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Dear experts,

 

When I start up my 2001 Forester (104,000KM - but just purchased by me) there is a tapping sound from the engine that goes away once it is sufficiently warmed up. It sounds like a sewing machine and is louder under load. This morning it was 16 degrees C and the noise was most noticable, but again, once the engine is sufficiently warmed up the noise ceases.

 

I'm told that these 2.5L boxer engines just do this. Some say it takes a little while for the oil to fully distribute others say it's got something to do with the exhaust system. Though I've not had it fully inspected by a Subaru mechanic, the one I spoke with didn't think anything was unusual - but of course the engine was warm at that time.

 

Any advice would be most welcome.... Thanks!

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Dear experts,

 

When I start up my 2001 Forester (104,000KM - but just purchased by me) there is a tapping sound from the engine that goes away once it is sufficiently warmed up. It sounds like a sewing machine and is louder under load. This morning it was 16 degrees C and the noise was most noticable, but again, once the engine is sufficiently warmed up the noise ceases.

 

I'm told that these 2.5L boxer engines just do this. Some say it takes a little while for the oil to fully distribute others say it's got something to do with the exhaust system. Though I've not had it fully inspected by a Subaru mechanic, the one I spoke with didn't think anything was unusual - but of course the engine was warm at that time.

 

Any advice would be most welcome.... Thanks!

 

My 1998 Forester has been doing that for 228,000 miles now. When it stops, I'll be worried.

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It's "piston slap" - and normal.

 

The pistons have become so short in the search for less friction and better economy that they rattle a bit when cold. A number of Hondas do this too.

 

Take it easy on the throttle while it's cold. Like only open it halfway and don't rev above 4000.

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The 2001 Forester is an automatic (first automatic I've ever owned). I'm rather light on the throttle normally - so avoiding high revs is easy.

 

But the taping noise is annoying, especially given that I didn't notice it when I checked out the car. I've had the car for less than 1,200KM so it may be that I'm reacting too strongly to every little thing.

 

So, is this really normal and I have to live with it? Is there a definitive test/check to confirm piston slap?

 

Thanks.

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Well, there is no test as such, but if you get a slight Diesel like sound when cold, worst around 2000rpm, and it goes away after a few miles, then it's most likely piston slap.

 

Loud clicking, that is also present at idle is valve tappets and that would need curing.

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Thanks for the reply,

 

Well, there is no test as such, but if you get a slight Diesel like sound when cold, worst around 2000rpm, and it goes away after a few miles, then it's most likely piston slap.
I've had a chance to listen to a neighbour's '99 Outback with piston-slap. That noise is unquestionably like a diesel which is quite different than the sound I hear.

 

Loud clicking, that is also present at idle is valve tappets and that would need curing.
I do hear this loud ticking that is present at idle - when cold. It is also louder under load (accelerating or going up a hill). However, it generally goes away after the engine temp passes the 1/3 mark on the gauge. In other words, by the time I drive 7-10 minutes to the dealer's, the engine is up to temp and the mechanic can't hear anything.

 

I have been told by the Subaru mechanic that piston slap has a range of sounds and that they need to diagnose it when the car's cold - fair enough.

 

Here's some potentially good news... the dealership has said that even though the car is slightly over 100,000km but is less than 5 years "roaded" Subaru will cover the costs of the inspection and any repairs that might be required. I did flag the issue with the dealer from whom I purchased the Forester (different city) about 2 weeks after I bought it (approx 102,500km).

 

If indeed Subaru handles this whole thing under warranty (which I think they should), then I am pleased that they stand behind their products and don't hide behind the product being marginally out of warranty.

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Well... I'm now told bythe dealer that they were in error saying the inspection would be covered under warranty but will not charge me anything, having indicated such earlier (that's honourable).

 

They tell me the sound meets all the criteria Subaru have for "normal". The sound essentially goes away when the engine is up to temperature.

 

I I am not satisfied with this, the next step would be to have the dealer call in the Subaru regional rep for his action (apparently he is empowered to make a decision as to whether there is a need to affect a repair or not and if Subaru will cover the costs).

 

I'm told there are two types of possible repairs for "piston slap" - put in a "short-block" engine or replace the pistons on the left side with, I guess, ones designed for this purpose.

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Yes, due to tolerance in production, some pistons will slap even when warm. These have been replaced in some engines.

 

You don't want to pay for that, or for the short block - thats and engine bottom end, without heads on it.

Still, that dealer does seem to have a high moral standard, so you should probably take their advice seriously.

 

Back to the sound: Can you make a recording? It might help, but sometimes the microphone doesn't pick up the correct sounds.

 

At idle you will be able to hear the fuel injectors tick, but only with the hood open. That sound is very "sharp" and short. It's the electromagnets working.

 

Ticking, audible from the cabin, could also be valve tappets. I guess you need to remove one of the valve covers and have a look at the assemblies. Not all Subaru engines have hydraulic lifters. The solid lifters need adjustment at 100,000km :-)

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It may also be the timing belt tensioner. Do you know for sure when the belt was replaced? A lot of folk will swap the tensioner along with the belt. If the belt doesn't look new, I'd replace it and the tensioner along with it.

