Piston Slap: Snowballing Concerns with Auto Start-Stop Systems
Greg writes:
I just read your article about someone wanting to disable their Start/stop function.
I have a 2022 MB GLS 450 (with the M256-E30 DEH LA-R, in-line six engine) with the ISG (Integrated Starter-Generator). My concern is that the engine oil does not lube the turbo bearings when the engine shuts off.
I read that MB did include an electric water pump to keep coolant flowing, but I could not find any information about oil pump flow. I keep my ISG off to safeguard the turbo bearings. I have noticed that when I have not manually turned off the ISG, under some conditions the engine will maintain a slightly higher RPM or may even re-start even when stopped.
Perhaps, MB has allowed for some conditions when the engine should not be off. My issue is when exiting a highway and then stopping at a red light, waiting for my turn to continue. This is when higher RPMs were present and then an immediate stop. I’m hoping for a good solution.
Sajeev answers:
Just so everyone is on the same page, running the engine to let the turbocharger’s bearings cool down is a real concern. It even resulted in an aftermarket solution called the Turbo Timer. The value of such a “cool down” has been deemed irrelevant with the advent of water-cooled turbochargers. That’s provided you change the oil and coolant regularly and don’t run your car in a 24 Hours of Lemons endurance race.
My confidence increases because I suspect Mercedes has another solution in place—as you’ve noticed, the system will restart when necessary. Finding documentation is difficult, but oil temperature is likely one (of the many) variables that factor into the ISG’s system tuning, with a measurement taken from the oil temperature sensor.
Something like an electric oil pump (similar to the aforementioned water pump that remains active) would theoretically be nice, but odds are it’s unnecessary. And implementation would be nearly impossible, as all vehicles use a mechanical oil pump buried within the engine. Even a complex and expensive dry-sump design still needs a mechanical pump at the bottom of the motor to get the system primed and pumping.
Mercedes’ ISG system (and all the others like it) are already exceedingly complex, and engineering a workaround for the oil pump introduces more points of failure. If there’s one place you want less complexity, it’s the oiling system. Failure in this area is far more likely to cause permanent engine damage, so the solution for you is simple:
- Trust Mercedes’ ISG programming to keep the engine running when oil temperatures mandate it.
- Change the oil and coolant regularly.
- Don’t skimp on oil quality.
- Do an oil analysis test as often as you need to ensure your vehicle is operating in a healthy manner.
- Have the “plumbing” for both oil and cooling systems inspected on a regular basis, and fix leaks to the system as soon as possible.
All this talk is enough to make me want a new EV over a new turbocharged vehicle. But that’s neither here nor there, so now I leave it up to the Hagerty Community to chime in!
I know this compares apples to oranges; however, I have a 2014 Mercedes E350 with an M276 3.5 V6 and 78,000 miles. Of those, the Auto Start-Stop function has never been defeated. I have also had similar experiences where I will be stopped at a stop light long enough, and the system will self-restart after stopping. It does seem to have a mind of its own on how long the “STOP” time is.
I have also noticed, though, that these conditions, as you started, have many factors, but one of them must be based on the temperature of the oil. I tend to run the same route daily, and the first stoplight I come to from my house in the summer, at 70+ degrees ambient temperature, the engine will “Stop.” However, during the winter months, when the ambient temperature is 50 degrees or below traditionally, the engine will not “Stop” at the first stop light I reach from the house.
I’m not worried much about the drivetrain’s longevity with the auto-start system being activated. I recently had my car in for service and was given a 2014 E350 with 275,000 miles on the original drivetrain. The car ran flawlessly and gave me hope for my car. I asked the mechanic how much work it has taken to keep the 275,000-mile car running, and he said, “I’m cheap labor, but it’s not needed anything out of the ordinary; it’s on the original starter and, of course, engine. Just keep up with your maintenance and listen to me; your car will go that far if not longer. ”
So now Auto Stop-Start is no longer on my ‘worry list”.
However, the hydraulic braided convertible top lines are a real fear that comes closer day by day!
You have a very large V engine large pistons and best styled engine for dynamic balance and and most probably well overpowered for your journeys. Try the rubbish they are pumping out now, underpowered 1ltr. 3 cylinder all in the name of environment friendly, what a load of rubbish from brain dead politicians and armchair engineers who obviously would need to be told what a spanner was for.
It is the coolant temp that determines if the engine can be shut off. It is done for emissions reasons to keep the engine above the temp where warm up enrichment isn’t required.
