Volvo S70 mystery wobble/vibration/rattle

Post by **Ocelot** » 07 Jan 2021, 12:19

Hey guys,

I really don't like posting topics like this because I can't really specify what's going on, but I'm a bit desperate after checking different things and dismissing them as the culprit. Here's what's going on...

From time to time, when I'm driving down the highway going about 100 km/h, a certain vibration can be noticed. It kinda feels like the wheels are not properly balanced. Then, it gradually go's worse and the vibration shakes the whole car. It's like driving with a flat tire or something, it feels like that, but the tyres are fine. Yesterday it happended again and the vibrations/rattle were so severe, I called the Dutch equivalent of the Triple A. He checked the brakes, the wheelbearings, the tyres and couldn't find anything (and I kinda hoped he would).

Some background information

I did notice a few days before it all started that the brake caliper on the rear axle (on the right) was making noises. When I got home I noticed that the brakes on the right rear wheel was way hotter than on the left side and the disc turned a bit blue. So I ordered a new caliper, I'm gonna replace that this weekend.

I hope you guys can help me out on this quest. Love to solve this riddle

Post by **scot850** » 07 Jan 2021, 16:41

It is a strange thing with Volvos but I have found the rear calipers have a habit of seizing way more than the fronts. I think it may be either because people tend to service the fronts more or the rear brakes just don't work hard enough.

Either way, it sounds like the caliper is seizing and that will cause the brakes to get hot and snatch/vibrate. Try to figure out when this happens if it is being felt by your butt though the seat or more by your hands on the steering. Seat = rear end of car issue, steering but not so much from seat is most likely the front but it is only a guide.

I would suggest checking the parking brake is releasing correctly and also the rear parking brake shoes have not separated from their backing.

Neil.

Post by **MoVolvos** » 07 Jan 2021, 23:29

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The vibration is typical of rear brakes grabbing as I've experienced this firsthand. Imagine someone much stronger pulling you on a rope. If your legs were strong enough you would slide on your shoes. The springs being like your legs will flex upwards and you wind up stomping your feet to stop the pull. Since the tire is being hindered from normal rotation speed by the brakes resisting the forward motion, it will go up and down due to the spring and irregularities in the road bumping the tires up and down.

Although you've ordered the caliper I suggest opening the old caliper and taking a look at the piston to see what it looks like. My O3 Odyssey has burn through two sets of rear pads on the passenger side in recent years. The ones on the car when purchased in 2013 lasted till around 2018 and was metal to metal in the end. The driver's side was only half worn. The second set went much quicker on the same side again.

Took the caliper apart this time and it was highly polished without any signs of rust or dirt so just cleaned it up and installed new Rotors, Pad, Brake Shoes and did a complete flush (10-31-20). Lubed all the guide pins as well so hope the flush solved the problem. The brake fluid was clean by the way so don't really know sometimes.

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Post by **abscate** » 08 Jan 2021, 02:32

If you replaced your calipers, ever, with non-Volvo rebuilts, it is likely that the guide pins are made of cheap pot metal, also called silver cheese.

These rust and then the caliper grabs and overheats.

The OEM Volvo slide pins are about $15 each but won’t do this. There are several write ups on this

viewtopic.php?f=1&t=90075&hilit=Brake+caliper+pin

Post by **Ocelot** » 08 Jan 2021, 03:10

Thank you all for your replies! Like I said, I will replace the faulty caliper this weekend/begin of the next week. I orderded TRW calipers and I was suprised to find Volvo emblems on all of them. I'm gonna take the old caliper apart to check it for any faults. I'm gonna get back to you guys soon!

Post by **abscate** » 08 Jan 2021, 03:46

All the rebuild are in Volvo cores but they don’t use Volvo parts. The slide pins seem to be a place they cheap out and cut corners.

ollebompa · Post by **ollebompa** » 09 Jan 2021, 10:06

I had a very similar thing a few years back. Turned out to be rear brakes so could definitely be the caliper. For me it was the pads getting stuck on the sliders and caliper walls and not releasing properly. Warped the rotors as well. Make sure you invest in a fit for purpose lube for the pins and the parts of the caliper next to the pad edge. I have also found over the years that it's essential whenever you change pads to clean the caliper of any rust in parts where the pad might catch.

Post by **Ocelot** » 03 Feb 2021, 04:59

So this topic is solved. Finally, I had some time of yesterday and I rented the DIY garage. Changed the rear caliper and it was stuck as hell. Replaced it, serviced the sliding pins in the caliper (also from the caliper that was renewed a few months ago), bleeded the brakes and took it out for a testdrive. No more wobble, no more weird noises and I'm very happy with the results!

P.s.: I also used an micrometer because I suspected the rotor to be a bit warped. It was, but not that much, somewhere around 3 micrometers. On the worst part it was 4 micrometers.

Post by **abscate** » 03 Feb 2021, 05:22

What’s the business model for the DIY GARAGE ocelot?

Charge by hour , half day, full day?

Post by **Ocelot** » 03 Feb 2021, 05:38

Hey Abscate!

The owner has two ways to charge for the use of his garage. The first, if you do everything on your own, it costs 15 euros for the first hour and 10 hours for every hour after that. If you wanna stay the whole day, he charges you a special price (like 75 euros even though you're there for 10 hours). The second scenario costs 25 euro per hour (welding is 30-45 euros per hour depending on what needs to be done) and then Marcel (the owner) helps you. He's a very experienced welder and mechanic and a awesome dude to spend the day with.