mutant_dan Posted January 14, 2005 Share Posted January 14, 2005 Here is a head gasket solution I picked up from another board that I thought might be appropriate to post here... ___________________________________ From: Gene Goldenfeld <genegold@h... Date: Thu Jan 13, 2005 8:06 pm Subject: Re: [outback] Head Gasket failure info on Subaruvanagon mailing list dyerlytle wrote: There is an interesting discussion about head gasket failure in 2.5L Subaru engines over on the subaruvanagon mailing list. (This is a mailing list for people with VW Vanagons who have swapped in a Subaru engine to replace the VW water boxer.) Indeed. In the interest of getting the discussion over here (and providing me a copy to archive), I've copied Al Wick's posts on head gasket failure from the Subaruvanagon group. I let him know. Gene ------------- I was in unusual situation where I was able to find the head warp "gasket fail" problem before the dealers were getting any failures. Many years ago I adapted a new 2.5 (10k miles) to my airplane. I have sensors galore on the plane, so when the head first started leaking, I was able to look at the data on my laptop and see that the head leaked pressure to coolant system 3 seconds after I hit full throttle. It then dissipated 5 seconds later. I really learned a lot and deliberately operated at full throttle for long periods (hour or two). All the time logging the pressures and temps every few milliseconds. So here's the deal. All failures are caused by air in the cooling system. No air, no problem. If you have air bubble AND you operate at high throttle settings, the head will warp. It takes a long time to show up. So if there was trapped air 6 months ago, then you might now start to see discolored coolant, overheating. Or it might only occur climbing a hill in hot weather. Only the 2.5 has this marginal condition. All other Subaru's bullet proof. My flying partner makes a living replacing gaskets on 2.5's these days. Number one repair item. It appears that the 2.5 has an area at center of block/head interface which doesn't have enough coolant flow. When a bubble passes by, it boils locally. This eventually causes head to warp, gasket to give out. Subaru has tried 3 different style gaskets, even adding coolant conditioner to improve heat transfer. Still a problem. But absolutely all failures caused by trapped air in system. All models of 2.5 liter the same. The solution is very simple. Just drill and tap your coolant crossover pipe and add a fitting that allows air to leave engine and rise to your swirl pot. You will never have a problem. I operate my engine full throttle for hours at a time. Fabulous engine. -al wick -------------- I got a couple other private messages regarding the same. I'll try to clarify... The crossover tube is the aluminum coolant tube that lives under the intake manifold. It's rectangular in shape and the main coolant hose attaches to one end of it. It's the one everyone reverses. I'm unable to say there is a "best place" to add a fitting to the tube. Likely it does not matter where you place the fitting. Just somewhere in the top of this tube. The fitting needs to be on this cross over tube because this is the highest point in the ENGINE cooling system. Your goal is to purge any air that happens to be in the engine. This is different than purging air from your radiator or from your heater core. Air in the engine causes head warp. Air in other components just reduce their efficiency. We imagine that air flows with the moving coolant, but actually it only does to small degree. Drill and tap this tube. Install a fitting, and run hose from that fitting to your swirl pot. No dips in hose, it must gradually rise to swirl pot. As long as the swirl pot is above the engine it will automatically purge all air from the engine. This results in a "robust" cooling design. Robust meaning it handles unusual conditions. If your brother in law borrows your vehicle, blows a hose, and doesn't realize he needs to bleed air, no problem. Because your system automatically purges all air from engine. Quote Link to comment Share on other sites More sharing options...
outback_97 Posted January 14, 2005 Share Posted January 14, 2005 mutant_dan: Thanks for posting this, it is very interesting. Are there any differences in how these engines are used in a plane that would change how this is implemented in a car? Do you have any photos that you could add to it? That would be most helpful. I'll consider adding this to my page with links to information regarding the head gasket issue: http://users.sisna.com/ignatius/subaru/headgasket.html Thanks again! Steve Quote Link to comment Share on other sites More sharing options...
mutant_dan Posted January 14, 2005 Author Share Posted January 14, 2005 I just picked this advice up from another forum. I know that the airplane application would have the engine running full throttle for extended periods of time compaired to normal highway driving. Here is a link to the Aircraft conversion to Subaru engine. http://www.maddyhome.com/canardpages/pages/alwick/engine.html In the link he discusses running the bleeder tube to the overflow tank. I think since he posted this on his web page, he now runs it to the swirl pot (whatever that is). Here is a more recent reply concerning running the bleeder to the overflow tank: ----------- 1st.Only air in the block and higher power settings will cause the head warpage. Every single occurrence (per my mechanic source) is traced back to the owner changing the coolant and not knowing how to purge the air. 2nd. It's a design oversight by Subaru. Due to sloping hood and vehicle height, the air in block can't move to radiator. It stays in block. The radiator isn't mounted high enough relative to engine. There are a number of other manufacturers that have this problem, without the head warping. They just overheat until customer takes it to dealer and he burps it. Some place a bleed valve at the engine block. Just open valve until water starts coming out, close it. True, you would not want to run the tube to overflow. Your cooling system would then no longer be under 7 psi it normally is during operation. You just want the air in block to move higher and out of the coolant flow. My bleed line is the most robust approach, but you could also just make sure you loosen hose clamp until fluid comes out. That's what dealer does. ---------------------------------------- Meanwhile, my Outback is in the shop for some transmission work. I am going to present this info to my mechanic later today to see what he thinks. He specializes in subaru and I am very interested in his take. If we go ahead and make the modification I will be sure to take pictures. Quote Link to comment Share on other sites More sharing options...
