Sluggish starter when hot - S212 E500 (M273)

[ChrisPDuck]

My car always starts very easily when cold - the starter spins fast and the engine kicks into life very quickly. But I've noticed a couple of times that the starter motor is much more sluggish, and the engine takes a few turns before it will start, after a longish journey - I hesitate to call it a hot starting problem, because the weather hasn't been particularly hot since I bought the car in August, but it does only seem to do this when restarting after running for a while. And it usually doesn't do this - it's only really happened 2 or 3 times that I can recall.

The battery is a Bosch S5 that's just over a year old, and as far as I can tell the charging system is working fine. I've only just discovered the in-dash voltage/current display though, so will get into the habit of checking that before every start, to see if anything is different when it's hot. My iCarSoft doesn't show any errors.

Any suggestions for where I should be investigating?

 

[Will]

@Londonscottish has a similar vintage S212 E500 and I’m sure he had a starter motor issue not that long ago.

Unsure of the symptoms he had before replacement but thought it might help so have tagged him in your thread

 

[ChrisPDuck]

Thank you, yes, it seems our cars were separated at the factory gates (almost) so I think his starter motor issues could be relevant.

 

[MikeInWimbledon]

I would be calling my tame suto electrician, asking him whether it’s starter or ignition.

What’s the general state of the car otherwise? Do you use it regularly or irregularly? Just short trips, or more usual usage? How many miles on it and have the plugs ever been replaced? If it’s six figure mileage it’s not unknown for the heavy V8 to be calling for a new starter

 

[Londonscottish]

My car always starts very easily when cold - the starter spins fast and the engine kicks into life very quickly. But I've noticed a couple of times that the starter motor is much more sluggish, and the engine takes a few turns before it will start, after a longish journey - I hesitate to call it a hot starting problem, because the weather hasn't been particularly hot since I bought the car in August, but it does only seem to do this when restarting after running for a while. And it usually doesn't do this - it's only really happened 2 or 3 times that I can recall.

The battery is a Bosch S5 that's just over a year old, and as far as I can tell the charging system is working fine. I've only just discovered the in-dash voltage/current display though, so will get into the habit of checking that before every start, to see if anything is different when it's hot. My iCarSoft doesn't show any errors.

Any suggestions for where I should be investigating?

Mine was getting more and more sluggish over a period of months and I assumed it was because the car stands a lot and the battery needed a more frequent trickle charge. Then one day I couldn't restart the car after I pulled up outside a friend's house in London having driven it back from Malvern.

The AA towed me home. The next day I had the guys from Replacement Car Keys come and have a look at it as I thought it might have been the ignition barrel - but that was fine. Then the AA came back and found the fuse for the motor had popped, ran some tests and found the starter was trying to pull a ridiculous current. One new starter later and it's been fine ever since.

 

[Londonscottish]

I would be calling my tame suto electrician, asking him whether it’s starter or ignition.

What’s the general state of the car otherwise? Do you use it regularly or irregularly? Just short trips, or more usual usage? How many miles on it and have the plugs ever been replaced? If it’s six figure mileage it’s not unknown for the heavy V8 to be calling for a new starter

Mine made it to 13 years/80-odd thousand miles.

 

[Londonscottish]

My car always starts very easily when cold - the starter spins fast and the engine kicks into life very quickly. But I've noticed a couple of times that the starter motor is much more sluggish, and the engine takes a few turns before it will start, after a longish journey - I hesitate to call it a hot starting problem, because the weather hasn't been particularly hot since I bought the car in August, but it does only seem to do this when restarting after running for a while. And it usually doesn't do this - it's only really happened 2 or 3 times that I can recall.

The battery is a Bosch S5 that's just over a year old, and as far as I can tell the charging system is working fine. I've only just discovered the in-dash voltage/current display though, so will get into the habit of checking that before every start, to see if anything is different when it's hot. My iCarSoft doesn't show any errors.

Any suggestions for where I should be investigating?

The other possible culprit is the crank position sensor; I replaced that on my previous 3 MBs. It causes a hot start problem. If you let the car cool down for a while it'll restart. Doesn't slow down the starter though.

 

[ChrisPDuck]

I would be calling my tame suto electrician, asking him whether it’s starter or ignition.

What’s the general state of the car otherwise? Do you use it regularly or irregularly? Just short trips, or more usual usage? How many miles on it and have the plugs ever been replaced? If it’s six figure mileage it’s not unknown for the heavy V8 to be calling for a new starter

The car seems to me to be in very good condition, inside, outside and mechanically. It's been well maintained and came with a big stack of service records all the way up to this summer. It's currently on 96,000 miles. I use the car regularly, for a mixture of journeys - 160 mile round trip a couple of days ago, which is when the issue last occurred.

The spark plugs seem to have been last replaced two and a half years and 20,000 miles ago. What is the recommended interval for plugs?

The slow turning of the starter does lead me to suspect the starter motor, rather than the ignition system, but I wondered whether the fact that it doesn't seem to happen when cold might be a clue to a specific fault.

 

[ChrisPDuck]

Mine was getting more and more sluggish over a period of months and I assumed it was because the car stands a lot and the battery needed a more frequent trickle charge. Then one day I couldn't restart the car after I pulled up outside a friend's house in London having driven it back from Malvern.

The AA towed me home. The next day I had the guys from Replacement Car Keys come and have a look at it as I thought it might have been the ignition barrel - but that was fine. Then the AA came back and found the fuse for the motor had popped, ran some tests and found the starter was trying to pull a ridiculous current. One new starter later and it's been fine ever since.

