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Very Bad Leak Down Test and Okay Compression Test - Need to figure out what is wrong.

8K views 62 replies 8 participants last post by  praha-sti 
#1 ·
Hello!
I have an 08 Sti Hatch with about 14k on the latest motor looking for insight into what may be going on with the car. Subaru performance shop did a leak down and compression test and the results, are not that great...

Cylinder 1: 125 PSI - 25%
Cylinder 2: 130 PSI - 55%
Cylinder 3: 135 PSI - 33%
Cylinder 4: 125 PSI - 28%
And it is noted that ALL 4 cylinders SPARKPLUG GAPS WERE blown open .040-.045 (From the tech who looked at it)

They said I would probably need to spend the money to get a new long block at worst. But at the minimum, they would have to pull the engine to see what was going on for sure.

Images are Attached for Cylinder 2 and a video showing the leak-down test.
Video Link: VEED - C7F61BAF-13CC-4D7D-9A71-263509D2DD51.mov

As far as mods here is what we got:

Engine and Transmission:
  • IAG Performance Stage 2 Tuff short block
  • COBB Tuning Accessport V3
  • COBB Tuning flex fuel kit
  • Boost Controlled Performance X500 turbocharger
  • Injector Dynamics ID1000 injectors
  • Aeromotive 340 stealth fuel pump
  • IAG air-oil separator
  • Go Fast Bits TMS Respons hybrid blow-off valve
  • Motive Autowerks EBCS
  • Motive Autowerks composite TGV delete
  • Killer B Motorsport oil pickup and windage tray
Intake and Exhaust:
  • Perrin cold air intake, turbo inlet, and titanium-wrapped equal-length header
  • Invidia wrapped cat-less downpipe
  • PTP turbo blanket
  • MadDad Essentials Street Series cat-back exhaust
  • GrimmSpeed ceramic coated up-pipe
This car was built at a reputable shop in the Midwest, about 5 years ago. No additional modifications powertrain-wise have been done.

As far as how the car feels:

I have had two close friends that know Subarus very well and say everything sounds and feels fine.
As far as knock I get minor Feedback/Fine Knock Learn of about -1.40 sometimes. It is not consistent by any means. I do not have any CEL's on the only one in recent time has been for the ABS wheel sensor. When I have the car in Sport Sharp it opens the boost up to 25 PSI and Sport at 16 PSI. I have not noticed any boost issues regarding the turbo.
I really want to take it upon myself to learn and disassemble anything myself when I get the time to do so. I don't have the time right now and need the car at least running for my short commute to work for the next couple of months (in between jobs). As far as oil consumption goes. I burn maybe a quart at most every 2500-3000 miles after having a few beating sessions. I know I am probably driving a ticking time bomb, but if she goes, she goes. That's the Subaru Tax!


Any help is appreciated thanks in advance!

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#2 ·
few things. 1 - that gfb bov/bpv, yeah, ditch that. those things are complete shit, constantly leak, and break. i had one, lasted like 3 weeks. although i dont think that was the root of the issue.

just a general question, how much power was this setup making? that turbo has a flow rate of about 60lb/min, and your engine is rated at 675bhp, which, pending dyno, comes to about 525whp (assuming a dynojet). granted this can vary with the type of dyno. Just curious if you were very close to this or above it. if you were, that could possibly be the culprit of the issue. if you were not.....could be a BUNCH of other things.

it's hard to say without tearing apart the motor, could just be that you need a refresh with new rings/bearings (although 14k miles is really, really early for needing that). i too, have an iag s2 tuff block, and mine has around 40k ish miles on it. still going strong, although i'd guess you are making a good bit more power than i am.
 
#3 ·
few things. 1 - that gfb bov/bpv, yeah, ditch that. those things are complete shit, constantly leak, and break. i had one, lasted like 3 weeks. although i dont think that was the root of the issue.

just a general question, how much power was this setup making? that turbo has a flow rate of about 60lb/min, and your engine is rated at 675bhp, which, pending dyno, comes to about 525whp (assuming a dynojet). granted this can vary with the type of dyno. Just curious if you were very close to this or above it. if you were, that could possibly be the culprit of the issue. if you were not.....could be a BUNCH of other things.

it's hard to say without tearing apart the motor, could just be that you need a refresh with new rings/bearings (although 14k miles is really, really early for needing that). i too, have an iag s2 tuff block, and mine has around 40k ish miles on it. still going strong, although i'd guess you are making a good bit more power than i am.
Thanks for your response,
This build is making 430 WHP/TQ I was looking to push it up more. But I had not had a compression test done in a while and wanted to make sure everything was good. The leak-down numbers really shocked me. Is there something I should look for in everyday driving that I am not seeing? It does not make sense the results would be this bad when I have been driving it to and from work and elsewhere. And is there a recommendation you have on a BOV? I did not know if it had anything to do with the leak-down test numbers because a lot of smoke was coming out of it. Would it be wise for me to get a test done elsewhere?
 
