2015 Peugeot 308 - Severe vibrations after maintenance, mechanics are at loss

My car is a 2015 Peugeot 308 1.6 HDI 120 cv manual with 60.000 kilometers (37k Miles), scrupulously taken care of and maintained. I’m aware french brands aren’t popular at all outside of Europe, but I’m desperately hoping that someone knowledgeable might do a miracle and point me in the right direction.

Immediately after the last periodic maintenance performed in october I noticed strong but silent vibrations everywhere - steering wheel, gear stick and pedals mostly, both at idle and while driving. Accelerating aggravated the vibrations, and engaging the clutch didn’t have any noticeable effect. The entire external chassis was shaking badly too, but there wasn’t any unusual noise coming from under the bonnet.

During said service, the techs (official network shop) did replace the following components:

  • Serpentine belt and tensioner;
  • Oil and oil filter;
  • Brake fluid;
  • Air filter and fuel filter.

Right after picking up the car, the vibrations were unbearable, almost like an oversized electric massager was strapped onto the car and activated at full power, even with the car idling in neutral.

Long story short, after the official techs refused to admit there was any issue, my odyssey begun: I had my car checked by at least a dozen of reputable mechanics (or at least considered as such) and several attempted fixes later, the issue still persists - albeit greatly reduced. What has been done up until now:

  • Serpentine belt and tensioner replaced for the second time: vibrations were noticeably reduced, but not eliminated. No issues supposedly noticed with the pulleys;
  • One faulty injector - which didn’t raise any CEL - replaced and the other three serviced, no changes. Current correction values are negligible.
  • Motor mounts (three in total) replaced: vibrations slightly dampened, still very noticeable in the pedals and gearstick;
  • Battery replaced: no changes;
  • Engine decarbonization (I’m aware it’s considered snake oil): no changes.
  • Dual mass flywheel and clutch kit replaced: vibrations almost eliminated, some fine “buzzing” still noticeable in the floorboard, seats, pedals and gearstick at specific RPM. Replaced flywheel was in bad condition, with a lot of play and full of blackened debris.

Except for a moderate correction value of one injector, which was replaced, all the diagnostics performed with official Peugeot equipment were negative. Engine throughput is fluid and linear, rpm at idle completely stable.

The vibrations right now are concentrated in the lower part of the car, floorboard and pedals, and in the gearstick. They feel like a fine “buzzing” and are RPM dependent, 1500 and 3000 rpm being the critical spots (3000 being a multiple of 1500 could be a hint?) in any gear, and generally couldn’t almost be felt at all at idle, between 1600 and 2900 rpm and over 3000 rpm. Sometimes they’re more noticeable, sometimes they’re less evident. There’s no obvious aggravating factor - e.g. engine being cold or hot. It’s almost random.

The car otherwise runs absolutely fine: engine performance is flawless, acceleration is linear without gaps or hiccups until redline, and there are no unusual noises, not even when driving at the critical RPM ranges (~1500 and ~3000).

I’ll provide a final recap, for clarity:

  • Vibration intensity after the first service: 10/10, everywhere;
  • " " after serpentine belt and tensioner 2nd replacement: reduced to 4/10, mostly on steering wheel, pedals and gearstick;
  • " " after injector replacement/rebuild: still 4/10;
  • " " after engine decarbonization: still 4/10;
  • " " after dmf and clutch replacement: 1/10, mostly on pedals and gearstick, critical spots 1500 and 3000 rpm, feel like a fine, noiseless buzzing.

Every mechanic I consulted throughly checked my car, but while admitting the issue is there, they’re stumped.

A couple of final thoughts: the mechanic who replaced dmf and clutch said that the transmission mount was still in good shape. Could it still be the culprit? Maybe the new flywheel is able to absorb the strongest vibrations, but the finer ones aren’t dampened by the transmission mount, visually fine but somehow compromised.

Could it be an internal balance issue? I can’t really fathom how an engine could be damaged during a simple routine maintenance, performed by official technicians at a very well known shop…

Does anyone encountered a problem similar to mine in their car? I’d greatly appreciate even the tiniest hint, as I’m quite desperate. I’m attached to my car, and I’m very reluctant to give up.


Have someone inspect the harmonic balancer for damage/wear.


These can cause major vibrations when they fail.



Thank you for your advice. I may be mistaken, but I believe the technician who replaced for the second time the serpentine belt stated that the crankshaft pulley was spinning fine and in his opinion the symptoms weren’t typical of an harmonic balancer failure, but I’ll ask another technician to unequivocally check if the harmonic balancer is damaged.

+1 for Tester…

I was thinking Harmonic balancer or clutch related almost from the start of your post… If the balancer is coming apart changing the belt would have disturbed the balancer somewhat (part going bad not the shops fault) and or the new found tension from the new tensioner helped the already failing balancer show itself… And after the 2nd belt replaced the balancer could have shifted a little making it feel better…

The pulley would look fine and smooth running because it’s attached to the solid part of the dampener. The d (sorry, balancer) does serve a purpose. It helps prevent every bolt from shaking loose from the car body as well as keeping the engine together. So don’t give up because it could be a balancer problem.

