly. 2. Re-read my posts. A couple of things I mentioned turns out to explain what happened.

[WoodsWagon]

subaru water pump is unbelievably rare, it doesn't really happen. maybe on an old rusted beater that sat in pure water and salt not running for years and corrded the vanes away but on a 2006 high dollar car with low mileages that's highly unlikely.

 

they ocassionally leak, even that's rare. other than that a subaru water pump failure is so rare it's not even worth diagnosing unless you have some really weird issues....which these aren't weird.

 

the H6's routinely do the temp gauge-varies-by-throttle-input thing and bubbling in the overflow when not overheating - i've seen it multiple times, and i've never seen a failed water pump in 20+ years of Subarus.

I've seen it. If the pump seizes on an EJ, the timing belt will slip over the stopped pully. No squeeling, just a light hot rubber smell. The EZ's pumps are chain driven so I doubt it could seize and slip but maybe the sprocket could spin on the shaft. On both the vanes could erode. I've also seen an overheating EJ with the red plastic junkyard engine shipping plug in the lower radiator hose thermostat housing with the hose jammed over it. Both are circulation issues, both will boil bubbles and coolant into the overflow and overheat.

 

Pauldoug..... I don't see the point in finding out what the correct diagnosis was and then holding out so more people can guess. On this forum people are genuinely trying to help strangers fix their cars. It's not a game of who was right. What's more important is knowing what was right so that adds to the knowledge base and can help the next stranger in distress that shows up asking for help. I'm glad you got your car fixed.

Edited August 7, 2016 by WoodsWagon

[Pauldoug]

Grossgary:

 

I certainly didn't mean to make this into a game, but point well taken.

 

 

OK, here it is: there turned out to be a lot of air trapped in the system. First of all, the test for combustion gases, tested on my car that had been driven for 50 minutes (and cooled enough so the cap could be taken off) was negative. The tech then asked me about 20 minutes into their test if the coolant had been changed recently, and I answered that yes, I had done it within the last month or so. The operant word is "I". They were suspecting trapped air, because they noticed that with the heat on, the temperature coming out of the blower was going up and down. Later, he and a partner burped the system to an extent that I hadn't. With a large funnel on the radiator, filled with coolant mixture, one of them revved the accelerator repeatedly while the other squeezed the hoses and added to the funnel as needed. This went on for about twenty minutes. During this time the tech told me that quite a bit of air bubbled out.

 

After that was finished, he monitored the coolant temp with the Snap-On diagnostic tool, idling and revving, and took the car for a 10-minute test drive. The temp stayed at exactly at 205° the whole time. Mike at AZP told me even if it had moved up a couple of degrees, they would go back to suspecting a HG leak. It never did.

 

Total cost for this diagnostic, air purge and test drive: $115.

 

Mike told me that at AZP, when they do a coolant refill, they only do it using the vacuum method.

 

I then took a trip in the car -- 1 hour, then another hour home. No overheating, no coolant overflow tank overflow.

 

A key here is that that yes, I had burped the system after I replaced the thermostat and refilled, but I didn't do it long enough or correctly. Next time, I'll park the car uphill, and have someone else gun the engine periodically while I do the fill (having first warmed the engine enough to open the thermostat). And I'll keep at it as long as it takes.

 

BTW, I've noticed that in the past a few people on this forum have asked for a suggestion for an independent mechanic in northern NJ. I highly recommend these guys: azpinstalls.com.

 

Thanks again for everyone's comments.

[1 Lucky Texan]

wow - thanx for getting back to us.

 

kinda surprised the system couldn't purge itself when it cooled down - pulling coolant in from the overflow.

[Fairtax4me]

AZP certainly knows their stuff. A well respected shop for sure. Hopefully they got it taken care of, but be sure to keep an eye on the coolant level for the next few weeks and make sure it doesn't drop.

[DaveT]

+1 to keeping a close watch on the coolant & air level in the upper hose.

[1 Lucky Texan]

^^^ yeah what they said , and actually look in the radiator - don't just rely on the level on the overflow tank.

[mikaleda]

That's probably one of the most common overheating issues with Subaru's that I've seen on the forums aside from headgaskets. I have tried many different tricks to fill the cooling system on a Subaru. What I've found is it takes patience,there is no quick easy way to fill a Subaru's cooling system. I will generally let them sit for a night and recheck the fluid before sending them out as well.

 

Glad you found your problem and shared your experience with us.

[DaveT]

Looks like the newer ones are more of a pain to get the air out of than the ea82s.

[idosubaru]

We also would have suspected that - but you indicated the coolant change came ***in response too*** an overheating event, so presumably it was overheating before any coolant change/low on coolant. 

 

Hopefully that does it and you're done, but just because they worked on it and the symptoms went away at the moment, does not mean it is fixed.  The current description still has strong H6 headgasket marks on it. 

It would not be at all surprising to see another overheating event and confirm headgaskets in the next year or less - H6's can give arbitrary symptoms with huge gaps of time between them, even up to a year or so between symptoms.

 

As to failing water pumps - i've never seen a confirmed case on an online forum, ivansimports said he's seen 1 ever and it overheated within 3 minutes, a seized pump that frees itself most of the time, and only seizes after long drives, sounds like an unlikely starting point.