rottenweiler Posted April 21, 2012 Share Posted April 21, 2012 New member here with question. My son, with Impreza 2.5 just replaced his head gaskets w/felpro mls, etc. He only had a very, very minor coolant leak prior to replacing the gaskets. No overheating, no oil in coolant, no misfiring, and excellent compression in all four cylinders, etc. He decided to replace the gaskets so that he would not have any future problems. He reassembled and now has an overheating problem, but only after putting the transmission into gear. It will sit and idle for any length of time, even with fairly high rpm's, with no issues, but as soon as he engages the tranny, it begins to heat up. He was and is very meticulous in teardown and reassembly. Has checked, rechecked all fluids, lines, and everything else he can think of. Any help would be appreciated. I can only provide moral support, as I am a small-block chevy guy. Thanks. PRB Link to comment Share on other sites More sharing options...
mattocs Posted April 21, 2012 Share Posted April 21, 2012 Was the cooling system burped properly? Link to comment Share on other sites More sharing options...
Fairtax4me Posted April 21, 2012 Share Posted April 21, 2012 What kind of thermostat did he put in it? Felpro head gaskets are often frowned upon by the Subaru community for use in the 2.5 engines. They are known to fail immediately or within a very short time after installing. Dealer seems to be the only source for reliable gaskets. Also it's is vitally important that the heads be resurfaced before installing new gaskets. Link to comment Share on other sites More sharing options...
rottenweiler Posted April 21, 2012 Author Share Posted April 21, 2012 Thanks guys. He has filled and burped several times and does not believe that to be the problem. The Felpro gaskets may be my fault, because I recommended them to him. I use them exclusively in my engines. I can't think they are the problem, but you guys know better than me. Maybe I had better go in and do a leakdown test and try to see what is going on. Thank you for the suggestions. It may be several days before we find a solution. I will let everyone know how it is resolved. PRB Link to comment Share on other sites More sharing options...
Fairtax4me Posted April 21, 2012 Share Posted April 21, 2012 I'm really only going by what I've read here. The newer Felpro head gaskets are of MLS design that everyone recommends using, but I haven't read anything good about Felpro gaskets in the 2.5 engines. For the older 2.2 the Felpro gasket is the exact same part as what you would buy at a dealer, even has the FHI logo stamped in it. I've used Felpro gaskets on plenty of engines and have had mixed results. But I don't think I've ever had a set of their head gaskets go bad as fast as some of the claims I've read. I don't think they should work any differently than a dealer gasket as long as the surfaces are prepped properly. But they do have a bad rap among the more experienced Subaru gurus here, I think I'll stick to their advice rather than try to find out the hard way for once. :-p Thermostat on these is picky and I've seen that first hand. The cheapo replacements from the pars stores just don;t work that well. You have to get one from a dealer or get the Exactstat version from Stant. There's a part number in the sticky at the top of the forum page. Highly recommended by people who work on these cars all the time. Link to comment Share on other sites More sharing options...
johnceggleston Posted April 22, 2012 Share Posted April 22, 2012 it could be the gaskets but assume it isn't. as fair tax said use a ''subaru'' t-stat and then fill and burp correctly. i think you will be pleasantly surprised. assuming he didn't make a mistake during the install, torque sequence, clean head surface or what ever. but idling fine and over heating when driving sounds like a cooling issue, not a head gasket issue, to me any way. the 90s 2.5 L engines would leak internally and would often idle and drive around town fine, but over heat after 20 - 30 minutes on the hiway. this is / was especially true when the gasket leak was new. but overheating around town would have to be a pretty severe gasket leak / problem, i think. good luck. Link to comment Share on other sites More sharing options...
ccrinc Posted April 22, 2012 Share Posted April 22, 2012 Just a thought...is he absolutely, positively sure that the transmission cooling line is routed properly? If it's ok until he puts in in gear, sounds like the transmission cooler is involved somehow. Emily Link to comment Share on other sites More sharing options...
