Believe it or not, you are having the same problem as I have.
I have been filling up water for the pass weeks because of loosing water from the overflow tank. One thing I realized is it got worst boosting on the highway. Try constant boosting on the highway and after a while, stop on the shoulder and check for water leaking from the coolant tank. I got water overflowed and eventually got to the passenger side wheel.
The temperature will rise very quickly and overheat if you loose too much water. Be careful.

On thing I do not understand why Jeff said it's the oil cooler? Even if the oil pressure increase, it should not have an effect on the cooling system unless there is a leak somewhere. This is not good.
Another to think about is if there is a pinch on any cooling hose or pipe. That may cause pressure build up if it does not allow smooth flow.
However, I am very confident to say it's the HG. If not head warpage or head cracked.

I will be doing a heap swap in a few weeks, will keep you posted.

 

jw, that does sound pretty similar to my problem. My thing is the oil in the coolant deal. How is OIL in the COOLANT. Usually it's the other way around, right, w/ a HG going bad (COOLANT in the OIL). Anyways, Jeff said that the oil cooler being cracked or damaged may cause there to be oil in the coolant. And he said MAYBE under boost, since oil press also increases under boost that it may also be pressurizing my system. He's not too sure about that though. He said out of all the blown HG's he's seen 99.99999% of the time it results in coolant in the oil...NOT oil in the coolant (like in my case). But he said that he has seen about a dozen cases where a cracked or damaged oil cooler has caused there to be oil in the coolant. I'm just running out of ideas here. The car is running so damn strong that it just pisses me off b/c I know that whatever the problem is it is only going to get worse. I just wish I KNEW!!!!!! what the problem actually was! This is just so frustrating. I just really wish the DSM gods would smile on me (just once!)

 

Tell me about it. I have this problem a little before I get the MF1 turbo. I am also impatient to test this turbo out but loosing water and overheating is something I do not want to play with.
Anyway, it does make sense the oil pressure causing oil in your coolant. Good luck!

 

Here is a link to info on the oil cooler and how it lets oil get in the coolant w/ good pictures.
http://users.ticnet.com/randynet/oilcool.htm
Unless you had problems similar to what he had i doubt this is how the oil is getting in your coolant.

So I called Jeff at Turbotrix and he said it was probably due to my stock "shitty" cooling system and that somehow air was getting past the head gasket causing it to pressurize the system. So he said I should upgrade the cooling system and I may "cure" the problem (at least for now and possibly for a long timeto come).

If air is "somehow" getting past the head gasket a radiator and fans isn't going to cure it. It seems all your problems started after you flushed the cooling system. Did you use any type of radiator flush when you did it? I've heard that the flush can deteriorate gaskets. I know the compression is solid but it may be beneficial to do a leakdown test or have it done somewhere. If you are leaking it can pinpoint where the leak is. A small leak may not show up in a compression test but will under high boost and hard driving causing cooling system problems/pressurization. I would think if it could pressurize the cooling system it could push some oil in there too. Good luck with your car...hope this info helps.

 

Well, we can rule out the oil cooler. I did'nt even think about it when I talked to Jeff but I have an air cooled oil cooler on my car like the 90's have (mine must just be and early model 91). I'm leaning towards the HG now (even though I still can't figure out why it would have gone out on me!).
I "think" that when we topped off the coolant after it had pissed out the overflow we "possibly" did not wipe out the funnel that we had used to put the Amsoil in that same morning. SO, I am thinking (hoping!!!) that maybe it was just residual oil in the funnel that made it "look" like there was oil in the coolant. I am thinking that that may be what happened b/c Amsoil is so damn clear you can hardly see the shit! Looks like damn baby oil...feels like it too Oh well, I guess we'll see. I am going to do another flush on the system and then take it out and run it. I have a BIG!!!! feeling the pressurization problem is going to rear it's ugly head again, but am hoping that the oil issue will end up just having been a contaminated funnel. At least then I'll be "more" sure that it is the HG. Like I said, we'll see. If all goes like anticipated then I will probably try to find a shop around here that KNOWS how to do a leakdown test. Only other things I can think of would be a crack in the head or a crack in the block (both of which I REALLY!!!!!!!! hope are not the cause). I've just about had it with this car.......how can it run so DAMN strong and still have this underlying, potentially serious, problem???!!! Why can't I just catch a break with this damn thing!?

 

i had this problem about 2 years ago. i was on the highway going about 80-85mph (crusing). i looked down and the temp was almost pegged. that got the head gasket. but the reason the temp was hot is because the thermostat stuck closed and didnt open. for a couple of months before this, the head gasket was showing signs of failure by pressurizing the shit out of the coolant and making it shoot out like a whistle into the overflow. I put a metal gasket with ARP studs and it uses zero water. i dont even think the overflow tank really does any work! hope this helps:santa:

 

Did you check/change the obvious?
Thermostat (stuck closed/open)
Water pump
Fan(s)
Temp sensor for the fan