Gnuman Posted January 14, 2005 Share Posted January 14, 2005 Please define "Swirl Pot" it is a tern I have not heard before. . . Welcome to the board! What part of Northern Cal are you in? There is a Meet&Greet tomorrow at 10:00 AM in El Cerrito, CA (SF Bay Area). You can get more details on this by checking the events thread at the top of the page, or sending me a PM. Quote Link to comment Share on other sites More sharing options...
mutant_dan Posted January 14, 2005 Author Share Posted January 14, 2005 Please define "Swirl Pot" it is a tern I have not heard before. . .Welcome to the board! What part of Northern Cal are you in? There is a Meet&Greet tomorrow at 10:00 AM in El Cerrito, CA (SF Bay Area). You can get more details on this by checking the events thread at the top of the page, or sending me a PM. I am in Sacramento and would love to come the the meet and greet but the wife has to go to a funeral tomorrow and I have the kids. Their schedule dictates that I drive them all over the place and wait while they play soccer etc.... Anyway, the Swirl Pot is a mystery to me as well. It might be a British term or aircraft thing. I have e-mailed Al Wick for more details.. Quote Link to comment Share on other sites More sharing options...
Gnuman Posted January 14, 2005 Share Posted January 14, 2005 I am in Sacramento and would love to come the the meet and greet but the wife has to go to a funeral tomorrow and I have the kids. Their schedule dictates that I drive them all over the place and wait while they play soccer etc.... Anyway, the Swirl Pot is a mystery to me as well. It might be a British term or aircraft thing. I have e-mailed Al Wick for more details.. Thanks for looking for the info. If you want to meet at annother time, I'm in Oakley, just at the other end of 160. . . . PM me for contact info if you are interested. . . Quote Link to comment Share on other sites More sharing options...
outback_97 Posted January 14, 2005 Share Posted January 14, 2005 Googling for info on swirl pot... http://www.sbdev.co.uk/Fuel_Systems/Fuel_Filters/Fuel_Filters.htm Seems to go inline with the fuel system to stop "fuel surge" in this application. Still don't really know what that means. Here's a better one: http://www.beardmorebros.co.uk/website%20pages/new_project_engine_page7.htm The fifth picture down on the RHS is good, and a little explanation. Does seem to be primarily on .uk websites, so a British term. The point about all occurrences happening after recent coolant replacement is interesting. I'm sure there would be people who object to that on theotherskip's list of people who have experienced HG failure, but then again air could exist in the system for a long time and not cause a problem until heavy loads are put on the engine on a long uphill climb, etc. Steve Quote Link to comment Share on other sites More sharing options...
mutant_dan Posted January 14, 2005 Author Share Posted January 14, 2005 Is there a difference between a coolant reservior and coolant overflow? I am assuming they are the same thing! Here is the only swirl pot reference I have found so far... http://www.msport.co.uk/acatalog/bailey_swirl_pots.html Looks like the coolant would pass through while air would vent out the valve on the top. It would have to maintain pressure while doing this.. Quote Link to comment Share on other sites More sharing options...
Skip Posted January 14, 2005 Share Posted January 14, 2005 A coolant reservoir is much different than the overflow catch bottle we have. The main difference is that the reservoir is pressurized with the coolant system and is mounted higher than the radiator. My Jag XJ 6 had one as do some Bimmers and Mercs. Some old gen turbo Subaru owners have adapted them to their car primarily to increase the capacity of the system. Remember we blow head gaskets quite frequently also in our 1.8 L engines (both OHC and OHV models) The link to swirl pots for sale says "Bailey Swirl Pots Designed to be used in conjunction with a Bailey alloy header tank, a Bailey swirl pot fits into the top radiator hose and removes air bubbles and hence hot spots caused by cavitation." And interestingly enough are offered only for turbo cars. The missing entity is the capture tank that the small hose barb goes to. It would be similar to a coolant resevior. Quote Link to comment Share on other sites More sharing options...
Snowman Posted January 14, 2005 Share Posted January 14, 2005 So, rather than retrofitting a "swirl pot", would it be effective to tap into the crossover pipe, install a bleader fitting of some sort, and periodically bleed off any bubbles? Quote Link to comment Share on other sites More sharing options...
99obw Posted January 14, 2005 Share Posted January 14, 2005 This theory about trapped air is BS for a couple of reasons: 1. Many head gaskets have failed without the cooling system ever being touched by anyone but the factory or a dealer. Are Subaru and their dealers incapable of getting all of the air out? 2. My heads were straight as an arrow after the gaskets failed. Clearly not a gasket failure due to warped heads. The gasket failed at the bottom of the cylinder, not near the top where trapped air might be. I put the original heads back on with no machining, filled the cooling system with no fancy bleeder, and almost 60k later everything is hunky-dory. Proving anything beyond a shadow of a doubt is impossible, and proving the nature of complex problems such as the Phase I EJ25 head gasket failures requires a huge sample size of data. Does this person have that? No. Does Subaru? Probably. I'm not saying that an air bleeder is a bad idea, I have seen and used them on other makes and they are great. What I am saying is that trapped air does not fully explain the HG failures on these engines. I think the answer is closer to open-deck design, poor gasket design, thermal cycles. Do I think that air in the cooling system can contribute to HG failures, yes. Quote Link to comment Share on other sites More sharing options...
blitz Posted January 14, 2005 Share Posted January 14, 2005 It's deja-vu all over again. A post of mine 13 months ago: http://www.ultimatesubaru.org/forum/showthread.php?p=69951#post69951 Quote Link to comment Share on other sites More sharing options...
Setright Posted January 15, 2005 Share Posted January 15, 2005 I would just like to butt in and say that I agree with 99obw. Quote Link to comment Share on other sites More sharing options...
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