Given the age of these cars and most people running a lot more boost these days it would be wise to see if the belt tensioner is within spec - to make sure you are getting all that boost
this will confirm;
1) the belt is the correct length
2) belt not stretched (worn)
3) tensioner weak
you will see mark A. the line B has to be somewhere in between A.
a very similar marking is on the tensioner for the water pump, power steering etc. check to see if its in spec.
Top tip. Just checked mine. Both belts were replaced just under 30,000km ago. The supercharger belt is now at the max wear limit, the power steering /AC belt is half worn.
Snap! Just checked mine. The same, S/C belt tensioner @ 90%, P.A.S.belt almost perfect. I've got a new Gaitorback belt, I'll fit it and see what happens. Replacing the belt might cure the chirping noise I get on cold start up.
I came across this info on a site some time back:
''Diagnosing Belt Noise. The supercharger drive in high-performance applications is often noisy, and finding the source of the noise is not always easy. We have found that an audible squeak or a chirp that is present upon engine start-up but disappears as the engine warms is often caused by the supercharger belt itself. When the engine is cold and the belt is cool and stiff, noise is created as the belt transitions from one pulley to another. As the belt warms, it becomes more pliable and the noise diminishes. In this case, the solution is to replace the belt.
In all supercharged applications, supercharger belt life will be significantly shorter than the service life for a typical accessory belt. Supercharger belts should be replaced regularly with the highest quality belts available. We have found the Goodyear Gatorback belt and the Gates Micro-V Greenstripe to be the longest lasting and the most noise-resistant. ''
The original MB belt P/N A0119975892 is quoted as being 1295mm long. The old belt in mine was stamped 1335mm long when I removed it. My new Contitech belt- supposedly MB OEM- is 1330mm long and the tension indicator is halfway down the scale. I'll just have to keep an eye on it. I know from several older cars I have that replacement parts are a matter of doing the best you can with what parts you can find.
I replaced my tensioner and my alignment is still off. its where the yellow mark is. I currently run an ASP pulley and smaller clutched s/c pulley. the belt which came with my ASP pulley kit was a 6PK1390. i never bothered to re-check once i got a smaller s/c pulley.
note the dust off the belt which has built up on the tensioner... belt was considered too loose.
the ideal tension should be between the green marks - if its in there its considered OK.
I have done some measurements and a 6PK1375 should put me right at the top of the green mark (new yellow mark). and a 6PK1380 should put me in the middle. these belt sizes aren't common and had to order them online...
Can say that with my setup, 220mm Speer crank adapter and a 86mm clutched supercharger pulley I got all the way up to 1.1bar boost after changing the tensioner and putting on a 6pk1400 belt.
Before I could hit 1 bar but it started to slip like crazy after a few months and I could barely get 0.7 bar on it and it dropped so many times on a single pull.
I went from a 1415 to 1400, 1415 worked well with the stock supercharger pulley, but as soon as it got reworked to 86mm it was on its way out and wearing the belt more than it should normally. Also my tensioner was bad, I could move it with my hands and no tools while the new tensioner was impossible to move with my hands, so yes big difference.
I am still waiting for my belt to come. the new belt (gates HD 6pk1390) i think was worn very quickly as i cant even hit 11psi now. I go WOT and it drops to 5psi and then spikes up to 13psi. its slipping too much - i might go back to "gatorback"
M111.975 C230k, but I am here on the R170 page because engine specs are the same.
I am not sure what brand it is, it is only referred to on the page I bought it as a 6PK1400 multirib belt. I need to check under my hood and see what it says. But it works
It's a good tip but I guess it only really tells you the state of the belt rather than the condition of the tensioner? I'm in the process of changing belts anyway because they look really old on my'97 - dry brown and ragged around the edges and unfortunately I'd taken them off before I read this thread. Just to note, the markings for the compressor tensioner can only be read from the underside of the car. I've decided to change the tensioners anyway since I'm changing all the pulleys as well. One was rumbling slightly when I spun it and I reckon the others were probably not far behind at 240,000km.
thats true - but the thing is, if you replace your belt and its still out of spec then you can assume its a weak spring in the tensioner. given the age of these cars they should be replaced...
I was able to take a pic of mine from the top of the car. this is with the new tensioner. the mark is still out of spec. its higher than before with older tensioner but still out of spec - this means my belt size of 6pk1390 is too long. it cant have stretched that much as i just had this new Gates HD belt for 1 mth and did 1 track day with it.
