300TDi aircon belt problem

**metaljong** · 6th February 2008, 09:05 PM

Hi all,

I've got a problem with my aircon belt. I replaced the main serpentine and aircon belts not more than 10 months ago when they were looking worn. When I replaced the aircon belt I put too much torque (don't have a torque wrench) on one of the three tensioner securing bolts in the timing cover and stripped the thread. I decided to see how it went with two bolts holding the tensioner and it hasn't moved so seems to not be the problem. I didn't want to pay for a new timing cover if I didn't need to.

Today my aircon belt shredded itself. It'd been squealing quietly but noticeably for a while when the aircon clutch engaged the pulley, but I checked the belt a month ago and it was OK, no wear evident. I checked all the pulleys today, aircon, tensioner and the routing pulley and all looked fine, not seizing and seemed to be running straight. The aircon's been working no problems all this time too.

The only thing I can think is that because I don't have a torque wrench, I incorrectly torqued the tensioner last time and had it too tight or loose and that caused the premature wear. I used a ratchet handle (about 1' long) in the centre of the tensioner pulley and my usual scientific method, which for something like the tensioner involves torquing it as much as I possibly can while trying to do up the securing bolts with another socket/ratchet. It did seem tight, but I'd be surprised that too much tension could cause it to fail so soon.

Any ideas?

**damienb** · 6th February 2008, 09:54 PM

Too much tension can cause it to fail, but 35 Nm is quite a lot. Sand, dust, or mis-alignment can also cause failure. Get the bolt out and replace it, and change the belt, or just replace the belt - it's not like it's expensive, and get a deflection type torque wrench from supercheap for $10. They work well for lots of things.

/Damien

**metaljong** · 6th February 2008, 10:14 PM

Originally Posted by damienb

Too much tension can cause it to fail, but 35 Nm is quite a lot. Sand, dust, or mis-alignment can also cause failure.

This belt lasted literally < 10,000km. I would've thought I royally screwed something up to cause that but inspecting the pulleys and spinning by hand at least it's all fine to my untrained eye. The main serpentine belt changed at the same time looks like new.

Originally Posted by damienb

Get the bolt out and replace it, and change the belt, or just replace the belt - it's not like it's expensive

The bolt's fine, it's the thread in the timing cover that's stripped. I didn't think I was tightening it that much, but obviously I was.

Originally Posted by damienb

and get a deflection type torque wrench from supercheap for $10.

Yeah, I think it's a good idea to get one.

Thanks for your help damienb.

**rick130** · 7th February 2008, 02:39 AM

heli-coils are your friend when stripping threads in aluminium

(could be fun trying to get to that one, though)

Can't help on the belt shredding, other than check your alignments. The only time this has happened to me was the idler pulley bearing seizing. The squealing gets your attention pretty smartly. New bearings in the idler and tensioner cured that.

**metaljong** · 7th February 2008, 08:21 AM

Thanks rick130. Helicoiling that thread would be almost impossible I would've thought. I dunno if there'd be enough room to get a drill in there to widen it out.

Yeah, there's no seizing of bearings. The squealing I mentioned wasn't an attention getting noise, and it only happened on one part of the rotation of the belt i.e. as the engine was idling you could hear it squealing rhythymically maybe 3-500rpm. That's why I didn't worry apart from checking the belt a month back when it was still fine (to a quick examination).

**stock** · 7th February 2008, 08:25 AM

My guess is rough bearing either on the tensioner or or the idler ,had this problem but I drive a 4.5 ton hydraulic winch instead of an aircon unit took a while to figure it out,but the good news is the bearings can be changed ,6203 i think, or is that the serpintine tensioner

**rick130** · 7th February 2008, 08:32 AM

Originally Posted by metaljong

Thanks rick130. Helicoiling that thread would be almost impossible I would've thought. I dunno if there'd be enough room to get a drill in there to widen it out.

<snip>.

a lot of times with aluminium you can just run the heli-coil tap through without drilling it out

**87County** · 7th February 2008, 10:10 AM

BWOA & FWIW, take the opportunity to replace all the tensioner/idler bearings (they're cheap and simple to do), and if the standard fan setup is retained, check the fan hub bearing too, as it could be time for a new front cover...

**zulu Delta 534** · 7th February 2008, 10:47 AM

I would suggest an a/c check or service wouldnt be a silly idea either as well as those suggestions posted earlier. You may be running low on gas, or running at extra ordinary head pressures periodically and that can put extra strain on belts.

951cxn · 7th February 2008, 11:03 AM

I have a 98 Auto 300TDI Disco, the mechanic who has worked on it since new mentioned to me when I first complained about belt noises it makes that as far as he can remember it always made those noises. Purchased when it had 104k, Since then it has 211k, engine rebuilt @ 124k, gone thru 1 a/c and 2 serpetine belts, both a/c and serpentine belts take it in turn to shread about every 10 months. It has been checked every time for alignment when snapped, no visable cause could be found, also has had all bearings replaced just recently but still squeals on start up. I think it is one of those "Land Rover Moments" that they seem to have from time to time, the only cure is to carry a set of spare belts.

Thread: 300TDi aircon belt problem

Thread Tools

300TDi aircon belt problem

Bookmarks

Bookmarks

Posting Permissions