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Thinking Internal head gasket leak, but not sure.

7K views 16 replies 5 participants last post by  Schaeff58 
#1 ·
I've got a 2004 Subarau Outback 2.5 EJ259 with california emissions. We got the car with 6,700. Cars got 204k miles on it. I changed head gaskets at 100K because of an external coolant leak. Never caused an issue, but was preventative with a timing belt replacement. I do all my own wrenching.

Anyway this spring around 190K miles I did the second timing belt water pump job. I used a gates kit. When I pulled off the 190K water pump the impeller was crooked on the shaft and you could see where it made slight marks on the engine block. I feel stupid for not changing it at 100K, but live and learn. I wasn't overly concerned about the grooves and installed the kit and all was well for a few weeks. The water pump was leaking coolant when changed.

Since the water pump job the car has had an intermittent issue with pushing coolant out to the overflow but never reclaiming it. Over the summer I would top the radiator off every few days and never had an issue. But it wasn't right so I wanted to fix it. I pressure checked it and found a leaky hose. I tightened it. I also found the thermostat inlet seemed to leak so I put a new one of those on.

Seemed fine. drove it and checked it for 2 weeks no issues. We took it on a 8hr drive and it was great until we went to the Black Hills of SD. Then we started pushing coolant out and running warm from the air pocket. I keep it topped off every day and we made the trip no issues. We made it about 3.5 hours on way home until we had issues. I pressure test it again and find another hose leak. I tighten it up and all seems OK.

Go on a 3hr drive and it's fine. On the way home it starts funning warm again and it's low on coolant.

So Here's where I'm at. I'm fairly confident i have a small internal gasket leak that is pushing the coolant out. Why i've had several weeks with no visible change in coolant in the recovery tank or radiator doesn't make sense. If it was a bad head gasket I would have thought it wouldn't come and go, but just get worse.

Installed parts so far:
Coolant Temp sensor
Water pump -Gates
Thermostat - Subaru
Thermostat inlet - New
Ac condensor - New old one was full of rocks

What I've got to install:
Radiator - Old one has 200K and is full of rocks we live on gravel road
Radiator hoses - 100K just needs it.
New water pump gasket - The one has a slight crease in it from shipping. and I'd like to inspect the block again to see the slight scratches from the bad impeller.

I do loose pressure within a few minutes of pressure testing it and that's why I think I have an internal leak. Or an external I can't find.

I did do the idle and warm test with the pressure kit as described in the instructions to test for head gasket issues and those came back OK. which doesn't support a bad head gasket.

I did perform a block test with the special fluid and test apparatus for the radiator and it came back OK.

I don't have noticeable bubbles in the cooling system when the engine runs.

So what should I do next? Is the next step the overnight pressure test
that I read about on here?

Sorry for the book. i'm an engineer and tend to be very analytical and collect lots of data.

Thanks
Jeremy
 
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#2 ·
Ok so the fact I have issues on freeway drives and mountainous drives pushes me to 99% that I have an internal head gasket leak.

Is an overnight cooling system pressure test the sure fire way to verify this?
 
#3 ·
replaced headgaskets have alternate failure modes than OEM installed (which always leak externally).
Symptoms can vary wildly and correlates to ambient temps, engine load, driving conditons, etc.

I've seen multiple H6 engines of this era bubble in the overflow - pushign exhaust gases out during hot summer days - and go 6 months without issues during winter.
Older EJ25D's from the 90's could overheat once - then not again for months. Of course they get worse quickly from there.
Seemingly random symptoms aren't uncommon.

freeway drives and mountainous drives alone point to radiator. drag being proportional to velocity squared and the physics of climbing mountains (try pushing a huge trailer in a flat parking lot by hand and then pulling it up the slightest incline to feel how drastic the load differential is.

but since you also have coolant loss -

a leak or headgaskets.

Seems like it's definitely not leaking - you keep blowing hoses when pressure testing suggesting the hoses are degrading somehow - is there a neighbor that doesn't like you?!

to verify...you said it's already bleeding off pressure, so i'm not sure what doing it overnight would show - the same thing?
 
#4 ·
Yeah the only big thing I was thinking an overnight pressure test would show is that for sure I have coolant in the cylinder. And maybe pinpoint what side has an issue.

This is my next test and i'll do it with the engine bottom cover off so I can look for any misc leaks. I'm not expecting leaks. I'm expecting water in the cylinders.

thanks
Jeremy
 
#6 ·
I was wondering about a compression test or even a leak down test also. I don't have a leak down so I'd probably just put compressed air into the cylinders looking for coolant bubbles.

I did have an new aftermarket cap on for a while, but went back to the factory cap. I noticed no change with the different radiator caps.

The car drove fine locally for two weeks. Coolant was always full in radiator and coolant bottle level never changed. This is what confuses me. I've always assumed that once you have a head gasket issue they get worse quickly. But grossgary's experiences seem to support it being intermittent.

I hate to say it, but I kind of enjoy the troubleshooting process so I generally over troubleshoot issues before actually tearing into it. I'm a couple weeks out from being able to really dig into this anyway.

