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Mercedade's SLK 230 Kompressor 1997


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Yep - that one https://autoshite.com/topic/40893-1997-mercedes-slk-£850

I picked it from @95 quid Peugeot on literally the hottest day of the year, so he was treated to the sight of an extremely sweaty man emerging from a train station having had to actually run for a train at Liverpool Street.

As ever, he was a gent and a pleasure to deal with, and so began the gentle slog back to Manchester (via a night in Ely)

I think this picture is ridiculous. I clearly creatived the shit out of some TV adverts in 1997.

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I had a front seat passenger for the trip - three alloys (with another in the boot). Arrange like this, so I could get the roof down still 

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I'd been planning on a run-it-for-a-few-months-and-sell kind of strategy, but I'm unable to let things go when they bug me, so it's a got a bug list (mostly small, one big)

First and foremost - the supercharger.....doesn't. That's just the way it goes sometimes - it's a perky car in any case, (2.3 litre in a shoe-sized car) so up until 30 mph or so, you'd be hard pressed to tell. But after the 200 miles back, it was obvious that at about 45 mph, you put your foot down to engage the kickdown, a bit more noise happens, but speed doesn't really pick up like it should. I honestly don't think the various previous owners will have clocked it unless you have something to directly compare it with. I do. My Vitesse (2.0 turbo) is very similar levels of performance, but on a 50-70mph sprint, currently the Rover would leave the Merc for dead.

This seems to be a fault with many potential causes. The supercharger is driven by a pulley on an ECU-controlled  electromagnetic clutch which engages at around 2000rpm. There are many reasons why the ECU may not engage the clutch, and finding them is something of a battle!

MAF - without getting a clean MAF readings, the ECU will refuse to play ball. There seemed to be quite a lot of oil around when I pulled the air intake system apart, but after I cleaned the MAF with contact cleaner, I managed to get the following readings which look pretty sensible to me

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The Merc is, like the Vitesse, too old for ODB2. However, it's possible with a cheap but impressive adaptor, to connect a standard bluetooth ODB2 module to the 38 pin Mercedes connector under the bonnet.

So I'm pretty confident that the MAF is OK actually.

It could be the magical K40 relay module (what is it about Mercs? Each model seems to have its own Achilles heel relay - for the W124 it was the fuel pump relay and the 'OVP' relay), but I would expect some other running problems, and I don't have any. The car itself runs well and pulls very quickly until about 40mph. What it has is a deadzone above that, which should be plugged by the supercharger. 

I got the K40 out - but it looked OK to my eyes (NB - my eyes may not know shit) 

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I thought I'd better check the S/C clutch wiring, and it turns out I'm not the first person to start looking into the supercharger clutch wiring.

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But with 12v applied, I can hear and see it engage (not yet tried with the engine running, I must admit)

 

The car starts perfectly every time, it runs pretty smoothly - it's just underpowered.

 

Any tips for my next moves would be hugely appreciated. What else stops R170s from telling the s/c clutch to engage?

Other, more mundane stuff to follow...

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1 hour ago, B4lljoints said:

https://forums.mbclub.co.uk/threads/supercharger-not-working.118814/

Don't know if this link might help? It's a CLK they're talking about but the same engine. 

Thanks for that. That was my attempt over the weekend, funnily enough.

What I'm discovering as I work through it, is that all the common elements have been tackled before, so this is clearly a longstanding issue.

When I got the ECU apart, I shit myself at the terrifying number of sensitive electronic components, I could see that the MOSFET had already been replaced. I had mine new one to hand anyway, so I replaced it anyway. The 'old' one had lost most of the plastic backing that insulates it from the casing, so I figured it might have shorted. Since replacing it, it definitely runs differently, but still no supercharger. It now hangs on to the revs for slightly longer and is keener to change down, so perhaps that was knackered and now it's not.

Same goes for the K40. The one in there is an aftermarket one - it's in waaay too good condition to be 23 years old, but it's got no MB branding on it. I've reflowed some of the joints, but I'm not super confident I've made the best job of it. I am tempted to get a new one, but it's a £100 gamble.

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1 hour ago, 95 quid Peugeot said:

Blimey,  that really demonstrates what an old giffer i am, i thought it sprightly 

Thing is, it is - in the first two gears. It actually drives very much like my old 260e, which is why it took me nearly 200 miles to work out something wasn't quite right. It's just the way of it - I'm still driving it every day because it is such an easy drive around town, so I'm not surprised you wouldn't have picked it up. It just makes motorway/A road overtakes more of a struggle than it should be

It's a nice puzzle for me to get stuck into

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I also decided to resolve the appalling handbrake - totally non-existent. Thankfully, the parking brake is a drum/shoe arrangement, and they just needed adjusting. Take a wheel off, rotate until you can see the adjuster wheel through one of the wheel bolt holes.

Could I find the adjuster? Could. I. Fuck. In the end, I was struck by inspiration and used a cheap boroscope camera and my phone to look through a bolt hole into the drum.

Turn the adjuster until the drum can't be turned by hand, then back off the wheel 4/5 clicks.

Whilst I was there, I discovered the pads for the rear foot brake had braked their last...

20200815_123000.jpg

Pads are cheap, and they're fixed calipers, so no bolts to undo, just a couple of taps to move the retaining pin - I love this easy work!

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When I picked up the car, Keith mentioned it had a dodgy front  left speaker which had been cutting in and out.

These have a fancy Bose amp set up, so it takes the signals from whatever headunit is installed and pulls it through a Bose staging amp. Then, using only the front channels, it powers a mid-range and tweeter in each door, plus two miniature woofers, one behind each seat mounted in the bulkhead. 

