Making Head gaskets Last on my Subaru

Subaru head gaskets are about as hot of a topic as national health care lately.  If you own a Subaru you know what I mean.

Since the 2.5 liter Subaru engine was put into production there have been thousands of head gaskets replaced across the country. We’ve done a good portion of those ourselves. In another post I’ll go into further detail about the details of Subaru head gaskets but for today I would like to offer some suggestions on how to help prolong the ones you have.

Subaru head gaskets can fail for numerous reasons. Failure of sealant, improper torque, surface imperfections in the cylinder head or engine block and of course heat or excess heat.

Click here to view our quality head gaskets

I’m going to focus on excess heat. Within the engine block the coolant is circulating to keep the engine cool due to internal combustion occurring. The coolant remains in contact with the metal and is able to absorb heat, travel to the radiator and release the heat to the atmosphere.

Two important things must occur to for the coolant to do it’s job. It must have adequate flow to move the heat away from the internal areas of the engine and it must remain in contact with the areas it’s trying to cool.

There are 3 very important items that may individually have a negative impact on the coolant’s ability to do it’s job. If all 3 components are bad or inferior,  problems could develop even sooner.

Subaru Radiator Caps OLD vs NEW

Subaru Radiator Cap

Subaru Radiator Cap

Click here to view our cooling system products

Radiator cap:

Keeps coolant in a sealed system, allows overflow to exit and return as coolant expands and contracts,  but most importantly it raises the boiling point of the coolant in the system by keeping the cooling system pressurized.  Most radiator caps for stock vehicles keep the system pressurized between 13-15psi. This can raise the boiling point depending on the mix of coolant/water an additional 35-40 degrees.  A 50/50 mix of anti-freeze and water has a boiling point around 265 degrees. Add to that a radiator cap that holds 13psi and now you have coolant that won’t boil until 300 degrees .

There are areas throughout the engine where the coolant circulates that become very hot. So hot that it can boil coolant. Since we must have the coolant in contact with the metal to perform it’s heat transfer duties we now have a problem. Scenario: Radiator cap is weak (which we run into all the time on Subarus). A weak radiator cap not holding pressure may not let all of the coolant get hot enough to boil but there are areas within the engine that are now boiling. Boiling coolant has air bubbles that now keep the coolant from contacting the cylinder walls and other extremely hot areas within the engine. This heat is more than the engine and gasket were designed to withstand on a regular basis and thus a situation that will accelerate the failure of the gasket.

Flow of the coolant is important also. To keep from boiling the hot coolant must be quickly moved away from the hot cylinder walls up to the radiator so it can release it’s heat. Below is a picture of a Subaru water pump and also a quality Japanese aftermarket water pump. Although we for the most part believe in genuine Subaru parts, here’s a case where genuine Subaru part’s may not  be the best choice. Note the  stamped steel vanes on the Subaru pump vs the quality cast and machined impeller on the Japanese counterpart. The tight clearances and  defined impeller vanes are very efficient at moving coolant through your Subaru engine. (an interesting side note that  older Subaru water pumps  were made nearly identical to the pump on the right).

Subaru Water Pump1

Genuine Subaru Water Pump VS Aftermarket Japanese Waterpump

Genuine Subaru Water Pump VS Aftermarket Japanese Water Pump

UPDATE: WATERPUMPS WITH CAST IMPELLERS AS IN THE PICTURE ARE NO LONGER AVAILABLE. ALL WATERPUMPS HAVE SUPERSEDED TO WATER PUMP SIMILAR TO THE LEFT.  UNFORTUNATELY PROBABLY THE RESULT OF A MANUFACTURER TRYING TO LOWER THE COST OF PRODUCTION.

Another important part of keeping the hot coolant flowing out to the radiator and away from the internal hot spots in the engine is a high quality thermostat. I’ve shown below the comparison between a generic aftermarket brand on the left and a genuine Subaru thermostat on the right.

 

Aftermarket Thermostat VS Subaru Thermostat

Aftermarket Thermostat VS Subaru Thermostat

Note the Subaru version has a much larger spring, larger diameter central area for coolant flow and is made of steel and brass. The generic brand contains copper, a big no no with Subaru. Subaru actually states that copper in a Subaru cooling system is ill advised and may cause excessive electrolysis and corrosion.

