June 17, 20178 yr A couple of days ago I picked up a 1998 Forester, the main issue I am concerned with is a knocking sound in the engine. I think the knocking sound is a lifter. It is a small hammer tapping type sound. If the car is idling in neutral and I increase the rpm's a bit, the tapping normally stops. But if I am driving around town, just normal easy driving, the tapping stays. Under load 20-25 on a steep hill,level ground 20-35+, going downhill, etc, it seems to stay pretty much the same other than the tempo changing with rpm's. I keep thinking it sounds like a sticky lifter. A rod bearing should get louder under load? and a wrist pin quieter under load? If I remembercorrectly. I have looked up videos and they show the timing belt tensioner gone bad making a rattle, but this is not a rattle, it is a definite tapping that is in tune with the rpm's of the engine. The engine has 246,000 miles on it. I am considering pulling it and rebuilding it. Any opinions appreciated, Thanks.
June 17, 20178 yr Sounds like it's just a "lifter tick." Try adding a bottle of MMO (Marvel Mystery Oil) to the crankcase and driving like normal for a few days. Then, if the tick goes away, change the oil & filter .
June 17, 20178 yr On that engine Piston slap is an order of magnitude more common than other possibilities. Timing tensioners can sound nearly identical to rod knock. The ones I've seen fail knock, not rattle. Have you use a stethoscope yet to identify bouaento left, right, front, rear, or center?
June 17, 20178 yr It IS NOT a lifter since a 98 Forester doesn't have hydraulic lifters unless someone swapped in an older 2.2 engine or a 96 2.5 engine. Could be piston slap, could be timing belt tensioner, could be rod bearing. Don't attempt a rebuild. It's not for a DIY'er. Get another engine or bring it to me if you really want a rebuild. GD
June 17, 20178 yr Also make sure it's not something else or simple like heat shields or a pulley bearing or belt issue? How positive are you it's related to the block? Have you popped the hood? I've seen the lower bellhousing plates being belt cause tapping that varies as well as the teeth in the TC hit it like spokes in a tire. Tapping stops and tapping not being heard can be interchangeable so that's not an easy online diagnostic aid.
June 17, 20178 yr Author Sounds like it's just a "lifter tick." Try adding a bottle of MMO (Marvel Mystery Oil) to the crankcase and driving like normal for a few days. Then, if the tick goes away, change the oil & filter . I was planning on doing oil change, the oil looks pretty clean but I have no clue what they put in it. I will give the MMO a shot, I have used it in the past.
June 17, 20178 yr Author On that engine Piston slap is an order of magnitude more common than other possibilities. Timing tensioners can sound nearly identical to rod knock. The ones I've seen fail knock, not rattle. Have you use a stethoscope yet to identify bouaento left, right, front, rear, or center? I know what piston slap sounds like, this is not piston slap. I was watching some videos on the timing belt tensioners and they sounded nothing like this to me. I do not have a stethoscope, I will have to pick one up.
June 17, 20178 yr You can use any piece of hose, like 1/2" diameter. Also, a long night screwsriver, touch to block etc, handle to ear area.
June 17, 20178 yr Author It IS NOT a lifter since a 98 Forester doesn't have hydraulic lifters unless someone swapped in an older 2.2 engine or a 96 2.5 engine. Could be piston slap, could be timing belt tensioner, could be rod bearing. Don't attempt a rebuild. It's not for a DIY'er. Get another engine or bring it to me if you really want a rebuild. GD Ok, so they have a solid valve train. Single overhead cam I believe so it should be a tappet system, I can do a valve adjust and see if that helps. I had a tappet fall out in a motorcycle one time and it sounded identical to this noise except it would never stop when increasing rpm's from idle like this does. Personally I think the sound is too consistent to be a tensioner, though I can check that easy enough as well to rule it out. A rod bearing should get louder with increased rpm's, this really does not change other than in tempo. If it gets rebuilt I will do the rebuild myself, I am capable of the job and have the tools for it. Thanks for the re-build offer, but I just can not afford to have the work done by a shop. Any work that gets done will have to be done by me. My Harley is currently all torn down in my garage for the same reason. I will start checking things out soon and see what I come up with. I might make a video of it as well. Can we post video here?
June 17, 20178 yr Tapping sounds can usually be tracked down with a stethoscope. At least narrow it down to one side of the engine or the other. Front/rear, or left/right. It would also be helpful to know exactly which engine you have. Like GD said it could have been swapped at some point.
