Jump to content
Ultimate Subaru Message Board
Sign in to follow this  
TeamPanic

Bubbles in coolant reserve tank

Recommended Posts

Ok, here's the deal. I have a 99 Outback with 67k miles on it. The car has never overheated. After I drove it for about 15 minutes and reached home I decided to look under the hood. I had the car running and I opened the reserve tank and noticed some small bubbles, not too many, just a few every couple of seconds or so. I was/still am pissed. I've been reading nothing but blown HG stories on here for the last month, so it really made me feel sick to my stomach. Is it normal at all to have some bubbles in the reserve after driving. Also, the coolant looks green and there is no sign of sludge or oil in the reserve tank. Someone tell me some good news please! Thanks

Share this post


Link to post
Share on other sites

The best thing to do now is don't PANIC! Take out the reservoir and empty it into a pan and manually observe the coolant and see if there is sign of oil. Often times, there may be bubbles when the radiator just finishes puking some from its stomach to the reservoir. Hope it's not what we are all afraid of!

Share this post


Link to post
Share on other sites

bubbles are only one sign... have you had work done on the cooling system recently (a flush/fill)? you should refill and burp the system (search the board for instructions), then keep an eye on it. since you haven't had any overheating, it may not be the hg... but do keep an eye on it...

Share this post


Link to post
Share on other sites

Bubbles can be from air being pushed out the rad cap as the engine is heating up. More apt to be the case IF the rad cap is not sealling on the rubber under the center metal disk on bottom of the cap. (One way valve that allows the coolant to be recovered into the rad as the engine is cooling down. Try a different cap or clean/check under that valve. If it continues after the engine has been warmed up for some time, could be a head gasket or such allowing compression/blowby to be making its way into the cooling system. Not sure what else could cause ecsessive air in the cooling system. OH, if you are running water only, have a bad cap that does not pressurize the cooling system, the water may be boiling. Water/coolant under pressure boils at consideraly higher temps than unpressurized liquids. Water boild at lower temps than antifreeze, etc.

 

 

Good luck.

Share this post


Link to post
Share on other sites

Thanks for all of the help, well I went back out and checked it the reserve tank and it appears to have a sligh oil film on the top, f'n a. I'm fecked aren't I? It's only got 67k miles, this is truely dissapointing. Anyone want to buy a 99 Outback? :-\ Well, back to the drawing board. I'm scared to take it in, hell to even drive it.

Share this post


Link to post
Share on other sites
Thanks for all of the help, well I went back out and checked it the reserve tank and it appears to have a sligh oil film on the top, f'n a. I'm fecked aren't I? It's only got 67k miles, this is truely dissapointing. Anyone want to buy a 99 Outback? :-\ Well, back to the drawing board. I'm scared to take it in, hell to even drive it.

Very sorry to hear that. Hope for the best.

Share this post


Link to post
Share on other sites

Hold your horses! What is a slight oily film? The glycol that makes up most of the antifreeze is slimely stuff, and after a few thousand miles in a normal engine, some of it tends to collect, along with corrosion particles and form a thin film on top the coolant.

 

Engine oil in the coolant will form small globules first, and form a thicker layer as it builds up.

 

A few bubbles coming through is normal. Especially if the coolant is gettting old.

 

I say: Drain it fully, flush it with pure water, and refill with a good 50/50 anti-freeze, and then keep an eye on the levels.

Share this post


Link to post
Share on other sites

Don't panic yet!

 

I also have a '99 Outback. Same symptoms occured last summer - a bubble every few seconds. New radiator cap, and the bubbles vanished. I still keep an eye on it, but have had no further signs of the dreaded head gasket failure.

 

The radiator cap's job is to keep the cooling system under pressure, I think the spec is 13PSI. The boiling temperature of a liquid is directly related to pressure. If the pressure is too low, the coolant will boil. Boiling can occur at hot spots within the engine, and cause local overheating, which may lead to head gasket leaks.

 

Of course, the reverse is also true - head gasket leaks can cause overheating. Chicken and egg problem - did a failed HG cause overheating, or did the overheating cause a failed HG?

 

Pressure also increases with temperature - the other part of the rad cap's job is to let some coolant into the overflow tank as the temperature rises, thus keeping the pressure within spec. When the car cools down, coolant is sucked back in from the overflow.

Share this post


Link to post
Share on other sites

I would take the car into the shop and have a block check done. This is a simple and inexpensive test to see if there are hydrocarbons in the coolant. There will be no guessing with this test. I had to have my '88 wagon resealed at around 60k miles and then again about 1000 miles later. I had a shop that trained student techs do the first job. Saved a lot of money over a regular shop but they didn't use Subaru headgaskets so I had to do it again, and really paid a lot then. The second go around was done by independent factory trained techs and that lasted. The moral of the story... don't trust repair of your Soob to anyone except a trained Soob tech and one that uses genuine factory gaskets at least.