rottenweiler Posted April 22, 2012 Author Share Posted April 22, 2012 I really appreciate every reply. I will be going in this afternoon to check on his progress and will let you know. I too believe that it is cooling related. PRB Link to comment Share on other sites More sharing options...
hankosolder2 Posted April 22, 2012 Share Posted April 22, 2012 One key thing you're failing to mention here is the year of the Impreza 2.5. It could be a phase I (two camshafts per head) or a Phase II (single camshaft per head) engine-- totally different kettles of fish head-gasket wise. Link to comment Share on other sites More sharing options...
rottenweiler Posted April 22, 2012 Author Share Posted April 22, 2012 Yeah, I should know better. It is a 1992 Impreza RS 2.5. I am in at my son's house now, but he is working today. I found the box from his new thermostat and it is a Stant 14147. Looks like the wrong one?? I will check around the parts stores in the area, but doubt they have the 48457. Maybe have to order one. PRB Link to comment Share on other sites More sharing options...
bratman18 Posted April 22, 2012 Share Posted April 22, 2012 They only made the RS 2.5 Impreza from 98-03 I believe. What style is the motor? DOHC or SOHC? Link to comment Share on other sites More sharing options...
rottenweiler Posted April 23, 2012 Author Share Posted April 23, 2012 Sorry, it is a 2002. The local parts stores do not carry this xstat thermo. but he is ordering one. Also, he added more coolant and drove it on the express way with no issues, but then turned around and increased his speed to ?? and it began to heat up some. He will be double checking the coolant again, because it does seem to be taking some after each heat/cool cycle. I don't think he has it burped properly yet. Time will tell. Again, I will let everyone know the final solution. PRB Link to comment Share on other sites More sharing options...
Fairtax4me Posted April 23, 2012 Share Posted April 23, 2012 Did he fill the engine through the upper radiator hose? The only good way to refill the coolant is to fill the engine through the upper hose before filling the radiator. Or after, either way, coolant doesn't flow from the radiator into the engine very well if you just fill the radiator. You end up with about half the amount of coolant in the system that there should be. When I fill, I expect to put in about a gallon and a half. If it takes less than that I think somethings wrong. Link to comment Share on other sites More sharing options...
ShawnW Posted April 24, 2012 Share Posted April 24, 2012 Or use a spill free funnel and let the car idle until the thermostat opens, radiator fans cycle on and off and heat is coming out of the heater ducts when you turn the fan switch on. (otherwise idle it with the fan off or it takes an hour to cycle). Filling thru the upper does help but the funnel is the only sure shot way. Even using a vacuum filler doesn't work. I own one. I wish it worked better. Its absolutely the thermostat in this case though. I would bet on it. Link to comment Share on other sites More sharing options...
rottenweiler Posted April 25, 2012 Author Share Posted April 25, 2012 Update. He installed the new correct thermo., but not much change. Runs fine around town and up to 55/60 with no problems or overheating. Drove it to work today 30 miles on expressway, no problems. Coming home it overheated . If he turns the heater on, the temperature drops back very quickly. He has also flushed the radiator. he is almost ready to pull the heads again and change out the head gaskets. PRB Link to comment Share on other sites More sharing options...
johnceggleston Posted April 25, 2012 Share Posted April 25, 2012 typically, these gasket leak internally and turning on the heat will not change the over heat condition. the over heat is due to exhaust gas in the cooling system and not enough coolant, or not enough coolant circulating. an external leak would also eventually lead to low coolant and over heating. but with both gasket leaks, low coolant will eventually lead to no coolant circulating and no heat from the heater, usually. imho, if turning on the heat reduces the overheat then there is a ''cooling issue'', not a gasket issue, but i'm no expert. the coolant on these engine moves through the heater core all the time, turning on the heat only cools it more, not circulate it more. back flush the cooling system? replace the rad? i don't know but pulling heads should be last on the list. was the rad flushed when the gaskets were done? was any type of ''stop leak'' ever added to this engine? stop leak in the cooling system that is / was not flushed out when the system was drained will / can / could clog up stuff. the cooling system should be flushed when drained before the ''stop leak'' has time to ''dry and glog'' any open passages used for cooling. Link to comment Share on other sites More sharing options...
