HELP: PO304 Engine Misfiring, Radiator Boiling Over after Cooling System Flush

[dirty_mech]

Hi all,

This is a 2000 Subaru Legacy L Wagon EJ25, just recently cracked 200k miles.

Replaced the valves, head gaskets, and timing belt about 5 years back when the belt snapped and crunched the valves.

Replaced the spark plugs, wires, fuel pump and filter less than 2 years ago. 

Last week, I realized my overflow reservior was empty and that there was tons of rust colored water in my cooling system. I knew that I at LEAST needed to flush it and replace the coolant.  Pretty concerned as to the source of the rust; could be the water pump impeller, lower radiator hose spring, etc.  Considered just replacing the water pump out of an abundance of caution, but decided I would let it ride as long as the cooling system is working, and just flush it.  Noticed rust colored residue at one side of my lower radiator hose and realized that it was leaking, but so very slowly that it didn't leave a puddle as it did so.  Probably just evaporating off the hose as the car ran.  Cause was a worm drive hose clamp that had come slightly loose.  I think I might need to get a more reliable type of hose clamp, but just tightened it up for now.

First I removed the thermostat (not rusted), then did a couple water flushes, then a 50/50 vinegar/water flush for a day, then ran water through the radiator and engine with a garden hose.  That was all this last weekend.  On Sunday, after flushing with the garden hose, I put a bottle of Prestone Flush + Cleaner in the system plus water.  Instructions say you can drive with the cleaner in the system for up to 6 hours over the course of a few days for "heavy duty cleaning".  I planned to drain and flush the system again today, when my new thermostat was scheduled to arrive, then fill up with coolant.

However, this afternoon the engine started idling rough and the CEL started flashing, which I've never seen before.  The engine also starts to overheat.  I check the radiator and find it's missing a good half gallon, which is confusing as hell because there is no leaking under the car and no white smoke has been coming out of my tailpipe.  The overflow reservoir is also completely full and bubbling when I check it.  Removed the timing belt cover; no rust colored splattering as you might expect from a weeping water pump.  I could see the water pump too; no signs of problems.  No problems in the engine oil either as checked via the dipstick.

I refilled the radiator and emptied the overflow reservoir, but the overflow reservoir keeps filling up, bubbles and all, and then I overheat again.  The engine also idles rough.  The CEL will flash when I am idling at a stop, but then cease to flash when I'm driving and just stay on instead.  Code is P0304 - Cylinder 4 misfire.

I have a sinking feeling that I may have damaged my head gaskets with this Prestone cleaner, and now have a damaged head gasket leaking coolant into cylinder 4.  I've drained and flushed my cooling system again and refilled it with just water.  After watching the level at the filler neck, it seems it may be very slowly draining drop by drop, with no external leakage visible, which could mean coolant is going into the engine. I am going to investigate further tomorrow morning.

I used an otoscope to peer into cylinder 4 and didn't see any water or rust stains.  I even tried lightly pressurizing the engine with the garden hose when I was flushing it and still didn't see any water inside.  However, the cylinder 4 spark plug is reddish with black, while the cylinder 1 spark plug is white with some black deposits.  I've attached 3 photos of the spark plugs as well as 1 of the inside of the cylinder 4 using the otoscope. 

If this problem sounds familiar, or anyone has any advice on what more tests I can do to diagnose this issue, I would much appreciate it!

[lmdew]

Search the form for burping the coolant system.  Subaru engine like to trap air in the coolant system if not filled properly.

It can lead to overheating.  Overheating is not good and can contribute/cause HG leaks.  

Make sure you have a Subaru Thermostat and not an aftermarket one.  Properly fill the coolant system and burp out all air.  Drive it and watch the overflow for air and coolant being pushed out of the system.  When the engine cools, the overflow coolant should be drawn back into the radiator.  Check the radiator fluid level in the radiator when engine is cold.

[nvu]

If it's constantly bubbling from the reservoir, that's a sign of headgasket failure.  Exspecially if it does this while idling.

[dirty_mech]

Started it up again this morning, and there is white smoke coming from the tailipipe (just not enough to see from inside while driving).  The smoke is so moist that the concrete becomes visibly wet.  There is also bubbling inside the coolant reservoir, even though the engine is completely cold.  100% a head gasket failure. 

I found this informational page about Subaru head gaskets in another post:

https://allwheeldriveauto.com/subaru-head-gasket-problems-explained/

And I realized I checked almost all the boxes on stuff that causes a head gasket failure:

- Used aftermarket head gaskets when I did this job 5 years ago

- Not changing the oil often enough (was trying to do 10k interval changes with full synthetic and Wix XP filters)

- Not changing the coolant often enough (might've been 5 years ago that I did it).

