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Loud tapping on cold start

('03-'05) 
9K views 17 replies 5 participants last post by  dave5358 
#1 ·
Hi all. I have a 63000 mile 2004 2.5XS auto. One morning a few months ago, on a morning start, there was a *loud* tapping when I started the car. I shut off straight away. No oil under the car. Oil level was fine. On the next start, it was softer, and after about 30s idling it went away. I took the car to a local auto shop and they said it might be piston slap, but they test drove it and said it's fine. They did an oil change. However, since then it has done this ticking/tapping every time I start the car in the morning. The noise goes away entirely after about 30s and the car seems to drive normally. It does *not* do it on subsequent starts during the day, only after standing overnight.

Some observations:

-I understand high mileage boxers can have piston slap, but my engine is still 'young'.
-It never did it before that one morning.
-It *seems* to be louder on the left (from the front, facing the car).

Can anyone recommend a diagnosis method? Thank you for reading.
 
#2 ·
Thanks for your reply. The car gets new oil and OEM filters once a year. It had Castrol 10w40 semi-synth when it first happened. The shop said they get better results from LiquiMoly 20w50, so that's what in there now. The coldest we ever get is about 0C, summer gets up to 40C.
 
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#7 ·
First of all, don't use 20W50 under any circumstance, pumpability worsens at low temperatures and it's very viscous at high temperatures where engine it's normally running after warming.

Try to put in your engine an oil 5W40 or 0W40, with that millage you have expanded specification clearances in your engine.
This ^^^^^^^^.

Assuming it is a cold-start lubrication issue, the last thing you want to do is go to an oil which is thicker when cold (e.g. 20w30 or 20w40). Better to go with an oil which is very thin when cold - 5w30 or 0w40, etc.

Besides, if your vehicle is not using oil (i.e. pumping oil past the rings), then the weight of oil you are using is about right. If it ain't broke, don't fix it.

You might try an additive like MoS2 (e.g. Liqui Moly MoS2 Anti Friction). Regardless of how it is packaged, it's a dry powder that coats and clings to internal metal engine parts. Once attached, it does not drain down into the pan. When you start the car, it lubricates from the get-go. It provides some other benefits as well. On the downside, it turns your oil black or very dark brown (don't laugh, that's a major issue with some folks).
 
#3 · (Edited)
As above, 20W50, really? Our motors use FULLY synthetic 5W30 and due to a legal case some years ago involving the major motor oil makers, just because it says "FS" on the label doesn't mean it has to contain such, bizarre but there you go. Stick with well known or recommended brands, much advice in that area to be had here.

Nearly all modern cars (except Alfa Romeos apparently) including those with turbo charged engines have tighter tolerances and create greater bearing pressures due to the much higher power outputs (or that certain parts spin at speeds in excess of 100K rpm in the case of turbos) and use much higher oil pressures than older cars thus requiring the extra integrity and shearing strength that Fully Synth has over semi synth, which is really just an unspecified mix of mineral and FS of some description.

If you think of holding a syringe in your hand with water in it, that's 5W oil. Now squeeze it all out. Refill that syringe with cooking oil, that's roughly like 10W and a bit harder to get out quickly. Now use something like single cream which will require a lot more pressure from your hand to evacuate the cylinder, that's kind of like 20W oil. In those first few seconds the oil pump must be able to attain as close as possible to full pressure and blast the oil around the engine separating the bearings from their pressure points while maintaining that pressure, not unlike human circulatory systems. The unattained initial pressure can sometimes make all kinds of odd noises in the first 0-20 seconds after which the lube catches up.A look at writings by "Bob is the oil guy" is wrist slittingly boring but if one can stay awake he explains and describes what FS, how it's made and why it's needed in modern engines after which most of us will forever after buy branded FS. SS is a false economy.

You mention an oil and filter change once a year but not the mileage covered in that time nor the type of driving conditions your car deals with. Stop start urban and city traffic as well as short journeys particularly in the winter months, takes a higher toll on your oil than 60-80mph higher mileage highway driving. Some folks reckon top brand FS is good for up to 10k miles between changes, personally I do it around 6k but my engine has just shy of 200k and is fairly well tuned. On factory suspension the Forester is one of the easier cars to do an engine oil change and unless one has an aversion to getting messy, sending it a garage to have the job done, particularly one who recommends 20W50, is a questionable practice (although I'm not saying this is what the OP does). Far too many shops buy bulk discount oils and will tell you they've put the correct one in yours however, if you do it, you know it's been done properly. With all the exposure and information available now, those who go to places like Jiffy Lube really don't have any comeback nor are they likely to elicit too much sympathy when it goes wrong.
 
