Another Alternator Belt Tensioner - 3VX belts?

[Rudolph Diesel]

https://lh5.googleusercontent.com/_ewFi ... loded1.jpg



Any idea where I could find the shields for this. My 1991 TD came to me with parts missing here (fell off with previous owner) and I have been chewing through belts and pulleys. Yesterday the pulley bearings imploded on the way home.

[the vegenator]

Are you referring to the thin steel washers that shield each side of the idler pulley? Or the bushing that is partially encircled? I just pulled the whole idler pulley assembly off a car. Let me know what specific parts you need.
-mike

[TylerDurden]

Update:

The setup just passed 193,800mi and is holding pretty well. It may need a tightening in another 1k... we'll see.

Hard to say why MagicBus' belts had problems after the bearing installation, they might have had other issues.

[TylerDurden]

Update:

Just passed 194,800mi.

No noise or squeal, but I can move the alternator fan by pushing it w/ my little finger. I'll probably tighten it a bit.

[TylerDurden]

Update: 196,500mi.

Re-tensioned belt.

Recent observations, when the belt is getting loose:
- belt will slip more in wet weather (did MK2s have a splash-shield under the engine?)
- slipping causes tach to function poorly in low RPMs
- no squeals or chirps
- minimal additional tension required to restore grip on alternator pulley.

Driving up a steep hill, the oil pressure light started blinking. Not sure if the belt slipping tripped the OPCU, or just the hill/oil-pump. Oil was at proper capacity.


At this point, I'd say the modification is stable and safe to use. If others with un-modified setups are changing/losing belts at 1500mi, this modification may be a benefit.

[Fatmobile]

The oil pump runs off the back of the timing belt.
I wonder if that was slipping too.

Hagar suggests some belt dressing for the back of the timing belt.

[TylerDurden]

Well, I give myself a royal dope-slap today...

Last night I tightened up the AC belt and then re-tensioned the Alternator belt. I was going to post that we reached 197,600mi.

I forgot to tighten the stock tensioner lock-nut. I might have been interrupted by a phonecall or visitor, I don't know.

So, on the way to the store today, the belt went "bye-bye". Fortunately, it did not take the AC belt with it!

6,600mi before the first re-tension of the AC and re-tensioning of the Alt belt at ~1000mi intervals (two tanks of fuel). I think the Alt belt would have gone another few thou miles before reaching the tensioner limit.


So... we are going to start the next belt test at 197,600mi.

[Una]

So it's normal to have to re-tension the alternator belt every 1000 miles? I had to do mine today, and I was baffled that it had come loose. It wasn't just a little bit loose, it was flapping in the breeze loose.

[TylerDurden]

So it's normal to have to re-tension the alternator belt every 1000 miles?

I am trying to use the minimum effective tension (with the extra modification), to reduce component stress. More tension might increase the interval.

Others have reported belt loss/damage as frequent as 1500mi, presumably from tension required on a stock AC-equipped setup.

A spring-loaded tensioner could be better.

[diesel freak]

I also lost my alterantor belt after doing the modification at 1500 mile but I started running the stock air conditioning too. I think that may have caused the dismise of my belt. Replaced the belt with one slightly smaller and do not use my air conditioning. Is presently holding strong.

[TylerDurden]

UPDATE:

Current belt installed at 197,600.

Just tightened it at 198,900.

It has been "chirping" for about a week. That's my cue to tighten before any wet weather.

[littlematt]

I have an 89 NA 1.6 Jetta that I got for $200 not running, but delivered about 6 or 7 years ago. The PO had attempted to replace the water pump, but was frightened off by having to remove and then retime the injection pump to get at the water pump. As part of his trial, the alternator and all associated brackets were in the trunk. Lovely.

It (embarrassingly enough) took me quite a while to finally figure out the correct position for everything (though I still have one small piece left over to this day). My first attempts were failures due to the overly long belt I got from NAPA. There was just no way to take up all that slack. Once I got a smaller belt I was having trouble with slippage. (I also didn't have a voltmeter in the car, so I didn't realize I had to "goose" the engine up to like 4k RPM after starting to get the alternator to put out.) I went through many belts trying to find the right balance between slip and snap. I even got the plastic pulley cover mentioned in the VW tech bulletin to try and help. The car was pretty unreliable electrically due to all of this, and living in Upstate NY meant I needed every last cold cranking amp to get it started in winter.

Then this past winter, my employer was acquired and I found out I would be moving to San Francisco.

Knowing I'd be taking this car across the country, I did a ton of work on it before I left, however that work was mostly radiator, a/c condenser, power steering or body related. The VW dealer (Conti) belt on there now has been pretty quiet. I get much more squeaking from the power steering pump than I do from the alternator. The belt had been installed for a bit before the cross country trip. When I took the car to get inspected in late November, it was squealing so I tightened it up. I hadn't touched it since. (I did have two spare belts with me for the trip along with 100 pounds of tools. I was prepared.) The odometer on this car has never worked, so I have no idea how many miles it has on it, but it has at least one trip across the country and a bunch of running around SF.

That said, the tension I had to put on that belt really was bothering me. It just seems like it can't be good for the bearings, and even with how tight I had it, you could see a ton of wobble on the side next to the timing belt cover when the car was running.

Today I bit the bullet and installed this mod. I had bought the parts from Grainger back in February, when I was heading back to NY for a bit. I was hoping to be able to use my vise and other tools left in NY to cut the threads, but the bolts didn't make it to NY in time. I have no vise in SF, so I improvised by putting the die in a 10" C-clamp and threading the bolt in with a ratchet.

After installing this, I didn't need to tighten up the tensioner nearly as much. Tensions just felt better all around. I've still got my two spare belts in case, but I am going to continue running with this VW/Conti and see how it does. I still need to "goose" the engine after startup to get the alternator to output, but that's a pretty minor thing. Since I have no odometer I can't "check in" on regular mileage intervals, but I'll try to remember to update the thread every so often -- especially if it breaks.

[TylerDurden]

Hey, good to hear another brave soul is willing to be a guinea-pig.

I keep a 17mm and 13mm wrench in the door-pocket and spare belts in the trunk.


4k rpm seems a bit high to achieve field self-excitation. The rigs around here usually kick-in around 2k. I'd check the integrity of the connections from the alternator to the dash indicator.

[TylerDurden]

Bah.

Broke the belt at 199,176.
Started that belt at 197,600 - only 1500mi.

The tension I used 4 days ago was tighter than my usual "just enough to resist a single finger pushing on the alt fan".

Maybe it was too tight.


Start the clock again...

[bbob203]

i bought my 91na jetta 3000 miles from home not knowing much about them at all i drove 3000 miles homes and had no problems with the belt. boy was i lucky i guess. im gonna try this out before i break a belt i definitely get squeal in he rain and smell burning belt.