Engine clatter when starting cold.

Hi,

 

I have a 2018 Legacy 2.5, <10,000 mi. & it's garaged. When I start the Legacy in the morning, the increased RPM sounds like valve clatter for several seconds because of engine racing. Subaru 0-20 Syn. Oil & filter has been changed 4 times in <10,000 mi., not counting the car's original oil. No clatter when engine is warm.

 

I brought this up with the dealer & several service people several times & was told that it's a characteristic of the Boxer engine.

 

About a month ago I had a conversation with service mgr. about the engine clattering & I brought up the inverted oil filter located on TOP of the engine. The service mgr agreed; however she went on to say govt. reg's. required increased startup rpm to limit pollution. The engine would warm up faster.

 

Other than the clatter, legacy runs fine.

 

Am I getting "fake news" or is this a Subaru Boxer engine characteristic?

 

Regards,

 

klxdrt

I agree with the people that told you it's a characteristic of boxer engines. After 11 years and 235k my car has always done that. I've read it's the injectors making all the noise, and not the valves, as strange as that may sound.

the only time i hear that is when the car sits for extended periods of time and i first start it and i think it is due to oil drain back

Normal.

Yes this seems to be normal.

My first year with this legacy I used to park in a heated garage. But once i started parking outside, especially in the colder months, the engine was noisier when it was warming up.

Thanks,

 

You made my day by hitting the nail on the head

Almost forgot about this "character" since I park in garage now. I think especially in the first year I bought my 16 legacy, in the winter same thing happened. It's almost like the first 5 minutes with cold engine my car won't get enough power to accelerate it over 35 mph.

Almost forgot about this "character" since I park in garage now. I think especially in the first year I bought my 16 legacy, in the winter same thing happened. It's almost like the first 5 minutes with cold engine my car won't get enough power to accelerate it over 35 mph.

 

I remember that trait as well.

Can confirm the reduced acceleration on cold start ups and the strange noises. I definitely don't recommend putting yourself in a position where fast acceleration is required while the engine warms up.

Hi,

 

I have a 2018 Legacy 2.5, <10,000 mi. & it's garaged. When I start the Legacy in the morning, the increased RPM sounds like valve clatter for several seconds because of engine racing. Other than the clatter, legacy runs fine.

 

Am I getting "fake news" or is this a Subaru Boxer engine characteristic?

 

Regards, klxdrt

 

Coincidentally I'm currently watching a video series on replacing a Subaru head gasket. If you fast forward to the 28:50 sec mark you will hear the mechanic comment on Subaru valve chatter.

 

I thought this was called piston slap, no? I have this pretty bad when my car is cold as well. Initially I thought something was wrong with my car when I first got it because my Impreza never sounded like it.

 

 

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Normal. My 2013 2.5 with 100,000 miles does the same thing.

I also garage mine, and it's loud in the garage in the enclosed space.

And yes, it has a high-idle RPM upon startup, apparently to get warm faster for reduced emissions. (and it can help to get heat in the cabin a little faster in the winter)

all is normal.

 

You changed the oil 4 times in under 10,000 miles??? That's really not needed.

Every 3-5000 miles (or even more) is fine unless you are under super extreme driving conditions.

Hi,

 

We live in NJ & we could not register our Stryker Vehicle. This a great vehicle for driving in NJ. We lived in 7-8 states plus military and NJ is cattiwampus especially when it comes to drivers, hence the Stryker Vehicle, no one messes with this thing.

 

So we bought a Legacy & to honor the warranty, you have to change the oil/filter every 6 mo or 6000 mi.

 

We were able to get a gift cert from Subaru. Used it to extend our oil/filter changes for several more yrs.

 

Legacy is a keeper.

 

Regards,

 

klxdrt

Hydraulic valve lifters need to pump up for a few seconds upon cold start. The longer the car sits, the longer it will take for the lifters to get full oil pressure. What you are hearing is a little bit of valve train noise due to excess clearance before the lifters are pressurized. It just lasts for a few seconds on my 3.6R.

