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Well first I have over heated 3 times in the last week, babied the car, got home and bled the coolant system. Today was the third time so I did the same babied the car turning the car off when it got hot then went a little further then stoped again. Get home let the car cool down fill up the radiator bleed the radiator let the car idol and just rev it in park and the coolant temp is fine. I take the car out boost a bit and who haw my coolant temp start increasing, get off the boost it seems to level out. Get on the boost temp increases again. Ok just so we are clear by bleeding the sys I took the radiator cap off and the little one on the pass side and filled up the radiator, next started the car with the heat on high and keept feeding the car coolent till it would not take anymore. Also I bought a new rad cap made no diffrence still overheated, and I pressure tested the rad cap and it held 13lb fine. The oil looks fine does not look like a milk shake, next the only time I see bubles in the coolent is when I have been reving my car for 30min and the coolent is steaming / boiling. So what I am thinking is that I have blown head gasket just when I boost and not when I am reving the car? What do you'all think??

I think you should look at the #3 spark plug wire boot and report back.

Looks perfect. I dont understand what the spark plug wire would have to do with a blown head gasket or an overheating problem?

I think you have a small leak in the headgasket. That would be the cause of the small bits of bubbles in the overflow tank. Maybe just some Subaru conditioner and good to go?

I could give that a try, but that only seems to be a temporary fix? I have been iching to put on these 2.5 dohc heads I have. But I just want to make sure that I have a blown head gasket before doing to much more.

I've seen a couple Subaru engines that had coolant/oil leaking around #3. The spark plug boots had oil and nasty stuff that looks like old milk on them.
I think I've seen discussion about this being because of the cooling system design.

Oh ok that makes sense, also I think I have confermed the blown head gasket do to that I have oil residu in coolant run off tank.

what about a compression test to check the engine?

or a vacuum gauge.

Vacum is fine right around 20 at idol, also if I have blown head gasket only under boost how would a compression test tell me anything. But it doesnt matter the heads are pretty much of.

I would think that a head gasket causing this much repeated overheating would show white smoke out the tail pipe?

subytech wrote:I would think that a head gasket causing this much repeated overheating would show white smoke out the tail pipe?

Yes, in most cases.

If I were you, I would retorque the heads and make sure they are tight. I had this problem and thought it was a headgasket though there was no white smoke. Turned out the head was a little looser than it should have been. After reading your post closer, you seem to have the exact symptoms mine had. After driving it for a while, it would blow all the coolant out. If under heavy boost, It was only a matter of seconds to pressurize the crap outta it.

These are stock head gaskets with over 178,xxx on them so its about time, and I also have some oil in my coolant, so this sounds like a great time to do a dohc head swap , and the car is already half way torn apart.

waldo320 wrote:Vacum is fine right around 20 at idol, also if I have blown head gasket only under boost how would a compression test tell me anything. But it doesnt matter the heads are pretty much of.

if a head gasket is blown than it is blown, not some of the time but all of the time.

a compression test would tell you that.

seeing that it is all apart, it is a moot point.

bet it is something other than a head gasket.

What else could it be? Where else would the oil and coolant some how mix?

cracked head, cracked block, heads not torqued correctly.

Well I am switching heads, also I noticed when taking the head bolts out that some of them were rusted and dry while only few actually still had the lube on them. Is there any way I can check to see if there are cracks in the block?

you have to either buy block dye from like napa or you can send it out and have it magnafluxed. Obviously the dye would be much cheaper

how goes the fix?

Right now I have everything I need to do the 2.5 swap, and the heads are at the shop getting resurfaced I guess thats what you get when you buy used heads, but other than that everything is going good. After talking a look at the head gasket it did not look like it was blown, so maybe it was a loose head bolt since I have been boosting. I also talked with a subby tech who said not to do that stupid head bolt tighting sequence like the 90 back 180 back he said just go in incraments to the final torque ratio. Also after taling with a few DSM friends they say they have blown numerous head gaskets with out any diffrence in a compresion check. The reason for this would be due the fact that 10-15psi on the head gasket at boost and not on a compression check thus only showing the blown head gasket at boost. But my friend runs 30 psi on a massive dsm 62-1 and blows head gasket once a weeks, and look at the gasket after taking it off it has the begings of a blown water jacket, and same goes with his tsi that if we do a compression test it would have been the same with a good gasket or a slightly blown gasket. The exception would be if the gasket is completely blown than you would have a compresion issue, and water oil mix problem