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XC90 V8 Idler pulley shaft (Boss) damage

A mid-size luxury crossover SUV, the Volvo XC90 made its debut in 2002 at the Detroit Motor Show. Recognized for its safety, practicality, and comfort, the XC90 is a popular vehicle around the world. The XC90 proved to be very popular, and very good for Volvo's sales numbers, since its introduction in model year 2003 (North America).
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Joined: Sat Jun 23, 2018 2:14 pm
Year and Model: 77 244dl
Location: OR

XC90 V8 Idler pulley shaft (Boss) damage

Post by grizzle »

So I just passed 200k and had that thought, wondering if my vehicle will survive much longer.

I have had minimal issues with my 2006 XC90 V8 considering I have put 120k miles on it in 3 years.

Just as I passed 202k miles, I broke down. I thought it was just a serpentine belt but turns out it was a failed pulley.


I had to tow it home and once I inspected it, I found the bad pulley and felt lucky, it wasnt the water pump or alternator that failed. But turns out I wasn't so lucky.

In the process of the pulley failing, it completely destroyed the pulley boss.


At this point I figured the vehicle was done, considering the age and miles. A repair at a shop would be somewhere around $3-4k and a new motor the same. It just is not worth the expense.

So I decided to attempt the repair as found here: [url]viewtopic.php?t=61115/[url]

Thanks to user mhcrra1 and his recommended fix my Volvo is now driving again.

I decided to post some more pictures and details in hopes of helping someone else out.

Here is a closer shot of the damaged boss.

This is what it original is supposed to look like. This is a non damaged boss just above the lower damaged one.

So my goal now was to cut off the damaged boss, and file down the timing cover to install a homemade boss or shaft in place of the damaged one.

It is very important that the new boss be near perfectly level with the other pulleys on the motor, or it will "walk" the serpentine belt off every time.

This part took the most amount of time. I removed the two other pulleys to allow for extra room to cut and file the old boss level.

After an hour of filing with a hand file and Dremel tool I was able to get the timing cover cleaned up and close to flat. You can see it filed down, on the bottom right.

When the new pulley showed up I found a socket, that fit as tight as possible. I used a 7/16 3/8 drive socket. I believe a 12 or 13mm may work as well. Just ensure its a tight fit.

I then found a washer with similar I.D. (Inner diameter) than the socket itself and a O.D. (Outer diameter) small enough to not interfere with the I.D. of the pulley.

The washer is probably not completely necessary, but I wanted to add JB Weld, to the backside of the washer to give additional support to the new idler boss (socket).

I had the washer then welded to the socket and belt sanded it even and smooth. I also drilled out the inner part of the socket to allow for room for the bolt. Then you will have to cut/grind the socket to the same length as the pulley bearing.

I then used a new slightly larger 10.9 grade bolt with the same length and thread pattern but a slightly larger shaft. In hopes to limit any movement or flexing. The old bolt is on the left.

Now I bolted the new pulley with the washer/socket in place and also bolted at least 1 other pulley back in. This is to measure and eyeball the new pulley for level. I used a straight edge from the undamaged pulley to the new one to measure for level.

I had to install these two pulleys and uninstall about 6 times. Every time I would pull it off, I would also slowly file the surface down just a little at a time. Then reinstall, measure, uninstall, file some more, and so on..... This took a couple hours in total, but mainly because one of my wrists were in a cast.

Here is the new pulley boss bolted in without the pulley in place.

I wanted to add some additional strength, and that was the main purpose for the washer. The washer is just slightly wider in diameter than the old boss on the timing cover. This allowed for a small lip on the backside (timing cover side) of the washer to allow some area for the JB Weld to affix to. I then bolted the boss in place and used JB Weld to build up around the entire washer.

I let the JB Weld cure for a few days and then pulled the bolt out. So far, so good, as the washer/socket seem to be held in place without the bolt. Picture is blurry

I took a hand file and Dremel again and filed off any extra JB Weld that could interfere with the pulley sitting flat or it's rotation.

Once filed down, I had to install the pulley and remove it a few times to get everything filed down interfering with its free rotation.

After this I installed the new pulley as well as the other pulleys and reinstalled the serpentine belt.

Started the V8 up and could see no signs the new pulley had any kind of wobble or noise.

I am now 100 miles into this fix and no issues so far. I would not say this is something that will give me piece of mind, but it should last some time for now.

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Post by jimmy57 »

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