Slow trickle of bubbles in EA82 coolant reservoir

[idosubaru]

1988 XT non-turbo.

 

When the engine is running there's a very slow trickle of bubbles coming through the overflow coolant reservoir. Like a bubble a second, it's not boiling.

 

I hate to hear suggestions on what this is.

But....these bubbles point to some head problem right - crack or gaskets?

 

How can I track this down besides waiting for it to get worse!?

Drop the exhaust manifold and see if coolant comes out of the exhaust port of the heads - does that work?

[McDave]

What you need is a Combustion Leak Detector. Pour the test fluid in the top of the test cylinder, put the bottom of the cylinder into the radiator neck (or remote tank of it doesn't have a neck), making sure the coolant level is low enough so you don't suck up any coolant, then stick the hose in a vacuum port of the running engine.

 

The vacuum will pull air out of the radiator and if there is exhaust gas in the cooling system the test fluid will turn from green to yellow.

 

We've been using one for years at the shop, though it has a vacuum squeeze bulb instead of a vacuum hose. I guess every Subaru owner should have one.

 

Drop the exhaust manifold and see if coolant comes out of the exhaust port of the heads - does that work?

It does if the head is cracked enough leading into the exhaust port. A head gasket blown into the cooling system wouldn't show in the exhaust port.

[idosubaru]

if this engine previously had a blown headgasket - could that give it a false positive? maybe i'd have to drain all the coolant and refill? even still i probably wouldn't get all the old coolant and contaminated gases out? not sure how sensitive they are in terms of PPM?

[McDave]

if this engine previously had a blown headgasket - could that give it a false positive? maybe i'd have to drain all the coolant and refill? even still i probably wouldn't get all the old coolant and contaminated gases out? not sure how sensitive they are in terms of PPM?

That's a good question. I don't think I've ever tested one after doing the job. I would think a good flush would be enough to get rid of any trapped gasses. They are sensitive, but you would think all the gas would have had a chance to dissipate while the engine is torn down.

[McDave]

That's a good question. I don't think I've ever tested one after doing the job.

I take that back. My boss/sidekick reminded me we did recheck one when it was taking a long time for the exhaust to quit smoking. It retested good (though maybe a little bit of yellowing of the test fluid), so we waited for the exhaust to clear, and it did.

 

It's a tool we don't use that often, but for the $40 we paid for it back then, it's paid for itself many times over. We even get refills of the fluid from the local Snap-on driver.

[Bucky92]

Gary..did you notice this problem in the over flow right? So the radiator cap was on I am guessing? Have you tried replacing that first..I know someone who had the exact same concern..swapping the cap solved the problem.

 

Having just done and been dealing with a minor head gasket failure I have learned a good bit. I checked mine by removing the radiator cap and running the car..letting it get up to temp and letting the T stat open up.. ( Note there wasn't any bubbling until the T stat opened)

 

Then I had this:

 

 

Is this the motor you were questioning the cracks in on a previous thread BTW?

[Frank B]

Does this happen after it gets up to temp also, when the t-stat opens and engine temps stabilize? Or just when you first start it? You may have some air space in the rad, even with an overflow, to allow for expansion of the coolant. That air space may be pushed out into the reservoir and that's what your seeing.

But I bet it's a cracked head. Does it overheat at all? If the exhaust is getting into the coolant, it will super heat the coolant to the point where the rad cannot compensate.

[Bucky92]

I wouldnt jump to conclusions that its the worst possible thing..mine bubbled alot worse and it was a minor gasket leak..Gary..you should know ..since you deal with alot of XT6s its usually something simple first;)

[idosubaru]

well i tried the ghetto "press hard on the radiator cap" and it didn't make the bubbles go away. i can snag one off my XT6 and put it on there, looks to be the same cap.

 

no overheat yet but i haven't run it much either.

 

and yes it is the one with the head cracks - i went with GD's recommendation that the cracks on a non-turbo were not likely to be into the coolant jacket.

 

i'm going to drop the exhaust and check there too.

 

i have two crack-less heads already in the mail just in case.

[daeron]

buy a new cap and be certain.. also make sure that the radiator filler neck is nice and smooth in the sealing area for the cap. It doesn't take much to damage the rubber seal, and you cannot always know when it is your problem without using a new one.

[idosubaru]

tried another radiator cap and flushed the coolant. let it run for 15 minutes and after it got up to temps there was a slow and steady trickle of bubbles...like two bubbles/per second in the overflow reservoir.

 

i tried looking up the exhaust ports and i didn't see anything....hmm...maybe i should have turned the engine over by hand a few times? i'll try that later tonight or tomorrow.

 

since i flushed the system i'm going to pick up an exhaust gas tester tomorrow and give that a try.

 

the new heads are in the mail and i'm dropping them off at the machine shop tomorrow no matter what so if i have to i'll do those again.

[idosubaru]

Update:

 

new radiator cap, flushed the cooling system a lot, and i drove about 40-50 miles today. never overheated or ran hot. when i got home though there was a slow and steady stream of tiny bubbles in the overflow tank.

 

it shouldn't do this right?

there shouldn't be any bubbles i wouldn't think.

so it has to be either a cracked head or head gasket?

 

if i hook my compressor up to each spark plug hole will that pressure escape into the coolant and through the to the overflow tank too so i can verify what's going on or which head is bad?

[McDave]

I guess you haven't found a leak detector yet. Check with the tool trucks - Snap-on, Mac, Matco, ect.

 

Or if you know someone with a tail pipe sniffer, they will be able to check for hydrocarbons in the radiator as long as the coolant level is an inch or two below the fill neck.

[idosubaru]

I guess you haven't found a leak detector yet.

i don't even know what that is or if i'd know how to use it properly? seems like i'd see it if it were a leak, i know where most of the hoses/connections are...but i should double check all of those.

[McDave]

i don't even know what that is or if i'd know how to use it properly? seems like i'd see it if it were a leak, i know where most of the hoses/connections are...but i should double check all of those.

 

Huh? Go back and reread post #2 and click on the Combustion Leak Detector link.