Even after trying to be dilligent about providing the best possible cooling for your Subaru you still may need to cross the head gasket bridge some day. If you ever get to that point, Smart Service will have a solution for you. We now offer  new and improved aftermarket head gaskets which we believe will be the last ones your car will ever need. I’ll make a future post with more details about their construction.

Cheers,

Mike

Mike Corbin

About Mike Corbin

Smart Service is a Subaru service repair and maintenance shop operated independently of Subaru of America or Fuji Heavy Industries. We are a family run business that combine high quality Subaru care, personal friendly atmosphere and a cost savings over the Subaru dealer. We have been supporting the Subaru community since 1999. Follow Mike on Google+.

435 thoughts on “Making Head gaskets Last on my Subaru

  1. Mike CorbinMike Corbin Post author

    Hi Finn, Nice car!

    First of all, depending on the temperature outside, the exhaust can have condensation that appears to be smoke to alot of people. If it doesn’t smell oily or fuel like, it’s probably fine. Also, 1qt every 3750 miles is impeccable for a turbo vehicle. Compression and leakdown tests are a good gauge but can have some errors from time to time so it may be worth having another one done with it fully warmed up to see if it is the same. Either way I’d probably still monitor it for now and if you want to be on the safe side, have the valve clearances on that cylinder checked. It’s probably fine but it never hurts to be proactive.

    Take care,
    Mike Corbin
    Smart Service
    Your Independent Subaru Expert
    http://www.smart-service.com

  2. gentry richardson

    Just put six star gaskets on my 2002 forester. The reservoir tank is filling up on its own and there is antifreeze around the radiator cap . could this be anything but head gaskets? Heads were pressure tested and plained. The block was also checked. Any advice would be appreciated. Thanks

  3. Mike CorbinMike Corbin Post author

    Hi Gentry,

    If it is immediately after the installation it’s likely something wasn’t right during installation. (that is assuming you put in a new thermostat and have properly bled and warmed up the system). I have seen in a few cases where the gaskets were installed backwards and although it should be pretty obvious that they don’t fit right, if installed this way, coolant passages don’t line up and will cause immediate problems.

    I hope it’s something simpler than that for your sake.

    Good luck,
    Mike Corbin
    Smart Service
    Your Independent Subaru Expert
    Seattle Wa
    http://www.smart-service.com

  4. Ryan D

    I had developed issues with my 2002 Subaru Legacy L coolant system. It was not properly cycling coolant from the overflow back into the radiator. The first thing I did was replace the radiator cap. This didn’t solve the issue. I then found a leak at the radiator filler neck. I had my radiator replaced. After the new radiator was installed I noticed coolant lose. I found it leaking from the upper radiator hose where it meets to the engine block. I brought it back to the shop and they put a better clamp on the hose. They said that both the upper and lower radiator hoses are hard while the vehicle is at normal operating temperatures and running. Any advice on how to approach this?
    Thanks

  5. Mike CorbinMike Corbin Post author

    Hi Ryan, I guess I’d ask them to pressure test the system to make sure there are no further leaks. The coolant hoses being hard at operating temp. is a sign that there is pressure in the system (which indicates the new cap is likely working).

    Sometimes if the hoses are aftermarket, they don’t seal up as well as genuine Subaru hoses. If you still have leaks around the clamps, I’d suggest replacing the hose or hoses.

    Take care,
    Mike Corbin
    Smart Service
    Your Independent Subaru Expert
    http://www.smart-service.com

  6. Mon

    Good day sir i would like to ask is how reliable it is to rebuild my ej20 non turbo engine from a subaru forester sg5? The engine overheated to the point that it stop and loose all water to the radiator cause i’m considering just change the engine because of the expensive parts i have to change like cylinder headgasket, all the tensioner bearings, water pump and thermostat. Thanks in advance

  7. Mike CorbinMike Corbin Post author

    Hi there,

    If the engine overheated to the point it actually stopped running then it is likely too damaged to just reuse as is. Most likely it will at least need the engine short block replaced. For a car to get hot enough to stop running, it usually ends up doing damage to the pistons and cylinder walls as well as weakening the tensile strength of the aluminum block.

    Good luck,

    Mike Corbin
    Smart Service
    Your Independent Subaru Expert
    http://www.smart-service.com

  8. Nit

    hello to you all,

    i attempted a total engine rebuild on a 1994 gc8 wrx engine,ej20g to be exact,
    after assembly the car ran smoothly but drastically lost power upon attempting to accelerate
    and the heads constantly dripped OIL ONLY,the timing was double checked and the direction of the belt and marks on it were on the relevant pulley marks perfectly,however i didnt go through any torquing sequence when attaching the heads ,is this the problem?if not please suggest the possible causes ,
    thanks in advance

  9. Mike CorbinMike Corbin Post author

    Hello Nit,
    If you did not go through a torquing procedure during the installation of the head gaskets then I would focus on that. It is the most likely culprit.