Share this post


Link to post
Share on other sites

setright and ron, thanks for those posts that made me feel a lot better about the situation. I'm going to flush the coolant ASAP and hopefully it'll clean the system out. About the radiator cap, i'll look into that also, where can I get a replacement? I've got bad luck, so I always tend to think of worst case scenario right off the bat. Thanks guys!

Share this post


Link to post
Share on other sites

TP, if it makes you feel any better, I'm driving around with the same symptoms right now. I have bubbles in my overflow tank too, and I just got a new radiator! But the temp in holding steady. What I have found is that some of the "tests" for HG failure have pointed to yes, some have pointed to no. You just don't know, I'm waiting until another overheat before I think about getting it work on. Change the coolant, try the radiator cap(cheap enough to try it),keep an eye on the gauge, and keep driving!

 

Follow up question(sorry to piggyback on your thread TP), can radiator caps be bad from the start? Is there an OEM Subaru cap, and would it make a difference against a generic? I just got a new radiator, and wanted to ask.

Share this post


Link to post
Share on other sites

13psi is the old cap pressure. To me thats 0.9 Bar, new ones are 1.1 Bar, which is close to 16psi. STi rad caps are 1.3 Bar, but that might be taking chances with the standard coolant hoses...

 

TeamPanic, I know how you feel. Whenever I hear just the slightest odd sound from my car I immediately go into panic and assume the absolute worst. It's very stressful, wish I could convince myself to stop!

 

For the record, my Impreza was bubbling in the coolant expansion tank until I recently drained/flushed/refilled the system. Only replaced the upper and lower hoses, same old rad cap.

Search for "coolant replacement" if you want to read my version of how to do it right :-)

Share this post


Link to post
Share on other sites

The dealer will have a rad cap, of course. I just bought one at my local auto parts store. I don't even remember the price - they're cheap.

 

The new cap felt tighter than the old one. Not a scientific test, but there was a difference.

 

-Ron

Share this post


Link to post
Share on other sites

I have a 99 GT with the 2.5 DOHC engine, had same problem which turned out to be exhaust gas blowing by the head gasket into the cooling ports in the engine. Not pretty kept filling the expansion tank by pressurizing the cooling system and not allowing the collant to cycle thru the radiator. Leads to major overheating and a $1220 repair. Keep an eye on it and ask about Subaru's recall on some of the 2.5 engines. They were extending warranties to 100K and using some additive to the cooling system.

 

 

Hope for your sake it's just a rediator cap. The head gaskets are a BIG problem and perhaps covered elsewhere on this site.

 

 

Ok, here's the deal. I have a 99 Outback with 67k miles on it. The car has never overheated. After I drove it for about 15 minutes and reached home I decided to look under the hood. I had the car running and I opened the reserve tank and noticed some small bubbles, not too many, just a few every couple of seconds or so. I was/still am pissed. I've been reading nothing but blown HG stories on here for the last month, so it really made me feel sick to my stomach. Is it normal at all to have some bubbles in the reserve after driving. Also, the coolant looks green and there is no sign of sludge or oil in the reserve tank. Someone tell me some good news please! Thanks

Share this post


Link to post
Share on other sites

I just noticed the same thing happening in my '97 OBW, but there's no sign of oil, the coolant is old (will be flushed this week), and the car otherwise runs perfectly. Just took it through the mountains, with the AC on 90% of the trip, and got around 30 MPG. As far as I'm concerned, it's not a head gasket issue (at this stage, anyway).

Share this post


Link to post
Share on other sites

The headgaskets don't have to blow between the water and oil passages, oftentime they blow between the cyl ring and the water passage, so you wouldnt get oil in the coolant or vice versa.

Share this post


Link to post
Share on other sites

When my head gaskets went on my 97 OB, I had an oily sludge / residue in the coolant expansion tank. I assumed it was engine oil, but in hindsight, I think it was merely a byproduct of exhaust gases pushing thru the coolant. I never saw any overheating on the gauge. The oil tested fine. The anti-freeze was not contaminated (except for the sludge). As best as I know, my leak was from combustion chamber into the coolant passages.

 

I caught it early. As I said, no overheating. The expansion tank never overflowed, but it did fill up. And I had the telltale bubbles.

 

Commuter

Share this post


Link to post
Share on other sites

unfortunately your car was overheating, if it weren't the level in the coolant wouldn't had risen. THe gauge just didnt show the change in temperature.

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
Sign in to follow this  

×