Polybelt/tension problems???

[taz1964]

Hi all.

This is my 2nd post and I hope someone can help shed some light on the following problem.

I had to replace a perished poly v belt last year which ran fine until a couple of months ago.

My van started to turn over very lazily, almost like a flat battery and too slow to start.

Upon inspection I noticed the belt was very, very tight so I took it off and the van started immediately.

When I got home I refitted the belt and all was fine for a couple of days and then the same symptoms appeared. Once again I removed the belt and it fired up.


Can a faulty tensioner cause enough tension in the belt to create enough resistence resulting in the motor turning over so slowly?

or is there a problem elsewhere, eg bearings on water pump/alternator etc.?

TIA


taz.

 

[Danny DeVito]

Cant you try turn each pulley by hand with the belt off ? After this happens ? I dont think the tensioner can increase its own spring strength. However the alternator free wheel pulley can jam. It should turn freely one way and the other it should turn the alternator. When mine was stuck it made the belt hop about while running the engine. I have a 2nd hand new tensioner if you find that you need one. MB part less than 1 year old. But i dont think you need it.

 

[taz1964]

The alternator is less than 2 years old and less than 3k put on it.

I will try to check the pulleys tomorrow and report back though they spun freely when I checked them though this was by hand before I refitted the belt.

Thanks.

 

[Danny DeVito]

I had alternator *repaired*..... bearings and rings and reg. He said the pulley seems fine, shortly after the pulley seized permanently making the belt hop and it was very noisy

 

[taz1964]

The fact the engine wont turn enough to start(sometimes) with the belt on but as soon as it is taken off it starts confuses me. The belt is really tight and very warm when the fault occurs.

Intermittent seizing of a pulley?

The battery is fully charged so no problems there.

 

[Danny DeVito]

I think the alt pulley was slowly getting stuck on mine because it would be noisy for about 30 seconds after cold start then fine for the day. Then it stayed stuck.

Remember too, friction is the cause of the heat. So its lateral like a wobbly pulley or rotational like a sticky pulley. Usually water pump squeals so not likely to be that either. My tensioner pulley had small movement so dont mistake this for a fault.

 

[taz1964]

Last night I refitted the belt and as usual it started fine and did so about 6 times. This morning it started fine, on the button.

After I had driven it for a short distance(2 miles) I noticed(whilst at traffic lights)a sort of rattle/grind, a bit like the rattle from a loose front grill which stopped when the revs were upped.

I parked up for ten minutes and when I returned it was a little lazy turning over but fired up after a couple of seconds and the rattle was still there.

 

[grober]

I would concur that it sounds like one of the poly v belt ancilliaries is seizing intermittently. Chances are its the alternator but the other driven unit likely to seize is the air conditioning compressor. [ assuming you have one??] If its the clutch type make sure its disengaged . Newer types of compressor are always engaged and its their displacement that is varied.

 

[Danny DeVito]

Last night I refitted the belt and as usual it started fine and did so about 6 times. This morning it started fine, on the button.

After I had driven it for a short distance(2 miles) I noticed(whilst at traffic lights)a sort of rattle/grind, a bit like the rattle from a loose front grill which stopped when the revs were upped.

I parked up for ten minutes and when I returned it was a little lazy turning over but fired up after a couple of seconds and the rattle was still there.

there now... a rattle i wud call it, then it goes when u rev up comes back at idle

 

[taz1964]

I took the belt off again as it did the same as before..........refitted the belt and tried to start it without luck................I checked the belt and noticed the tensioner had moved.

The tensioner was correct before I had tried to start it but when I looked it had tightened and moved to within 3mm of maximum travel and was almost on the stopper.

Tensioner knackered?

 

[Danny DeVito]

Sounds like the pulley jamming, then the belt is pulling the pulley back against the spring

 

[taz1964]

Well I got it started(again)and looked at the alternator and there was the odd spark coming from behind the pulley so I guess that's the problem.


Thanks for the advice/help.


So now I have to change the alternator....................how easy/hard is that?

I was told you need to drop the engine slightly to get to the bolts.................is this info correct?



Cheers.

 

[Danny DeVito]

Easy enough, a bit tricky to get at top bolts but its straightforward. Drop engine by removing top mount. Remove the vacuum controller on the chassis behind alternator. I undid drive shaft and pulled to one side. I also undid the anti roll bar. This was the only way i could get the alternator out. The pulley can be replaced insitu by dropping the engine and the tool barely squeezes in.