o5 Primary belt tensioner concerns

[Mbl35]

05 e350 Ambulance mod. Third belt tensioner in two months.

The first time one of the tensioner pulley bearings siezed up 3 weeks after an ac compressor replacement.

Also at that time the front cover gasket was replaced. I changed all the pulleys and tensioners,fanclutch,belts and waterpump and ps pump well. The vacuum pump stayed as well as the crank pulley. The belt sits straight on the pulleys.

 

Now a month later it comes in on the hook, pop the hood and take a look to find the main belt sitting loose on the pulleys.

I hoist it up and see the primary tensioner pushed to the loose position almost a half inch passed the unload stop set lever.

The belt appeared to be fine. I replaced the tensioner, gave it a good run with everything loaded, i let it sit and idle for a while-everything good....

Yesterday it came back in with the exact same concern.

One of the am shift techs replaced the tensioner. When i arived i ripped it apart, inspected all the pulleys- all ok.

The belt was fine as well. I replaced the primary belt and gave it a good run, no strange noises or anything.

I just hope this is the last time i will see this lance for this concern. This lance does alot of idleing from what i understand as compared to others.

[Keith Browning]

First, welcome to the DTS. From your description it sounds like the tensioner arm is failing... the pivot is seizing or the spring is breaking... things we have seen over the years. I don't see anything in our resources to indicate a pattern failure with the tensioners but anything is always possible. Since the original tensioner failed because of the pulley bearing and the two replacement tensioners failed at the pivot this suggests either you have a batch of defective parts, incorrect parts or something with the installation is causing the failure.

 

Did you closely inspect the failed tensioners? Can you see anything about them that doesn't look right?

[Mbl35]

Thanks.We replace alot of tensioners and only this lance exibited this.

Btw the engine was out last august for rocker arm carier gaskets and i think the bedplate was resealed whet it was out.

[LARRY BRUDZYNSKI]

I hoist it up and see the primary tensioner pushed to the loose position almost a half inch passed the unload stop set lever.

 

This sounds like a bearing is going bad somewhere. I have seen that when a alt. bearing is going bad that it will drag on the belt when the alt. engages. Also I think we had a similar situtation quite a while ago and was the alt. mount bracket that was causing belt problems. Being that this is a vehicle with dual alts. this may be somewhere you may want to look at.

[Mbl35]

Oh shoot i knew i forgot something, the alternators were also replaced on the fr. cover job also. But ok that sounds interesting, a problem with the lower alternator bracket.

[ktmlew]

I would check the A/C system to see if the compressor is binding up? Seems like your issues started after the compressor was replaced?

[LARRY BRUDZYNSKI]

Good call, I just re-read the posts and makes sense.

[Mbl35]

Definitly does,now that i think about it i didn't replace the compressor-not that it really matters anyway but im going to check the compressor. Thanks.