    Good luck,
    Mike Corbin
    Smart Service
    Your Independent Subaru Expert
    http://www.smart-service.com

  10. Gil

    I had a guy do a premioum gasket job on my subaru and a week afterwards the coolant hoses totally leaked out all my tranny fluid ( while it was parked). It was the hoses and I got this fixed. Later from another of his client found out he used a sealant on the gaskets. He insists this isnt going to be a problem. I see different on the internet. Is it possible to go back in and remove a sealant?

  11. Daniel F

    Hello Mike. I have a 2002 wrx. I had a problem with coolant loss, with only a coolant leak on top of the radiator cap plate. I’d get lots of steam (sometimes) right under the radiator plate thing. I replaced the cap plate, along with the hose. No more coolant on top. But the cars still eating coolant. But now, a couple weeks later..As I’m driving home, I see the temperature start to rise. I pull over. Fill it with fluid. Let it cool down. Drive . Starts to overheat again, check the coolant, and it’s full? But it’s overheating. What do you think it is?

    I did have my timing belt and water pump replaced about a month ago. The coolant loss started after that btw. Car has 110000 miles on it.

    Thanks Mike for what you do. Your appreciated.

    -Dan

  12. martin Kariuki

    Hey all,
    my Subaru impreza gh2 2007 has an issue.at times the radiator fills the coolant container with water,I replaced the radiator cap and after driving for 300kms,it had drained all the coolant.
    what could be the problem and the solution?

  13. Mike CorbinMike Corbin Post author

    Hello Martin,

    I would have a shop check for the presence of exhaust (hydrocarbons) in your cooling system. This can cause a similar symptom when the exhaust gas is forced past the head gasket into the cooling system which then displaces the coolant.

    I hope this helps.
    Take care,

    Mike Corbin
    Smart Service
    Your Independent Subaru Expert
    http://www.smart-service.com

  14. Mike CorbinMike Corbin Post author

    Hi Daniel,
    On your 2002 WRX, it’s possible that the coolant was never purged properly when the shop did the water pump replacement. I only mention this because you said it started happening right after they did the work. It’s also possible that the system was purged properly and there is exhaust pushing past the head gaskets displacing the coolant. I would start by taking it to a shop with an exhaust gas analyzer and having them test for hydrocarbons in the cooling system. If there are none present, then have them go through a bleeding/burping procedure to insure the cooling system is fully purged of all air pockets.

    One other item to be sure of is that the cooling fans are coming on when they should.

    Good luck,

    Mike Corbin
    Smart Service
    Your Independent Subaru Expert
    Seattle, WA
    http://www.smart-service.com

  15. Mike CorbinMike Corbin Post author

    Hi Gil,

    If you are referring to Subaru head gaskets then I would agree that there should be no sealant used during the process. There is no gasket for the 2.5 engine that I know of that requires sealant. On the contrary they need all contact surfaces to be completely clean and free of imperfections to have the best chance of sealing. There is no way to remove the sealant with out removing the cylinder heads.

    It doesn’t mean that the job won’t last, it just may not last as long as it otherwise would have.

    Take care,

    Mike Corbin
    Smart Service
    Your Independent Subaru Expert
    Seattle, WA
    http://www.smart-service.com

  16. Rozano R.

    Hi Mike,
    I have a 2002 wrx. Some time last week, when I was warming up the car I noticed the heater wasn’t blowing hot air. I thought nothing of it and drove off. My car started to overheat on the interstate. I noticed coolant leaking from the bottom of the radiator. So I replaced it. When I try to burp the radiator, the bubbles never stop. I’m talking big bubbles. And lots of white smoke come out from where I am filling it. I also recharged the ac a few days before this happened. I may have overcharged it a little. And also, when I put the radiator cap back on, the overflow tank starts bubbling, but no white smoke. When I turn the heat on, sometimes it blows warm air but most of the time it doesnt. I just bought the car in November. Previous owner “supposedly” replaced the coolant, water pump, and thermostat 1000 miles prior from the time I bought it. Also when I smell the oil from the dip stick it kind of smells burnt.