The bigger issue to me is valve health. In my Ecoboost, the only time the throttle body injector runs (the only means of cleaning the valves) is at idle. If the valve stems aren’t cleaned they cake in DI motors, meaning the auto start/stop negates the TBI’s ability to clean valve stems. Considering how many manufacturers are now recommending valve stem cleanings now, this is clearly a known issue. Prior to DI motors, the injectors sprayed fuel over the valve stems, cleaning the cake caused by the CCV. No engine will last long with carbon caking on the stems for a miriad of reasons. Considering auto start/stop isn’t mandated, I really wish manufacturers would offer some means of disabling it.
Lots of cars have a button, or screen icon, that disables the stop-start.
My auto start stop button on my 2023 Jeep GC L resets to active upon every restart. Seperatly I thought the restart was triggered by battery voltage drain when motor is off rather than oil temp. I mean how much can oil temp drop at a red-light?
The greatest issue here is the lack of understanding on just how these auto stops work and all that is programmed into them.
There is a ton of variables that determine when a system stops or not.
Things like running AC full, heater full, stopping for more than 2 min in some will restart, if the engine is running hot, if the engine is not up to temp and more.
The Turbo oil remains in the turbo after stopping, the water cooled housing stops coking. Synthetic oil also plays an important role.
I think many will find Turbo failure is often due to poor oil changes, wrong oils and poor coolant.
Also these small turbo chargers are not always the best they could be due to cost constraints.
The reality with many of today’s cars these smaller and boosted engines are just not long lived. I know many of us watch the Car Wizard on YouTube. He points out many cars todsy are good gor 100k miles and after that they become money pits.
Things like failed timing belts and chains along with other major issues can make it impossible to repair at a price worth saving the car.
He just had a Lincoln on this week with just over 100k miles and two failed Turbochargers. It would cost more to fix than it was worth.
This is not just a ICE issue. EV and Hybrids can bleed even more money. I saw a Malibu Hybrid eith just over 100k miles but the battery needed replaced. The car looked great but the battery cost more than the car is worth.
Many Hybrids and EV as they age will be like an old IPhone with a dying battery and an old tech no one wants.
The government regulations on MPG and Emissions mean well but we have passed a tipping point of affordability and reliability. They need to balance this for the consumer or no one will afford these cars.
But beware. There is a move to oust for less lanes in the roads and to make traffic more an issue. I’m sure you seen the 4 lane streets cut to two lanes with a bike lane no one uses.
They also are promoting trains and public Busses that most of us can’t and won’t use. We are too spread out vs much of Europe. What works there is not going to work here. Texas is proof of that.
Hey Hyper, I am curious about this comment you made about the move to congest streets. Can you cite some sources or a published bill or plan? I feel like that’s a pretty big claim and would like to be better educated if you have a trusted article or a bill you can share.
And personally, I don’t mind public transportation as long as it keeps crummy drivers off my streets.
Hey Joe, the city of Cincinnati is doing this all over the city for bicycle. And it really causes a lot of congestion!
The same thing has happened in my city and cities near me. They are changing roads from 4 lanes to 2 with bike lanes and a turning lane in the center. (I have heard it’s due to federal regulations or something)
https://highways.dot.gov/safety/other/road-diets/road-diet-informational-guide/1-introduction#:~:text=The%20reduction%20of%20lanes%20allows,parking%20(see%20Figure%202).
This summer on a street I use in my daily commute they did convert a big stretch of it from 4 lanes into 2 with bike lanes on either side and a bunch of barriers between the bike lanes and the road. You are correct that I have never seen a bicyclist on it. I think a big chunk of that is due to the fact that just a block or so away there is a dedicated bike/pedestrian path on an old railway right of way. But the city got a bunch of money to make for safer biking. Now to be fair it is not a high volume road so the change to 2 lanes hasn’t had an impact on traffic at least during the times I drive it.
On another section of road on my commute path they changed it from 4 lanes to 2 in one direction, 1 in the other and a two way left turn lane and it was promoted by that city as a “traffic calming measure” that they claimed would lower speeds. Of course it hasn’t done that as people still drive 10+ mph over the unchanged speed limit.
Yes much of this is federal funding and counter to the smooth traffic we once had.
Same on round abouts. They are claimed to be safer. They may have less deaths which were few but accidents are up. People have no clue how to use them.
We have a few you have to cut off the other driver to move to exit if you go 3/4 away around it.
The speed rams have damaged some low sitting cars that were not speeding.
