Hi Juan....

"VWStuart" put it perfectly... the serpentine belt is the one you can see, the timing belt is under the covers.

The serpentine belt drives accessories such as the alternator and power steering pump. If the serpentine belt were to break, the car would still run, although you'd be running off the battery since the alternator isn't turning, you'd have no power steering, and a whole bunch of idiot lights may come on. You can visually examine the serpentine belt, but the timing belt is another story.

The most important thing to keep in mind is that the timing belt, even if it appears perfect, may not be. Which explains why the timing belt MUST be changed every 70,000 miles. The timing belt will not actually suddenly fail at 70K, 80K, or more. But a timing belt failure is an absolute disaster!!! 850s have what is called "interference engines", which means that the valves and pistons will collide if the timing belt fails. That results in a minimum of a cylinder head rebuild (if you're lucky you get away with "only" a $1500.00 to $2000.00 repair)... if you're unlucky, you'll need a total engine rebuild... how does $5000.00 sound?

If it's time to change the timing belt, change the serpentine belt too. And each of the two belts has its own idler pulley and tensioner pulley. Each of these pulleys rolls on bearings which are an integral component, and are subject to wear. The pulleys should be changed when the belts are changed.... think "cheap insurance".

If you're interested in seeing what is involved in changing to timing belt (just in case you are a "do-it-yourselfer" like many of us on this board) take a look at this site:

http://www.volvospeed.com/Repair/timingbelt.php

Changing the serpentine belt is easy... just about anyone can do it. The only "trick" is retracting the tensioner so you can remove/install the belt... there are at least a dozen people on this site who can explain how to do it, if you post the question.

I'd say that you shouldn't attempt to replace a timing belt yourself unless:

a) you are somewhat mechanically inclined
b) have a decent set of tools
c) and are the type who is willing to stop in the middle of the job (in the event something goes wrong, or you have a question) so that you can ask for assistance or advice.

A competant independant mechanic can do the whole job for significantly less money than Volvo charges... somewhere around $500.00..... add probably $250.00 at a Volvo dealer. There may be some respondants on this site who know what the actual current Volvo charges are for such service... I've heard a few horror stories... get the quote in writing!!!

In my opinion, regardless of who does the job, for this task in particular, only genuine Volvo parts are acceptable.

Good luck

Marty
'96 855T

Juan--serpentine belt usually changes out at 60K miles, or 100K kilometers. Standard practice. Timing belt at 70K miles. If you're at 68K you should do the 100K kilometer maintenance thing, which is fuel filter, thermostat, serpentine belt, fluids, etc. Be aware that Volvo changed the routing on the serpentine belt on some models, and if and when you order it from Volvo (don't do aftermarket on this item), you will get a diagram showing you the new routing. The new routing takes a belt a fraction of an inch longer than the original, and if you use the old routing with the new belt it will be too loose when you release the tensioner pulley. If you buy an aftermarket belt, you probably won't get the diagram that comes with the new belt from Volvo. As a suggestion, when you take the old serpentine belt off and install the new, wrap it around the outside pulleys first and then pinch a small loop with the remaining belt and slip it last over the inside tensioner pulley. The outside pulleys all have a little shoulder on them, and it's a real bitch to try and slip the belt over the final pulley with a shoulder on it. Lots of swearing and stretching involved in that one. The idler pulley has no shoulder, and if you double the belt with what's left, making a small loop, pray a little bit, bend down and look, it will slip right on the inside shoulderless pulley with no trouble. Release the tensioner pulley and you're home free. Dick

You can see the serpentine belt, but to see the timing belt, you have to remove the plastic timing belt cover. I have no idea about when the serpentine belt should be changed, but the timing belt should be changed, I believe, every 70,000 miles. I just fininshed (like, 2 hours ago) replacing my timing belt, idler roller, tensioner roller, and crankshaft (oil pump) seal. I gave the car a good test drive, and all is well.

It is VERY easy to change the serpentine belt. The only hard part is removing the tension without a 3/4 inch "thing" to move tensioner, but I improvised, and all is well. I think I could change the serpentine belt in about 10-15 minutes now.

I hope this helps,
Stuart