Gerald81

Yes, the cylinder wall is thicker, but it seems to me that means the water jacket is smaller. But I don't seem to be able to find evidence of this being a widely reported issue with cooling / reliability on the 2008 blocks.



Yes they have, and I have seen the gaskets myself too, although I don't have a trained eye. I should have snapped some pictures, but there is a greyish ring around the cylinders and it does indeed look to be intact with no signs of coolant burning through.

ditchmyster

iTrader: (7)

Wasn't the block pressure tested before the rebuild?

Gerald81

Is there a way to pressure test the block? How does this work? Would love to do so if possible to rule out any cracks. Have only heard of pressure testing the cooling system...

Or is this a leakdown test you're talking about?

Gerald81

It seems I must have the worst luck ever. I ended up buying a brand new block and heads from Subaru Japan, along with new stroker pistons and original head gaskets gaskets, and had a different shop bore out the cylinders to 92.5mm again, and assemble the engine.

It immediately started leaking oil upon startup. It seems to be coming from both HG, at the bottom of the engine. No mixture of coolant and oil observed for now. These are brand new blocks, heads and gaskets from Subaru, with original head studs...what could have gone wrong?

bustaMOVEs

iTrader: (31)

Ah ffs, it seems there a lack of specialists up there tbh.
Just leaking oil onto the floor or into coolant?

Gerald81

For now it seems the coolant is not contaminated and there's no mixing of oil into coolant and vice versa.


The shop that assembled the engine is supposed to be one of the trusted Scooby specialists who's been around for decades and is run by a former mechanic with the local Subaru dealer.


One question, another shop claims that the issue could be due to the lack of usage of gum on the head gaskets during installation, whereas the shop that put the engine together for me this time says gum should not be used and has never used it for all the engines built there. Is the use of gum/sealant part of the factory procedure or not?


Also, is there a known issue with GRB head gaskets, maybe a bad manufacturing batch or something that causes the gaskets not to seal properly?

bustaMOVEs

iTrader: (31)

Sealant/gum is NOT used for hg, and never heard of grb gaskets

bustaMOVEs

iTrader: (31)

When you say it's leaking oil, what do you mean it's leaking and how?

MOTORS S GT

iTrader: (2)

Why go to 92.5mm on a new block ?, 92mm forged pistons in a fresh block usually require a light hone for there extra running clearance, seems to have lost a rebuild life for no reason.


The only time I have seen headgaskets pushing out oil between head & block on a Subaru is when the gaskets been fitted the wrong way round, blocking the oil feed holes.

Gerald81

Some pictures:








It leaks when the engine is idling, not sure if it leaks when at rest. After the initial stains are cleaned, and if the engine is left running, more oil will appear.

Gerald81

I know what you mean regarding the fresh block, and it was a dilemma I struggled with for a bit. I wanted a Mahle-based low expansion stroker setup, and there were no off-the-shelf 92mm Mahle pistons that worked with a 79mm crankshaft, which was why I had to go with the 92.5mm.

bustaMOVEs

iTrader: (31)

The gasket wrong way finch suggested could be a point

Gerald81

I suppose, but given the experience of this particular shop that seems really really unlikely...

MOTORS S GT

iTrader: (2)

If its still running ok after a while it won't be the headgaskets on wrong, as it won't get any oil to the cams & turbo feed,& it will seize up.


Have you checked the oil gallery plugs on the inlet manifold face to head.

Gerald81

The shop says it's the gaskets, which had part number 11044AA760, and was intended for my 2008 block and heads. They want to try a different model of gasket, which is 11044AA680.


11044AA760:



11044AA680:



Heads (old ones but the new ones are the same design):



The main difference I note is that the correct gaskets (i.e. AA760 which apparently failed) has more material (or rather a longer continuous slot as opposed to more, smaller openings) at the passages near the top of the picture, that matches the head design. Do you foresee any issue in using the AA680 gaskets for my heads? Is it ok to not have the gaskets and head match up?

MOTORS S GT

iTrader: (2)

The 760 gaskets are the correct ones for your heads, the 680 are the earlier pre 07 gaskets, using 680 gaskets will cause issues on the later heads, as the cooling tracks do not line up.


Try using Cosworth or RCM gaskets if your confidence in Subaru gaskets is shaken, they are available in 0.78mm, 1.1mm & 1.5mm

Gerald81

Thanks, that's what I feared as well...sigh.

Gerald81

If I get the RCM gaskets, can I continue to use 11mm head bolts even if their holes are enlarged for 14mm studs?

bustaMOVEs

iTrader: (31)

Yes

Don Clark

I would also go with Head Studs/nuts (ARP or similar) rather than the oem bolts.

Much easier to get them torqued correctly.

Gerald81

Alright so as an update, I bought another set of gaskets and had the shop replace them. No more oil leaks.


Now while running in the engine (about 600km travelled so far), I recently noticed bubbles in the overflow again, after each drive.


The bubbles are fairly large, about 10-15mm. They go away once the fans kick in.


No overheating but some slight coolant loss each time the bubbles appear.


The upper reservoir is not pressurized when cold, and the coolant level is full.


Any ideas? It can't be gaskets, can it? This is a new block, new heads, new valves, new pistons, with no more than 600km on the clock

jaygsi

iTrader: (46)

So it's not loosing any water?

bustaMOVEs

iTrader: (31)

Have you tried another header tank cap? The spring in cap could be at fault letting water escape into overflow?