Thanks for the suggestions and keep them coming.

Thanks
Jeremy
 
#7 ·
Well I did a leak down test tonight. I didn't find any issues that screamed head gasket. While I have it pulled apart to do the plugs I'm letting it sit overnight with Pressure in the cooling system. It does loose pressure but i'm not sure if it's the cooling system or the test unit? So I'll let it sit tonight and see what I have in the morning. Figured if I need to pull the plugs to turn it over looking for coolant nows the time.

I left the pressure on it around 17PSI. Would it be reasonable for it to have lost some PSI? or should it still be at 17 overnight? This is the first car I've ever needed to do a pressure system test on.

Thanks
Jeremy
 
#8 ·
Well checked this morning. Had a leaky upper hose to engine connection. It was down to 14 psi.

I'm putting in my new hoses and radiator before refilling.

Hopefully this is it.
 
#9 ·
Well checked it again today and now it's at 13psi 24 hours after reading 14psi. I'm not worried about head gaskets now and feel pretty stupid a silly hose may have spanked me for this long.

Well as long as the hose fixes it.
 
#10 ·
So couple weeks back installed new radiator and hoses. Well still had a leak at the top hose connection to the engine. Put on a new clamp and all seems well. It was leaking on the hose where the clamp tightener is.

So moral of the story. Do an overnight pressure test to look for leaks. And consider changing clamps along with hoses. This is the first time I've had to replace a hose clamp because of leaking.
 
#11 ·
Well Here's an update. Started pushing coolant out again and on spirited driving it would raise the temp gauge quite quickly and push out more coolant in a short time frame. I also had an issue with it starting in the morning and missing for a short time. I decided it was time to do head gaskets. If it hadn't started missing after sitting overnight I would have ran it a little longer.

When I pulled the engine and got the heads off the passenger front cylinder had a "wet" look to it and had less carbon build up than the other cylinders. We also found a brown "burnt" looking spot on that cylinders head gasket ring. I put Fel Pro MLS gaskets in it again and reused the head bolts. I figure I have 8-10 hours in it with the engine removal.

We put about 200 miles on it so far and it seems to be running OK. Checked the coolant this morning and the level was plum full as it should have been. Just like my 2003 outback. Only concern I still have is the temp varies a little more than I would like. idling the temp sits where it always did. Running down the road at 70 it runs the same. Running 30-40 MPH at around 1500 RPM seems like it runs a little warmer. If you put it in neutral and the RPM's up to around 3000-3500 it cools back down. This is a touch peculiar to me, but not sure it's a concern. My 2003 doesn't do this. And I don't remember this car doing this before. I'm talking slight movement of the temp gauge.

Sorry for posting a book. I wanted to update this incase someone in the future is looking for information.
 
#12 ·
Well I forgot to hook up the Crank case air vents off the valve covers the the air intake. So we may have been getting a bit of a lean condition? I hooked those up and the wife said it's more stable.

So i'm still slightly concerned about the fluctuation of the heat gage. I'll dig into it as I have time. But for now it's a runner and like all good subaru's is getting driven!

Jeremy
 
#13 ·
Congratulations for staying with it. You have put a lot of hours into it. I think that the jury is still out as to what head gasket should be used. I put in the 6 stars in my 02 and with 3 1/2 years of no problems, but with low miles. I guess since you got 100K with Fel Pro they must be decent head gaskets. If I get 100K, I will be tickled pink. I hope you get another 100K at which point it should be ready for the junk yard.
 
#14 ·
Truthfully if we get another 50K out of this car I'll be happy. I figure that's another 5 years. By that time i'm hoping Subaru has a vehicle with 3rd row and hopefully diesel in the US. Or We'll get a used Tribeca.

I debated getting the 6 star gaskets, but figured I got a 100K out of the fuel pro's so I'll use them again.

What temp should this car be running? Like actual degrees? I was thinking 195-205? I was going to plug in my scanner and start watching the temps to see if they match the gauge.

Thanks
Jeremy
 
#15 ·
Well should learn to plug the scanner in earlier. My 2003 that's had no issues reads 160-205 at exactly the same spot on the gauge.

My 2004 that's had the head gasket issue reads up to 207, but has huge fluctuation on the gauge. Early on I put an aftermarket temp sender in. I'm going to change that back to a factory subaru sender.
 
#17 ·
@junk
Thanks for documenting your progress. This was helpful to me, even though I have a 3.0h. I ve done several of the 2.5's but never a 3.0. (always used six star gaskets) I put a used JDM in when mine had what I am pretty sure was a head gasket.. but it had all the symptoms you were having...
My pressure tests though were rock solid... half hour, or 24, always exactly what I started with... But... hot driving, hills etc... would get coolant pushed out the overflow tube... but when cool, in winter, never had an issue.. Job is done now... this thread coolant leak, don't think its head gasket, 05 h6 if you are interested...

I know this is an older post I am replying to, but I am so grateful when folks conclude their 'adventure' for the rest of us to learn from!

Thx for that sir!

Schaeff
 
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