uniberp Posted April 25, 2012 Share Posted April 25, 2012 are you sure the fans are plugged in and working? Link to comment Share on other sites More sharing options...
bratman18 Posted April 26, 2012 Share Posted April 26, 2012 The SOHC 2.5 that came in his 2002 RS lean externally. It was the DOHC 2.5's that leaked internally. typically, these gasket leak internally and turning on the heat will not change the over heat condition. the over heat is due to exhaust gas in the cooling system and not enough coolant, or not enough coolant circulating. an external leak would also eventually lead to low coolant and over heating. but with both gasket leaks, low coolant will eventually lead to no coolant circulating and no heat from the heater, usually. imho, if turning on the heat reduces the overheat then there is a ''cooling issue'', not a gasket issue, but i'm no expert. the coolant on these engine moves through the heater core all the time, turning on the heat only cools it more, not circulate it more. back flush the cooling system? replace the rad? i don't know but pulling heads should be last on the list. was the rad flushed when the gaskets were done? was any type of ''stop leak'' ever added to this engine? stop leak in the cooling system that is / was not flushed out when the system was drained will / can / could clog up stuff. the cooling system should be flushed when drained before the ''stop leak'' has time to ''dry and glog'' any open passages used for cooling. Link to comment Share on other sites More sharing options...
rottenweiler Posted April 29, 2012 Author Share Posted April 29, 2012 Okay, last update for awhile. Went in today and he has pulled the engine, disassembled both heads, and they are going to the machinist. He also will be purchasing all gaskets and sealers from a Subaru dealer. After he gets everything back together and in the car, I will let everyone know if this solves his problems. If not, I think he will be in the market for a high mileage Yugo. I appreciate all of the replies and suggestions. Thank you. PRB Link to comment Share on other sites More sharing options...
rottenweiler Posted May 20, 2012 Author Share Posted May 20, 2012 As I promised, here is an update on my son's Impreza. After getting both heads milled and reinstalling everything it is running great and seems sealed tight. The problem was owner/mechanic error. I have made many myself, so it must be hereditary. After replacing the first head gasket, which had a minor leak, the new one continued to leak a tiny amount. He purchased a bottle of leak detector and radiator sealant. Yep, the overheating was caused by the leak sealant. It had formed almost a solid block of all tubes across the top of the radiator core. He ended up reverse flushing and using strong agitation, large hunks of solid sealant kept coming out of the radiator. Lesson learned! He now considers himself a expert in r&r of the 2.5 Again, thanks for the help and suggestions. A couple of you hit it on the head. Pun intended. Richard. Link to comment Share on other sites More sharing options...
forester2002s Posted May 20, 2012 Share Posted May 20, 2012 Yep, the overheating was caused by the leak sealant. Is the same stuff that Subaru recommends? The 'Holts' sealant? Link to comment Share on other sites More sharing options...
Gloyale Posted May 20, 2012 Share Posted May 20, 2012 Heads should have been machined the first time. Link to comment Share on other sites More sharing options...
Suzam Posted May 20, 2012 Share Posted May 20, 2012 The best lessons are learned that way. Good job on getting the problem solved. Bet that engine will service him for a long time now. Link to comment Share on other sites More sharing options...
rottenweiler Posted May 22, 2012 Author Share Posted May 22, 2012 Don't know the name of the radiator sealant, but it was NOT Subaru's. Some junk from Auto Zone. Yes, the heads should have been milled the first time, about 5 thou. was taken off. On this last go-round he used all of Subaru's gasket sealers and turbo head gaskets. Richard. Link to comment Share on other sites More sharing options...
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