#5 ·
Hi proze,

Greetings from Oz! I think you might be getting some of that 'old school' type mechanic there is S.A, bit like Oz used to be until recently. Really if they're recommending 20W-50... you should be looking at a 70's car. Or perhaps high mileage 80's! If they can't give you a really good reason why they've gone outside the car's spec...go elsewhere (as said above). And they won't have a good reason, given they don't know the car's history. I still encounter this attitude in Oz so I specify what oil grade to use to the mechanic (and check afterwards).

It's likely they're using 20W-50 'cos they got it cheap. I've had people try to use it in my Mazda when it specs 10W-30!

Only reason you might go outside the spec is due to some sort of adverse running/conditions or the engine's on its last legs. Even so, it's often false economy, thick oil will increase fuel consumption beyond what you'll spend on say 1l oil/1000km.

If you're 'hot-n-high' in S.A. you might consider an 'extra 10' i.e. 10W-40 instead of 10W-30, to cope with the extra heat (and lower cooling) in summer at altitude.

The noise could be hydraulic valve lifter noise if that's what Subarus have (I really should know!). Likely caused by lack of oil when cold due to extra viscosity of 20W. Thinner oil, within spec, should alleviate the issue. If it doesn't, there's some other problem.

Moving from Sydney to Canberra, I encountered this valve tick on an older car. With the cooler temps in winter, I found I had to reduce the winter spec viscosity from ~20W-40 (pref. 15W-40) to 10W-40. Also differing brands had differing performance, I found that castrol magnatec worked best in that case, just had to top up occasionally. But this was an older engine designed for non-synthetics.
 
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#6 ·
Hi all. I have a 63000 mile 2004 2.5XS auto. One morning a few months ago, on a morning start, there was a *loud* tapping when I started the car. I shut off straight away. No oil under the car. Oil level was fine. On the next start, it was softer, and after about 30s idling it went away.
Other responders have described more logical issues: piston slap, valve adjustment, etc. If that doesn't solve the problem, you might look at your fuel rail dampers - two, round shiny black devils in the center of the picture:



When they get flaky, they make a tapping sound that's very noticeable inside the vehicle, but hard to hear when you're standing beside the running vehicle with hood up. To verify (or not) that this is the source of the noise, take a long metal rod (socket extension, long drill bit, screwdriver, etc) and touch one end to the damper. Press the other end to your lips. You can use this same technique to isolate a 'clicking' valve. If this is the source of the noise, it will be quickly obvious.

The only fix is replacement. They are very expensive - $100+ each. You can buy them from 3d part suppliers - still expensive, but not quite as bad.
 
#10 ·
#15 ·
An update: I did an oil change back to 5w40 and the noise is a lot softer, but still there. This makes sense when reading other threads about piston slap, where the weight of the oil made a difference. But, and this is the odd thing, why would it have started out of the blue one day, and when using thin (5w..) oil?

Anyway, then I have time and energy I'm going to take off the timing belt covers and check out the tensioner.
 
#16 ·
5W40 is still very heavy. Remember that your oil is lubricating the engine but also acting as hydraulic fluid for the AVCS variable valve timing.

I just re-read this thread and the comments... it could be that your variable valve timing is all gummed up. That might account for the noise and could also explain why it started out of the blue... the mechanism was gummy and did not move or return to the correct position.

Ungumming: get a quart of Marvel Mystery Oil (or some equivalent - very light oil with solvent) and add it to the crankcase. Run the engine for 1000 miles or so, then drain the oil when the engine is very hot. That should get the gum out. Replace the oil with 5w30 synthetic. Castrol is fine - great, really.

Peace of mind: Drain the oil (above step) into a very clean pan. Let the old oil settle. Carefully pour off the old oil so you can see what settles out. A few tiny metal particles are fine. But if it looks like metal mouth, something else is going wrong



Peace of mind, part 2: when you change the oil (above), change the filter as well. Cut the old filter open and look inside. Again, a few metal particles are normal.
 
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