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!
Nope, not a pun or even a typo but a real race….. I’m amused by commenters who rail against pushing a button every time they start the car, after opening a door, settling into the seat, closing the door, maybe pulling the seatbelt on, starting the engine and selecting a transmission position. But pressing that button is just too much to deal with!
My dad’s Cadillac XT4 Sport SUV has the auto-stop/start. I forget the years, but it’s only 3-4 years old and has the turbo 2.0L. I noticed that ti will sometimes re-start while stopped. It could be for turbo cooling, but I suspect it was for the AC compressor since the last time I drove it was in mid October in South Carolina — temps still in the mid 80s to low 90s (we had a rather warm October this year).
The round about is great. The Aussie V8 Supercar series races at Surfers Paradise once a year near the end of October. The use or curbs there is what traffic islands are all about.
Sure, I’m crazy but look at the next one as a chance for an overtake. Won’t happen but it’ll make you smile.
One of our cars remembers the last setting of the auto start/stop function and in our Kia I was able to find an aftermarket solution that does the same. The amount of gas saved is not justified by the extra work the starter has to do and for concerns like those raised in this article (our MINI is turbocharged)
I have this in my work vehicle and I think it’s a pain in my butt. I don’t like it and from what I have been told you can expect to be changing out your starter every 5 years or more. More wear on everything.
I’m old enough that having my engine srall when I stop makes me nervous. I just bought a ‘24 Nissan Pathfinder which has a button to defeat the ASS, but it has to be pressed every time you start the car. I’m looking through all the programming features to see if there’s a way to permanently disable it. It’s definitely the worst thing on the car.
I rented a few cars with that “feature.” Every time it kicked in, I released the brake just enough to get it running again.
I don’t own a car with either start/stop feature nor turbo. And very intentionally probably never will. Problem solved, this article is irrelevant to me, next article please.
I’m a new member and am finding this section to be very helpful. I just purchased 2024 XT5 and I have learned
more about this system than any mechanic at my dealer. I am 87 yrs. old and have owned 52 cars in my lifetime.
The last 16 cars have been Cadillacs along with 3 corvettes and I restored a 1931 Model A Ford Roadster so I guess you can call me a car nut. I also owned a 2004 Cadillac XLR. Enough said.
I own a 2017 BMW M2. It has a button which gives me the ability to turn off the auto start/stop. It does not reset each time I start the car. It is off always and has never given me a problem. There have been a couple of times when I have fat fingered the engine start/stop button but it was my fault, not the car’s.
most need to be pressed every time the car is started –
I run a 300k mile 1990 Toyota 2.4L pick up. Never had an issue with my Start-Stop system!! Same applies to the electric windows, ABS, lane departure and all the other crap that’s thrown in to new cars.
And this is one of many reasons that I have kept my 2006 BMW and 2007 Yukon. Too many computers that fail way too often. My mechanic says that 80% of his work is on computers. I will just keep maintaining them. “Leading edge is bleeding edge.”
When we ordered our 22 Ford 150 5 liter Auto start was deleted on order sheet for a cost of about $50. Money well spent.
Or just permanently disable tht ridiculous auto stop feature