I am trying a Gates 6pk1375 belt (yes hard to find but getting from O/S) and that should bring me to the max tension mark (purple). a 6pk1380 should get me in the middle. once the belt comes in, I will know!
Just checked my new belt. I probably used up half my initial free adjustment to the wear limit in just 500 miles of highway running. Hope it settles down now.
just swapped my belt out for a shorter belt - 6pk1370. when i put it on, it was at the top end of the tensioner, now that its settled its in the middle. car runs perfectly now!
Yep, I know it's an old thread but still seemed the best place to post.
The Contitech ribbed belt supplied with the larger S/C crank pulley (220mm) is 1413mm which lasted around 30,000 miles before the belt tensioner was almost maxed out (tensioner new at time when the larger pulley was fitted), the S/C pulley is still stock.
The replacement belt I fitted was a Contitech Elite 1410mm which is similar design to the Goodyear Gatorback belt which I originally intended to fit but couldn't get. The new belt only lasted 4-5000 miles, it stretched by a massive 15mm which maxed out the tensioner 100% and it was 3mm shorter when new compared to the previous belt!
I ordered a new Contitech 1400 mm belt this time as I think 1413 mm belt supplied with the larger crank pulley is too long. The 1400 mm is a little tight, the tensioner is right on the minimum mark and I'm somewhat concerned it's putting undue pressure on the S/C pulley and the belt tensioner. A 1405mm belt seems to be the best compromise but Contitech don't make one, I went with a Gates 6pk1405 which should be delivered soon.
Anyway, the bottom line is, avoid using the Elite belt for S/C's but I'm sure there are fine for the Alt, W/P & A/C etc.
from what ive seen gates have been pretty good if you cant get the goodyear gatorback in the correct size.
gates also have another range "gates hd" belts which are the same belt but very heavy duty for heavy duty applications. you can tell its the HD belt as its green. I've seen many people with dodge hellcats etc run the gates green belts and they cop a lot of abuse and still hold up!
Using some of the most advanced materials and manufacturing processes available, Gates Micro-V® Belts are engineered to outperform the competition. We’ve worked with most of the top automobile manufacturers in the world to produce our Micro-V® belts with OE quality to fit virtually any vehicle...
Just for reference. New belt fitted, (Gates 6PK1405) after 20 miles and several WOT applications the belt & tensioner have settled, tensioner now just under half way.
Red mark: indicator
Blue box : min-max guide.
This is an M111 2.3 M62 with a 218 mm crank pulley and stock S/C pulley. As previously mentioned the larger crank pulley came supplied with a 1413 mm belt which lasted c.30,000 miles before the tensioner was almost max'ed out, tensioner also new at the time of fitting larger pulley.
that's spot on, you can go a bit tighter too if you can find the right belt size in stock, for example, you could try 6PK1400 or 6PK1395 but those sizes may not exist or be easily available etc. when I did my belt I had a to try a few sizes to go as tight as possible.
when reading online about aftermarket superchargers and belt slip etc. they show just how much the tensioner moves under WOT boost (can youtube this). in our application the supercharger requires up to 25hp (that's to run 10psi) from the crank to turn it under WOT - that's a fair bit of load on the belt!
so if the belt is halfway, under WOT it may stretch to the bottom of the range - which is still ok but keep it in mind. the higher up (tighter you go) the more wiggle room you have!
Good point Subby, never considered that under load the tensioner would move again. Makes a lot of sense.
Yes, I did get a 1400 mm belt only a couple of weeks ago but it was right on the minimum mark and was a little concerned it may cause undue pressure on the S/C pulley and belt tensioner so I replaced it with the 1405 belt. I'll fit the 1400 again at some stage and give the car a good blast and see where the tensioner mark sits at.
just took a pic of mine. when the belt was fresh it was right at the max mark, now its moved a bit (after some heavy use (track day)).
no need to stress about over tensioning or bearings etc. this is a auto spring loaded tensioner selected for its tension for this application by MB. if its between the max and min its OK.
update to this thread just to show you how much the belt can stretch over time.
I've done a total of 6,500 km of driving on this new belt and two track days (sustained wide open throttle driving).
Belt started on 100% (green line) and now it's about 60%. Ideally would like to keep it within the 100% to 50% range. Less than 50% is OK, but that's for stock boost. Higher boost takes a fair bit of horsepower to turn that blower!!
Hello everyone.
I installed an additional pulley on my 200K Fl.
It is attached with the screw for the alternator.
This works quite well. The support area of the drive belt increases.
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