June 17, 20178 yr Author Also make sure it's not something else or simple like heat shields or a pulley bearing or belt issue? How positive are you it's related to the block? Have you popped the hood? I've seen the lower bellhousing plates being belt cause tapping that varies as well as the teeth in the TC hit it like spokes in a tire. Tapping stops and tapping not being heard can be interchangeable so that's not an easy online diagnostic aid. I plan to get it up on the ramps this weekend, I will look for those things as well. Yes, I have had the hood up? The only other Subaru's I have owned were a 77 wagon and a Justy with a 3 cyl engine. Just not familiar with the quirks of these engines. Thank you for the tips.
June 17, 20178 yr Author Tapping sounds can usually be tracked down with a stethoscope. At least narrow it down to one side of the engine or the other. Front/rear, or left/right. It would also be helpful to know exactly which engine you have. Like GD said it could have been swapped at some point. I can pick up a stethoscope. It sounds like it is coming from the left bank (driver side). I am not sure how to ID the engine to know if it was ever swapped, though I do not think so. Ok, time for me to go to bed, I have been up all night with a bad sinus headache, I need to try and sleep. Thanks for the help guys.
June 17, 20178 yr Author I just went out and looked at the engine, looks to be a DOHC engine, so I expect it is a shim setup to adjust the valves? looks pretty tight to do that with the engine in the car as well. Looks like I would have to post a link to a video stored off site? Anyway, off to bed now.
June 17, 20178 yr One of my high school auto mechanics teachers told me a story about a guy bringing an old Rambler into a shop he used to work at. The guy was a regular customer and told the shop owner, "Well, my old car's got a rod knocking." Three of the mechanics walked out to the car, the guy started it up, and, "Knock, knock, knock." "Yep, that's a rod alright," said one of them. And they all agreed, without even opening the hood. The guy sold the Rambler to the shop owner for parts, and they parked it out back. Six months later, one of the mechanics went out to get a part off the engine. When he started poking around, he noticed the generator had come loose. He then noticed a chunk of rubber missing from the v-belt... They called the customer to apologize, and ask if he wanted his car back. He told them he had a new car now and everything was fine, because he said "I'm the one who told you it had a rod knocking!"
June 18, 20178 yr Head rebuilds are easy. GD meant rebuilding the block probabiy would be problematic and limited shelf life. Another option is to buy a used head for $50-$100, resurface and swap it out.
June 18, 20178 yr The solid lifter valve trains don't get loose, they get tight. Look elsewhere for your noise. That won't be it. GD
June 18, 20178 yr Author The solid lifter valve trains don't get loose, they get tight. Look elsewhere for your noise. That won't be it. GD I could not get on the site last night to reply, was the site down? I have worked on motorcycles and air cooled Volkswagen's for years, solid lifter systems are pretty much the standard, and tolerances increase over time. I am curious how the valve train would become tighter over time? I am starting to believe you are right about the timing belt tensioner. I watched some more clips and found a couple that sound much like mine. I was looking at tensioners online and I am finding them selling for $37 to around $130, does it pay to buy the higher priced unit? if so what is the difference. Also, would it be wise to replace all the idlers and water pump at the same time. I was also reading that it is wise to pull the oil pump, inspect and replace the pump if worn or at minimum replace the seals. Another issue I ran into yesterday. I went shopping for a manual. Not one automotive store had one. Finally, a guy at AutoZone ask's me if I had Googled the internet for one, and proceeds to tell me that he has seen several vehicles they do not make manuals for. I can get a PDF of the Subaru Shop Service manual online for $15, but that is it. I'm not a fan of PDF and prefer a book. There appear to be no aftermarket manuals. Do you know if Subaru has a single shop service manual for the car and if so the cost? I have found some shop manuals on eBay but they were multi volume sets and quite expensive. I do appreciate your help and input, sorry if I seem a bit bullheaded at times. I am pretty stubborn and set in my way's. Thank you
June 18, 20178 yr The metallurgy on the Subaru engines is very, very good. The only wear that occurs in the valve train is the burning away of the valve face and seat. Thus causing (mostly the exhaust) valves to tighten and eventually to hang open and burn. This take 100k+ miles to become a problem though. They never make noise unless someone got in there and moved shims around. Tensioners definitely make knocking noises. Often sounds exactly like a rod. Stethoscope on the tensioner mounting bracket will tell for sure. There are no paper copies of service manuals for 95 and newer. They do not print them. You can download and print if you like. They are free over on sl-i.net. Just Google free Subaru factory manual sl-i.net, etc. GD Edited June 18, 20178 yr by GeneralDisorder
