tacoma5050

If you go to this link http://www.maddyhome.com/canardpages/pages/alwick/Ej%2025%20engine.html and scroll down to almost the bottom, you will read about "Trapped air in coolant in 2.5L engines". I will include text at end here. The article sez Subaru has since changed their cooling system design. Does anyone know when this design went into prodution? I called a subi dealer he was vague, he guessed late 2004. He said you will know it is the later 04 engine by not seeing the fuel filter near the back drivers side firewall. Can any one comfirm if the 2.5's were redesigned to address trapped air in coolant and when did that mod go into production? Trapped air in coolant: The 2.5 liter Subaru is sensitive to air bubbles in the coolant. It only takes about 1/2 cup of air in the engine block to cause heat transfer problems. This engine is particularly sensitive. Trapped air is easily 10 times more significant than any other cooling parameter. It's pretty conclusive that trapped air causes local boiling in the block. This affects the entire cooling sys and rapidly degrades heat transfer. ..snip.. All of these problems were caused by a small quantity of air trapped in the block at the highest point. Eventually, I added a small diameter tube to this block high point. This allows all the air to exit the block and move to the small reservoir under the radiator cap. Unfortunately, all of my deliberate overheating caused the heads to warp. This allowed compression gasses to flow into the cooling sys during high power settings. My computer detected this problem. 3 seconds after applying full throttle, the coolant pressure would rise to 24 psi. It would then slowly drop 5 seconds later. So trapped air causes head warp, which causes air to enter the cooling system. It was pretty amusing that at the same time I discovered this entrained air sensitivity in the 2.5 engine, so too did the auto dealers. Head warp caused by customers changing their coolant is now the number one warranty item with this engine. All caused by an engine block that was not plumbed to dynamically remove air from the high point. Subaru has since changed their cooling system design. It's essential that the 2.5 liter coolant crossover tube atop the engine be drilled and tapped. This allows user to add a small tube from there to the coolant reservoir. Any air inside the engine block then automatically purges. Proof of effective purging is that I can now drain all the coolant from the entire sys, then refill. Every drop can be refilled without hesitation. Before adding this air purge, I would end up with a few cups of fluid that I could not get back in to the system. Also, I now can't get the engine to gurgle after a hot shut down.

And there within lies another question: If the new gasket design REALLY fixes the problem, why then is SOA adding the conditioner to cars('03,'04...) with the new gasket? Who wants the equivilant of Stop-Leak running thru their radiator and heater core, if there is supposidly no need for it? I called SOA and they said the conditoner is even going in new 2.5L cars coming off the line today. I called a Subaru dealer and asked the service guy: If I were to have you flush a 03 outback cooling system, would you add the conditioner when you refilled it, he said yes, it is required by SOA. I am starting to wonder about buying a 2.5L Subaru, yeah any car can blow a HG and they do, but who wants to buy a brand new car with Stop-Leak in it from the factory? I normaly associate Stop-Leak type products as those you use when a car is on it's last legs and you are just trying to cheaply get another 10k miles out of it before you junk it. So you don't care if it causes other problems.

As you all must know by now, in FEB 2004 SOA announced a campaign that addressed the HG issue in the 2.5 engines. That campaige only includes the 2.5L engine of years ‘99 – ‘02 and not all 2.5 engines in that year range are covered. I am looking to buy an '01 to '03 outback, this will be my first Subaru, and this whole HG thing has me very nervous. I know this topic has probably been beaten like a dead horse here, but I have a few questions that I have not been able to find answers to before I buy: 1. I was all set to possibly buy an 03 Outback assuming that by 03 SOA must have addressed the HG issue in their new cars. But I have heard some owners of 03's have experienced HG problems. At what year is it safe to buy a 2.5L engine Subaru and not have to worry about the HG issue: 03, 04, and 05? 2. What did SOA do to eliminate the HG issue: newly designed HG? , new HG manufacturer? , new HG sealant?, new install procedure? , etc. Basically what was the original problem and how was it redesigned so it will not happen any more? 3. If your Subaru is one in the HG campaign, you are advised to put in a 'special conditioner'. What is that conditioner? What's in it? How does it stop or prevent the leaking? If the conditioner can plug or clog small leaking passages, why won't it clog or reduce the flow through small passages in the radiator or engine? (In regards to question 3: I just got off the phone with SOA. They told me that starting in late 02 and in all 03's and up, SOA started adding the conditioner(StopLeak I guess)and put a newly designed HG in all the 2.5L engines. So if you have a 2003 or newer, you supposidly have the conditioner. (I hope this stuff does not affect the radiator) Anyone out there with an '03 or newer who can look at their owners manual(or maybe a sticker somewhere) and tell me if the conditioner is in fact required on coolant changes. ) 4. If an engine is included in the HG campaign and SOA authorizes the HG to be replaced, when the new HG is put in are you still required to use the special additive? 5. I found a 02 outback for sale, it has a HG that leaks externally. I called SOA, they said that cars VIN is not part of the campaign and is not covered. How is that? Did this happen to many owners with the HG issue? Is this a way for SOA to say they are doing something for their customers, but in most cases they are not? 6. What percentage of the 2.5L phase II engines had the HG problem? Do some years have a worst percentage than others? If yes, which? 7. Does anyone know the VIN ranges that are included in the SOA HG campaign?