  17. Mike CorbinMike Corbin Post author

    Hello Rozano,

    Unfortunately from the sounds of your description it sounds like your WRX is suffering from blown head gaskets. Whether it was already occuring back when the prior owner installed a water pump thinking that was causing the overheating condition or if the overheat from the radiator failure weakened them but either way it sounds like exhaust gasses are being pushed into the cooling system and creating all sorts issues. I would minimize driving it any further until you have it diagnosed professionally. If you have a shop with an exhaust gas analyzer nearby, have them “sniff” the radiator and recovery bottle for hydrocarbons.

    It sounds like you’ve done everything you could to burp the system but as long as more exhaust keeps being pushed past the head gaskets you won’t succeed until they are replaced.

    Good luck,

    This site can’t provide a secure connection

    Mike Corbin
    Smart Service
    Your Independent Subaru Expert
    Shoreline WA
    http://www.smart-service.com

  18. Roland Gendreau

    We have a 2008 Outback 2.5i with 87k miles. I am concerned of reports that a head gasket repair is very likely required for this car.

    While I have maintained the car well, I am disappointed in the repairs required in the past year – 2 wheel bearing hub failures and both front axles due to inner CV joint boot failures, My other car is a 2006 honda accord whichI have driven it 190,000 miles without a single repair – brakes, tires and normal maintenance only.

    We are trying to decide whether to keep the Outback or trade it in the near future.

    If I decide to keep it, I was thinking of having the head gaskets changed out at the same time as changing the timing belt and water pump.

    What other maintenance might we be facing if we go ahead with those major repairs and try to keep it for another 100,000 miles?

  19. Jim Deckard

    Hi Mike.I am confused about heater core . 2010 Impreza 4dr 2.5i..does it make a difference if the lines are crossed? Just installed new WP, TB,HG….etc. Runs like a top , can’t find the air pocket.. Used all OEM parts.

  20. Pearson

    Hi. A guy installed my timing belt for me when I was sick. I am now changing the belt , idlers and water pump. I am seeing little circles of metal on the idler bolts. I am guessing that the guy over tightened the idler bolts. Any suggestions on how to re-secure the bolts properly back into the engine block when I reassemble?

  21. Mike CorbinMike Corbin Post author

    Hi Peter,
    For the most part they have been more reliable/less leaky than the EJ25. When they do have issues it is usually a head gasket failure that involves hydrocarbons pushing past the gasket into the cooling system which then causing overheating.

    I hope this helps.

    Cheers,
    Mike Corbin
    Smart Service
    Your Independent Subaru Expert
    http://www.smart-service.com

  22. Mike CorbinMike Corbin Post author

    Hi Pearson,

    It sounds like the bolts were overtightened and have pulled out the aluminum threads. You will want to look into a thread repair product called Heli-coil.

    Good luck,
    Mike Corbin
    Smart Service
    http://www.smart-service.com
    Your Independent Subaru Expert

  23. Mike CorbinMike Corbin Post author

    Hi Jim,
    I haven’t had it happen before but in the past, other Subaru models were sensitive to how the heater hoses were routed and it had an affect on how well the thermostat opened. I would check another Impreza or a diagram in a repair manual to make sure you have them correct.

    Good luck,
    Mike Corbin
    Smart Service
    Your Independent Subaru Expert
    http://www.smart-service.com

  24. Dave Myers

    Mike – great advice. Thanks for the effort.

    I just had my 2.5 2007 Legacy Sedan Engine rebuilt. I get a distinct smell of antifreeze inside car during startup and occasionally during higher demand ( going up a hill, passing, etc.).

    Is this normal burnoff? I have about 300 miles on the engine. The check engine light has come on but I do not know the code.

    Any information much appreciated.

  25. Doug

    Hello Mike,

    My 2013 Subaru Impreza Base 2.0 CVT has 22,000 miles on it and I have changed the oil every 6 months to hopefully prevent premature head gasket failure. Reading you article on excess heat contributing to head gasket failure caused me to think about my coolant. The Owner’s Manual suggests that the initial coolant replacement can be at 11 years or 137,500 miles; and every 6 years/75,000 miles thereafter.

    Will changing the coolant now help prevent head gasket failure better? Or can I really wait that long to replace the coolant? What would you recommend?

    Thanks much!