#4 ·
That piston to wall gap looks huge (I know the rings are hiding there, but still) ... was that engine blue printed? The compression looks good, but the leakdown doesn't which means you may have head issues (valve) ... but that's on both sides of the engine, that's sketch looking. Does it smoke when starting? Running? Does it eat oil? What motivated you to do the compression/leakdown?
 
#8 ·
It was blue printed, the heads were machined onto the shortblock, it uses the OEM heads and valves. I wanted to do a leak down test because I noticed some amount of an oil consumption. Between a half quart and quart every 2500-3000 miles. Is there any other values besides knock I should be checking on the access port for anything that could be wrong? Otherwise as far as smoke goes. There was a very minor amount of white smoke last week that came out of the hood scoop after I parked. I was not able to replicate it. Otherwise I get some exhaust smoke (very minor) under WOT full boost. Otherwise on startup, there is always some condensation, but no blue smoke or white smoke beyond that.
 
#6 ·
Bad tune could have burned out the rings which causes lower than expected horsepower, or you have lower than expected horsepower due to bad rings or head issues ...just a guess. What is in the 4th picture up? Valve seat or? Oily or carbon buildup? Those marks on the cross hatch look kinda like detonation, but not really (usually it's "whiter"). What is the AFR at idle? Is it steady?
 
#10 ·
They did the compression test after doing an inspection on the car to make sure everything else was good. And then the Leak Test after that. I would guess the car was probably sitting for a half hour before the compression test, and maybe an hour at most before the leak test. I am not 100% certain, they did not give me all the details. I was more concerned that they were saying I should not even drive the car home, even though I have been driving it for a while.
 
#11 ·
I should also note, as far as the last time it was on the dyno was 5 years ago. Since then adding the 14k miles onto the newest block. I was looking with this shop of what they could do power wise, and that was another reason I wanted to get this test done. For the sake of engine health. I know there should be more headroom in what I can get done with it. But it seems that since I still got the stock heads, it is probably the thing that is limiting me the most.
 
#15 ·
When you say stock heads, you mean stock cams, springs, valves? If yes, that 25psi is pushing them and they're probably fatigued a bit and causing the leak. Just a guess. If you have stock heads (ie... non-ported), but after market springs and valves, you'd be ok. I have ran 650/700 HP with E85 on my stock heads (not ported) with BC280 cams, BC valves and BC springs/retainers without issue.
 
#19 ·
I don't know what 'crankcase leaks on all 4 cylinders' would mean. I've never heard that before. Likely not related, but idle on any modern ECU car should be 14.7. You may have a vacuum leak or sensor issue.

I would still recommend a hot leak-down.

At those miles and boost level, even with all stock components, I doubt the valves are going to be shot... unless the heads were rebuilt poorly.
 
#21 ·
Here is a video of my startup after work, was sitting outside for about 9 hours. Outside temp was 86 F. With 65% humidity. When driving and sitting at a light on idle, I did notice that my AFR gauge would sometimes (like 2 times my 15 mi commute home) jump to 15.7 back to 14.1 for a moment.
 
#23 ·
Usually the enrichment map adds fuel to get the car up to temp faster, yours did that and slowly dropped down and the AFRs came up slowly as they should have ... a bit lower than I'd usually want and idle at temp, but a leak would generally cause a higher AFR not lower. You may have just ran too rich, washed out the rings, and they leak. When is the last time you changed your oil? I'd do a Blackstone or other oil analysis to see what the oil looks like. It sounds pretty ok otherwise ...

A blown ringland (and compression loss) looks like this (my old video of me killing my stock engine):

If you have a valve issue, it make take longer to crank ovr and start and you might "puff" out smoke (usually blue) ... head gasket issues puff out white (coolant) smoke.
 
#22 ·
Its hard to tell by those pictures but are those the face of the valves that are wet? If so, then I would suspect some valve seal leakage. If they are bad enough, I would think it would lead to some unfavorable leakdown results. It would also contribute to your oil consumption.

Have you noticed any smoking while driving/accelerating or smoking on start ups? What about smoking from the exhaust after you have let the engine idle for let say 20 mins and then revving it?
 