June 18, 20178 yr Author The metallurgy on the Subaru engines is very, very good. The only wear that occurs in the valve train is the burning away of the valve face and seat. Thus causing (mostly the exhaust) valves to tighten and eventually to hang open and burn. This take 100k+ miles to become a problem though. They never make noise unless someone got in there and moved shims around. Tensioners definitely make knocking noises. Often sounds exactly like a rod. Stethoscope on the tensioner mounting bracket will tell for sure. There are no paper copies of service manuals for 95 and newer. They do not print them. You can download and print if you like. They are free over on sl-i.net. Just Google free Subaru factory manual sl-i.net, etc. GD That explanation on the valves makes sense. It does not look like adjusting the shims would be possible with the engine in the car? What does having the valves adjusted in your shop generally run? I am might go buy a stethoscope today, cheap from Harbor Freight and they are close by. I will check on the manual download, thanks for the tip. I am getting ready to go pressure the engine and get it ready to get into the timing belt. I might have apart something this week. I've been dealing with really bad allergies, felt like I have had the flu the last two weeks, makes getting much done difficult. Thanks
June 19, 20178 yr Valve lash *can* be done without pulling the cams. There is a special tool just for 97 to 99 25D engines made by Kent moore.... no one does it often enough to buy the $300 tool though. The only other thing that uses bucket-shim is 2002 WRX's for which you need a different tool.... after 02 they went to shimless buckets and removal of the cams is mandatory. We do it as part of the 105k service. It is typically around $1150 to $1250 for everything. That includes all timing components, water pump, valve cover gaskets, cam seals, valve lash, any shims required, spark plugs, etc. This is the same as any 03+ turbo model so it's the same price for a 25D as it is for a 2016 STI. To put it in perspective.... GD
June 19, 20178 yr Author Valve lash *can* be done without pulling the cams. There is a special tool just for 97 to 99 25D engines made by Kent moore.... no one does it often enough to buy the $300 tool though. The only other thing that uses bucket-shim is 2002 WRX's for which you need a different tool.... after 02 they went to shimless buckets and removal of the cams is mandatory. We do it as part of the 105k service. It is typically around $1150 to $1250 for everything. That includes all timing components, water pump, valve cover gaskets, cam seals, valve lash, any shims required, spark plugs, etc. This is the same as any 03+ turbo model so it's the same price for a 25D as it is for a 2016 STI. To put it in perspective.... GD I just gave a listen to it with the stethoscope. It seems to be the loudest under the AC pump. I can also hear it from the rear of the block, slightly less so. On the heads it seems more muted yet. I'm guessing it is the tensioner. Getting ready to pressure wash it now. All that would need to be done is the valve lash, valve cover gaskets and cam seals. I will be putting in a new timing belt, tensioner, idlers, water pump myself soon. Thank you
June 19, 20178 yr I just gave a listen to it with the stethoscope. It seems to be the loudest under the AC pump. I can also hear it from the rear of the block, slightly less so. On the heads it seems more muted yet. I'm guessing it is the tensioner. Getting ready to pressure wash it now. All that would need to be done is the valve lash, valve cover gaskets and cam seals. I will be putting in a new timing belt, tensioner, idlers, water pump myself soon. Thank you You have to pull the timing belt components to change cam seals and pretty much gott pull cams and do a fair bit of tricky math to get your correct shims swap them around whatever. PITA. I doubt the issue is valve lash. It's the tensioner or it's rod knock. both are common failures in 25Ds. Put a 2.2 in it. lol
June 19, 20178 yr Author You have to pull the timing belt components to change cam seals and pretty much gott pull cams and do a fair bit of tricky math to get your correct shims swap them around whatever. PITA. I doubt the issue is valve lash. It's the tensioner or it's rod knock. both are common failures in 25Ds. Put a 2.2 in it. lol Unfortunately I can not afford to drop that kind of money right now, Maybe later I could, but it will be a long way's down the road. I could justify the $300 tool easier right now. I just finished pressure washing and the knocking was gone after the engine sat running all that time. Now when I bump up the throttle the engine is making a rattling type knock, completely different sound. Possibly detonation from water that has not dried out yet. Give a bit to see what it is doing and let things dry out. Thanks Edited June 19, 20178 yr by My64bit
June 19, 20178 yr Author I think I will pick up the tensioner & timing belt soon, install those and see what it sounds like after that. If I can get the thing to sound decent I will keep it and drive it. If not I will off it and get a small truck, which I would have a lot more use for anyway. Right now I am not in this thing very deep money wise, I am not going to bury myself putting money into a car with 250k miles on it. The engine oil looks fresh and clean, straight out bottle clean.
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