Drivebelt tension

[190Edriver]

Just had a slight disaster on my 1993 190E 2.0L this morning. Tried to align the pointer for the drivebelt tension in line with the mark on the engine block. Unfortunately the after loosening the pulley tension and then trying to adjust the tension by turning the tensioner bolt (on the top of the engine), the tensioner bolt went tight and then snapped off !!
Fortunately the belt tension doesn't seem to have moved so re-tightened pulley tension, but what can I do about the tensioner nut / further adjustment ?

 

[Stevie A]

You can replace the part you snapped as it'll slide in the back of the big tensioner (17mm ish) nut. You need to loosen the main 17mm nut enough so it will slide out to allow the snapped part to be replaced. Go into a dealer and ask for a diagram of the tensioner assembly and you'll can work out what you'll need.

Or try pushing down in that area where the part snapped and you should feel tension increasing on the belt, depending on what is left of the snapped part. So if you push down with a bar while a pal tightens the main nut then this method can be used as a stop gap.

 

[190Edriver]

Hi,
many thanks for your reply.
It was my fault that the tensioner broke, I stupidly loosened off the tensioner pulley wheel and not the tensioner assembly (I should have realised with all the talk about a nut, whilst I was undoing an allen bolt !).
I will be more careful next time.
I will take your advice with a diagram, I just didn't want to get into stripping off the power steering reservoir etc to allow a repair, but it seems from what you say this will not be necessary.

Many Thanks,

Steve

 

[Stevie A]

When I got my 190E the tensioner adjuster was snapped but I didn't notice until I had to replace a water pump. Try and feel in the back of the tensioner assembly to see where it snapped then you'll know what you need once you get a diagram.

 

[MW]

Exactly this happened to me on my 1992 W124 230 after I had changed the water pump and was retensioning the adjuster. The key is that when all is floppy and loose one must point the adjuster at the start of the scale. Mine was somewhere near the middle as I upped it... bang, it snapped and the adjusting rod and nut could be pulled out.
This was at a holiday time and I was desperate.
I undid the bolts holding it all together and as stated above there is a ring pressing that moves the unit around. It is cam shaped with a hole into which the rod hooks into. Amazingly, the rod had pulled right through the medal. I reversed the cam ring (it just pushes on), and drilled a new hole on the other undamaged side. On reassembly the rod is hooked into the hole (a little bit off centre - but no problem) and tightened up as normal. 3 years later it is still holding. I meant to get it replaced, but never got around to it.
It all confirms my fear of overtightening drive belts, ever since my old Hillman Imp would destroy the bearings of a new water pump in 4 weeks if the fan belt was too tight. These days I have belts a wisker on the loose side. One can always tighten up if need be, but I never have had the need. Most belts can run remarkable easy a bit off dead tight. Much easier on bearings.

 

[190Edriver]

Hi,
Thanks for your note.
I will look into the adjustment problem, and as soon as I identify what part/s are need i will replace or repair to put the adjuster back to normal operation.
I get frustrated if things don't work as they should do and I will sort this out before i tackle anything else.

Cheers.

 

[MW]

I would replace the part. It is just a soft metal pressing, and even at MB it probably is only £10-15. As you have to take it to bits anyway, it is probably worth replacing it and then you have peace of mind. On reassembly grease just under the adjuster nut so that the takeup of tension is smooth and doesn't put a lot of pressure on the thread, which isn't very wide. Best to just underdo it a tad. Let us know of your progress.

 

[190Edriver]

Not going as well as I hoped for.
Loosened off 19mm tensioner nut and slackened off belt.
Noticed that to remove the tensioner assembly I would need to remove the bolts that hold the bracket that the 19mm bolt passes through.
One bolt is behind the p/s pulley.
Removed p/s pulley bolts only to find that I cannot remove the pulley wheel (tried tapping with a soft mallet, but would not come off), I dare not hit it any harder in case i end up damaging the p/s pump.
I am now in the position that I have a drivebelt that is too slack (even when I tried to lever a screwdriver underneath the tensioner pulley arm to tension it).
(The tensioner arm has a damper attached above the tensioner arm, if this makes any difference).
The tensioner nut assembly that I snapped off in the first place has no influence in the tension whatsoever at the moment.
I cannot feel anything behind the tensioner.
Any suggestions gratefully received as to what to do next...........:???:

 

[Stevie A]

Loosen off the big 19mm bolt. Then keep turning it until it starts to slide forward, (or pull it forward) enough to let you slip off the snapped component at the back of the tensioner assembly. Hold the tensioner assembly components together with one hand whilst doing so, so as not to lose any other parts from the assembly. You don't need a whole new assembly, probably just the adjuster bolt part, sleeve and the little hinged part that probably snapped.

 

[190Edriver]

OK, loosened off the 19mm bolt completely and removed it.
Still cannot pull the assembly forward because there is a bracket through which the bolt passes through directly in front of the tensioner.
I have attached a photgraph this time to help explain what I mean.
It still looks to me that i need to remove the power steering pulley to access one of the bolts that secures the bracket to the engine (and the other nut feels accessable under the engine.
The question i have is how do i remove the p/s pulley (as i explained in previous thread).
Do you agree that this is what needs to be done ?

(many thanks for your help / patience with this).

 

[Stevie A]

When I changed the broken part of the tensioner assembly the power steering pump was already off I think, as I had to take it off to replace water pump.

Regards, the big 19mm bolt, I loosened it off and was able to move the back of the tensioner barrel assembly up enough to let me slide on the bit at the back that had snapped.

See if you can move the tensioner barrel in situ. But be careful as there are bits in there in sequence and I would slide the big 19mm bolt back in about 3 quarters of the way first. Be careful not to lose anything.

Have you bought a complete new tensioner barrel? Regards the power steering pump pulley you'll have to spray lots of wd40 round it and keep tapping til it comes off. It's the engine heat that almost "melts" it on.

Is it a 2litre engine you have? I'll have a look in the Haynes manual to see what it says about your engine type. Mines is a 2.6.

 

[190Edriver]

Drivebelt tension - sorted

Removed p/s pulley after using release oil on it overnight.
Had to remove the tensioner assembly completely to get into the rear of it to find the broken component.
This turned out to be the washer lug that the adjuster rod fits into.
Went to MB dealer and bought new washer (inc. rod) for under £9, fitted at the weekend in under an hour, retensioned belt (being careful not to overdo it just by watching pointer on tensioner, as this is something that should not be soley relied on).

19mm nut torqued to correct setting, and all is well again.

 

[Stevie A]

Glad your sorted. It's saves money just buying the snapped part like I explained. Well done.