#25 · (Edited)
Looking at the pictures closely, there is some piston damage and very worn cylinder walls.

In this picture you can see where it looks like the edge of the piston crown is missing. The red line follows the 'ledge' where material is missing.
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Similar comment as above, missing material from the piston along the edge of the crown.
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The bore area in the red box is suspect. The red line follows a very distinct difference in cylinder wear pattern. The bore below the line is almost polished where the cross-hatch can be seen above it.
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Many different scenarios could have caused these issues so I'm not going to venture a guess; however, it appears you have a few problem areas at play here.
 
#28 ·
Very interesting observations. I couldnt tell if it was piston material or not. I assumed it was just built up carbon/oil since there is wetness. I also did notice a strange marking on the piston dome. Cant tell if that just the scope or not. Scope pictures are hard to decificer most times
 
#29 ·
It would be awesome to do a post-mortem on this engine. I would love to put my profilometer on the bores. I would also be interested in the piston ring free gap on the damaged pistons.
 
#38 ·
Update for over the weekend.
I drove the car a collective 300 miles + over the long weekend, with no issues. Here are my findings. I was checking the oil every other day. And there was not a drop missing it all stayed consistent to when I changed the oil last week. There was zero knock outside of a few readings from shifting. I kept the boost under 5 psi the entire time. No change in coolant level and everything else is working as it should. I revved the car to about 3k to see if any smoke came out, there was none. On cold starts with 10w-40 smoke starts within about 1 min and goes away within a few. There is not color to it. As I can see the condensation forming and steaming off the top the exhaust pipes. I am planning to take this to another shop some time next week for a second opinion, but this is giving me hope. I know the photos are not pretty, so if that is true and the images reflect the state of engine. I was glad to take the right steps and asking knowledgeable individuals about the issue. I will have an update after the next leak down test.
 
#39 ·
Alright this is what I got as a second opinion.
They did a hot test right after I dropped off the car.
Compression was worst with all cylinders sittings at 100-110 PSI. Leaks between 30-50%
They said they can hear the leak coming from the crankcase using an auto stethoscope. And that I really should not be driving the car at all.
They quoted me about $2,200 to pull the block inspect to see what is going on with it. Again, no oil was leaked or burned since the last oil change and I have been checking it frequently. I need to figure out what I am going to. They said just to pull the block it is going to be between 2-3 weeks. And that is not including the lead time it will take to source parts. I am not going to sell the car, I do not want to dick someone over and I defiantly do not want to sell it for a loss. I love the car, I want to get it fixed. I am deciding if I save money to do a full rebuild with a long block, new injectors, fuel lines, turbo and tune ect. Or do I just get it fixed to get it back to where it is. My goals with this car power wise are not out of reach at about 500 WHP. Thanks in advance.

Side Note: as another backup. I am awaiting results from blackstone on an oil sample to see what they have to say.
 
#40 ·
If that's your plan, just drive it till it dies.

If the drivability is not impacted I see no reason to park it especially if you're going to do a long block anyway.

It doesn't make sense you have such bad leakdown but the car drives fine. When I lost compression on both my OEM and built motor it was definitely noticeable and the drive ability was poor.
 
#41 ·
It doesn't make sense you have such bad leakdown but the car drives fine. When I lost compression on both my OEM and built motor it was definitely noticeable and the drive ability was poor.
It also doesn't make sense for all cylinders to compression test within 10psi of each other and to burn zero oil... Something still just doesn't add up to me.
 
#44 ·
Did we ever find out the cause of this? I literally just went through the something very similar yesterday on another 4 cyl car. The car had a dead cyl 4. Misfires all kinds of ways on that cylinder. So much that the ecu would just shut that cylinder down after the first fire up. The engine had ok compression of 190-180psi all around cold. Cylinder 4 had terrible leak down of 30%. After scoping the cylinders, I found cracks in the cylinder walls at the bottom of both 1 and 4.
 
#56 ·
Haha, you guys bantering is making my day.
Anyways as far as an update goes. I really don’t have time with work at the moment to do this myself. I’m having a local performance shop that has good rep pull the block and let me know what to do. They were really straight with a buddy of mine who had blown rings. So I will most likely go with what they say. I’m fine with putting in a new long block. This is my fun car. I have a Q50 as my daily. I wanted built heads anyway so it’s either.
1. Fix my bottom end, build the heads
2. Replace short block, build heads
3. Long block.
Let me know what y’all think. Ty in advance. Money isn’t necessarily the biggest issue. I just can’t go crazy!
 
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