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Yeah, I was gonna mention the timing belt tensioner, but redwagon beat me to it. :)

 

Subaru issued a TSB on it, although I swear the noise was only a problem at temperatures well below what you are experiencing.

 

IIRC, the tensioner noise was nothing more than an annoyance just like the piston slap (nothing critical).

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and I am really glad all these folks have told me not to worry about the noise. I have a new tensioner and it made no difference at all in noise, I just had it changed since I was having everything else serviced on the front of the engine.

I've occasionally been tempted to tear it down and go for the new pistons, but I supect It would cost me a couple of grand for only a small result.

Since I added 15-50 Mobil 1 a few thousand miles ago the sound is far less noticeable except on cold start up. I think all the heavy oil is doing is taking up a bit of the clearance on the piston skirts until the car sits long enough for it to drain down. Before the heavy oil it rattled every time I started the car.

I guess I will just run it and see what happens, after all I have run noisy diesels for years will little problem.

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I was going to post a similar question about the rattling noise which disappears when the engine is warmed through, about 7 miles driving.

 

If it is piston slap, which seems likely as worn bearings would get louder under severe load ,has anyone had any success with thicker engine oil (as per the operators handbook for operating under arduous conditions -- say 20/40 or even the old standby 20w 50.

 

How about an additive like S.T.P.??

regards Yewman.

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As stated in my post above I have gotten a very good reduction in noise from the Mobil 1 15-50. I have not tried anything heavier.

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I have bought some S.T.P. oil additive which I will put in when oil is changed soon. Will report results.

 

 

 

yewman

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Loud clicking, that is also present at idle is valve tappets and that would need curing.

 

you wouldn't know how difficult it is to adjust or fix the valve tappet prob?

 

if first i thought maybe it's a stuck valve or something but i ran something that's supposed to clean but to no prevale....

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Some engines have hydraulic tappets which are non adjustable, if faulty, then replace. Not an easy job.

 

Others like my legacy 2 litre have good old fashioned adjustable cam rockers.

To check, remove the cambox cover from the side where the noise is coming from.

Look at the rockers operating on the camshaft ,If you can see screws and locknuts, then all you need is simple tools and a set of feeler gauges and something to cure the backache you will get bending over the engine.

 

 

hope you understand my uk terms

Regards Yewman

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Some engines have hydraulic tappets which are non adjustable, if faulty, then replace. Not an easy job.

 

Others like my legacy 2 litre have good old fashioned adjustable cam rockers.

To check, remove the cambox cover from the side where the noise is coming from.

Look at the rockers operating on the camshaft ,If you can see screws and locknuts, then all you need is simple tools and a set of feeler gauges and something to cure the backache you will get bending over the engine.

 

 

hope you understand my uk terms

Regards Yewman

 

i hope my 2.2 doesn't have hydraulic tappets.

 

and yes i can understand you fine :grin:

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Dear folks,

 

I thought I should post a summary. I've now had two dealers inspect the 2001 Forester and both declare that the tapping sound from the engine when it is cold is piston-slap. It's not valves or timing belt tensioner, or anything else, so they tell me.

 

They base this on the sound going away once the engine is up to temperature. That takes me roughly 10 minutes and perhaps 15km of driving, but it is not cold here, yet. I'm told to expect that warm up period to increase, obviously, in winter, and so the noise will last longer.

 

Perhaps people might be interested in the letter Subaru Canada sent after I spoke to their warranty people:

 

September 13, 2005

 

Dear Sir,

 

In response to your concerns about the engine noise sometimes heard in your vehicle, following is a brief explanation of how your dealership and Subaru Canada, Inc. have determined that your vehicle is not in need of repair. We understand that it is quite natural for you to be concerned about unexpected engine sounds, so we hope that the information below will put your mind ease and assure you that the durability and longevity of your vehicle is not being compromised.

 

Your engine is considered not to be defective or damaged because the tapping sound sometimes when your vehicle is first started is no longer audible once your vehicle has normal operating temperature. This type of engine noise is commonly referred to as 'piston slap' throughout the automotive sector; it is a natural by-product of the improvements made to our engines to increase fuel efficiency, improve performance and lower emission levels which we have continually achieved since 1997. Subaru engineers have disassembled and thoroughly inspected numerous engines like yours and found no evidence that piston slap during the engine's warm up phase causes engine damage.

 

The occurrence of piston slap in earlier generations of Subaru's 2.5L naturally aspirated box engine (up to and including 2004) is not cause for alarm from a technical standpoint. Throughout the engine design and refinement phases, our engineers deemed it to be an acceptable condition in light of the performance and environmental advances made.

 

Once again, sir, I trust that the above explanation helps you to better understand our decision regarding your vehicle. Please do not hesitate to contact your Subaru dealer should any unusual engine noise be present while operating your vehicle at normal temperature.