    Doug

  26. Mike CorbinMike Corbin Post author

    Hello Doug,

    Your 2013 Impreza comes equipped with the Subaru “Long Life Coolant” which has been in use since 2008 and seems to be holding up very well. I don’t think changing it will assist in making the head gaskets last longer unless you see it developing corrosion or buildup in the radiator. (when it’s cold, pop the radiator cap and look with a flashlight to see if any scale or corrosion is building up on the tubes) If they look clean then I’d leave well enough alone until it needs changing.

    Changing the oil every 6 months is great too and I woule keep it to a max of around 4000 miles too depending on your driving habits.

    Take care,

    Mike Corbin
    Smart Service
    Your Independent Subaru Expert
    http://www.smart-service.com

    Also for Six-Star and Subaru parts online visit http://www.smartqualityparts.com

  27. Wale

    Hi, my GC8 V6 STi behaves funny lately i wen i start it an let it warm to normal temperature, then when i take it for a drive it spikes to Hot and comes back when i get into boost it spikes up and down till half,tried changing watet pump no difference, n additional to that my spedometer is also bouncing it revs with the engine when gear is in neutral it goes all the way to max speed at 4k rpm but car isnt moving. Any ideas out there?

  28. Matt Hoffman

    Hey Mike,

    Thanks for all of your responses here and keeping up with all the questions. I just got what seems to be a good deal on a 2009 Impreza sedan with 98k miles. I took it in to see if any visible signs of fluid weeping and got an all-clear that everything looked good from outside. Any suggestions on steps I could take to at least reduce the probability of future head gasket issues?

    Thanks again!

    Best,

    Matt

  29. Mike CorbinMike Corbin Post author

    Hi Wale, hmm… sounds like it may be more than one issue but I would first start with having the coolant system checked for the presence of hydrocarbons with an emissions gas analyzer. The symptom of going immediately into the red zone then coming back down somes suspisciously like a head gasket issue. The other problem may or not be related but you’ll need to solve the overheat condition first. There is a possibility that if the engine coolant temp sensor has an air pocket around it, the computer will think the engine is cold and will increase the rpm accordingly.

    Good luck,
    Mike Corbin
    Smart Service
    Your Independent Subaru Expert
    http://www.smart-service.com

    Also, parts online at http://www.smartqualityparts.com

  30. Mike CorbinMike Corbin Post author

    Well congratulations on your new purchase and I hope it gives you years and many miles of enjoyment. I don’t have any good advice on how to reduce the possibility of Head Gasket issues other than perform the proper maintenances at the time they are due, use only Genuine Subaru coolant when any coolant changes are involved and make sure it gets driven. It seems that sitting around and short trip low mile cars sometimes have more issues with leaks than the ones that are warmed up and driven 20 miles a day.

    Good luck,
    Mike Corbin
    Smart Service
    Your Independent Subaru Expert.

  31. Rob Durbois

    Hi Mike – I have a 2004 Subaru impreza 2.5 TS. I had the head gaskets replaced at the local Subaru dealership at 90,000 miles which was 25000 miles and 4-5 years ago. I figured I was all set for another 70K at least which is why I was willing to drop the dealership $$ on the repair. Well its in for a recall right now and the technician who is working on the car is reporting that the head gaskets are leaking. It runs great and doesn’t overheat. I have 2 questions.

    Should I be surprised enough to have a conversation with the Repair manager that they are leaking after 25K miles, or is this expected performance of a dealership repair given the 4-5 year time frame?

    I cant afford a head gasket currently. What should I look for / at what point does it need to be repaired to avoid damaging the engine?

    Thanks for your time

    Rob

  32. Mike CorbinMike Corbin Post author

    Hi Rob,
    First of all you need to qualify the level of leak from the head gasket or gaskets and which fluid is leaking. It is common for a little oil to seep out over the years and in many cases this never amounts to anything further. Sometimes it proceeds to get worse and eventually makes a large enough mess that you’re forced to repair it. If the car is leaking coolant from the head gasket, it is a more pressing matter. This can cause the Impreza to become low on coolant over time and lead to overheating. This can range from slight residual coolant that needs to be topped up once every couple of months all the way to a leak that is needing to be topped off daily.

    All of this is to make sure you educate yourself on what is leaking and how severe. Once that is established further discussion can be had with the dealer. If it is a substantial leak and you choose to repair it, I would advise changing over to the Six-Star brand gasket to help avoid this occuring in the future.

    Good luck,
    Mike Corbin
    Smart Service
    http://www.smart-service.com

    Also parts online at http://www.smartqualityparts.com

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