Hydraulic valve lifters need to pump up for a few seconds upon cold start ... What you are hearing is a little bit of valve train noise due to excess clearance before the lifters are pressurized.

Neither the H4 (FB25) nor the H6 (EZ36) engine uses hydraulic lifters. Valve clearance is adjusted manually, using hardened shims. Consult the Factory Service Manual.

Neither the H4 (FB25) nor the H6 (EZ36) engine uses hydraulic lifters. Valve clearance is adjusted manually, using hardened shims. Consult the Factory Service Manual.

This.

 

I swear people make shit up to sound smart.

 

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Neither the H4 (FB25) nor the H6 (EZ36) engine uses hydraulic lifters. Valve clearance is adjusted manually, using hardened shims. Consult the Factory Service Manual.

 

That is surprising. I wonder how they get away with hardly ever needing adjustment. So the sound is just the injectors then? Because There is little else in an engine that makes those kind of "clattery" sounds.

I wonder how they get away with hardly ever needing adjustment.

In an OHC or DOHC head design, the path between the cam lobe and valve stem is usually a very short distance. This is nothing new; in the venerable Jaguar XK engine (ca. 1948) the path was dead simple: cam lobe -> inverted bucket tappet -> adjusting shim -> valve stem. The Subaru valve trains are slightly more complex.

 

So the sound is just the injectors then? Because There is little else in an engine that makes those kind of "clattery" sounds.

I don't think it's just the injectors. The relatively long timing chains on the FB25 and EZ36 engines can clatter at startup, until oil pressure comes up in the tensioners, which only takes a few seconds. Running clearances are generally higher at startup, due to temperature, and that results in more noise until oil begins to circulate throughout the engine and parts approach normal operating temperatures. Ignition, cam, and/or injector timing may be unusual during cold startup, for reduced exhaust emissions, and that can affect noise levels as well. In addition, the boxer engine format means that there's a lot of external surface area to radiate noise when compared with more compact inline or V engine designs. Edited August 30, 2019 by ammcinnis

This.

 

I swear people make shit up to sound smart.

 

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No, I didn't make anything up. I believe that most engines these days have some sort of hydraulic lifter, or cam-follower, to avoid having to adjust valves periodically. For example, I used to work on a lot of SOHC and DOHC Ford 4.6L and 5.4L V8s... they have hydraulic "lash adjusters" that can get noisy with age/wear. Even the newer 5.0L Ford DOHC engines use them. GM uses them in almost every DOHC/SOHC engine they have ever made. I'm not going to check to see who else uses them, but it's not like everybody uses the shim/adjustment like Subaru.

I thought this was called piston slap, no? I have this pretty bad when my car is cold as well. Initially I thought something was wrong with my car when I first got it because my Impreza never sounded like it.

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I think it might be a little different, if it's the sound I'm thinking of. I believe my car gets piston slap in the winter when the engine is cold, but I never hear it when the temps are over like 50F or so.

 

The sound that I get in the winter has more of a low pitch knock sound to it, whereas the sound I'm thinking of when he says "clatter" is more of a high pitch tapping sound. Being Summer, I forget what the cold weather sound is like exactly.

No, I didn't make anything up. I believe that most engines these days have some sort of hydraulic lifter, or cam-follower, to avoid having to adjust valves periodically. For example, I used to work on a lot of SOHC and DOHC Ford 4.6L and 5.4L V8s... they have hydraulic "lash adjusters" that can get noisy with age/wear. Even the newer 5.0L Ford DOHC engines use them. GM uses them in almost every DOHC/SOHC engine they have ever made. I'm not going to check to see who else uses them, but it's not like everybody uses the shim/adjustment like Subaru.

No, you are right about what you said. Your error was in applying it to the Subaru engine. Sorry I came off as an ass with my response. It was uncalled for.

 

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