I have a 2017 Toyota Highlander with the auto start-stop. It works OK, I guess. But it IS annoying when the light turns green and you have to wait for the engine to turn on.. also, during the summer with the AC blasting and the engine (and the AC compressor) turn off and you are blowing hot air.
The biggest contributor I’ve seen for the engine cycling back on when stopped is the battery level. It takes a lot of power to run the HVAC, lights, and radio.. I especially noticed this when we got a new battery… With the old battery, we didn’t really notice, but the auto-stop-start hardly operated.. once the new battery was in, it would activate AT EVERY LIGHT. So clearly battery health and capacity have a significant role to play in how aggressive it is.
But here is a real kicker.. the computer keeps track of the engine starts and will REQUIRE you to replace the starter motor after 384,000 starts, weather it still works or not.
The one thing I find especially annoying is we will pull into the driveway and stop, the engine will stop, then we put it in park, which reactivates the engine.. then we turn it off and get out…. It’s an unnecessary stop-start just to turn off again.
THE START AND STOP FEATURE ON MY LINCOLN CORSAIR IS THE DUMBEST IDEA I’VE EVER DEALT WITH AND IT’S JUST ONE MORE WAY OF CAUSING PREMATURE STARTER FAILURE AND ADDING UNNECESSARY STRESS ON A DRIVER WHO THINKS A VEHICLE SHOULD STAY RUNNING UNTIL THEY DECIDE TO TURN IT OFF. THERE IS NO WAY TO PERMANENTLY DISABLE THIS UNWANTED AND UNNECESSARY FEATURE THAT MAKES ME HATE DRIVING MY CAR. IT’S A STUPID AND FORCED FEAUTURE THAT SHOULD BE ILLEGAL.
There is no need to have a complicated electric oil pump to provide a little oil pressure on restart, or to send some through the turbo on shut down. An accumulator like an Accusump would do the trick. With an electronically controlled valve you can hold and then release the pressure just before the restart event to prevent a “dry start”. W/o a valve it can provide some oil flow after shut down to prevent oil coking in the turbo bearings. I am a bit surprised that to the best of my knowledge no mainstream mfg has implemented such a strategy.
On the other hand Toyota implemented a heat harvesting and storage system in certain years of their hybrids. Essentially a thermos type device that has a coolant loop just through the head. On shut down as the coolant in the head continues to increase in temp the electric pump harvests that extra heat often significantly above the normal operating temp and then stores it. Upon restart it dumps that coolant into the head to shorten warm up time and reduce the need for warm up enrichment.
Do your homework. There are several sources that make plug-in modules to allow the user to set the start/stop default to disabled. In other words, every time you make a fresh start in the vehicle, there’s no need to press the button to disable the system.
I paid about $100 for the plug-in module I bought. I don’t know about any potential effects with regard to warranty. I don’t think the ECM or BCM can see the module. I can see any difference in scan codes or live data.
Ok, first and foremost engine start stop is based on electrical load and the battery state of charge. If you have many accessories running and the battery is not above a specified charge level the engine will not stop or may prematurely start back up. There are other factors involved sure but the system is first looking at the electrical system.
As far as the turbos are concerned there should be a check valve or a few to prevent oil from escaping right away. And unless you are constantly hot rodding around I would be concerned with burning the oil in the turbo bearings under normal driving conditions.
I bought a new Mazda in the past year with the SkyactivG engine and was pleasantly surprised that 2024 versions of my specific model and trim didn’t have either auto stop/start or cylinder deactivation due to supply shortages. Both features are back in the cars this year. I don’t care about the single city mpg the features were said to have gained me, especially when cylinder deactivation is known to cause multiple troublesome issues on these engines. I went for the non-turbo engine, too. Less complexity, cost and maintenance down the road.
I had a cls63 with auto start/stop. If I spent more that 10 mins in traffic I used to turn it off, because that big 5.5l twin turbo V8 didn’t like it. Otherwise a fantastic, wonderful car.
Very good info
This is one of those interesting and probably unnecessary disputes like which direction to hang the toilet paper roll. My collection is too old for me to have to deal with this feature, and will probably stay that way because the government and picky consumers have all but killed anything interesting about the automobile. In the few cars that I have driven that has this particular feature, when it gets on my nerves, I just push the little button. The starters are designed for the extra service, and your warm, previously running engine isn’t that hard to start anyway. If I was going to disable a feature on a newer car, it would probably be the link to Skynet and all of the nanny driving aids, and this one would be very low on my list.