- Possibly not using OEM style spark plugs

Sigh...

Now what I need to know is this: Can I do the head gaskets without removing the EJ25 engine from the car?  I think I've read that it's possible but much more difficult.  I just don't have an option at this point.  Going to pull and inspect the water pump as well, given the rust in my cooling system. 

Any further advice is much appreciated.

 

[nvu]

Did you switch to all metal gaskets when you rebuilt it?  If you were still using aftermarket composite gaskets, they were a flawed design on the ej25's and would leak eventually.

[dirty_mech]

Hi nvu.  No I used Fel-Pro MLS gaskets.  Exact kit was the Fel-Pro HS26170PT1, from Amazon here:

https://www.amazon.com/gp/product/B000C2AISU/

Going to pull the water pump; gasket is $5 from the dealer so not bad.  I am currently considering doing only the head gasket on the driver's side rather than doing both.  I see some forum post saying DON'T DO IT.  But I also see that doing the passenger side requires disconnecting the engine and transmission mounts while moving the drivetrain up 5 inches and over to the other side to make room, per this web page:

https://www.subaruforester.org/threads/how-to-replace-ej25-head-gaskets-without-removing-engine.57335/

Any opinions on doing just ONE head gasket?  I am going with OEM gaskets from the dealer, per advisement in other threads.

I'm also considering reusing the valve cover and exhaust gaskets.  I don't think reusing exhaust gaskets is controversial, but what about the valve cover gaskets?  Probably going to wipe them off then wipe them down with AT-205.  The intake gaskets are only like $12 for a pair from the dealer, so I will replace those, but the valve cover gaskets are $30 plus tax, which is why I am thinking to reuse them.  Only 5 years old as well.  If they end up leaking later, well they aren't too hard to access. 

Any opinions on that?

[lmdew]

If I was going to do all that work, I'd pull the motor and do both sides and T-Belt, water pump, seals while its out.

[Rampage]

Heat makes the valve cover gasket rubber get hard as a rock and come out in pieces. Also, the spark plug tube seals come in some of the kits. They keep oil from getting on the spark plugs and causing a misfire.

As lmdew said, do both sides. Both sides would have gotten hot.

You flushed the engine and radiator, I would also flush the heater core both directions. On a cold engine water is first circulated through the engine and heater core.

[dirty_mech]

Okay thank you for the input.  I've picked up parts and am doing both sides, with a new timing belt.  Replacing intake gaskets, have valve cover gaskets on hand if needed.  Also going to replace all 5 cooling system hoses, belts, and spark plugs, later when they arrive via shipment.  Already pulled the water pump; it actually looks great, and idosubaru in another thread posted a comment indicating that these things rarely fail:

 

On 8/3/2016 at 7:07 AM, idosubaru said:

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.

 

Therefore I"m not replacing it.  Way easier to get to than the head gaskets anyways, if it does happen later.  I'll post an update with my progress once the job is done.

Edited August 28, 2020 by dirty_mech

[dirty_mech]

Here's the head gasket with the misfiring # 4 cylinder.  Pretty clear where the head gasket failed.  So much for the Fel-Pro Perma Torque MLS.  Going with Subaru gaskets this time.  Don't know what the blue coating is; I thought MLS meant it was only made of steel layers.

[Rampage]

Once the surface is clean (block and heads) use a good straight edge length wise and diagonal to see if they are flat. Gaps can be checked with a feeler gauge.

[nvu]

That coating looks flaked off everywhere, likely the same on the other side.  It should've been an all metal gasket.  Chances are high the heads are warped.  Check head flatness as stated above and consider sending them for resurface.  MLS gaskets aren't forgiving as composite if there's even a bit of warpage.

[dirty_mech]

Alright guys.  I actually got this vehicle fixed on the early hours of Sunday morning but haven't had time to write about it.  The repair was a success and the engine is purring like a kitten after a couple hundred miles of mixed driving.  Best of all, I DID NOT need to disconnect the motor and transmission mounts so that I could move it out of the way with a jack.  You can replace EJ25 head gaskets with the block still bolted into the engine bay.  The angle is awkward, frustrating, requires physical strength, and might give you a stiff back, but it is doable - and a good bit easier than unmounting the powertrain or even removing the engine.  If you don't have the ability to remove the engine, or have to do this job in your driveway or on the side of the street, then this is a viable option.  If you are the kind of mechanic that excels at removing parts from tight angles and awkward places, then this will be a breeze. 