 

Sincerely,

 

Christina Morris

Senior Bilingual Consumer Support Representative

I hope this is indeed the case an that there's nothing for me to worry about.

 

Doesn't it seem a bit weird that Subaru engineers (and apparently Honda and Toyota as well) would accept an engine design that made such a noise when cold? Perhaps they should have made these engines run on deisel, then we'd all accept the noise and be worried only if it dissappeared!

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Dear folks,

 

I thought I should post a summary. I've now had two dealers inspect the 2001 Forester and both declare that the tapping sound from the engine when it is cold is piston-slap. It's not valves or timing belt tensioner, or anything else, so they tell me.

 

They base this on the sound going away once the engine is up to temperature. That takes me roughly 10 minutes and perhaps 15km of driving, but it is not cold here, yet. I'm told to expect that warm up period to increase, obviously, in winter, and so the noise will last longer.

 

Perhaps people might be interested in the letter Subaru Canada sent after I spoke to their warranty people:

 

 

I hope this is indeed the case an that there's nothing for me to worry about.

 

Doesn't it seem a bit weird that Subaru engineers (and apparently Honda and Toyota as well) would accept an engine design that made such a noise when cold? Perhaps they should have made these engines run on deisel, then we'd all accept the noise and be worried only if it dissappeared!

 

90% of Jeep 4.0 engines (one of the longest lifespan motors available) have piston slap. Those engines run for 200K miles + with NO oil changes...Maintain them well, and 500K miles are not unheard of. If it IS piston slap, the cure is more trouble than it's worth. Piston slap WILL NOT hurt your motor.

 

And as for the engineers designing a motor WITH noises...well, EPA regs, and the ever constant search for better MPG, and Easier production, will ensure that motors will get tighter, and parts lighter.

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thanks for that post, I had a listen to my knock/rattle the other morning, using a long screwdriver.KEEP WELL CLEAR OF THE IGNITION LEADS.

 

Starting on the cambox covers I could hear the valve gear tapping away happily. Moving further inboard across the heads the noise began to sound like a hammer on an anvil , on the lhs only. Conclusion the noise is piston slap, and I hope your experts are right to leave it alone.

 

Regards Yewman.........

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like stuff on oil changes. I was not sure if this was just to charge me another seven bucks, but now I think they may have been trying to cut piston slap.

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Throw 1/2 a quart of Lucas Oil Stabilizer in at the next oil change. If that does not cure the noise, NEXT oil change, put in 1 quart of Marvel Mystery Oil(ask for it by name). If it's slap, the Lucas will quiet it down...if it's a stuck, noisy lifter, the MMO will free it up.

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i hope my 2.2 doesn't have hydraulic tappets.

 

and yes i can understand you fine :grin:

 

'94, your engine has the hydraulic tappets if your nick is any indication of the year of your car. the 2.2 went to solid lifters in 97. the hydraulic tappets, however, are not as hard to service as Yewman sugests. I just repaired a 90 Legacy wagon that had a loud talve tap that needed to be repaired. I pulled the offending rocker arm assy and cleaned all the lifters (tappets) in carb cleaner (using the recomended procedure for filling them, I pumped the carb cleaner through them until they moved freely) then I checked that they still held pressure. When I was satisfied that each of the lifters was working properly, I filled them with oil and put them back in the place that they came out of on the rocker arms. Only one had to be replaced as it would not hold pressure like the others did. After all this, I put the rocker arms back in the engine and buttoned everything up, and did an oil change on the car. when I started it up the engine bucked and shook for a while until the internal oil pressure backed off the valves on that side, then the engine ran like a dream. no noise at all. I used carb cleaner to clean the tappets(lifters) as that is what is recomended to free them from the rocker arms if they are stuck in place because of a buildup of varnish (as tends to happen over time, when engine oil is getting hot). It is actually a varnish buildup that causes most of the problems on these lifters. Sometimes the ball berring that seals the oil in place gets weak (well, actually the spring that holds it in place) and it starts to leak. If that turns out to be the case, that particular lifter has to be replaced. The engine I repaired had 180K miles on it and only needed one lifter (tappet). I would say that that is a good indication that this tech works pretty well. Not sure why they went back to the solid lifters except that perhaps the solid ones are cheaper to build. They are really no easier to maintain over the long run. . .

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Throw 1/2 a quart of Lucas Oil Stabilizer in at the next oil change. If that does not cure the noise, NEXT oil change, put in 1 quart of Marvel Mystery Oil(ask for it by name). If it's slap, the Lucas will quiet it down...if it's a stuck, noisy lifter, the MMO will free it up.

 

How long does it usually take for the MMO to free up a noisy lifter? On the engine I repaired we ran MMO in it for a couple of hours without results. . .

 

Granted I did put in a quart when I changed the oil, and it got quieter over time as the engine ran (to warm it up and get the proper level on all of the lash adjusters). Perhaps it is a degree of "stuckness" that was the issue here. . . There may have been a couple of HLAs that were just starting to stick on the left and the MMO cleared them up when running with the new oil and MMO mix. . .

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