Thank you - your symptoms do seem to suggest my starter is reaching the end of its life. Was that episode outside your friend's house after short stop, or had it cooled down a lot?

Mine made it to 13 years/80-odd thousand miles.

Similar to mine then - 14 years and 96,000.


If I'm going to tackle fitting a new starter myself, does anyone know what access is like? Presumably it has to be accessed from below, but does anything other than the undertray need to be removed?

 

[ChrisPDuck]

The other possible culprit is the crank position sensor; I replaced that on my previous 3 MBs. It causes a hot start problem. If you let the car cool down for a while it'll restart. Doesn't slow down the starter though.

Good info, thanks. So the slow starter motor probably rules that out on this occasion, but I'll keep it in mind for the future.

 

[ChrisPDuck]

After a bit of Googling, it does look as though a section of exhaust has to come out, and maybe an engine mount has to be moved (although this was for a W211 E500). I'm not keen on doing that much lying on my back under the car, with it jacked up onto ramps on my sloping drive. This might be a job for my trusted local garage.

 

[MikeInWimbledon]

Mine made it to 13 years/80-odd thousand miles.

Yep, and with mainly weekend usage, methinks.

 

[MikeInWimbledon]

Thank you - your symptoms do seem to suggest my starter is reaching the end of its life. Was that episode outside your friend's house after short stop, or had it cooled down a lot?
Similar to mine then - 14 years and 96,000.
If I'm going to tackle fitting a new starter myself, does anyone know what access is like? Presumably it has to be accessed from below, but does anything other than the undertray need to be removed?

"ShortArmsAndDeepPockets" here again: wouldn't it be much quicker, and cheaper, to get your local Auto Electrician / Halfrauds / Garage to fit a refurbished starter ?

It's routine everyday stuff for them, and they have trade access to reliable refurbished kit, and it's a very crowded engine bay for you.

Plucking a number from the air, I would have thought it's maybe £500, which might be a third less than buying a brand new unit and fitting it yourself.

(BS numbers plucked out of the air, but you'll get my drift)

 

[ChrisPDuck]

"ShortArmsAndDeepPockets" here again: wouldn't it be much quicker, and cheaper, to get your local Auto Electrician / Halfrauds / Garage to fit a refurbished starter ?

It's routine everyday stuff for them, and they have trade access to reliable refurbished kit, and it's a very crowded engine bay for you.

Plucking a number from the air, I would have thought it's maybe £500, which might be a third less than buying a brand new unit and fitting it yourself.

(BS numbers plucked out of the air, but you'll get my drift)

Don't worry, my arms-to-pockets ratio is similar to yours I think
I definitely won't be taking the car to a main dealer for this - the garage I'd use is a local all-makes family business who I've been using for over 30 years.

If I was doing this myself, which I haven't entirely ruled out yet, I'd drop the starter and then leave the car in the air for a few days while I have my starter refurbished locally. There's a place I've used a few times for alternators, and they also do starters.

A new starter from MB Newcastle is £500, but I'm sure I can do much better elsewhere for a new OE-equivalent part from a friend in the trade, and a refurbished part is also an option.

 

[Londonscottish]

Thank you - your symptoms do seem to suggest my starter is reaching the end of its life. Was that episode outside your friend's house after short stop, or had it cooled down a lot?

Similar to mine then - 14 years and 96,000.

If I'm going to tackle fitting a new starter myself, does anyone know what access is like? Presumably it has to be accessed from below, but does anything other than the undertray need to be removed?

The episode was after a short stop after a long journey. In retrospect, the load had blown the fuse there and then.

But, prior to that, when starting hot or cold it would often struggle to spin up quickly in a very similar manner to when the battery was low on charge.

So for ages I thought it was battery even after I'd changed it. I thought my usage pattern was to blame as (in the past) I'd seen that happen with this and with my previous E500. My 211 in particular don't like sitting around for long periods

 

[Londonscottish]

Yep, and with mainly weekend usage, methinks.

Yes, I try to use my wife's Fiat 500 for all the local stuff.

Or Ubers/Limebikes/public transport.

 

[Londonscottish]

"ShortArmsAndDeepPockets" here again: wouldn't it be much quicker, and cheaper, to get your local Auto Electrician / Halfrauds / Garage to fit a refurbished starter ?

It's routine everyday stuff for them, and they have trade access to reliable refurbished kit, and it's a very crowded engine bay for you.

Plucking a number from the air, I would have thought it's maybe £500, which might be a third less than buying a brand new unit and fitting it yourself.

(BS numbers plucked out of the air, but you'll get my drift)

My local garage charged £200 for a new Bosch one. Plus £120 for fitting. With VAT, £384.

Really can't complain.

 

[Bellow]

Before going any further, have the security at the battery terminals been checked? It's far from uncommon for them to be a touch loose - possibly more so when heat soaked.
I'd expect a failing starter motor to be at its worst turning over a cold engine - unless the heat is affecting the motor.

 

[ChrisPDuck]

Before going any further, have the security at the battery terminals been checked? It's far from uncommon for them to be a touch loose - possibly more so when heat soaked.
I'd expect a failing starter motor to be at its worst turning over a cold engine - unless the heat is affecting the motor.

Good point - I'll check that.

 

[Londonscottish]

Before going any further, have the security at the battery terminals been checked? It's far from uncommon for them to be a touch loose - possibly more so when heat soaked.
I'd expect a failing starter motor to be at its worst turning over a cold engine - unless the heat is affecting the motor.

Yeah mine was sluggish hot AND cold. Like you say, probably worse cold - it could really struggle to get the first couple of revolutions done.