Neither the mid nor the tweeter in the left door work, so I did wonder if perhaps some dodgy cabling had got snagged/broken.

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However, no amount of wiggling and wobbling could get a signal up and running. I suspect the amp, which lives on a cool little board under the passenger's feet

20200814_123504.jpg

I can see one on ebay for £30 so, once I've done a final shake and wobble, I'll probably just replace it.

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9 minutes ago, SRi05 said:

I never even noticed the supercharger the short time I had it either, the go pedal never touched the floor as the wife was mainly in it with me ?

If this comes up for sale again can I call dibs please ? I'd like to steal my Saab back at some point from her and she quite liked this ? 

Absolutely - my plan is to keep it for as long as it's fun. It's not going to replace the Vitesse as my daily, but I am enjoying the blezz around the place.

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Just now, mercedade said:

Absolutely - my plan is to keep it for as long as it's fun. It's not going to replace the Vitesse as my daily, but I am enjoying the blezz around the place.

Nice one, cheers. She sold her newish modern to her dad literally a few weeks after I moved this on, I'd have kept it if I'd known. She pinched my Saab floppytop off me as it's auto, but she's not keeping it ?

Good luck sorting the speaker issue out, it drove me crazy. I swapped a couple of headunits/ ISO adapters over hoping that would cure it but no dice. Once I read up on issues with amps etc I was out, way beyond my very limited capabilities 

 

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24 minutes ago, SRi05 said:

I never even noticed the supercharger the short time I had it either, the go pedal never touched the floor as the wife was mainly in it with me ?

If this comes up for sale again can I call dibs please ? I'd like to steal my Saab back at some point from her and she quite liked this ? 

Oi oi  id have it back as well  ?

 

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On 9/15/2020 at 2:19 PM, 95 quid Peugeot said:

Blimey,  that really demonstrates what an old giffer i am, i thought it sprightly 

Me too , i think half of autoshite has owned this without realising there was a problem with it :D

I just thought it was made for old american women to tootle about in 

It sounds like it's in the right hands now though 

 

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I’m disappointed in all of you! 
Old farts that shouldn’t be trusted with a wheelbarrow. Even after 40 years on the road( if you include me Fizzy, I’m proud to say I still have to try every new car out properly. This means foot to the floor all the way to either top speed, or these days more likely a speed where I think I might just get away without  getting locked up. 
An early 230k auto should be good for almost 150 and a 0-60 time of about 7 seconds, which isnt slow even by modern standards.  Fatha N’s one wasn’t left behind that badly when he followed me recently. And he is an old fart and I was in a Golf R.

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16 hours ago, SRi05 said:

Nice one, cheers. She sold her newish modern to her dad literally a few weeks after I moved this on, I'd have kept it if I'd known. She pinched my Saab floppytop off me as it's auto, but she's not keeping it ?

Good luck sorting the speaker issue out, it drove me crazy. I swapped a couple of headunits/ ISO adapters over hoping that would cure it but no dice. Once I read up on issues with amps etc I was out, way beyond my very limited capabilities 

 

Yeah, the speaker one is frustrating. I worked out that the headunit is fine, because the woofer in the bulkhead was working and, seeing as the amp only utilises the front channels, it was clearly getting the correct signal from the headunit.

So, thinking only about the left channel:

The amp receives 'FRONT left' from the headunit. It then splits this, and sends one + and - output for the bulkhead woofer (using the head unit's left/front signal), and one + and - signal for the door speakers (ALSO using the headunit's left/front signal).

The door speakers are then split into tweeter and mid-range circuits using a crossover (i would guess).

It's this that makes me think it's an amp problem, because a) I can't get a dodgy connection, it's just silent, and b) it affects both the mid and tweeter in the door.

Green circuit below:

bose.thumb.png.8813a9303f26bed5aa8c0126f5296370.png

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15 hours ago, NorfolkNWeigh said:

I’m disappointed in all of you! 
Old farts that shouldn’t be trusted with a wheelbarrow. Even after 40 years on the road( if you include me Fizzy, I’m proud to say I still have to try every new car out properly. This means foot to the floor all the way to either top speed, or these days more likely a speed where I think I might just get away without  getting locked up. 
An early 230k auto should be good for almost 150 and a 0-60 time of about 7 seconds, which isnt slow even by modern standards.  Fatha N’s one wasn’t left behind that badly when he followed me recently. And he is an old fart and I was in a Golf R.

Exactly! I'm hoping to make it as much of a surprise to the unsuspecting as the Vitesse currently is  (0 - 60 in 7 seconds).

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11 hours ago, HMC said:

Love your driveway shot with the 800 there. Did they ever offer the 230k in these with a manual box? I know they did in the CLK but it was rarely specified.

Cheers man.

I love that both my cars are 23 years old, but feel like they are approaching it from completely opposite angles.

I can't believe that the Merc is already 23 - it's a car from the future, with a folding metal roof for god's sake.

I can't believe the Rover is only 23. It's got wood and leather and was basically designed in 1984

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1 hour ago, Supernaut said:

Would it cause the engine to go pop if you just engaged the supercharger clutch permanently? Maybe with a switched 12v feed with the ignition?

I didn't realise these even had a clutch on the supercharger, I thought they were like any other supercharged engine, as in always on.

That's the last resort, I think (at which point I'll probably discover the supercharger is goosed). Plenty of people seem to have either put a relay-swtiched 12v supply to it, or gone properly mechanical and wedged the clutch with a couple of copper washers to jam the outer pulley permanently.

I'd like to get it working properly if possible, but if it can't be fixed with soldering and wiring (ie it needs a new k40 relay, or the wiring has broken down inside the clutch), then permanent supercharge is the way forward.

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