In-Car Head Gasket Replacement Tips

Be prepared to hold the weight of the cylinder head for a while to maneuver it out of the engine bay.  Once you have fully unscrewed all 6 head bolts, the cylinder heads are best removed after taking out the top 3 bolts. This is because you are going to want clearance to raise and tilt the head forward towards the centerline of the engine to get the bottom bolts clear of their holes bottom holes.  If you don't remove the top bolts, they will bang into the top of the engine when you tilt the head towards it.  As the head face approaches a 45 degree angle, the bottom bolts clear their holes and you can slide it forward a bit before being clear to pull it out of the engine bay.  The back bottom bolt on each head is the one that has the least clearance due to interference with the frame, so this is why you bring the head forward before lifting it out of the bay along with the bottom 3 bolts.

Reinstalling the heads: I recommend you put the gasket on right before mating the head to the block.  You first need to maneuver the block back into place with the bottom 3 bolts inside, then add the top 3 bolts once you have gotten the cylinder head close enough to the block.  Do NOT put the head gasket on the block dowels beforehand.  You are guaranteed to contact and mar it with the tips of the bolts, as well as knock it off the dowels and onto the ground.  Instead, have it ready on the top of the block.  Once you have all 6 bolts in and right before closing the gap between the bolt tips and the block, put the new head gasket in between the gap and slide it onto the cylinder head bolts.  This is the only way to avoid marring the surface of the new gasket while installing the head.  The gasket did not catch on the block dowels as the head was mated to the block, and tightening the bolts went smoothly thereafter. 

Review

Very glad I replaced both gaskets; the other one was of course rusting and wearing down like the one that failed.  With picking up parts, this job took me 3 days.  That is 1 day longer than I expected because I didn't account for all the cleaning that needs to be done prior to reinstallation.  The cylinder heads, block face, and piston heads all need to be cleaned.  I very carefully scraped as much gasket material off with a high quality, sharpened and honed metal gasket scraper as I could, then used green scrub pads in combination with acetone and brake cleaner.  Inside the heads on and around the valve faces, I used the same thing, along with a stiff plastic bristle brush and some Brasso, to remove carbon deposits. Around the perimeter of the valve seats, and on the piston heads, I also employed a pick to remove large flakes of carbon.  A pick will definitely be needed to remove the carbon that builds up in the piston head depressions for the valves. I opted to spray clean the cylinder heads in a bath tub after cleaning the face and combustion chamber areas, to get rid of the Brasso paste and cleaning debris.

I also replaced a lot of other parts; the timing belt, drive belts, spark plugs, and 5 cooling system hoses I could identify (2 radiator, 2 heater core, 1 bypass elbow).  Timing belt was at 40k after 5 years.  If it had been a bit less, I might have reused it.  Fresh oil and coolant, of course.  Coolant color is staying clean now.  and best of all not "evaporating".  I suspect my head gasket has been leaking for a while, but only got bad enough to cause engine failure recently, as I have been periodically having to refill it along with the oil that the engine eats.  Replaced the intake gaskets but not the valve cover gaskets; just cleaned them and rubbed them down with AT-205 before reinstalling; no oil leaks from them.  Turns out all that rust was from the head gaskets themselves, rusting away on the coated outer layer as seen in the pictures. 

The first head on the driver side with the misfiring cylinder was very clean on the piston head and cylinder head valve areas.  This is because coolant was leaking into the cylinder, and it got a steam cleaning.  You can see the cleanliness in a picture I posted above using an endoscope through the spark plug seat prior to disassembling the engine.  If I had bothered to look inside a different cylinder, I would've seen how dirty the other piston heads were looking and known right away what was going on.

The water pump was in good condition, so I reused it.  However, one bolt hole at the top had been previously stripped5 years ago, to which I had added a bunch of silicone sealant as some insurance.  When reinstalling the water pump bolts at the specified 108 inch-pounds, a second adjacent bolt began stripping.  So now I have two partially stripped bolts on the top of the water pump.  I slathered the affected area with Ultra Grey as insurance against a leak.  Next time I take this engine apart, I will have to drill out, tap, and install repair inserts into those bolt holes. 

The engine seems to have more power and acceleration now.  Glad I cleaned the combustion chamber areas prior to reassembly.  The top reason I think this head gasket failed is because I didn't change my coolant, it became acidic, and ate away at the head gaskets.  I also added water to the coolant reservoir rather than coolant, which diluted the coolant and facilitated rusting.  It probably didn't help that I was trying to get away with 10k oil changes by using a top quality filter and full synthetic oil.  It also probably didn't help that I was using platinum plugs rather than the OEM NGK plugs.  I'm going to check my coolant more often and change it regularly now, perhaps even annually, and make more frequent oil changes and spark plug inspections/changes.   

I only took a couple pictures of the job because this is my only vehicle and I needed to fix it ASAP.  I'll attach what I have, a couple before and after cleaning pictures of the heads, below. 

Thank you for all the responses and help guys. 

 

Edited September 5, 2020 by dirty_mech