Thanks to both of you for your replies, you gave me that tiny bit of hope I was desperately looking for! Tomorrow I’ll call the mechanic who replaced my clutch and flywheel and I’ll ask him to check and replace the dampener ASAP.

Not familiar w/your car. Does “HDI” mean it has a diesel fuel-injected engine? If so, I think that’s the main problem. Diesel engines have a tendency to vibrate. Tom and Ray (Car Talk radio program hosts) had a great deal of fun teasing the diesel-owning callers: “so do you still have any fillings left in your teeth?” … lol … My guess, that vibration has always been there, but you are noticing it now b/c just prior to this the engine was really vibrating b/c of the problems (now corrected) you outlined above, and got sensitized to it.

Years ago I owned a gasoline VW Rabbit, and experienced a bout of CIS fuel injection problems. What a shocker! …lol … Anyway, after I repaired those problems, I started to hear a very high pitched whine coming from the engine. It turned out that sound was always there, I just started to notice it then b/c it was coming from the fuel injectors, and b/c of my fuel injection system debugging work, knew what the CIS fuel injectors sounded like, so was “tuned in” to that exact sound frequency. I was being annoyed by a sound that had always existed, just not noticed.

It’s possible the vibrations you are noticing now are enhanced b/c stuff was worked loose over the 40K miles of driving, so it may well indeed be a little more noticeable than when the car was new. But it’s no longer a new car, so have to expect some minor imperfections.

Engine vibrations tutorial: Most often caused by a misfire. One cylinder not pulling its weight. This can usually be confirmed by feeling the exhaust stream at the exhaust pipe. It should feel like constantly repeating set of bursts. If there’s a misfire, the burst rate isn’t constant. You can also hold a piece of paper (paper money works well for this) near the exhaust pipe, letting it blow so it tends to hold the paper at the horizontal. The paper should never move towards the tail-pipe. If it does, pretty good chance there’s a misfire.

The other common engine-vibration cause is something that rotates isn’t properly balanced. In your case it appears the flywheel had accumulated some gunk and made it imbalanced. Probably some imbalance problems w/the serp belt stuff as well.

HDi (High Pressure Direct Injection ) is a diesel engine designed by the PSA Peugeot Citroen group provided with the common rail direct fuel injection system. The first generation HDi engines were launched in 1998.

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I doubt it. He didn’t have the problem before, it’s a new problem.

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I believe this car has a timing belt and that is what they replaced, Which in that case, as @Tester said, they got the harmonic balancer off by 180 degrees, So essentially instead of “balancing” the vibration, it is making it twice as worse. Have had someone make that mistake on one of my cars, had to have the dealer fix it and go back to them for the bill!


I think he said it’s damaged. Most harmonic balancers can only be installed one way, no way to get them 180 degrees off, I think. For those without a keyway, the alignment probably doesn’t matter, it’s only acting as a damper, not a combined damper/balancer. The damper part works by having a rubber ring in between the two parts, damping the crankshaft’s rotational vibrations. That’s why its other name is ‘harmonic damper’.

Harmonic balancers are keyed.


That means they can only go on one way.


Well, on my Mitsu Galant (my handle here), they got it off by 180 degrees, not sure how.
The dealer fixed it.

Watched this video, there’s a dowel that should have prevented them from putting it on 180 degrees off, it must have been pretty crooked the first time they put it on!
How to Remove and Replace the Timing belt and Water Pump - Mitsubishi 2.4L SOHC Engine PART 1 - Bing video

Your engine’s balance shaft was incorrectly timed.

Pretty sure OP said nothing about timing belt. He said serp belt. And new clutch and flywheel.

On some Ford 302 (5L) engines, maybe others, IIRC the harmonic balancer is matched to the flywheel. Both parts are designed to be a little off-balance, but between the two of them, the off-balances complement each other, & engine remains in balance. If either is replaced, have to make sure the replacement is balanced the same as the one removed. Otherwise engine vibrations. I don’t recall what motivates this complication, but I expect it was done for a reason.

I suppose some weird complication like that might explain OP’s problem. .

Thanks to everyone that offered their insight about my car issues. The timing belt was never touched, as the first mechanic replaced the serpentine (alternator) belt.

The last mechanic installed a new engine pulley (harmonic damper) and showed me the replaced one, which had quite a bit of wear marks on its rubber lining. The vibrations almost completely disappeared for one day, then they started to creep back in, especially at 1500 rpm. The mechanic admitted he could still feel the vibrations, albeit dampened, especially in the pedals, but he decided to give up.

I believe I should give up too - the vibrations are still there after a new serpentine belt, new motor mounts, new clutch kit and flywheel, new engine pulley and a new injector. OBD diagnosis is completely negative.

Time to wave a white flag and move on.

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Move on? Live with it? Or sell it?

May have gotten a defective part… Sounds like it worked for a short time…