Gerald81

It is losing small amounts of coolant after each moderately spirited drive. Perhaps roughly 1-2mm down on the overflow bottle for every 50km (measured near the full line).


What I meant about coolant being full is that when the engine has cooled, there is no pressure in the system and the coolant level in the upper reservoir is at the brim when opening the cap.


I'm using a relatively new STI 1.3 bar cap. I had tried changing caps (back to OEM 1.1 bar) and OEM thermostats before in the not too distant past when trying to diagnose the issues on the previous motor, but it never did help.


I am curious about the relationship between the fans and the bubbles. I wonder why the bubbles stop as soon as the fans kick in? Even if I rev the engine, no bubbles will appear so long as the fans are on. I have not yet tried waiting until the fans go off though to see what happens.

MOTORS S GT

iTrader: (2)

I think your getting paranoid over this, I would leave it alone & let it all settle down after the rebuild, in some instances it takes a few thousand miles to sort itself out level's wise, there can be hard to shift small air pockets that still come to the surface, if both fans are working when these air bubbles surface its around the 100 dec C, so you will see some.

Gerald81

I do kinda agree and hope I am just being overly worried as well. Although a few thousand miles seems like a really long time to get the system cleared of air?


Tried purging the system again and few very large bubbles came up through the upper coolant reservoir tank by the turbo. It also bubbles when revving, but generally does not bubble when at idle although I occasionally spot a few small ones when the coolant gets really hot and steam is coming up. The shop tells me it's normal...


Anyway, after purging, there were no bubbles observed on the first few drives but on my most recent drive where I once boosted up to about 1 bar, I saw a couple of bubbles after that. Will continue to monitor over the next few drives...

Gerald81

An update:


I am still observing occasional bubbles some 800km later, with none to very negligible coolant loss. I wonder if it is still some residual air? The bubbles are quite random, they can appear after a drive without boost, and sometimes after a hard drive with lots of boost and high rpm, there are no bubbles. Again the bubbles always stop just before the fans kick in. The upper coolant reservoir continues to be full and unpressurised when cold. The engine consumes zero oil.


I also did some leakdown and compression tests, as well as data logging using a SSM3.


Leakdown tests at 500km:
#1: 13%
#2: 31%
#3: 15%
#4: 12%


Leakdown and compression tests at 1,000km:
#1: 13% / 106
#2: 24% / 111
#3: 23% / 110
#4: 19% / 110


From the datalogs, I noted that the SSM3 registered a few instances of misfires on the roughness monitor, usually at idle or low rpm. Over a 1 hour drive, the highest roughness count registered was one instance of "2" on cylinder #1 at idle. There was also an instance of "1" on all four cylinders, also at idle. And finally there was an instance of "1" on cylinder #1 and #4, at 2200rpm.


What do you guys make of the above? The leakdown test results in particular has me confused. I wonder if it is a matter of getting more miles on the engine.

Gerald81

Another update, some 1,500km later... engine still bubbles and consumes small amounts of coolant.


Leakdown and compression tests at 2,500km:
#1: 20% / 112
#2: 21% / 112
#3: 24% / 112
#4: 22% / 112


The only positive is that the leakdown numbers are getting closer, but still seems higher than I would expect. But despite the high numbers, I can't hear or see any air rushing out the intake, exhaust, or oil filler, nor did I observe any bubbles in the coolant.


Speaking of the bubbling, I think I've figured out why the bubbling in the overflow tank stops when the fans turn on. I realised the bubbles only appear when coolant is being released from the upper radiator cap, i.e. when coolant temperature is increasing, which increases pressure, which the cap relieves by releasing coolant into the overflow.


So if my coolant temp rises normally up to 92C on during a drive (from a cold start), bubbles will appear when coolant is released into the overflow. When the fans kick in at 92C, the bubbling stops. When the coolant temp drops to 86C and is allowed to rise up to 92C once again, no bubbles will appear this time, which I'm guessing is because the leftover volume of coolant in the system at 92C is still within the cap's threshold pressure, such that no additional coolant is being released on the 2nd time hitting 92C, and therefore no bubbles are being expelled together with the coolant.


I also note the bubbling appears independent of engine revs, i.e. if it is not bubbling (i.e. the system is not relieving pressure), no amount of revving will induce any bubbles.


I also tried adding a fluorescent dye to the coolant to see if there are any small leaks, with the help of a UV torch. I found a small leak where the coolant pipe that feeds the oil cooler meets a rubber hose, and had that fixed, hoping that was the cause of the bubbling. However, after fixing it and flushing the coolant, I'm still getting bubbles (when coolant is expelled) and small amounts of coolant loss (about 20ml per 100km travelled).


I should also note that there has always been an occasional gurgling sound coming from the engine after shut down and even after the car has been parked for hours, but after swapping the oil cooler pipe and hose, it seems this is reducing somewhat.


As before, there has been no signs of overheating, in fact the coolant temps tend to drop initially when boosting and driving in higher rpms.

Gerald81

Anyone able to take a stab at what's happening here? Is the pattern of bubbling consistent with a leaking gasket, or would a leaking gasket be expected to bubble all the time, without any dependency on whether the coolant pressure / temperature is rising and coolant is being released from the cap?

1509joe

iTrader: (2)

Take small pipe of header tank put long pipe on in its place allow car to warm up place pipe under windscreen washer drive on boost and see what happens.